Stereospecific Synthesis of Phospholipids
J . Org. Chem., Vol. 64, No. 21, 1999 7735
It was chromatographed over activated silica gel (8 g) as soon
as possible with MeOH/CHCl3/H2O/HOAc 65:25:4:2 to give 0.53
g of 1b (0.59 mmol, 56.7%). Phospholipid 1b was freeze-dried
from benzene to give a white solid: mp 47-48 °C; IR (Nujol)
3365, 1734 cm-1; 1H NMR (CDCl3) δ 0.81 (br t, 3H), 1.19 (br s,
38H), 1.40-1.60 (m, 6H), 1.85-1.87 (s, 6H), 2.23-2.25 (m, 4H),
3.05 (t, 1H), 3.37 (s, 9H), 3.56 (m, 2H), 3.95 (m, 2H), 4.10 (dd,
1H), 4.15-4.30 (m, 2H), 4.30-4.40 (dd, 1H), 5.15 (m, 1H); Rf
(MeOH/CHCl3/CHCl3/H2O/HOAc 65:25:4:2) 0.32; [R25 +3.92
(c 1.02, CHCl3/MeOH 4:1). Anal. Calcd for C41H79ND2O10PCl‚
6.5HOAc‚H2O: C, 49.03; H, 8.23; N, 2.12. Found: C, 48.92;
H, 7.87; N, 2.49. FAB-MS MH+(C41H79N2O10PCl3) calcd
895.4538, found 895.4534.
2-(1′,2′-Dip a lm itoyl-sn -glycer o)-2-oxo-1,3,2-d ioxa p h os-
p h ola n e (11c) was prepared under the same experimental
conditions as 11a and was obtained as a colorless semisolid
in 90% yield: 1H NMR (CDCl3) δ 0.88 (br t, 6H), 1.25 (s, 48H),
1.54-1.60 (m, 4H), 2.23-2.33 (m, 4H), 4.00-4.18 (m, 2H),
4.20-4.30 (m, 2H), 4.30-4.40 (m, 4H), 5.15 (m, 1H, CH). Rf
(CHCl3/CH3OH 95:5) 0.47. This compound was used as early
as possible for the next reaction without further treatment.
1,2-Dip a lm itoyl-sn -glycer o-3-p h osp h och olin e (1c) was
prepared from 11c under the same experimental conditions
as 1a . The phosphatidylcholine 1c was obtained after silica
gel chromatography in 56% yield as an analytically pure
product: 1H NMR (CDCl3) δ 0.88 (t, 6H), 1.26 (s, 48H), 1.56-
1.63 (m, 4H,), 2.25-2.31 (m, 4H), 3.35 (s, 9H), 3.79 (m, 2H),
3.90-3.96 (m, 2H), 4.10-4.14 (dd, 1H), 4.31 (m, 2H), 4.38-
4.40 (dd, 1H), 5.21 (m, 1H); Rf (CHCl3/CH3OH/H2O 65:25:4)
0.38; [R2D5 +7.15 (c 0.47, CHCl3/CH3OH 4:1), for an authentic
reference sample from Avanti Polar Lipids [R2D5 +7.02 (c 0.47,
CHCl3/CH3OH 4:1).
Mosh er Ester of (L)-1,2-Dip a lm itoyl-sn -glycer ol (12). To
a stirred solution of (L)-1,2-dipalmitoyl-sn-glycerol (0.21 g, 0.37
mmol) in 10 mL of CHCl3 were added S(+)-R-methoxy-R-
trifluoromethylphenylacetyl chloride (S(+)-MPTA chloride,
0.11 g, 0.44 mmol) and DMAP (0.054 g, 0.44 mmol). The
mixture was stirred at room temperature overnight. To the
resulting solution was added 0.5 g of NaHCO3 in 20 mL of
H2O. Then it was extracted with 2 × 20 mL of CHCl3, washed
with 2 × 10 mL of brine, and dried over Na2SO4. Evaporation
of the solvent gave an off-white solid, which was chromato-
graphed on 10 g of freshly activated silica gel using chloroform
as eluant, yielding 0.25 g (0.32 mmol, 87%) of product 12: 1H
NMR (500 MHz, CDCl3) δ 0.87-0.89 (br t, 6H), 1.25 (br s, 48H),
1.54-1.60 (br m, 4H), 2.23-2.31 (m, 4H), 3.53 (s, 3H), 4.06-
4.09 (dd, 1H, J ) 11.9, 5.5 Hz, CH3OCOCH2), 4.26-4.29 (dd,
1H, J ) 11.9, 5.0 Hz), 4.35-4.39 (dd, 1H, J ) 11.8, 5.8 Hz),
4.57-4.61 (dd, H, J ) 11.8, 4.0 Hz), 5.28-5.30 (m, 1H), 7.38-
7.51 (m, 5H).
