Stereospecific synthesis of functionalized ether phospholipids

Article abstract of DOI:10.1021/jo990739v

A new stereospecific synthesis of functionalized alkyl ether phospholipids is reported. The synthesis is based upon the following: (1) the use of (R)-glycidyl tosylate as a chiral glycerol precursor; (2) the opening of a boron trifluoride catalyzed epoxide ring to introduce the functionalized sn-1-alkyl substituents; (3) the role of tetrahydropyranyl in protecting the sn-2-glycerol position; and (4) the elaboration of the sn-3-carbinol function, via the base hydrolysis of the acetoxy intermediate, obtained from the displacement of the toluenesulfonyl group of the substrate in dipolar aprotic media. Phosphorylation, using two different methods, has led to the development of two major classes of alkyllysophospholipids. For preparation of 'modulator-phospholipid' analogues, the substituted glycerol is coupled with 2,2,2-trichloro-tert-butyl phosphodichloridite and an N-protected amino acid ester, while elaboration of the phosphocholine headgroup of the target platelet-activating factor (PAF) analogues is achieved via the 2-chloro-2- oxo-1,3,2-dioxaphospholane/trimethylamine sequence. The synthesis provides rapid and efficient access to both types of phospholipids: (1) construction of the functionalized/substituted glycerol skeleton is achieved in a straightforward four-step sequence in better than 50% overall yield, and (2) phosphitylation or phosphorylation of the respective glycerol intermediates relies on reagents that require minimal use of protecting groups. The phospholipid compounds prepared include (1) the first synthetic analogue exhibiting modulator activity in conjunction with the glucocorticoid-receptor complex and (2) an sn-1-(ωamino)alkyl derivative of PAF, suitable for introduction of chain-terminal spectroscopic labels for biological and physicochemical studies to elucidate the mechanism of action of this highly potent alkyl ether phospholipid. The synthetic methods described herein have a great deal of flexibility, thus providing convenient general routes to a wide range of alkyl ether phospholipids.

Full text of DOI:10.1021/jo990739v

J . Org. Chem. 1999, 64, 9337-9347
9337
Ster eosp ecific Syn th esis of F u n ction a lized Eth er P h osp h olip id s
Abul B. Kazi,† Sean Shidmand, and J oseph Hajdu*
Department of Chemistry, California State UniversitysNorthridge, Northridge, California 91330-8262
Received May 3, 1999
A new stereospecific synthesis of functionalized alkyl ether phospholipids is reported. The synthesis
is based upon the following: (1) the use of (R)-glycidyl tosylate as a chiral glycerol precursor; (2)
the opening of a boron trifluoride catalyzed epoxide ring to introduce the functionalized sn-1-alkyl
substituents; (3) the role of tetrahydropyranyl in protecting the sn-2-glycerol position; and (4) the
elaboration of the sn-3-carbinol function, via the base hydrolysis of the acetoxy intermediate,
obtained from the displacement of the toluenesulfonyl group of the substrate in dipolar aprotic
media. Phosphorylation, using two different methods, has led to the development of two major
classes of alkyllysophospholipids. For preparation of “modulator-phospholipid” analogues, the
substituted glycerol is coupled with 2,2,2-trichloro-tert-butyl phosphodichloridite and an N-protected
amino acid ester, while elaboration of the phosphocholine headgroup of the target platelet-activating
factor (PAF) analogues is achieved via the 2-chloro-2-oxo-1,3,2-dioxaphospholane/trimethylamine
sequence. The synthesis provides rapid and efficient access to both types of phospholipids: (1)
construction of the functionalized/substituted glycerol skeleton is achieved in a straightforward
four-step sequence in better than 50% overall yield, and (2) phosphitylation or phosphorylation of
the respective glycerol intermediates relies on reagents that require minimal use of protecting
groups. The phospholipid compounds prepared include (1) the first synthetic analogue exhibiting
modulator activity in conjunction with the glucocorticoid-receptor complex and (2) an sn-1-(ω-
amino)alkyl derivative of PAF, suitable for introduction of chain-terminal spectroscopic labels for
biological and physicochemical studies to elucidate the mechanism of action of this highly potent
alkyl ether phospholipid. The synthetic methods described herein have a great deal of flexibility,
thus providing convenient general routes to a wide range of alkyl ether phospholipids.
Structurally modified analogues of platelet-activating
factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine,
PAF, 1) represent a series of synthetic phospholipid
compounds that exhibit high levels of activity in a wide
spectrum of biological systems.1-4 Included among these
are platelet-activating1 antihypertensive2 and antitumor
active3 alkyl ether phospholipids and immunological
response modifiers.4 PAF analogues have been shown to
inhibit phosphatidylcholine biosynthesis,5 protein kinase
C activity,6 and phorbol ester stimulation of protein
kinase C.7 Despite ongoing vigorous investigation of the
biochemistry and cell biology of ether phospholipids, their
physiological functioning and their mechanism of action
remain unclear.8,9
Amino acid derivatives of ether phospholipids are
recent additions to the family of highly potent PAF
analogues.10-15 Among these compounds, particular at-
tention has been directed toward a series of polar
carboxyalkyl phospholipid derivatives (2) that carry
amino acid substituents as a part of their sn-3-phos-
phodiester function; two such amino acid derivatives of
ether phospholipids, isolated from rat liver cytosol, have
shown potent inhibition of glucocorticoid receptor com-
plex activation.11-15 In addition, lyso-PAF 3 has been
shown to be a key intermediate in the metabolic conver-
sion of platelet-activating factor 1 to 1-alkyl-2-acyl-sn-
* To whom correspondence should be addressed. E-mail:
joseph.hajdu@csun.edu. Fax: (818) 677-2912. Tel: (818) 677-3377.
† Current address: Department of Natural Sciences and Environ-
mental Health, Mississippi Valley State University, Itta Bena, MS
38941.
(1) (a) Hanahan, D. J . Annu. Rev. Biochem. 1986, 55, 483. (b)
Snyder, F. Med. Res. Rev. 1985, 5, 107.
(2) Blank, M. L.; Snyder, F.; Byers, L. W.; Brooks, B.; Muirhead, E.
E. Biochem. Biophys. Res. Commun. 1979, 90, 1194.
(3) (a) Berdel, W. E.; Andreesen, R.; Munder, P. G. In Phospholipid
and Cellular Regulation; Kuo, F. J ., Ed.; CRC Press: Boca Raton, FL,
1985; Vol. 2, pp 42-77. (b) Berdel, W. E.; Munder, P. Platelet-Activating
Factor and Related Lipid Mediators; Snyder, F., Ed.; Plenum Press:
New York, 1987, pp 449-467.
(4) (a) Munder, P. G.; Weltzien, H. O.; Modolell, M. Immunopathol-
ogy, VIIth Int. Symposium, Bad Schachen; Niescher, P. A., Ed.;
Schwabe: Basel, 1976, pp 411-424. (b) O’Flaherty, J . T.; Wykle, R.
L. Clin. Rev. Allergy 1983, 1, 353.
(8) (a) Snyder, F. Biochem. J . 1995, 305, 689. (b) Snyder, F.; Lee,
T.-C.; Blank, M. L. Prog. Lipid Res. 1992, 31, 65.
(9) Kleuser, B.; Meister, A.; Sternfeld, L.; Gercken, G. Chem. Phys.
Lipids 1996, 79, 29.
(10) Brachwitz, H.; Langen, P.; Dube, G.; Schildt, J .; Paltauf, F.;
Hermetter, A. Chem. Phys. Lipids 1990, 54, 89.
(11) Bodine, P. V.; Litwack, G. Proc. Natl. Acad. Sci. U.S.A. 1988,
85, 1462.
(5) Vogler, W. R.; Whigham, E.; Bennett, W.; Olsen, A. C. Exp.
Hematol. (Charlottesville, Va) 1985, 13, 629.
(6) (a) Helfman, D. M.; Barnes, K. C.; Kinkade, J . M., J r.; Vogler,
W. R.; Shoji, M.; Kuo, J . F. Cancer Res. 1983, 43, 2955. (b) Zheng, B.;
Ioshi, K.; Shoji, M.; Eibl, H.; Berdel, W. E.; Hajdu, J .; Vogler, W. R.;
Kuo, J . F. Cancer Res. 1990, 50, 3025.
(7) Kiss, Z.; Deli, E.; Vogler, W. R.; Kuo, J . F. Biochem. Biophys.
Res. Commun. 1987, 142, 661.
(12) Bodine, P. V.; Litwack, G. J . Biol. Chem. 1988, 263, 1462.
(13) Bodine, P. V.; Litwack, G. Receptor 1990, 1, 83.
(14) (a) Bodine, P. V.; Litwack, G. Mol. Cell. Endocrinol. 1990, 74,
C77. (b) Schulman, G.; Bodine, P. V.; Litwack, G. Biochemistry 1992,
31, 1734.
(15) Bodine, P. V.; Litwack, G. J . Biol. Chem. 1990, 265, 9544.
10.1021/jo990739v CCC: $18.00 © 1999 American Chemical Society
Published on Web 11/24/1999

9338 J . Org. Chem., Vol. 64, No. 26, 1999
Kazi et al.
glycero-3-phosphocholine.8,16 Furthermore, compound 3
also serves as a substrate of the enzyme alkylglycero-
phosphocholine acetyltransferase,8,9 which catalyzes for-
mation of PAF 1 after the release of arachidonic acid,
showing that lyso-PAF 3 is central to the biosynthesis of
eicosanoids and platelet-activating factor from the same
lipid pool.8,9 Because the production of these compounds
is known to play an important role in transmembrane
signaling, there is great interest in elucidating the
mechanism of the catalytic reactions and the function of
lysophospholipid intermediates in the PAF cycle.9
Sch em e 1
1 , started with the Lewis acid catalyzed ring opening of
(R)-glycidyl tosylate 418 by a series of medium- and long-
chain primary alcohols carrying either an N-protected
ω-amino group or a chain-terminal carbomethoxy func-
tion. The resulting products (5) were obtained in good
yield (73-95%), high enantiomeric purity, and complete
regiospecificity. Significantly, both chain-terminal 2,2,2-
trichloro-tert-butoxycarbonyl and carbomethoxy groups
remained stable under the acidic conditions that existed
during the catalytic ring-opening reaction.
The development of new synthetic methods for prepa-
ration of ether-lysophospholipids, in a convergent path-
way leading to PAF analogues and modulator-phospho-
lipid analogues, is an important prerequisite to the
elucidation of the chemical-structural basis of their
biological mechanism of action. Availability of the com-
pounds should not only contribute to advancement in the
level of understanding of the chemistry and biology of
alkyllysophospholipids, but also provide important in-
sight into the design of new target molecules with the
desired activity and potency.8,17
As part of our research in this area, we now report
stereospecific syntheses of functionalized ether lysophos-
pholipids by two closely related sequences that should
be applicable to the preparation of a wide range of
synthetic-modulator and PAF analogues. Specifically,
both syntheses rely on (1) the use of (R)-glycidyl tosylate
as a chiral glycerol precursor, (2) the opening of a BF3-
catalyzed epoxide ring to introduce the functionalized sn-
1-alkyl substituents, (3) the role of tetrahydropyranyl in
protecting the sn-2-glycerol position, and (4) the elabora-
tion of the sn-3-carbinol function via base hydrolysis of
the acetoxy intermediate obtained from the displacement
of the toluenesulfonyl group of the substrate in a dipolar
aprotic media. The sequences diverge at the phosphor-
ylation step. For the preparation of modulator analogues,
the substituted glycerol is coupled with 2,2,2-trichloro-
tert-butyl phosphodichloridite and an N-protected amino
acid ester, while elaboration of the phosphocholine head-
group of the target PAF analogues is accomplished via
the 2-chloro-2-oxo-1,3,2-dioxaphospholane/trimethylamine
sequence.
The stereochemistry of the 1-O-alkyl-sn-glycerol prod-
ucts 5a ,b obtained in the ring-opening reaction was
determined through preparation and 1H-NMR spectro-
scopic characterization of their Mosher esters19 6a ,b in
comparison with the spectra of the corresponding dia-
stereoisomeric compounds 7a ,b, prepared from (S)-gly-
cidyl tosylate in a similar series of reactions. The chemi-
cal shifts recorded for the series 6a ,b versus 7a ,b turned
out to be sufficiently different from each other as to allow
clear distinction between the respective diastereoisomers.
1
Specifically, the 360 MHz H-NMR spectrum of 6a 20 in
CDCl3 exhibited a multiplet for the sn-2-glycerol proton
centered at δ 5.341, showing no traces of absorption
except at baselines of 5.399 and 5.413 ppm, which are
part of the multiplet centered at δ 5.833 and, therefore,
assigned to the corresponding CH-proton of the Mosher
ester prepared from (S)-glycidyl tosylate.
