Biological evaluation of de-O-sulfonated analogs of salacinol, the role of sulfate anion in the side chain on the α-glucosidase inhibitory activity

Article abstract of DOI:10.1016/j.bmc.2006.10.014

De-O-sulfonated analogs (10a, Y^- = CH₃OSO₃ and 10b, Y^- = Cl) of salacinol, a naturally occurring glycosidase inhibitor, and its diastereomer (12a, Y^- = CH₃OSO₃) with l-thiosugar moiety (1,4-dideoxy-1,4-epithio-l-arabinitol) were prepared. Their inhibitory activities against intestinal maltase and sucrase were examined and compared with those of the parent α-glycosidase inhibitor, salacinol (1a). Compounds 10a and 10b showed a potent inhibitory activity equal to that of 1a against both enzymes, although 12a was a weak inhibitor against sucrase and maltase. These results indicated that the O-sulfonate anion moiety of 1a is not essential for the inhibitory activity.

Full text of DOI:10.1016/j.bmc.2006.10.014

Bioorganic & Medicinal Chemistry 15 (2007) 3926–3937
Biological evaluation of de-O-sulfonated analogs of salacinol,
the role of sulfate anion in the side chain on the
a-glucosidase inhibitory activity
Genzoh Tanabe,a Kazuya Yoshikai,a Takanori Hatanaka,a Mizuho Yamamoto,a
Ying Shao,a Toshie Minematsu,a Osamu Muraoka,a,* Tao Wang,b
Hisashi Matsudab and Masayuki Yoshikawab
aSchool of Pharmaceutical Sciences, Kinki University, 3-4-1 Kowakae, Higashi-osaka, Osaka 577-8502, Japan
bKyoto Pharmaceutical University, 1 Shichono-cho, Misasagi, Yamashina-ku, Kyoto 607-8412, Japan
Received 12 September 2006; revised 6 October 2006; accepted 11 October 2006
Available online 13 October 2006
Abstract—De-O-sulfonated analogs (10a, Yꢀ = CH3OSO3 and 10b, Yꢀ = Cl) of salacinol, a naturally occurring glycosidase inhib-
itor, and its diastereomer (12a, Yꢀ = CH3OSO3) with L-thiosugar moiety (1,4-dideoxy-1,4-epithio-L-arabinitol) were prepared. Their
inhibitory activities against intestinal maltase and sucrase were examined and compared with those of the parent a-glycosidase
inhibitor, salacinol (1a). Compounds 10a and 10b showed a potent inhibitory activity equal to that of 1a against both enzymes,
although 12a was a weak inhibitor against sucrase and maltase. These results indicated that the O-sulfonate anion moiety of 1a
is not essential for the inhibitory activity.
Ó 2007 Published by Elsevier Ltd.
1. Introduction
tors 1a and related compounds.3 Total synthesis of 1a
was accomplished by two groups.4 Extensive
structure–activity relationship studies on 1a have also
been reported, its enantiomer4c,5f (2a), diastereomers
Salacinol (1a, X = S+) is a potent glycosidase inhibitor
isolated from aqueous extracts of roots and stems of
Salacia reticulata WIGHT (known as ‘Kotala himbutu’
in Singhalese), which is traditionally used for the treat-
ment of diabetes in Sri Lanka and the south region of
India.1 The structure of 1a established by the X-ray crys-
tallographic analysis is quite unique, the ring sulfonium
ion being stabilized by the sulfate counteranion by
forming a spirobicyclic-like configuration comprised of
1-deoxy-4-thio-D-arabinofranosyl cation and 1-deoxy-
L-erythrosyl-3-sulfate anion, as shown in Figure 1.1
The a-glucosidase inhibitory activities of 1a are potent,
and have been revealed to be as strong as those of vogli-
bose and acarbose, which are widely used clinically these
days.1 Thus, glycosidase inhibitors containing sulfonium
ions are of interest as mimics of oxacarbenium interme-
diates in glycosidase hydrolysis reactions,2 and much
attention has been focused on this novel class of inhibi-
HO
HO
HO
HO
HO
3'
HO
O
O
O
O
X
S O
-
-
O-
1'
SO3
SO3
X
X
1
HO
HO
HO
4
2
OH
OH
OH
HO
HO
HO
1
2
3
HO
HO
HO
HO
HO
HO
O
O
O
-
-
-
SO3
SO3
SO3
X
S+
S+
HO
HO
HO
OH
OH
OH
HO
HO
HO
4
5a
a : X = S+, b : X = NH+, c : X = Se+
6a
Keywords: a-Glucosidase inhibitor; Salacinol; De-O-sulfonated sala-
cinol; Thiosugar.
*
Corresponding author. Tel.: +81 6 6721 2332; fax: +81 6 6730
1394; e-mail: muraokai@phar.kindai.ac.jp
Figure 1.
0968-0896/$ - see front matter Ó 2007 Published by Elsevier Ltd.
doi:10.1016/j.bmc.2006.10.014