Mosh er Ester of (D)-1,2-Dip a lm itoyl-glycer ol (13). To
a solution of 2,3-dipalmitoyl-sn-glycerol, prepared in a similar
fashion as the (L)-enantiomer 10c from 2,3-isopropylidene-D-
methylglycerate, (0.10 g, 0.18 mmol) in 10 mL of CHCl3 were
added S(+)-MTPA chloride (0.053 g, 0.21 mmol) and DMAP
(0.026 g, 0.21 mmol). The mixture was stirred at room
temperature overnight. To the resulting solution was added
0.5 g of NaHCO3 in 10 mL of H2O. Then it was extracted with
2 × 20 mL of CHCl3, washed with 2 × 10 brine, and dried
over Na2SO4. Evaporation of the solvent followed by chroma-
tography on 10 g of freshly activated silica gel using CHCl3
afforded 0.12 g (0.15 mmol, 87%) of 13 as an off-white solid:
1H NMR (500 MHz, CDCl3) δ 0.87-0.90 (br t, 6H), 1.26 (br s,
48H), 1.54-1.61 (br m, 4H), 2.24-2.32 (m, 4H), 3.53 (s, 3H),
4.11-4.14 (dd, 1H, J ) 11.9, 5.5 Hz), 4.26-4.29 (dd, 1H, J )
11.9, 4.7 Hz), 4.35-4.39 (dd, 1H, J ) 11.9, 5.5 Hz), 4.58-4.61
(dd, 1H, J ) 11.9, 3.9 Hz), 5.30-5.32 (m, 1H), 7.39-7.52 (m,
5H).
with 2 × 10 mL of CHCl3, washed with 2 × 5 mL of brine, and
dried over Na2SO4. Evaporation of the solvent gave 0.25 g of
crude product. This yellowish solid was chromatographed over
10 g of freshly baked SiO2 with CHCl3. Evaporation of the
solvent gave 0.045 g of 14 (0.057 mmol, 81%) as an off-white
solid: 1H NMR (500 MHz, CDCl3) δ 0.87-0.90 (br t, 6H), 1.26
(br s, 48H), 1.55-1.60 (br m, 4H), 2.21-2.31 (m, 4H2), 3.57 (s,
3H), 4.11-4.14 (dd, 1H, J ) 12.2, 6.5 Hz), 4.17-4.21 (dd, 1H,
J ) 12.2, 7.0 Hz), 4.33-4.36 (dd, 1H, J ) 12.2, 3.8 Hz), 4.42-
4.45 (dd, 1H, J ) 12.2, 3.6 Hz), 5.53-5.54 (m, 1H), 7.38-7.55
(m, 5H).
2-(1′,2′-Diole oyl-sn -glyce r o)-2-oxo-1,3,2-d ioxa p h os-
p h ola n e (11d ) was prepared under the same experimental
conditions as 11a and was obtained as a single phosphate-
positive product in the form of a colorless semisolid in 93%
yield: 1H NMR (CDCl3) δ 0.88 (br t, 6H), 1.27 (s, 16H), 1.58-
1.62 (m, 4H), 1.98-2.02 (m, 8H), 2.28-2.32 (m, 4H), 4.12-
4.21 (m, 2H), 4.26-4.32 (m, 2H), 4.37-4.47 (m, 4H), 5.15 (m,
1H); Rf (CHCl3/CH2OH 95:5) 0.58. This compound was used
as soon as possible for the next reaction without further
treatment.
1,2-Dioleoyl-sn -glycer ol-3-ph osph och olin e (1d) was pre-
pared under the same experimental conditions as 1a and was
obtained from 10d as a hygroscopic white solid. Chromatog-
raphy on activated silica gel with chloroform/methanol/water
(65:25:4) afforded analytically pure 1d in 64% isolated yield:
IR (CHCl3) 2918, 2851, 1732, 1234, 1087 cm-1 1H NMR
;
(CDCl3) δ 0.88 (br t, 6H), 1.28 (br s, 16H), 1.59 (m, 4H), 2.01
(m, 8H), 2.20-2.30 (m, 4H), 3.35 (s, 9H), 3.78 (m, 2H), 3.95
(m, 2H), 4.13 (dd, 1H), 4.30 (m, 2H), 4.40 (dd, 1H), 5.20 (m,
1H), 5.30-5.40 (m, 4H); Rf (CHCl3/CH3OH/H2O 65:25:4) 0.36;
[R2D5 +6.07 (c 0.56, CHCl3-CH3OH 4:1). Anal. Calcd for
C
44H84O8PN‚2H2O: C, 62.39; H, 10.47; N, 1.82; P, 4.02. Found
C, 62.44; H, 10.69; N, 1.71; P, 3.98.