Similarly, the 500 MHz 1H-NMR spectrum of com-
pound 6b shows a glycerol CH-multiplet in the δ 5.351-
5.392 range with a baseline between δ 5.399 and δ 5.429,
which includes six broad peaks of the 5.410 ppm centered
multiplet assigned to the CH-proton of Mosher ester 7b.
In addition, the high-field proton of the sn-3-CH2 group
in compound 6b shows a four-line multiplet (doublet of
Resu lts a n d Discu ssion
Our synthetic approach to the preparation of ether
lysophospholipid targets involved three strategic compo-
nents. The first phase of the synthesis, shown in Scheme
(18) (a) Guivisdalsky, P. N.; Bittman, R. Tetrahedron Lett. 1988,
29, 4393. (b) The availability of this compound in high enantiomeric
excess (>99%) makes it preferable to other glycidol derivatives for the
stereospecific synthesis of phospholipids.
(16) Malone, B.; Lee, T.-C.; Snyder, F. J . Biol. Chem. 1985, 260,
1531.
(17) Kini, G. D.; Beadle, J . R.; Aldern, K. A.; Hostetler, K. Y.
Presented at the 211th National Meeting of the American Chemical
Society, New Orleans, LA, March 24-28, 1996; Abstr. MEDI 172.
(19) Dale, J . A.; Dull, D. L.; Mosher, H. S. J . Org. Chem. 1969, 34,
3543.
(20) Kazi, A. B.; Hajdu, J . Tetrahedron Lett. 1992, 33, 2291.

Synthesis of Functionalized Ether Phospholipids
J . Org. Chem., Vol. 64, No. 26, 1999 9339
Sch em e 2
doublets) at δ 4.10, while the corresponding proton in the
spectrum of 7b occurs 0.10 ppm higher. Absence of the
latter in the spectrum of 6b at baseline level separation
confirms the stereochemical purity of product 6b (and
consequently that of the corresponding glycerol compound
5b) at the NMR detection level (>99%).
Tetrahydropyranylation of the secondary hydroxyl
group of 5 was readily accomplished with pyridinium-p-
toluenesulfonate catalysis in methylene chloride at ambi-
ent temperature. The products 8a -c, purified by silica
gel chromatography, were isolated as analytically pure
mixtures of stereoisomers in the form of colorless viscous
liquids, in 69-95% yield. Next, the p-toluenesulfonate
function of 8 was displaced by “naked” acetate using
anhydrous tetraethylammonium acetate in acetonitrile
(68-90% yield). The yield and duration of this reaction
was greatly dependent upon successful drying of the
reagent and the dipolar aprotic reaction medium, as the
presence of even small amounts of water or other hy-
droxylic solvents slows the reaction down a great deal
and decreases the yields of the products drastically, due
to the formation of numerous byproducts.21
The base-catalyzed hydrolytic cleavage of the sn-3-
acetoxy group with methanolic potassium carbonate
provided the deprotected carbinol function in the final
step of this sequence (Scheme 1). The hydrolysis occurred
with high selectivity, as both the methyl ester (10a ) and
the 2,2,2-trichloro-tert-butoxycarbonyl function (10b,c)
remained unchanged in the course of the reaction.
Purification of the products by silica gel chromatography
followed by freeze-drying with benzene gave the substi-
tuted glycerol 10 in anhydrous form, suitable for phos-
phorylation (68-85% yield).
In the second phase of the synthesis, we turned to our
attention to the preparation of protected amino acid
derivatives to be used for elaboration of the polar head-
group of modulator phospholipids (2). As we had previ-
ously observed, N-triphenylmethylation, rather than tert-
butoxycarbonylation, of the amino group seemed to be a
better choice to provide protection during phosphoryl-
ation, because the former provides a more hydrophobic
substrate and lacks the electron rich carbonyl oxygen
present in the N-t-Boc function. The latter has been
known to interfere with the phosphorylation of the
hydroxyl group, resulting in longer reaction times and
decreased yields, due to the formation of numerous
byproducts.22 Thus, both serine methyl ester and its
corresponding threonine analogue were treated with 1
equiv of triphenylmethyl chloride/triethylamine in chlo-
roform at room temperature to give their respective
N-trityl compounds in high yield (89-91%).23
available yet are likely candidates to serve as part of the
target compounds. In this context, we focused on the
synthesis of γ-amino-â-hydroxybutyric acid (GABOB).24
Our approach, as shown in Scheme 2, relied on develop-
ment of the amino alcohol function by converting epoxide
1 to the corresponding oxazoline 11 by reacting it with
acetonitrile, using boron trifluoride as catalyst.25a Acid-
olytic cleavage of the oxazoline heterocycle 11 followed
by tritylation of the amino group yielded intermediate
12, whose primary toluenesulfonyl function could sub-
sequently be used to accomplish the desired chain exten-
sion. To that end, tosylate 12 was first converted to the
corresponding iodide 13, followed by nucleophilic dis-
placement of the latter with cyanide.25b Next, compound
14 was allowed to react with methanol in the presence
of potassium carbonate to produce cyanohydrin 15 which
was then treated with trifluoroacetic acid in chloroform
and concentrated sulfuric acid on a steam bath to give
the γ-amino-â-hydroxybutyric acid target 16. The char-
acteristic physical parameters of compound 16, such as
its 1H-NMR spectrum and optical rotation, were found
to be in agreement with the literature values reported
(see the Experimental Section).
Considering that the authentic structure of the natu-
rally occurring modulator phospholipids (2) has not yet
been elucidated and the scope of structural variation of
the amino acid component in the polar phosphodiester
headgroup has not yet been determined, it seemed
necessary to develop a sequence for preparation of
hydroxy amino acids that are not readily commercially
The third phase of the synthesis focused on assembling
the target phospholipid (2) via phosphite coupling of the
substituted glycerol 10 with a series of N-protected
hydroxy amino acid methyl esters, as shown in Scheme
3. We chose 2,2,2-trichloro-tert-butyl phosphodichloridite
as a coupling agent because of its high reactivity and
ready availability. It was also selected because of the ease
with which the phosphitylated products can be manipu-
(21) In some cases, the addition of activated molecular sieves seemed
to be helpful in removing traces of moisture from the reaction mixture,
thereby increasing the reactivity of the anionic nucleophile (see the
Experimental Section).
(22) (a) Bhatia, S. K.; Hajdu, J . Lipids 1991, 26, 1424. (b) Bhatia,
S. K.; Hajdu, J . Tetrahedron Lett. 1988, 29, 31.
(23) The N-triphenylmethyl derivatives of serine methyl ester and
threonine methyl ester were prepared by the method described in ref
22a ; they were obtained in 91 and 89% yields, respectively.
(24) J ung, M. J .; Shaw, T. J . J . Am. Chem. Soc. 1980, 102, 6304.
(25) (a) Klunder, J .; Onami, T.; Sharpless, K. B. J . Org. Chem. 1989,
54, 1295. We found that, contrary to the previous report, the pure
oxazoline 11 is quite stable at room temperature (for at least several
weeks). (b) Preparation of iodide 13 turned out to be necessary, because
direct displacement of the tosylate with sodium iodide gave poor yields
of compound 14.

9340 J . Org. Chem., Vol. 64, No. 26, 1999
Kazi et al.
Sch em e 3
following silica gel chromatography in an analytically
pure form (61% yield). Sequential hydrolysis of the
protecting groups was accomplished by addition of 0.1 N
HCl, to remove the acid labile N-trityl and O-tetrahy-
dropyranyl groups and treatment with 0.2 N NaOH in
aqueous tetrahydrofuran to obtain the deprotected target
phospholipid 20a as its trisodium salt in 62% yield. The
corresponding threonine derivative 20b was obtained in
a similar series of reactions in 59% overall yield. Depro-
tection of the phospholipid derived from γ-amino-â-
hydroxybutyric acid 21 was achieved by treating com-
pound 19c first with 0.3 N NaOH in aqueous dioxane,
followed by trifluoroacetic acid in chloroform, and finally
with 0.1 N HCl in aqueous tetrahydrofuran. Deprotected
phospholipid compound 21 was isolated as the trisodium
salt following silica gel chromatography in 61% overall
yield.
Biologica l Act ivit y of t h e Syn t h et ic Mod u la t or
An a logu es. Compounds 20a ,b and 21 have been tested
for their ability to inhibit in vitro glucocorticoid-receptor
complex activation, in conjunction with a series of
structurally related synthetic analogues and compared
to the naturally occurring modulator.26 Of the series
tested, 20b was the first synthetic compound possessing
modulator activity. Specifically, in the 10-3 M concentra-
tion range, 1-O-(5′-carboxypentyl)-sn-glycero-3-phospho-
threonine 20b was found to inhibit glucocorticoid-receptor
activation, as well as unoccupied glucocorticoid-receptor
hormone binding in a dose-dependent manner. The
inhibition was stereospecific, as evidenced by the fact that
the stereoisomer of 20b, prepared from (S)-glycidyl
tosylate in a similar series of reactions, did not show any
activity in either one of the systems tested. Furthermore,
since the degree of steroid-binding inhibition by 20b was
found to be the same as its ability to inhibit steroid-
receptor complex activation (40%, at (3-4) × 10-3
M
concentration), it has been suggested that the synthetic
modulator may interact with the steroid-binding domain
of the glucocorticoid receptor.26 Although the potency of
20b is ∼2-3 orders of magnitude lower than that of the
naturally occurring modulator, it is the first and only one
of the 26 synthetic phosphoglycerides examined thus far
that exhibited any modulator-like effects.12,26,27 Hence,
although the activity of the natural modulator is not
exactly mimicked by 20b, it provides a useful lead
compound for the design of analogues, including com-
pounds that aim to confirm the exact structure of the
naturally occurring modulator.
Syn th esis of F u n ction a lized P AF -An a logu e P r e-
cu r sor s. Because of the well-recognized importance of
phospholipid hydrolyzing enzymes in cellular signaling,
as well as the importance of the enzyme alkylglycero-
phosphocholine acetyltransferase in the formation of
platelet-activating factor, functionalized alkyllysophos-
phocholines have been shown to be valuable synthetic
analogues in studying the enzymatic reactions involved
in the interconversion of biologically active ether phos-
pholipids, with a particular emphasis on the elucidation
of the PAF cycle.8,9,28 However, spectroscopically labeled
metabolic PAF intermediates have only been available
lated, upon subsequent oxidation and deprotection, to
produce the desired amino acid substituted phosphodi-
esters 20 and 21. Along these lines, alcohol 10 was
coupled with N-tritylserine methyl ester using stoichio-
metric amounts of 2,2,2-trichloro-tert-butyl phospho-
dichloridite in the presence of 3 equiv of diisopropylethyl-
amine in tetrahydrofuran at -78 °C to give the trialkyl
phosphite (17) (69%). This compound was then reacted
with 30% aqueous hydrogen peroxide in a biphasic
system, including methylene chloride, at room temper-
ature for 2 h, to obtain phosphotriester 18a in 95% yield.
The corresponding threonine derivative (18b ) and the
phosphotriester derived from γ-amino-â-hydroxybutyric
acid (18c) were prepared in a similar way, except that
in those reactions, the secondary alcohol derived from the
corresponding amino acid was first phosphorylated and
then followed by addition of glycerol-alcohol 10 to the
reaction mixture. Phosphotriesters 18b and 18c were
obtained from the respective alcohols in 45% and 42.5%
overall yields.
(26) Bodine, P. V.; Hajdu, J .; Litwack, G. Biochem. Biophys. Res.
Commun. 1994, 203, 408.
(27) Bodine, P. V.; Garcia, M. L.; Pascual, J .; Bastida, E.; Carganico,
G.; Litwack, G. Receptor 1991, 1, 167.
(28) Baker, R. R.; Chang, H. Biochim. Biophys. Acta 1996, 1302,
257.
Reductive cleavage of 18a by zinc powder in the
presence of acetylacetone/triethylamine in anhydrous
acetonitrile at room temperature gave phosphodiester
19a as the single major product, which was isolated

Synthesis of Functionalized Ether Phospholipids
J . Org. Chem., Vol. 64, No. 26, 1999 9341
Sch em e 4
through “total synthesis” rather than via the derivati-
zation of appropriately functionalized synthetic alkyl-
lysophospholipid precursors.9 Thus, in extending our
synthetic method to the preparation of such derivatives,
we focused on the synthesis of ω-NH2-substituted ana-
logues of 1-O-alkyl-sn-glycero-3-phosphocholine 3, to
provide a chain-terminal site for the introduction of
spectroscopic labels. Specifically, it has recently been
shown that ether phospholipid analogues, functionalized
at a position remote from the catalytic site, are highly
suitable substrates for the study of PAF-metabolizing
enzymes, with a view toward mechanistic elucidation of
the PAF cycle.9,28
For the synthesis of chain-terminal amino-substituted
analogues of compound 3, we first prepared 2,2,2-trichloro-
tert-butoxycarbonyl-protected 12-aminododecanol via the
diborane reduction of commercially available 12-amino-
dodecanoic acid, followed by triethylamine catalyzed
carbamoylation using 2,2,2-trichloro-tert-butyl chlorofor-
mate in 79% overall yield. The corresponding six-carbon
analogue was prepared similarly, from 6-aminohexanol
(91%). These N-protected amino alcohols were then
subjected to the four-step synthetic sequence outlined in
Scheme 1, which gave rise to the alkylated/protected
glycerols 10b,c in ∼52% overall yield. Next, the sn-3-
hydroxyl group of 10c was phosphorylated using 2-chloro-
2-oxo-1,3,2-dioxaphospholane in benzene at room tem-
perature for 3 h (Scheme 4). The cyclic dioxaphospholane
intermediate 22c, which formed as a single phosphate-
positive product, was immediately transferred into a
pressure bottle and allowed to react with anhydrous
trimethylamine at 60 °C for 16 h. The phosphocholine
product 23c was chromatographed on silica gel to afford
the analytically pure phospholipid in 74% yield. Finally,
deprotection of the amino group using zinc/acetic acid/
methylene chloride (78%) followed by acid-catalyzed
cleavage of the sn-2-tetrahydropyranyl function gave the
target compound 25c in 66% yield.
function for the synthesis of ether phospholipids. Specif-
ically, the use of 2,2,2-trichloro-tert-butoxycarbonyl func-
tion provides an acid- and base-resistant protection
strategy that is more stable and more convenient to
handle than the corresponding 2,2,2-trichloroethyl-
carbamoyl alternative previously used in phospholipid
synthesis.29 Moreover, because the trichloro-t-BOC group
is stable under both acidic and basic conditions, it
provides orthogonal protection in the presence of both
t-BOC30 and FMOC31 derivatives of amino groups, such
that it is likely to receive further attention for side-chain
protection in peptide chemistry as well.
Preparation of an O-tetrahydropyranyl protected sub-
stituted glycerol, such as compound 5, in a rapid four-
step sequence from readily available starting materials
should provide a convenient general method for the
synthesis of mixed-chain glycerolipids and phospholipids
that incorporate a wide spectrum of different substitu-
ents. Despite the temporary presence of a second chiral
center that is introduced on the tetrahydropyranylation
of the secondary alcohol function, the resulting mixture
of stereoisomers is readily purified. This provides a
hydrophobic neighboring group that promotes efficient
phosphorylation/acylation and allows convenient depro-
tection, under very mild reaction conditions, to obtain the
desired target compound.
Finally, the third element of general synthetic signifi-
cance involves the use of trichloro-tert-butyl phospho-
dichloridite for coupling the two alcohols en route to the
desired phosphodiesters. This reagent, which has been
shown to be useful for the construction of internucleotide
linkages between sugar moieties in nucleic acid chemis-
try,32 has now been applied to the synthesis of lipid
phosphodiesters as well. Specifically, the compound was
shown to be reactive toward both primary and secondary
alcohols, even at low temperatures, allowing simple
(29) Srisiri, W.; Lamparski, H. G.; O’Brien, D. F. J . Org. Chem. 1996,
61, 5911.
(30) Kocienski, P. Protecting Groups; Verlag: New York, 1994, pp
192-195.
(31) Carpino, L. A. Acc. Chem. Res. 1987, 20, 401.
(32) (a) Letsinger, R. L.; Bach, S. A.; Eadie, J . S. Nucleic Acids Res.
1986, 14, 3487. (b) Letsinger, R. L.; Groody, E. P.; Tanaka, T. J . Am.
Chem. Soc. 1982, 104, 6806.
In addition to developing an efficient method for the
preparation of functionalized ether lysophospholipids, a
number of useful synthetic strategies have emerged from
the sequences herein presented. The first strategy con-
cerns the introduction of the N-protected aminoalkyl

9342 J . Org. Chem., Vol. 64, No. 26, 1999
Kazi et al.
performed by Desert Analytics, Tucson, AZ; Oneida Research
Services (ORS), Whitesboro, NY; and Galbraith Laboratories,
Inc., Knoxville, TN. Fast atom bombardment (FAB) mass
spectra were obtained at the University of California Riverside
Mass Spectrometry Facility.
sequential addition of the alcohols to be coupled. Phos-
phite triesters are easily purified, readily oxidized, and
reductively deprotected to afford the desired phosphodi-
esters. Such features should make this reagent an
attractive choice for the phosphorylation of glycerol
derivatives for cases in which the nature of the polar
headgroup precludes the use of the conventional phos-
phorylating agents that are commonly used in lipid
chemistry.
In conclusion, the syntheses that we have presented
provide rapid and efficient routes to a wide range of
functionalized alkyllysophospholipid compounds. The
strength of the methods lie in their simplicity and
flexibility. They are likely to become applicable to the
preparation of additional types of phospholipid deriva-
tives for biological and physicochemical studies. Work
toward this goal is underway in our laboratory.
1-O-(5′-Car bom eth oxypen tyl)-sn -glycer yl-3-tosylate (5a).
To a solution of 6-hydroxyhexanoic acid methyl ester (8.05 g,
55 mmol) and (2R)-(-)-glycidyl tosylate 4 (8.4 g, 36.6 mmol)
in 200 mL dry of dichloromethane was slowly added boron
trifluoride etherate (1.2 mL, 9.76 mmol), at room temperature,
and the resulting solution was stirred for 4 h. The reaction
mixture was then washed with saturated brine (2 × 50 mL),
the organic phase was dried over anhydrous MgSO4, and the
solvent was removed with a rotary evaporator. The residue
was chromatographed (SiO2, hexanes/EtOAc 2:3) to give 12.3
g (89%) of the product 5a as a colorless liquid: IR (Nujol) 3510,
1
1732 cm-1; H NMR (CDCl3, δ) 0.98-1.89 (m, 6 H), 2.37 (t, J
) 7.5 Hz, 2 H,), 3.44 (m, 4 H), 3.67 (s, 3 H), 4.04 (m, 3 H), 7.35
(d, J ) 8.3 Hz, 2 H), 7.80 (d, J ) 8.3 Hz, 2 H); [R]25 -7.5 (
D
0.2 (c 1.00, MeOH); Rf (hexanes/EtOAc 2:3) 0.50; FAB-MS [M
+ H]+ calcd for C17H27O7S 375.1477, found 375.1488.
Exp er im en ta l Section
1-O-[6′-(N-2′′,2′′,2′′-Tr ich lor o-ter t-bu toxyca r bon yla m i-
n o)h exyl]-sn -glycer yl-3-tosyla te (5b). (i) 6-(N-2′,2′,2-Tr i-
ch lor o-ter t-bu toxyca r bon yla m in o)h exa n ol. To a solution
of 6-amino-1-hexanol (2.0 g, 17.1 mmol) in 50 mL of dry
chloroform was added 4-(dimethylamino)pyridine (2.09 g, 17.1
mmol) followed by 2,2,2-trichloro-1,1-dimethylethyl chlorofor-
mate (4.09 g, 17.1 mmol) at 0 °C. The yellow reaction mixture
was stirred at room temperature for 24 h. After complete
conversion, as shown by TLC, the reaction mixture was
washed with 50 mL of water. The organic layer was dried over
sodium sulfate. The solvent was removed by a rotary evapora-
tor, and the light yellow oil, which solidified upon standing,
was purified by column chromatography on silica gel using
chloroform/methanol (93:7) for elution. The resulting white
solid was isolated as an analytically pure product (4.99 g,
Gen er a l Meth od s. 1H NMR spectra were recorded at 200,
360, and 500 MHz. (2R)-(-)-Glycidyl tosylate, (2S)-(+)-glycidyl
tosylate, boron trifluoride etherate, 3,4-dihydro-2H-pyran,
2,2,2-trichloro-1,1-dimethylethyl chloroformate, 6-aminohex-
anol, and 2 M lithium borohydride in tetrahydrofuran were
purchased from Aldrich. 12-Aminolauric acid 2-chloro-2-oxo-
1,3,2-dioxaphospholane, pyridinium p-toluenesulfonate, 2,2,2-
trichloro-tert-butylphosphochloridite, triphenylmethyl chloride,
and S-(+)-R-methoxy-R-trifluoromethylacetyl chloride were
purchased from Fluka. L-Serine methyl ester and L-threonine
methyl ester were obtained from Sigma, and anhydrous
trimethylamine (Kodak) were all used as received. Zinc powder
(-100 mesh, Aldrich) was used without treatment for phos-
photriester deprotection. Zinc dust (<10 µm, 98+ %, Aldrich)
was activated using 6% aqueous HCl followed by washing with
water, ethanol, and anhydrous acetonitrile for reductive cleav-
age of the 2,2,2-trichloro-tert-butoxycarbamoyl group. Alter-
natively, zinc powder (7 µm, Aesar) was used as received.
Acetonitrile (spectrograde, Burdick & J ackson) and triethyl-
amine (spectrograde, Fluka) were dried over activated molec-
ular sieves (3 Å). Reagent grade chloroform and dichloro-
methane (Fisher) were freshly distilled from phosphorus
pentoxide. Benzene (HPLC grade, Aldrich) was kept over
sodium wire and distilled from calcium hydride prior to use.
Diethyl ether (reagent grade, Fisher) was kept over sodium
wire. Dioxane (J . T. Baker), ethyl acetate, hexane (reagent
grade, Fisher), and tetrahydrofuran (spectrograde, Burdick &
J ackson) were used without further treatment. Tetraethyl-
ammonium acetate tetrahydrate (Aldrich) was dried in an
anhydrous acetonitrile solution over activated molecular sieves
(3 Å) for at least 2 days prior to use. Methyl 6-hydroxyhex-
anoate was prepared by esterification from 6-hydroxyhexanoic
acid (Sapon Laboratories, Aurora, OH) in anhydrous HCl/
methanol. Commercially available reagent grade, or better,
inorganic reagents were used as received. Regular column
chromatography was carried out with silica gel 60 (70-230
mesh ASTM, E. M. Science), and flash column chromatography
was carried out with silica gel 60 (230-400 mesh ASTM, E.
M. Science). The silica gel was activated at 120 °C and then
cooled to room temperature prior to its use in a desiccator over
P2O5. Thin-layer chromatography was carried out on Whatman
diamond MK6F silica gel 60 Å plates. AG 50W-X8 ion-
exchange resin (100-200 mesh) was obtained from Bio-Rad
Laboratories. Sephadex LH-20 and Sephadex G-10 were
obtained from Pharmacia. The TLC plates were visualized by
iodine vapor and UV light, where appropriate. The phospho-
lipids were visualized by molybdenum spray,33 and the primary
amines were sprayed by 0.25% ninhydrin in acetone solution.
Trityl compounds were visualized by using concentrated
hydrochloric acid solution vapor. Elemental analyses were
1
91%): IR (CHCl3) 1722 cm-1; H NMR (CDCl3, δ) 1.36-1.60
(m, 8 H), 1.92 (s, 6 H), 3.12-3.18 (m, 2 H), 3.65 (t, J ) 6.4 Hz,
2 H), 4.85 (br. m, 1 H); Rf (CHCl3/MeOH 93:7) 0.49. Anal. Calcd
for C11H20NO3Cl3: C, 41.20; H, 6.29; N, 4.37. Found: C, 41.10;
H, 6.26; N, 4.35.
(ii) 5b. To a solution of 4 (1.03 g, 4.51 mmol) in 20 mL of
dichloromethane were added 6-(N-TCBOC)aminohexanol (2.20
g, 6.86 mmol) and boron trifluoride etherate (75 µL, 0.083
equiv) at room temperature. The reaction mixture was then
refluxed at 45 °C for 6 h, followed by stirring at room
temperature for 20 h. The solvent was evaporated, and the
resulting viscous oil was purified by silica gel chromatography
with a dichloromethane/methanol (95:5) solvent system to
afford pure 5b (2.34 g, 95%) as an oil: IR (neat) 1724 cm-1
;
1H NMR (CDCl3, δ) 1.35-1.60 (m, 8 H), 1.93 (s, 6 H), 2.48 (s,
3 H), 3.15 (m, 2 H), 3.44 (m, 4 H), 4.03 (m, 3 H), 7.36 (d, J )
8.4 Hz, 2 H), 7.82 (d, J ) 8.4 Hz, 2 H); Rf (CH2Cl2/CH3OH
95:5) 0.45; FAB-MS, [M + H]+, calcd 548.1043, found 548.1046.