1,2-Dip a lm it oyl-sn -glycer ol-3-p h osp h oet h a n ola m in e
(15). A solution of phosphotriester 11c (0.960 g, 1.42 mmol)
in 25 mL of anhydrous acetonitrile was placed in a pressure
bottle cooled in a dry ice bath, and to this was added 25 mL of
a saturated solution of ammonia in acetonitrile. The pressure
bottle was sealed and then heated in an oil bath at 65 °C for
24 h. The reaction mixture was then cooled, and the product
15 crystallized, yielding 0.96 g (87% overall from alcohol 10c)
as a white hygroscopic solid. Chromatography of the product
on activated silica gel eluting with chloroform/methanol/water
(65:25:4) gave analytically pure phosphatidylethanolamine
0.55 g (56%), which was freeze-dried from a suspension of 30
mL of benzene as a white solid: IR (CHCl3) 3367, 2915, 2848,
1732, 1221, 1066 cm-1; 1H NMR (CDCl3) δ 0.88 (br t, 6H), 1.26
(s, 48H), 1.58-1.60 (m, 4H), 2.28-2.33 (m, 4H), 3.20 (m, 2H),
4.03 (m, 4H), 4.17 (dd, 1H), 4.38 (dd, 1H), 5.25 (m, 1H); [RD25
+6.74 (c 0.45, 1:9 CH3OH/CHCl3); Rf (CHCl3/CH3OH/H2O 65:
25:4) 0.59. Anal. Calcd for C37H74O8PN‚H2O: C, 62.59; H,
10.50; P, 4.30; N, 1.97. Found C, 62.49; H, 10.20; P, 4.00; N,
1.85.
1,2-Dip a lm itoyl-sn -glycer o-3-p h osp h oeth a n ol (16). Di-
oxaphospholane 11c (0.700 g, 1.04 mmol) was transferred to
a pressure bottle with dry acetonitrile (40 mL), and to this
was added 1.5 mL of double-distilled water while cooling in a
dry ice bath. The pressure bottle was sealed and then heated
at 65 °C for 24 h. The reaction mixture was cooled, and the
product 16 precipitated as a white hygroscopic solid. It was
then chromatographed on activated silica gel eluting with
chloroform/methanol/water (65:25:4) and freeze-dried from
benzene to give analytically pure phospholipid 16 (0.45 g,
62%): IR (CHCl3) 3345, 2913, 2849, 1732, 1224, 1069 cm-1
;
1H NMR (CDCl3) δ 0.88 (br t, 6H), 1.25 (s, 48H), 1.58-1.60
(m, 4H), 2.26-2.32 (m, 4H), 3.70-3.74 (m, 2H), 3.93-3.98 (m,
4H), 4.18 (dd, 1H), 4.40 (dd, 1H), 5.25 (m, 1H); [R2D5 +6.54 (c
0.52, 1:4 CH3OH/CHCl3); Rf (CHCl3/CH3OH/H2O 65:25:4) 0.30.
Anal. Calcd for C37H73O9P‚1.25 H2O: C, 62.11; H, 10.62; P,
4.47; Found: C, 62.08; H, 10.69, P, 4.44.
Mosh er Ester of 1,3-Dip a lm itoyl-sn -glycer ol (14). S(+)-
MTPA chloride (0.040 g, 0.14 mmol) was added to a solution
of 1,3-dipalmitoyl-sn-glycerol (Aldrich) (0.041 g, 0.07 mmol)
in 5.0 mL of CHCl3 followed by addition of DMAP (0.018 g,
0.14 mmol and stirring for 24 h. To the resulting solution was
added 0.25 g of NaHCO3 in 5 mL of H2O. Then it was extracted
1,2-Dip a lm it oyl-sn -glycer ol-3-p h osp h oet h ylt h ioa ce-
ta te (17). To a mixture of compound 11c (0.800 g, 1.41 mmol)
and 40 mL of anhydrous acetonitrile in a pressure bottle was