Anal. Calcd for C21H33NO7SCl3C0.5 H2O: C, 45.28; H, 6.15;
N, 2.51. Found: C, 45.15; H, 6.06; N, 2.46.
1-O-[12′-(N-2′′,2′′,2′′-Tr ich lor o-ter t-bu toxyca r bon yla m i-
n o)d od ecyl]-sn -glycer o-3-tosyla te (5c). (i) 12-Am in od o-
d eca n ol H yd r och lor id e. To a suspension of 12-aminodo-
decanoic acid (2.0 g, 9.29 mmol) in 13 mL of tetrahydrofuran
was added 37 mL of 1 M BH3‚THF (37 mmol) under N2
atmosphere at room temperature. The reaction mixture was
refluxed overnight and then cooled. Next, 30 mL of 10% AcOH
in methanol was added dropwise, followed by stirring at room
temperature for 30 min. The solvent was removed in vacuo,
and the solid was dried by subsequent addition and evapora-
tion of 3 × 30 mL of methanol. The resulting white solid was
suspended in 20 mL of water, followed by addition of 40 mL
of 9 M aqueous HCl. The suspension was stirred for 48 h. The
white solid was isolated by filtration to give 12-aminododecanol
hydrochloride (1.86 g, 99%): 1H NMR (CDCl3/CD3OD 9:1, δ)
1.26-1.67 (m, 20 H), 2.84 (t, J ) 7.7 Hz, 2 H), 3.52 (t, J ) 6.6
Hz, 2 H).
(ii) 12-(N-2′,2′,2′-Tr ich lor o-ter t-bu toxyca r bon yl)a m in o-
d od eca n ol. To a suspension of 12-aminododecanol hydrochlo-
(33) Dittmer, J . C.; Lester, R. L. J . Lipid Res. 1964, 4, 126.

Synthesis of Functionalized Ether Phospholipids
J . Org. Chem., Vol. 64, No. 26, 1999 9343
ride (2.03 g, 8.54 mmol) in 75 mL of freshly distilled chloro-
form, was added triethylamine (2.38 mL, 17.1 mmol) under
nitrogen. After the mixture was stirred at room temperature
for 30 min, 2,2,2-trichloro-tert-butyl chloroformate (1.92 g, 8.00
mmol) was added. The reaction mixture was stirred at room
temperature for an additional 30 min, and the precipitate that
formed was gravity filtered. The chloroform filtrate was
washed with water (3 × 50 mL), and the combined aqueous
layer was extracted with chloroform (2 × 30 mL). The
combined chloroform solution was dried with magnesium
sulfate, the solvent was evaporated, and the resulting white
solid was dried in a vacuum desiccator over P2O5 to give 2.80
(0.20 g, 0.316 mmol) in 12 mL of freshly distilled chloroform
was added DMAP (0.046 g, 0.377 mmol), followed by MTPA
chloride (0.096 g, 0.380 mmol). The solution was stirred at
room temperature for 5 h, another portion of MTPA chloride
(0.048 g, 0.190 mmol) was added, and the reaction mixture
was kept overnight at room temperature. The solution was
then washed with 5% NaHCO3 (2 × 10 mL); the combined
aqueous layers were extracted with 10 mL of CHCl3, and the
organic solution was dried with MgSO4. The solvent was
evaporated under reduced pressure to give the Mosher ester
6b as a colorless oil. This residue was chromatographed on
silica gel using CHCl3/EtOAc (95:5) and then freeze-dried from
benzene to obtain the pure product 6b (0.240 g, 89%): 1H NMR
(500 MHz, CDCl3, δ) 1.20-1.29 (br s, 16 H), 1.40 (br s, 2 H),
1.60 (br s, 2 H), 1.92 (s, 6 H), 2.44 (s, 3 H), 3.14 (m, 2 H), 3.27
(t, J ) 6.6 Hz, 2 H), 3.46 (dd, J ) 10.8, 5.3 Hz, 1 H), 3.51-
3.54 (m, 1 H), 3.52 (s, 3 H), 4.20 (dd, J ) 11.0, 6.9 Hz, 1 H),
4.28 (dd, J ) 11.0, 3.2 Hz, 1 H), 5.35-5.40 (m, 1 H), 7.32 (d,
J ) 8.3 Hz, 2 H), 7.38-7.52 (m, 5 H), 7.75 (d, J ) 8.3 Hz, 2
H); Rf (CHCl3/EtOAc 95:5) 0.74.
3-O-[12′-(N-2′′,2′′,2′′-Tr ich lor o-ter t-bu toxyca r bon yla m i-
n o)dodecyl-2-(r-m eth oxy-r-tr iflu or om eth ylph en yl)acetyl-
sn -glycer o-1-tosyla te (7b). Compound 7b was prepared
under conditions similar to those described for 6b using alcohol
5c′ obtained from (S)-glycidyl tosylate under the same reaction
conditions as shown for the (R)-enantiomer: 1H NMR (500
MHz, CDCl3, δ) 1.24-1.29 (br s, 16 H), 1.51 (br s, 4 H), 1.92
(s, 6 H), 2.44 (s, 3 H), 3.12-3.16 (m, 2 H), 3.35-3.40 (m, 2 H),
3.50 (s, 3 H), 3.56-3.60 (m, 2 H), 4.10 (dd, J ) 10.9, 6.4 Hz, 1
H), 4.20 (dd, J ) 10.9, 3.7 Hz, 1 H), 5.39-5.43 (m, 1 H), 7.30
(d, J ) 8.3 Hz, 2 H), 7.36-7.53 (m, 5 H), 7.68 (d, J ) 8.3 Hz,
2 H).
g (86%) of analytically pure product: IR (CHCl3) 1724 cm-1
;
1H NMR (CDCl3, δ) 1.28 (br s, 16 H), 1.40-1.62 (br m, 4 H),
1.92 (s, 6 H), 3.15 (m, 2 H), 3.65 (t, J ) 6.5 Hz, 2 H), 4.85 (br
m, 1 H); Rf (CHCl3/MeOH 94:6) 0.61; FAB-MS [M + H]+ calcd
404.1526, found 404.1528. Anal. Calcd for C17H32NO3Cl3: C,
50.44; H, 7.97; N, 3.46. Found: C, 50.37; H, 7.98; N, 3.43.
(iii) 5c. To a solution of 4 (0.42 g, 1.84 mmol) in 20 mL of
freshly distilled dichloromethane was added 12-(N-2′,2′,2′-
trichloro-tert-butoxycarbonylamino)dodecanol (1.12 g, 2.77
mmol), followed by boron trifluoride etherate (0.72 mL, 5.85
mmol) under N2 at room temperature. The reaction mixture
was refluxed at 45 °C for 5 h. Most of the glycidyl tosylate
had been converted to the product, as shown by TLC. The
solution was cooled to room temperature, added to methylene
chloride (30 mL), and washed with 50 mL of water. The
resulting emulsion was broken with 50 mL of methanol. The
organic layer was separated, and the aqueous layer was
extracted with 50 mL of CH2Cl2. The combined organic layer
was washed with 50 mL of water; the combined aqueous layer
was washed with 30 mL of CH2Cl2. The organic solution was
dried with MgSO4, the solvent was evaporated, and the
semisolid residue was chromotographed on silica gel using
CHCl3/EtOAc (86:14) to obtain the pure product 5c as a
1-O-(5′-Ca r bom eth oxyp en tyl)-2-tetr a h yd r op yr a n yl-sn -
glycer o-3-tosyla te (8a ). To a solution of alcohol 5a (5.3 g,
14.2 mmol) in 110 mL of dry dichloromethane were added
pyridinium-p-toluenesulfonate (0.36 g, 1.42 mmol) and 3,4-
dihydro-2H-pyran (1.78 g, 21.2 mmol), and the resulting
mixture was stirred at room temperature for 4 h. The solution
was then washed with saturated brine (2 × 40 mL), the organic
phase was dried over MgSO4, and the solvent was evaporated
under reduced pressure with an evaporator. The residue was
chromatographed on silica gel with hexane/EtOAc (2:1) to give
4.5 g (69%) of product 8a as a colorless liquid: IR (Nujol) 1734
colorless oil (0.85 g, 73%): IR (CHCl3) 1724 cm-1 1H NMR
;
(CDCl3, δ) 1.26 (br s, 16 H), 1.42-1.62 (br m, 4 H), 1.92 (s, 6
H), 2.46 (s, 3 H), 3.10-3.18 (m, 2 H), 3.40-3.46 (m, 4 H), 3.96-
4.09 (m, 3 H), 4.85 (br m, 1 H), 7.37 (d, J ) 8.3 Hz, 2 H), 7.81
(d, J ) 8.3 Hz, 2 H); Rf (CHCl3/EtOAc 86:14) 0.58; [R]25 -4.3
D
(c 1.00, CHCl3/MeOH 4:1); FAB-MS [M + H]+ calcd 632.1982,
found 632.1994. Anal. Calcd for C27H44NO7Cl3S: C, 51.23; H,
7.01; N, 2.21. Found: C, 51.06; H, 6.99; N, 2.18.
Mosh er Ester of 5a : 1-O-(5′-Ca r bom eth oxyp en tyl)-2-
(r-m eth oxy-r-tr iflu or om eth ylp h en yl)a cetyl-sn -glycer o-
3-tosyla te (6a ). To a stirred solution of 5a (0.141 g, 0.38 mmol)
and 4-(dimethylamino)pyridine (0.065 g, 0.53 mmol) in 5 mL
of dry chloroform was added dropwise a solution of S-(+)-R-
methoxy-R-trifluoromethylphenylacetyl (MTPA) chloride (0.114
g, 0.45 mmol) in 1 mL of dry chloroform under nitrogen
atmosphere. The reaction mixture was stirred at room tem-
perature overnight. The chloroform was removed under re-
duced pressure, and the residue was purified by preparative
thin-layer chromatography (SiO2, hexanes/EtOAc 2:1) to give
the Mosher ester 6a as a colorless oil (0.176 g, 79%): 1H NMR
(360 MHz, CDCl3, δ) 1.21-1.25 (m, 2 H), 1.39-1.43 (m, 2 H),
1.51-1.58 (m, 2 H), 2.25 (t, J ) 7.5 Hz, 2 H), 2.43 (s, 3 H),
3.26 (t, J ) 6.5 Hz, 2 H), 3.43-3.52 (m, 2 H), 3.49 (s, 3 H),
3.64 (s, 3 H), 4.18 (dd, J ) 11.0, 6.8 Hz, 1 H), 4.25 (dd, J )
11.0, 3.2 Hz, 1 H), 5.32-5.36 (m, 1 H), 7.31 (d, J ) 8.2 Hz, 2
H), 7.36-7.71 (m, 5 H), 7.74 (d, J ) 8.2 Hz, 2 H).
3-O-(5′Ca r b om et h oxyp en t yl)-2-(r-m et h oxy-r-t r iflu o-
r om eth ylp h en yl)a cetyl-sn -glycer o-1-tosyla te (7a ). Com-
pound 7a was prepared under conditions similar to those
described for 6a , using the alcohol 5a ′ obtained from (S)-
glycidyl tosylate under the same reaction conditions as shown
for the (R)-enantiomer: 1H NMR (360 MHz, CDCl3, δ) 1.23-
1.32 (m, 2 H), 1.46-1.61 (m, 4 H), 2.27 (t, J ) 7.5 Hz, 2 H),
2.42 (s, 3 H), 3.35-3.40 (m, 2 H), 3.47 (s, 3 H), 3.56-3.58 (m,
2 H), 3.64 (s, 3 H), 4.08 (dd, J ) 10.9, 6.4 Hz, 1 H), 4.18 (dd,
J ) 10.9, 3.7 Hz, 1 H), 5.36-5.41 (m, 1 H), 7.29 (d, J ) 8.2
Hz, 2 H), 7.36-7.51 (m, 5 H), 7.66 (d, J ) 8.2 Hz, 2 H).
Mosh er Ester of 5c: 1-O-[12′-(N-2′′,2′′,2′′-Tr ich lor o-ter t-
bu toxycar bon ylam in o)dodecyl]-2-(r-tr iflu or om eth ylph en -
yl)a cetyl-sn -glycer o-3-tosyla te (6b). To a solution of 5c
cm-1 1H NMR (CDCl3, δ) 1.21-1.85 (m, 12 H), 2.31 (t, J )
;
7.5 Hz, 2 H), 2.45 (s, 3 H), 3.26-3.56 (m, 6 H), 3.67 (s, 3 H),
3.85-4.23 (m, 3 H), 4.64-4.74 (m, 1 H), 7.32 (d, J ) 8.3 Hz, 2
H), 7.82 (d, J ) 8.3 Hz, 2 H); Rf (hexane/EtOAc 2:1) 0.40. This
compound was used for the next step without further treat-
ment.
1-O-(5′-Ca r bom eth oxyp en tyl)-2-tetr a h yd r op yr a n yl-sn -
glycer o-3-a ceta te (9a ). To a solution of tosylate 8a (4.70 g,
10.25 mmol) in 80 mL of anhydrous acetonitrile were added
tetraethylammonium acetate (8.04 g, 30.75 mmol) and acti-
vated molecular sieves (type 3A, 10 g), and the resulting
mixture was stirred at room temperature for 36 h, at which
time the TLC analysis showed that the conversion of the
tosylate to the acetate was complete. The reaction mixture was
then filtered through a pad of Celite, with suction, and the
filtrate was evaporated under reduced pressure. The residue
was chromatographed on silica gel with hexane/EtOAc (2:1)
to give the product 9a (3.2 g, 90%) as a colorless liquid: IR
1
(Nujol), 1742 cm-1; H NMR (CDCl3, δ) 1.31-1.91 (m, 12 H),
2.07 (s, 3 H), 2.31 (t, J ) 7.5 Hz, 2 H), 3.30-3.59 (m, 6 H),
3.75-4.35 (m, 3 H), 4.79 (br s, 1 H); Rf (hexanes-EtOAc 2:1)
0.42. Anal. Calcd for C17H30O6: C, 58.94; H, 8.73. Found: C,
58.66; H, 8.49.
1-O-(5′-Ca r bom eth oxyp en tyl)-2-tetr a h yd r op yr a n yl-sn -
glycer ol (10a ). To a solution of 9a (3.20 g, 9.23 mmol) in 30
mL of dry methanol, cooled in an ice-water bath, was added
anhydrous potassium carbonate (1.5 g). The resulting white
suspension was stirred at 0 °C for 30 min, at which time the
TLC analysis showed complete conversion of the acetate 9a
to alcohol 10a . The solvent was evaporated under reduced
pressure; the residue was dissolved in dichloromethane and
passed through a short pad of silica gel, with suction. Further

9344 J . Org. Chem., Vol. 64, No. 26, 1999
Kazi et al.
elution with dichloromethane, followed by ethyl acetate, and
subsequent evaporation of the solvent afforded the crude
product 10a which was chromatographed on silica gel using
hexanes/ethyl acetate (1:1) to give pure 10a (2.1 g), 75%) as a
for 3 h. After complete conversion, as shown by TLC, 30 mL
of water was added, and the resulting solution was extracted
with 3 × 50 mL of dichloromethane. The combined organic
layer was dried over sodium sulfate, and the solvent was
removed by rotoevaporation. The oily residue was chromato-
graphed on silica gel using CH2Cl2/MeOH (95:5) as eluant. The
resulting oil was dissolved in 40 mL of benzene, and the
solvent azeotrope solvent was removed by rotoevaporation. The
product 10b was further dried in benzene solution over
molecular sieves (type 3 Å) for 24 h. The molecular sieves were
removed by vacuum filtration, and the solvent was removed
under reduced pressure. The resulting oil 10b (0.89 g, 75%)
was used for the next step without further treatment: IR
(neat) 1726 cm-1; 1H NMR (CDCl3, δ) 1.26 (br s, 6 H), 1.46 (br
s, 8 H), 1.92 (s, 6 H), 3.10-3.18 (m, 2 H), 3.45-4.10 (m, 9 H),
4.60 (br s, 0.5 H), 4.70 (br s, 0.5 H), 4.95 (br s, 1 H); Rf (CH2-
Cl2/MeOH 95:5) 0.41. Anal. Calcd for C19H34NO6Cl3‚0.5H2O:
C, 46.77; H, 7.02; N, 2.86. Found: C, 46.68; H, 6.84; N, 2.92.
1-O-[12′-(N-2′′,2′′,2′′-Tr ich lor o-ter t-bu toxyca r bon yla m i-
n o)d od ecyl-2-tetr a h yd r op yr a n yl-sn -glycer ol (10c). Com-
pound 10c was prepared according to the method described
for compound 10b and was afforded in 87% yield: IR (neat)
1723 cm-1; 1H NMR (CDCl3, δ) 1.27 (s, 18 H), 1.52 (br s, 8 H),
1.92 (s, 6 H), 3.10-3.18 (m, 2 H), 3.40-4.05 (m, 9 H), 4.60 (br
s, 0.5 H), 4.76 (br s, 0.5 H), 4.95 (br s, 1 H); Rf (CH2Cl2/MeOH
95:5) 0.46; FAB-MS [M + Na]+ calcd 584.2288, found 584.2295.
Anal. Calcd for C25H46Cl3NO6: C, 53.33; H, 8.24; N, 2.49.
Found: C, 53.05; H, 8.40; N, 2.48.
2-Meth yl-5-p-tolu en esu lfon ylm eth yloxa zolin e (11). Bo-
ron trifluoride etherate (1.89 mL, 15.35 mmol) was added
dropwise to a stirred solution of (R)-(-)-glycidyl tosylate (3 g,
13.14 mmol) in dry acetonitrile (120 mL) at 0 °C under
nitrogen. The resulting solution was stirred at 0 °C for 15 min
and then quenched with excess saturated NaHCO3 solution
(150 mL). The resulting mixture was stirred at room temper-
ature for 2 h and then exhaustively extracted with ether (3 ×
150 mL). The ethereal solution was washed with saturated
brine (2 × 100 mL) and dried over anhydrous MgSO4. Removal
of the solvent gave a white solid which was crystallized from
chloroform-hexane to give the desired oxazoline 11 as a white
semicrystalline solid, 3.2 g (90%):25 mp 109-112 °C; [R]25D -43
(c 2.1, CHCl3); 1H NMR (CDCl3, δ) 1.87 (t, J ) 1 Hz, 3 H),
2.45 (s, 3 H), 3.46 (ddq, J ) 15.0, 7.1, 1.0 Hz, 1 H), 3.85 (ddq,
J ) 15.0, 10.2, 1.0 Hz, 1 H), 4.05 (m, 2 H), 4.62-4.73 (m, 1 H),
7.34 (d, J ) 8.3 Hz, 2 H), 7.80 (d, J ) 8.3 Hz, 2 H); Rf (CHCl3/
EtOAc 1:3) 0.32.
1
colorless oil: IR (Nujol) 3436, 1736 cm-1; H NMR (CDCl3, δ)
1.08-2.00 (m, 12 H), 2.32 (t, J ) 7.5 Hz, 2 H), 3.25-4.12 (m,
9 H), 3.68 (s, 3 H), 4.52-4.90 (m, 1 H); Rf (hexanes/EtOAc 1:2)
0.46. Anal. Calcd for C15H28O6: C, 59.19; H, 9.27. Found: C,
59.27; H, 9.24.
1-O-[6′-(N-2′′,2′′,2′′-Tr ich lor o-ter t-bu toxyca r bon yla m i-
n o)h exyl]-2-tetr ah ydr opyr an yl-sn -glycer o-3-tosylate (8b).
To a solution of 5b (2.35 g, 4.28 mmol) in 20 mL of dry
dichloromethane were added pyridinium-p-toluenesulfonate
(0.11 g, 0.429 mmol) and 3,4-dihydro-2H-pyran (0.60 mL, 6.58
mmol). The reaction mixture was stirred at room temperature
for 20 h. After completion of the reaction, as shown by TLC,
30 mL of dichloromethane was added, and the resulting
solution was washed with 2 × 50 mL of brine. The organic
layer was dried over sodium sulfate, and the solvent was
removed by a rotary evaporator to give a viscous oil that was
purified by silica gel chromatography using dichloromethane/
methanol (95:5) as eluant. The analytically pure product 8b
was obtained as a viscous oil (2.58 g, 95%): IR (neat) 1725
cm-1 1H NMR (CDCl3, δ) 1.32 (br s, 6 H), 1.60 (br s, 8 H),
;
1.92 (s, 6 H), 2.45 (s, 3 H), 3.16 (m, 2 H), 3.42 (m, 5 H), 4.65
(br s, 0.5 H), 4.75 (br s, 0.5 H), 4.85 (br m, 1 H), 7.36 (d, J )
8.3 Hz, 2 H), 7.80 (d, J ) 8.3 Hz, 2 H); Rf (CH2Cl2/CH3OH)
0.67; FAB-MS [M + H]+ calcd 632.1618, found 632.1617. Anal.
Calcd for C26H40NO8SCl3: C, 49.33; H, 6.37; N, 2.21. Found:
C, 48.98; H, 6.32; N, 2.09.
1-O-[12′-(N-2′′,2′′,2′′-Tr ich lor o-ter t-bu toxyca r bon yla m i-
n o)dodecyl]-2-teth ydr opyr an yl-sn -glycer o-3-tosylate (8c).
Compound 8c was prepared according to the method described
for compound 8b and was afforded in 90% yield: IR (neat) 1723
cm-1 1H NMR (CDCl3, δ) 1.26 (s, 16 H), 1.46 (br m, 10 H),
;
1.92 (s, 6 H), 2.43 (s, 3 H), 3.15 (m, 2 H), 3.32-3.54 (m, 5 H),
3.96-4.13 (m, 4 H), 4.64 (br s, 0.5 H), 4.74 (br s, 0.5 H), 4.8
(br m, 1 H), 7.32 (d, J ) 8.3 Hz, 2 H), 7.80 (d, J ) 8.3 Hz, 2
H); Rf (hexanes/EtOAc) 0.69; FAB-MS [M + Na]+ calcd
738.2376, found 738.2408. Anal. Calcd for C32H52Cl3NO8S: C,
53.59; H, 7.31; N, 1.95. Found: C, 53.40; H, 7.30; N, 1.89.
1-O-[6′-(N-2′′,2′′,2′′-Tr ich lor o-ter t-bu toxyca r bon yla m i-
n o)h exyl]-2-tetr ah ydr opyr an yl-sn -glycer yl-3-acetate (9b).
To a solution of 8b (2.56 g, 4.04 mmol) in 2 mL of dry
acetonitrile was added 48 mL of 0.25 M tetraethylammonium
acetate (12.13 mmol) in anhydrous acetonitrile. The reaction
mixture was stirred at room temperature for 5 h. The solvent
was then removed under reduced pressure; the resulting oil
was dissolved in 50 mL of dichloromethane, and the resulting
solution was washed with 50 mL of water. The organic layer
was dried over sodium sulfate, the solvent was flash evapo-
rated, and the crude product was chromatographed on silica
gel with dichloromethane/methanol (95:5) to give a viscous oil,
9b (1.64 g, 78%): IR (neat) 1731, 1210 cm-1; 1H NMR (CDCl3,
δ) 1.26 (br s, 6 H), 1.50 (br s, 8 H), 1.92 (s, 6 H), 2.08 (s, 3 H),
3.10-3.17 (m, 2 H), 3.36-3.62 (m, 6 H), 3.87-4.20 (m, 3 H),
4.75 (br m, 1 H)), 4.9 (br m, 1 H); Rf (CH2Cl2/MeOH 95:5) 0.56;
FAB-MS [M + Na]+ calcd 542.1427, found 542.1455. Anal.
Calcd for C21H36Cl3NO7: C, 48.42; H, 6.97; N, 2.69. Found: C,
48,17; H, 6.72; N, 2.77.
3-p-Tolu en esu lfon yl-2-a cetoxyp r op yl(tr ip h en ylm eth -
yl)a m in e (12). To a stirred solution of the oxazoline 11 (2.9
g, 10.77 mmol) in tetrahydrofuran (33 mL) was slowly added
0.5 N HCl (33 mL, 16.5 mmol) at 0 °C. The cooling bath was
removed, and the reaction mixture was stirred at room
temperature for 2 h. The reaction mixture was diluted with
water (120 mL) and washed with ether (3 × 100 mL). The
aqueous layer was freeze-dried to give 3.0 g of white amor-
phous solid. The crude material was suspended in dry chlo-
roform (55 mL), and to it was added triethylamine (2.34 g,
23.15 mmol) with stirring at 0 °C. After the mixture was
stirred for 5 min, triphenylmethyl chloride (2.57 g, 9.26 mmol)
was added. The cooling bath was removed, and the resulting
solution was stirred at room temperature for 3 h. The reaction
mixture was washed with water (3 × 35 mL), and the organic
layer was dried over anhydrous MgSO4 solvent and then was
evaporated. The crude oily residue was chromatographed
(SiO2, hexanes/EtOAc, 3:1) to yield the desired trityl derivative
1-O-[12′-(N-2′′,2′′,2′′-Tr ich lor o-ter t-bu toxyca r bon yla m i-
n o)dodecyl]-2-tetr ah ydr opyr an yl-sn -glycer yl acetate (9c).
Compound 9c was prepared according to the method described
for compound 9b and was afforded in 88% yield: IR (neat) 1731
cm-1; 1H NMR (CDCl3, δ) 1.26 (s, 18 H), 1.54 (s, 8 H), 1.92 (s,
6 H), 2.07 (s, 3 H), 3.10-3.16 (m, 2 H), 3.40-3.62 (m, 4 H),
3.82-4.24 (m, 5 H), 4.75 (br m, 1 H), 4.9 (br m, 1 H); Rf
(hexanes/EtOAc 3:2) 0.71; FAB-MS [M + Na]+ calcd 626.2394,
found 626.2406. Anal. Calcd for C27H48Cl3NO7: C, 53.60; H,
8.00; N, 2.32. Found: C, 53.69; H, 7.78; N, 2.10.
1-O-[6′-(N-2′′,2′′,2′′-Tr ich lor o-ter t-bu toxyca r bon yla m i-
n o)h exyl-2-tetr a h yd r op yr a n yl-sn -glycer ol (10b). To a so-
lution of 9b (1.28 g, 2.46 mmol) in 20 mL of dry methanol was
added anhydrous potassium carbonate (0.68 g, 4.92 mmol) at
0 °C. The reaction mixture was stirred at room temperature
12 as a white sticky solid (3.8 g, 67% overall): [R]25 -22.3 (c
D
1.00, CHCl3); IR (CHCl3) 1742, 1599 cm-1; H NMR (CDCl3,
1
δ) 2.0 (s, 3 H), 2.30 (m, 2 H), 2.45 (s, 3 H), 4.25 (d, J ) 5 Hz,
2 H), 5.00-5.10 (m, 1 H), 7.10-7.45 (m, 17 H), 7.75 (d, J )
8.3 Hz, 2 H); Rf (hexanes/EtOAc 2:1) 0.42; FAB-MS [M + H]+
calcd 530.2001, found 530.2011. Anal. Calcd for C31H31NO5S‚
0.25H2O: C, 69.72; H, 5.95; N, 2.62; S, 5.99. Found: C, 69.76;
H, 6.02; N, 2.48; S, 5.71.
3-Iod o-2-a cet oxyp r op yl(t r ip h en ylm et h yl)a m in e (13).
To a stirred solution of the tosylate 12 (4.3 g, 8.12 mmol) in
dry acetone (100 mL) was added excess sodium iodide (12 g,

Synthesis of Functionalized Ether Phospholipids
J . Org. Chem., Vol. 64, No. 26, 1999 9345
81.2 mmol), and the resulting mixture was refluxed under
nitrogen for 6 h. The acetone was evaporated under reduced
pressure, and the residue was taken up in ether (150 mL) and
washed with 10% sodium thiosulfate (2 × 50 mL) and water
(2 × 50 mL). The organic solution was dried over anhydrous
MgSO4, the solvent was evaporated, and the crude residue was
chromatographed (SiO2, hexanes/EtOAc, 8:1) to furnish the
desired iodide 13 as a semipure white solid (2.6 g, 66%). This
was used in the next step without further purification: IR
(CHCl3) 3328, 2858, 1738, 1597 cm-1; 1H NMR (CDCl3, δ) 2.10
(s, 3 H), 2.35-2.55 (m, 2 H), 3.32-3.54 (m, 2 H), 4.84-4.96
(m, 1 H), 7.10-7.55 (m, 15 H); Rf (hexanes/EtOAc, 5:1) 0.48.
3-Cya n o-2-a cetoxyp r op yl(tr ip h en ylm eth yl)a m in e (14).
Sodium cyanide (0.66 g, 13.59 mmol) was added to a stirred
solution of the iodide 13 (2.2 g, 4.53 mmol) in dry DMSO (45
mL). The resulting mixture was stirred at room temperature
for 3 h. The reaction mixture was diluted with water (400 mL)
and extracted with ether (4 × 120 mL). The organic extract
was washed with saturated brine (2 × 90 mL) and dried over
anhydrous MgSO4. Evaporation of the solvent was followed
by chromatographic purification (SiO2, hexanes/EtOAc, 3:1)
and gave the nitrile 14 as a white gummy solid (0.87 g, 50%):
IR (CHCl3) 2248, 1742, 1597 cm-1; [R]25D -5.1 (c 1.00, CHCl3);
1H NMR (CDCl3, δ) 2.10 (s 3 H), 2.40-2.50 (m, 2 H), 2.76-
2.84 (m, 2 H), 5.04-5.12 (m, 1 H), 7.15-7.50 (m, 15 H); Rf
(hexanes/EtOAc 3:1) 0.36; FAB-MS calcd for C25H24N2O2 (M+)
384.1838, found 384.1863. Anal. Calcd for C25H24N2O2: C,
78.10; H, 6.29; N, 7.29. Found: C, 77.89; H, 6.36; N, 7.21.
3-Cyan o-2-h ydr oxypr opyl(tr iph en ylm eth yl)am in e (15).
Anhydrous potassium carbonate (0.5 g, 3.62 mmol) was added
to a stirred solution of the acetate 14 (0.6 g, 1.56 mmol) in dry
methanol (10 mL) at 0 °C. The cooling bath was removed, and
the suspension was stirred at room temperature for 30 min.
The methanol was removed under reduced pressure, and the
residue was taken up in water (20 mL) and extracted with
ether (3 × 25 mL). The ethereal extract was washed with water
(20 mL) and saturated brine (20 mL) and was then dried over
anhydrous MgSO4. The solvent was evaporated, and the crude
product was chromatographed (SiO2, hexanes/EtOAc, 3:1) to
give the cyanohydrin 15 as a white sticky solid (495 mg,
chloridite (4.0 g, 14.45 mmol) and diisopropylethylamine (4.67
g, 36.12 mmol) in 20 mL of dry THF was added dropwise a
solution of N-tritylserine methyl ester (4.79 g, 12.04 mmol) in
20 mL of dry THF at -78 °C over 10 min, and then a solution
of alcohol 10a (4.4 g, 14.45 mmol) in 15 mL of dry THF was
added slowly with vigorous stirring. The resulting mixture was
stirred at -78 °C for 2 h. The reaction mixture was then slowly
warmed to room temperature with continued stirring for an
additional 1.5 h. The solvent was then removed under reduced
pressure, and the residue was taken up in ethyl acetate and
filtered through a pad of Celite, under suction, to remove the
precipitated ammonium salt. The solvent was evaporated, and
the oily residue was chromatographed on silica gel with
hexanes/EtOAc (3:1) to give 17a as a colorless viscous oil (7.5
g, 69%): IR (Nujol) 1743 cm-1; 1H NMR (CDCl3, δ) 1.10-1.73
(m, 12 H), 1.79 (br s, 6 H), 2.23 (t, J ) 7.5 Hz, 2 H), 3.18 (s, 3
H), 3.51 (m, 6 H), 3.65 (s, 3 H), 3.96 (m, 6 H), 4.81 (m, 1 H),
7.19-7.55 (m, 15 H); Rf (hexanes/EtOAc 3:1) 0.58; FAB-MS
[M + H]+ C42H56O10NPCl3 calcd 870.2707, found 870.2715.
1-O-(5′-Ca r bom eth oxyp en tyl)-2-tetr a h yd r op yr a n yl-sn -
glycer yl 2,2,2-Tr ich lor o-ter t-bu tyl 1-Ca r bom eth oxy-1-N-
tr ip h en ylm eth yla m in o-1-ca r bom eth oxy-2-p r op yl P h os-
p h ite (17b). To a vigorously stirred solution of 2,2,2-trichloro-
tert-butylphosphodichloridite (767 mg, 3.30 mmol) and diiso-
propylethylamine (1.07 g, 8.25 mmol) in 5 mL of dry THF was
added dropwise a solution of alcohol N-tritylthreonine methyl
ester (1.4 g, 3.30 mmol) in 5 mL of dry THF at -78 °C under
nitrogen. The solution was stirred at -78 °C for 15 min, and
a solution of alcohol 10a (0.84 g, 2.75 mmol) in 4 mL of dry
THF was added slowly with vigorous stirring. The resulting
mixture was stirred at -78 °C for 1.5 h. The reaction mixture
was then slowly warmed to room temperature with continued
stirring for an additional period of 1.5 h. The solvent was
removed under reduced pressure, and the residue was taken
up in ethyl acetate. The precipitated ammonium salt was
removed by filtration through a pad of Celite, with suction.
The solvent was evaporated, and the oily residue was chro-
matographed on silica gel using hexanes/EtOAc 3:1 as eluant
to give 17b, a colorless viscous oil (1.1 g, 45%): IR (Nujol) 1743
1
cm-1; H NMR (CDCl3, 2 H) 1.10-1.71 (m, 15 H), 1.76 (bs, 6
93%): IR (CHCl3) 3472, 3328, 2249, 1599 cm-1; [R]25 -3.0 (c
H), 2.26 (t, J ) 7.5 Hz, 2 H), 3.13 (s, 3 H), 3.24-3.57 (m, 6 H),
3.66 (s, 3 H), 3.74-4.17 (m, 5 H), 4.79 (m, 1 H), 7.20-7.45 (m,
D
1
1.00, CHCl3); H NMR (CDCl3, δ) 2.31 (d, J ) 6.2 Hz, 2 H),
2.50 (d, J ) 6.2 Hz, 2 H), 3.86-3.98 (m, 1 H), 7.10-7.50 (m,
15 H); Rf (hexanes/EtOAc 2:1) 0.59; FAB-MS calcd for C43H56
-
15 H); Rf (hexanes/EtOAc 2:1) 0.37; FAB-MS calcd for
NO10PCl3 [M + H]+ 882.2707, found 882.2734.
C
23H21N2O [M + H]+ 341.1654, found 341.1660. Anal. Calcd
1-O-(5′-Ca r bom eth oxyp en tyl)-2-tetr a h yd r op yr a n yl-sn -
glycer yl 2,2,2-Tr ich lor o-ter t-b u t yl 1-N-Tr ip h en ylm et h -
yla m in o-3-ca r bom eth oxy-2-p r op yl P h osp h ite (17c). Com-
pound 17c was prepared in the same manner as that described
for phosphite triester 17b and was obtained in 42.5% yield:
for C23H22N2O: C, 80.67; H, 6.48; N, 8.18. Found: C, 80.77;
H, 6.43; N, 8.05.
(S)-γ-Am in o-â-h yd r oxybu tyr ic Acid (GABOB) (16). To
a stirred solution of the cyanohydrin 15 (0.93 g, 2.72 mmol)
in dry chloroform (15 mL) was added trifluoroacetic acid (465
mg, 4.08 mmol) at room temperature under nitrogen. The
resulting solution was stirred for 30 min. The solution was
then diluted with water (20 mL) and extracted with ether (2
× 20 mL). The aqueous layer was freeze-dried to give a pale
brown viscous oil (500 mg) that was dissolved in concentrated
H2SO4 (2.5 mL, 67.5 mmol) and heated on a steam bath for 15
min. Water (25 mL) was added and the solution was refluxed
for 3 h. After cooling, the solution it was neutralized by the
addition of solid lead carbonate. The solution was then heated
on the steam bath for 1 h. The mixture was filtered under
suction to remove the suspended solid, and the clear aqueous
solution was freeze-dried to give 380 mg of pale brown
amorphous solid. The solid was dissolved in a small amount
of water (1 mL) and diluted with ethanol (50 mL), yielding a
white solid precipitate. Filtration and drying under vacuum
furnished the desired amino acid 16 as a white amorphous
IR (CHCl3) 3328, 2950, 2866, 1732, 1597 cm-1 1H NMR
;
(CDCl3, δ) 1.10-1.80 (m, 18 H), 2.25 (m, 4 H), 2.88 (m, 2 H),
3.40 (m, 6 H), 3.66 (superimposed singlets, 2 × 3 H), 3.86 (m,
4 H), 4.75 (m, 1 H), 7.10-7.50 (m, 15 H); Rf (hexanes/EtOAc
2:1) 0.50; FAB-MS calcd for C43H58O10NPCl3 [M + H]+ 884.2864,
found 884.2848.
1-O-(5′-Ca r bom eth oxyp en tyl)-2-tetr a h yd r op yr a n yl-sn -
3-glycer oyl 2,2,2-Tr ich lor o-ter t-bu tyl 2-N-Tr ityla m in o-2-
ca r bom eth oxyeth yl P h osp h a te (18a ). To a stirred solution
of 17a (7.59 g, 8.36 mmol) in 80 mL of dichloromethane was
added 30% aqueous H2O2 (1.2 mL, 11.7 mmol). After being
stirred for 2 h, the reaction mixture was washed with brine (2
× 30 mL). The organic layer was separated, dried over
magnesium sulfate, and evaporated under reduced pressure.
The oily residue was chromatographed on silica gel with
hexanes/EtOAc (1:1) to give phosphotriester 18a as a colorless
viscous oil (7.4 g, 95%): IR (Nujol) 1737 cm-1; 1H NMR (CDCl3,
δ) 1.11-1.77 (m, 12 H), 1.92 (s, 6 H), 2.28 (t, J ) 7.5 Hz, 2 H),
3.20 (s, 3 H), 3.29-3.61 (m, 6 H), 3.65 (s, 3 H), 3.81-4.44 (m,
6 H), 4.78 (m, 1 H), 7.20-7.45 (m, 15 H); Rf (hexanes/EtOAc
1:1) 0.41; FAB-MS calcd for C42H56O11NPCl3 [M + H]+ 886.2656,
found 886.2612.
solid (311 mg, 96% overall: mp 209-212 °C (mp 214 °C); [R]23
D
+7.8 (c 1.7, H2O) (lit24 [R]25D -7.09 for the (R)-isomer); 1H NMR
(200 MHz, D2O, δ) 2.33 (d, J ) 6.6 Hz, 2 H), 2.80-3.12 (m, 2
H), 3.93-4.07 (m, 1 H). The NMR spectrum agrees exactly with
that reported24 and that of an authentic sample.
1-O-(5′-Ca r bom eth oxyp en tyl)-2-tetr a h yd r op yr a n yl-sn -
glycer yl 2,2,2-Tr ich lor o-ter t-bu tyl 2-ca r bom eth oxy-2-(N-
tr ip h en ylm eth yla m in o)eth yl P h osp h ite (17a ). To a vig-
orously stirred solution of 2,2,2-trichloro-tert-butyl phosphodi-
1-O-(5′-Ca r bom eth oxyp en tyl)-2-tetr a h yd r op yr a n yl-sn -
3-glycer yl 2,2,2-Tr ich lor o-ter t-bu tyl 1-N-Tr ip h en ylm eth -
ylam in o-1-car bom eth oxy-2-pr opyl P h osph ate (18b). Com-
pound 18b was prepared by employing the same experimental

9346 J . Org. Chem., Vol. 64, No. 26, 1999
Kazi et al.
conditions described for the corresponding phosphotriester 18a
was converted to the free-acid form by passing it through a
cation-exchange column (AG 50W-X8, hydrogen form) and
eluting it with water: [R]25D -6.5 ( 0.3 (c 1.00, H2O); 1H NMR
(D2O, δ) 1.18-1.25 (m, 2 H), 1.42 (m, 4 H), 2.23 (t, J ) 7.4 Hz,
2H), 3.38 (m, 4 H), 3.70 (m, 2 H), 3.83 (m, 1 H), 3.93 (m, 1 H),
4.10 (m, 2 H); Rf (CHCl3/MeOH/H2O 3:6:1) 0.42; FAB-MS calcd
for C12H25NO10P [M + H]+ 374.1216, found 374.1194.
and was obtained as a colorless viscous oil in 92% yield: IR
(CHCl3) 2951, 2867, 1735, 1591 cm-1 1H NMR (CDCl3, δ)
;
1.09-1.78 (m, 15 H), 1.91 (bs, 6 H), 2.26 (t, J ) 7.5 Hz, 2 H),
3.15 (s, 3 H), 3.22-3.60 (m, 6 H), 3.66 (s, 3 H), 3.88-4.28 (m,
5 H), 4.74 (m, 1 H), 7.20-7.45 (m, 15 H); Rf (hexanes/EtOAc
1:1) 0.50; FAB-MS calcd for C43H57O11NPCl3 [M]+ 899.2734,
found 899.2693.
1-O-(5′-Ca r b oxyp en t yl)-sn -glycer o-3-p h osp h ot h r eo-
n in e (20b). Compound 20b was prepared by employing the
same experimental conditions as those described for compound
20a and was obtained as a colorless hygroscopic solid in 59%
1-O-(5′-Ca r bom eth oxyp en tyl)-2-tetr a h yd r op yr a n yl-sn -
glycer yl 2,2,2-Tr ich lor o-ter t-bu tyl 1-N-Tr ip h en ylm eth yl-
a m in o-3-ca r bom eth oxy-2-p r op yl P h osp h a te (18c). Com-
pound 18c was prepared under the same experimental condi-
tions as those described for phosphotriester 18a and was
obtained as a viscous oil in 97% yield: IR (CHCl3) 2951, 2867,
1735, 1597 cm-1; 1H NMR (CDCl3, δ) 1.20-1.70 (m, 12 H), 1.80
(m, 6 H), 2.25 (t, J ) 7.5 Hz, 2 H), 2.45 (br s, 2 H), 2.95 (m, 2
H), 3.42 (m, 6 H), 3.65 (superimposed singlets, 2 × 3 H), 4.0
(m, 4 H), 4.75 (m, 1 H), 7.10-7.50 (m, 15 H); Rf (hexanes/
EtOAc, 1:1) 0.45; FAB-MS calcd for C43H58O11NPCl3 [M + H]+
900.2813, found 900.2780.
overall yield: [R]25 -10 ( 0.5 (c 1.00, H2O); 1H NMR (360
D
MHz, D2O, δ) 1.18-1.25 (m, 2 H), 1.31 (d, J ) 6.6 Hz, 3 H),
1.41-1.51 (m, 4 H), 2.13 (t, J ) 7.4 Hz, 2 H), 3.35-3.49 (m, 4
H), 3.56-3.57 (m, 1 H), 3.66-3.87 (m, 3 H), 4.40-4.59 (m, 1
H); Rf (CHCl3/MeOH/H2O 3:6:1) 0.44. Anal. Calcd for C13H24
-
NO10PNa2‚0.5H2O: C, 35.46; H, 5.72; N, 3.18. Found: C, 35.32;
H, 6.11; N, 2.99.
1-O-(5′-Ca r boxyp en tyl)-sn -glycer o-3-p h osp h o-γ-a m in o-
â-h yd r oxybu tyr ic Acid (21). To a stirred solution of 19c
(0.897 g, 1.21 mmol) in 18 mL of dioxane was slowly added 1
N aqueous NaOH (6 mL, 6 mmol). After the reaction mixture
was stirred at room temperature for 2 h, an additional 3 mL
of 1 N NaOH was added. The solution was then stirred for
another 2 h. The reaction mixture was then neutralized by
the infusion of carbon dioxide bubbles, which resulted in the
formation of a white precipitate. The suspension was centri-
fuged, and the supernatant was freeze-dried to give 1.6 g crude
product. This was dissolved in 30 mL of chloroform and
extracted with 10 mL of water. The chloroform layer was dried
over magnesium sulfate, and evaporation of the solvent gave
the trisodium salt as a white solid (0.79 g): IR (CHCl3) 2945,
1-O-(5′-Ca r bom eth oxyp en tyl)-2-tetr a h yd r op yr a n yl-sn -
glycer o-3-p h osp h o-N-tr itylser in e Meth yl Ester (19a ). To
a stirred solution of phosphotriester 18a (1.5 g, 1.69 mmol) in
20 mL of dry acetonitrile were successively added triethyl-
amine (3.3 g, 32.7 mmol), acetylacetone (2.42 g, 35.36 mmol),
and zinc powder (1.5 g, 25.36 mmol). The resulting suspension
was vigorously stirred at room temperature for 2 h. The
reaction mixture was filtered with suction. The solvent was
removed under reduced pressure, and the oily residue was
chromatographed on silica gel with hexanes/EtOAc (1:1) and
then with chloroform/methanol (4:1) to give the phosphodiester
19a as a pale-yellow sticky solid (0.75 g, 61%). This was used
in the next step without further treatment: IR (CHCl3) 3329,
2948, 2864, 1733, 1599, 1443 cm-1; 1H NMR (CDCl3, δ) 1.02-
1.90 (m, 12 H), 2.27 (t, J ) 7.4 Hz, 2 H), 3.17 (br s, 3 H), 3.21-
3.55 (m, 6 H), 3.64 (s, 3 H), 3.71-4.20 (m, 6 H), 4.76 (m, 1 H),
7.17-7.46 (m, 15 H); Rf (chloroform/methanol 4:1) 0.50.
1-O-(5′-Ca r bom eth oxyp en tyl)-2-tetr a h yd r op yr a n yl-sn -
glycer o-3-p h osp h o-N-tr itylth r eon in e Meth yl Ester (19b).
Compound 19b was prepared by employing the same experi-
mental conditions as those described for compound 19a and
was obtained as a pale-yellow sticky solid in 66% yield. This
was used in the next step without further treatment: IR
1
2863, 1712, 1606 cm-1; H NMR (CDCl3, δ) 1.10-1.70 (m, 12
H), 2.10 (br s, 2 H), 2.20-2.60 (m, 4 H), 3.30 (m, 6 H), 3.70
(m, 4 H), 4.61 (m, 1 H), 7.00-7.40 (m, 15 H). The crude
trisodium salt was dissolved in 20 mL of dry chloroform, and
to the solution was added trifluoroacetic acid (0.806 g, 7 mmol)
with stirring, under nitrogen, at room temperature. The
reaction mixture was kept at room temperature for 1 h, and
the chloroform was then removed under reduced pressure. The
oily residue was dissolved in 15 mL of tetrahydrofuran, and
0.2 N aqueous HCl (15 mL, 3 mmol) was added. After being
stirred at room temperature for 2 h, the reaction mixture was
neutralized with 10% NaHCO3, diluted with water (25 mL),
and extracted with ether (2 × 50 mL). The aqueous layer was
freeze-dried, and the pale yellow solid that remained was
dissolved in 2 mL of water and passed through a Sephadex
G-10 column eluted with water. The ninhydrin positive frac-
tions containing the product were combined, freeze-dried, and
chromatographed on silica gel using CHCl3/MeOH/H2O (3:6:
1) to give the pure phospholipid 21 as a colorless hygroscopic
solid (0.285 g, 61% overall). The compound was analyzed as
the sodium salt, obtained by passing a sample through a
cation-exchange column (AG 50W-X8, sodium form), eluting
with water, and freeze-drying the collected aqueous solution:
(CHCl3) 3329, 2948, 2864, 1733, 1599, 1444 cm-1 1H NMR
;
(CDCl3, δ) 1.01-1.77 (m, 15 H), 2.12 (m, 2 H), 3.06 (br s, 3 H),
3.16-3.56 (m, 6 H), 3.64 (s, 3 H), 3.66-4.06 (m, 5 H), 4.78 (m,
1 H), 7.16-7.44 (m, 15 H); Rf (chloroform/methanol 4:1) 0.50.
1-O-(5′-Ca r b om et h oxyp en t yl)-2-t et r a h yd r op yr a n yl-
sn -glycer o-3-p h osp h o-γ-N-t r ip h en ylm et h yla m in o-â-h y-
d r oxybu tyr ic Acid Meth yl Ester (19c). Compound 19c was
prepared from compound 18c, as described for 19a , and it was
obtained as a pale-yellow sticky solid in 76% yield. It was used
for the next step without further treatment: IR (CHCl3) 3330,
1
2948, 2865, 1733, 1599 cm-1; H NMR (CDCl3, δ) 1.10-1.80
(m, 12 H), 2.25 (m, 4 H), 2.70 (m, 2 H), 3.20-3.60 (m, 6 H),
3.64 (superimposed singlets, 2 × 3 H), 3.80 (m, 4 H), 4.76 (m,
1 H), 7.10-7.50 (m, 15 H); Rf (CHCl3/MeOH 4:1) 0.49.
[R]25 -1.6 (c 1.00, D2O); 1H NMR (360 MHz, D2O, δ) 1.21 (m,
D
2 H), 1.40-1.48 (m, 4 H), 2.10 (t, J ) 7.5 Hz, 2 H), 2.40 (dd, J
) 15.4, 8.2 Hz, 1 H), 2.62 (dd, J ) 15.4, 5.0 Hz, 1 H), 3.06 (dd,
J ) 13.5, 7.3 Hz, 1 H), 3.19 (dd, J ) 13.5, 2.0 Hz, 1 H), 3.35-
3.48 (m, 4 H), 3.68-3.88 (m, 3 H), 4.49-4.53 (m, 1 H); Rf
1-O-(5′-Ca r b oxyp e n t yl)-sn -3-glyce r o-3-p h osp h ose r -
in e (20a ). Phosphodiester 19a (300 mg, 0.41 mmol) was
dissolved in tetrahydrofuran (6.2 mL). To this solution was
added dropwise 0.2 N HCl (6.2 mL, 1.24 mmol) with stirring
at room temperature. After the solution was stirred for 2 h,
the reaction mixture was made basic by the dropwise addition
of 2 N NaOH (1.2 mL, 2.46 mmol) and was further stirred for
an additional 2 h. The reaction mixture was then neutralized
by bubbling gaseous CO2, diluted with water (20 mL), and
washed with ether (2 × 35 mL). The aqueous layer was freeze-
dried to give 480 mg of white solid which was dissolved in
water (2 mL) and passed through a Sephadex G-10 column.
The column was eluted with water, and the fractions contain-
ing the product were collected and freeze-dried to give 198 mg
white solid. Chromatographic purification of this solid over a
silica gel column (chloroform/methanol/water 3:6:1) gave the
phospholipid 20a (trisodium salt form) as a colorless hygro-
scopic solid (106 mg, 62% overall). A sample of the compound
(CHCl3/MeOH/H2O 3:6:1) 0.36. Anal. Calcd for C13H24NO10
-
PNa2‚H2O: C, 33.40; H, 6.04; N, 2.99. Found: C, 33.52; H,
6.30; N, 2.89.
2-Oxo-2-{1′-O-[6′-(N-2′′′,2′′′,2′′′-tr ich lor o-ter t-bu toxyca r -
bon ylam in o)h exyl]-2′-O-tetr ah ydr opyr an yl-sn -glycer yl}-
1,3,2-d ioxa p h osp h ola n e (22a ). To a solution of 10b (0.89 g,
1.88 mmol) in 50 mL of freshly distilled benzene under
nitrogen atmosphere were added triethylamine (0.52 mL, 3.76
mmol) and then 2-chloro-2-oxo-1,3,2-dioxaphospholane (0.34
mL, 3.76 mmol). The reaction mixture was stirred at room
temperature for 24 h. TLC, using dichloromethane/methanol
(93:7), showed complete conversion to the phosphorylated
product 22a . The crystalline triethylamine hydrochloride that
formed was filtered, and the solvent was evaporated under
reduced pressure. The oily residue obtained, 22a (1.1 g), was

Synthesis of Functionalized Ether Phospholipids
J . Org. Chem., Vol. 64, No. 26, 1999 9347
used in the next step without further treatment: 1H NMR
(CDCl3, δ) 1.26-1.75 (m, 14 H), 1.93 (s, 6 H), 3.15 (m, 2 H),
3.45-4.10 (m, 7 H), 4.20-4.50 (m, 6 H), 4.70-4.75 (br m, 1
H).
min and used for the next step directly: 1H NMR (CDCl3, δ)
1.26-1.75 (m, 26 H), 1.93 (s, 6 H), 3.10-3.15 (m, 2 H), 3.45-
4.10 (m, 7 H), 4.20-4.50 (m, 6 H), 4.70-4.76 (br m, 1 H); Rf
(CHCl3/MeOH 93:7), 0.65.
1-O-[6′-(N-2′′,2′′,2′′-Tr ich lor o-ter t-bu toxyca r bon yla m i-
n o)h exyl-2-O-tetr a h yd r op yr a n yl-sn -glycer o-3-p h osp h o-
ch olin e (23a ). Compound 22a (1.09 g, 1.87 mmol) was
dissolved in 50 mL of anhydrous deaerated acetonitrile and
was transferred to a pressure bottle. The solution was cooled
in a dry ice/acetone bath (-78 °C). To the soluiton was added
1.5 mL of trimethylamine under nitrogen. The pressure bottle
was sealed and kept in an oil bath at 65 °C with stirring for
48 h. The solution was then cooled to 0 °C, and the solid that
precipitated was filtered and chromatographed on silica gel
using chloroform/methanol/water (1:9:1) to obtain 23a (1.03
g, 86% overall yield from 10b). The compouned was isolated
as a white powder after being freeze-dried from benzene: IR
(CHCl3) 1724 cm-1; 1H NMR (CDCl3/CD3OD 9.5:0.5, δ) 1.20-
1.75 (m, 14 H), 1.92 (s, 6 H), 3.15 (m, 2 H), 3.30 (s, 9 H), 3.41-
3.68 (br m, 6 H), 3.72-4.05 (br m, 5 H), 4.30 (br s, 2 H), 4.75-
4.85 (br m, 1 H); Rf (CHCl3/MeOH/H2O 1:9:1) 0.45; FAB-MS
[M + H]+ calcd for C24H46N2O9PCl3, 643.2085, found 643.2060.
1-O-(6′-Am in o)h exyl-2-O-tetr ah ydr opyr an yl-sn -glycer o-
3-p h osp h och olin e (24a ). To a solution of 23a (0.67 g, 1.04
mmol) in 7 mL of distilled dichloromethane was added glacial
acetic acid (0.35 mL, to achieve concentration of 5% (v/v))
followed by zinc powder (1.36 g, 20.8 mmol, 7 µm, 97.5%,
Aesar) under nitrogen atmosphere. The reaction mixture was
stirred at room temperature for 2 h, at which time TLC showed
major conversion to the deprotected compound 23a . The
solvent was evaporated under reduced pressure. The residue
was suspended in 20 mL of water, stirred for 5 min, and
separated from the zinc by vacuum filtration. The filtrate was
washed with 10 mL of chloroform. The organic layer was
washed with 10 mL of water, and the combined aqueous layer
was freeze-dried. The clear oily residue obtained was chro-
matographed first on Sephadex LH-20, with chloroform/
methanol (1:1), and then on silica gel (12 g, using CHCl3/
MeOH/H2O, 1:9:1) yielding 24a as a pure product that was
freeze-dried from a mixture of water and benzene (0.28 g,
61%): 1H NMR (CDCl3-CD3OD 9.5:0.5, δ) 1.35 (br m, 4 H),
1.50 (br m, 8 H), 1.70 (br m, 2 H), 2.80 (m, 2 H), 3.30 (s, 9 H),
3.38-4.02 (m, 11 H), 4.24 (br m, 2 H), 4.74-4.84 (br m, 1 H);
Rf (CHCl3/MeOH/H2O) 0.19. FAB-MS [M + H]+ calcd for
1-O-[12′-(N-2′′,2′′,2′′-Tr ich lor o-ter t-bu toxyca r bon yla m i-
n o)d od ecyl]-2-O-t et r a h yd r op yr a n yl-sn -glycer o-3-p h os-
p h och olin e (23b). Compound 23b was prepared by a method
similar to that described for compound 23a , with some
modification in the experimental conditions. Compound 22b
(1.34 g, 2.0 mmol) in 40 mL of anhydrous acetonitrile solution
was transferred, under N2, into a pressure bottle cooled in a
dry ice/acetone bath (-78 °C). To this solution was added 2
mL of trimethylamine and, after the pressure bottle was
sealed, the reaction mixture was kept in an oil bath at 65 °C
overnight. The reaction mixture was then cooled to room
temperature. TLC showed complete conversion to the product
23b. The solvent was evaporated under reduced pressure and
the oily residue was chromatographed twice on 12 g of silica
gel using CHCl3/MeOH/H2O (1:9:1) as eluant. The product was
isolated from the combined pure fractions and, following the
evaporation of the solvent, freeze-dried from benzene to afford
a white solid 23b (1.08 g, 74% overall from alcohol 10b): IR
(CHCl3) 1724 cm-1 1H NMR (CDCl3/CD3OD 9.5:0.5, δ) 1.23
;
(s, 18 H), 1.38-1.80 (br m, 8 H), 1.90 (s, 6 H), 3.10-3.15 (m,
2 H), 3.37 (s, 9 H), 3.38-3.60 (br m, 7 H), 3.72-3.96 (m, 4 H),
4.28 (br s, 2 H), 4.78 (br m, 1 H); Rf (CHCl3/MeOH/H2O 1:9:1),
0.68. Anal. Calcd for C30H58N2O9PCl3‚H2O: C, 48.30; H, 8.11;
N, 3.75. Found: C, 48.29; 8.45; N, 3.60.
1-O-(12′-Am in o)dodecyl-2-O-tetr ah ydr opyr an yl-sn -glyc-
er o-3-p h osp h och olin e (24b). Compound 24b was prepared
by a method similar to that described for compound 24a , with
some modification of the experimental conditions. To a solution
of 23b (0.56 g, 0.77 mmol) in 6 mL of freshly distilled
dichloromethane was added 0.3 mL of glacial acetic acid,
followed by zinc powder (1.0 g, 20 equiv, 7 µm, 97.5% Aesar)
under N2 atmosphere. The reaction mixture was stirred at
room temperature for 2 h. The solvent was then evaporated
under reduced pressure, and the residue was suspended in 20
mL of water. To the resulting suspension was added 20 mL of
chloroform/dichloromethane (1:1), and the solid was removed
by suction filtration. The emulsion was treated with 5 mL of
methanol, and after separation of the layers, the organic
solvent was extracted with 15 mL of methanol/water (1:2). The
aqueous solutions were combined, and the solvent was evapo-
rated under reduced pressure. The white semisolid residue was
chromatographed on 5 g of silica gel using chloroform/methanol/
water as eluent. The pure fractions were combined, and the
solvent was evaporated. The product was freeze-dried from an
emulsion of benzene/water (1:1). The deprotected aminoalkyl
product 24b (0.307 g, 78%) was used for the next step without
further treatment: 1H NMR (CDCl3/CD3OD 9.5:0.5, δ) 1.24 (s,
18 H), 1.40-1.80 (br m, 8 H), 2.80 (m, 2 H), 3.32 (s, 9 H), 3.35-
3.70 (m, 7 H), 3.72-4.04 (m, 4 H), 4.24 (br m, 2 H), 4.78 (br
m, 1 H); Rf (CHCl3/CH3OH/H2O 1:9:1), 0.24; FAB-MS [M +
H]+ calcd for C25H54N2O7P 525.3668, found 525.3678.
C
19H42N2O7P 441.2729, found 441.2730.
1-O-(6′-Am in o)h exyl-sn -glycer o-3-ph osph och olin e (25a).
To a suspension of 24a (0.22 g, 0.5 mmol) in 7.5 mL of
tetrahydrofuran was added dropwise 0.2 N aqueous HCl (7.5
mL). The reaction mixture was stirred at room temperature
for 2 h, at which time TLC showed the complete conversion to
product 25a . The solution was washed with 2 × 20 mL of ether,
and the aqueous layer was freeze-dried. The yellow oily residue
was dissolved in a minimum amount of water and then passed
through a Sephadex G-10 column, eluting it with water. The
pure fractions were combined, and the solvent was removed
by freeze-drying to give pure 25a (0.113 g, 58%): 1H NMR
(D2O, δ) 1.28-1.36 (br m, 4 H), 1.48-1.68 (br m, 4 H), 2.90-
2.96 (m, 2 H), 3.15 (s, 9 H), 3.42-3.58 (m, 4 H), 3.60-3.64 (m,
2 H), 3.72-3.88 (m, 2 H), 3.90-4.00 (m, 1 H), 4.25 (br m, 2
H); Rf (CHCl3/MeOH/H2O 1:9:1), 0.08; FAB-MS [M + H]+ calcd
for C14H34N2O6P 357.2154, found 357.2158.
2-Oxo-{1′-O-[12′′-(N-2′′′,2′′′,2′′′-tr ich lor o-ter t-bu toxyca r -
b on yla m in o)d ed ecyl]-2′-O-t et r a h yd r op yr a n yl-sn -glyc-
er yl}-1,3,2-d ioxa p h osp h ola n e (22b). Compound 22b was
prepared by a method similar to that described for compound
22a ; however, the reaction conditions were somewhat different.
To a solution of 10b (1.13 g, 2.01 mmol) in 20 mL of freshly
distilled benzene under nitrogen atmosphere were added
triethylamine (0.42 mL, 3.02 mmol) and then 2-chloro-2-oxo-
1,3,2-dioxaphospholane (0.28 mL, 3.02 mmol) in an ice-water
bath. The reaction mixture was stirred at room temperature
for 3 h, whereupon TLC showed complete conversion to 22b.
The solid Et3N‚HCl that precipitated was suction filtered, and
the filtrate was evaporated to give a colorless semisolid residue
22b (1.34 g), which was dried in a vacuum over P2O5 for 20
1-O-(12′-Am in o)d od e cyl-sn -glyce r o-3-p h osp h och o-
lin e (25b). Compound 25b was prepared following the same
experimental conditions as those described for 25a and af-
forded 25b in 66% yield: 1H NMR (D2O, δ) 1.23 (br s, 16 H),
1.46-1.68 (br m, 4 H), 2.90-2.96 (m, 2 H), 3.15 (s, 9 H), 3.42-
3.56 (m, 4 H), 3.58-3.62 (m, 2 H), 3.72-3.90 (m, 2 H), 3.92-
3.98 (m, 1 H), 4.24 (br m, 2 H); Rf (CHCl3/CH3OH/H2O 1:9:1),
0.12; FAB-MS [M + H]+ calcd for C20H46N2O6P 441.3093, found
441.3078.
Ack n ow led gm en t. This work was supported by the
National Institutes of Health, including grants GM41452,
S06 GM/HD48680, and T34 GM08395. We also thank
the Research and Grants Committee of California State
UniversitysNorthridge for support.
J O990739V