G. Tanabe et al. / Bioorg. Med. Chem. 15 (2007) 3926–3937
3927
R2
2. Chemistry
R1
2.1. Preparation of thiosugars (16 and 18) and cyclic
sulfate (13)
O
-
SO3
S+
7 : R1=H, R2=H
HO
According to the lit.7a thio-arabinitol (D-16) was prepared
starting from D-xylose via 3-O-benzyl-1,4-dideoxy-1,4-
epithio-D-arabinitol7a,8 (D-17). The perbenzylated
compound, 2,3,5-tri-O-benzyl-1,4-dideoxy-1,4-epithio-
D-arabinitol (D-18), was obtained in good yield by treat-
ment of D-17 with excess benzyl bromide. Its L-isomer,
2,3,5-tri-O-benzyl-1,4-dideoxy-1,4-epithio-L-arabinitol
(L-18), was synthesized starting also from D-xylose
according to the lit.9 The Birch reduction of L-18 gave
L-16 in 85% yield (Scheme 1).
8 : R1=OH, R2=H
9 : R1=H, R2=CH2OH
OH
HO
Figure 2.
(3a, 4a,c,5b,d,f 4a,5f 5a,5k and 6a5k) as well as their heterocy-
clic analogs (1b,5a,c 1c,5e,j 2b,5c,f 3c,5e and 4b5f) and related
compounds5l–p having been synthesized and evaluated.
The authors also synthesized analogs of 1a lacking the
hydroxyl and/or hydroxymethyl groups (7, 8, and 9),
and have found that both functionalities (C-20 hydroxyl
and C-30 hydroxylmethyl) in the side chain are essential
to maintain the inhibitory activity. Thus, structural
determinant for the glycosidase inhibitory activity has
been revealing to a certain extent (Fig. 2). On the other
hand, all these structure–activity studies have been
focusing on the onium sulfate inner salt structure so
far,5,6 and less consideration has been given to the role
of the sulfate anion moiety. This partial structure has
been considered to be essential for the inhibitory
activities.5d
The cyclic sulfate 13 was synthesized starting from
D-glucose according to the method which the authors
previously reported as a communication.5a D-Glucose
was first led to 4,6-O-benzylidene-D-glucose (19) by the
tosic acid catalyzed transacetalation.11 Compound 19
was then oxidized with sodium metaperiodate12 in the
presence of excess sodium bicarbonate, and subsequent
sodium borohydride reduction without isolation of the
resulting D-erythrose derivative gave 1,3-O-benzyli-
dene-L-erythritol (20) in 94% yield. Protection of the
dihydroxy group of 20 with 2-methoxypropene followed
by hydrogenolysis of the benzylidene moiety of the
resulting
1,3-O-benzylidene-2,4-O-isopropylidene-L-
As a part of our continuing study on the structure–activ-
ity relationship of 1a, the role of the sulfonate anion
moiety was explored in this study. The analogs (10a
and 10b) lacking the O-sulfate anion of 1a were prepared
and their inhibitory activity was examined. A diastereo-
mer (11) of 1a and its de-O-sulfonated analogs (12a)
were also synthesized in order to assess structure–activ-
ity relationship (Fig. 3).
erythritol (21) provided the diol 14 in good yield. Final-
ly, 14 was converted to the desired cyclic sulfate 13 via
the catalytic ruthenium tetroxide oxidation of the cyclic
sulfite 15 (Scheme 2).
It is important to note that the condensation of the diol
14 with thionyl chloride to give the cyclic sulfite 15 must
be carried out under completely anhydrous conditions.
Thus, the employment of the freshly distilled diol 14
was preferred. The reaction proceeded cleanly at 0 °C
in the presence of triethylamine to give the correspond-
ing cyclic sulfite 15 in almost quantitative yield. 13C
NMR spectrum of the crude product showed no signif-
icant peaks other than those corresponding to the de-
sired cyclic sulfite (see Fig. 4). On the other hand,
when the diol 14 purified by the column chromatogra-
phy was subjected to the condensation, highly polar side
products often formed to a considerable extent, and
Recently, Gallienne and co-workers5h have reported the
one-pot synthesis of the cyclic sulfate, 2,4-O-isopropy-
lidene-L-erythritol-1,3-cyclic sulfate (13), the key inter-
mediate for the synthesis of 1a and related
compounds, in which they claimed that the yield at the
stage of the cyclic sulfination reaction of the diol, 2,4-
O-isopropylidene-L-erythritol (14) leading to the cyclic
sulfite, 2,4-O-isopropylidene-L-erythritol-1,3-cyclic sul-
fite (15), was irreproducible when they tried our5a proto-
col published as a communication.5a Here, we also
present full details on the synthesis of the cyclic sulfate
13 including points to notice (Scheme 2).
S
S
HO
BnO
a
Ref. 7a
OH
OH
OBn
RO
BnO
O
HO
HO
HO
HO
HO
HO
HO
D-18
D-17 : R = Bn
D-16 : R = H
Ref. 7a
BnO
OH
D-xylose
Ref. 9
HO
O
OH
Y-
OH
Y-
-
SO3
S+
S+
S+
b
S
S
HO
HO
HO
HO
OH
HO
OH
HO
OH
HO
BnO
L-18
HO
OBn
OH
-
10
11
12
L-16
a :Y = CH3OSO3
b :Y = Cl-
Scheme 1. Reagents and conditions: (a) BnBr, NaH, DMF, 0 °C; (b)
Na, liq. NH3, THF, ꢀ60 °C.
Figure 3.

3928
G. Tanabe et al. / Bioorg. Med. Chem. 15 (2007) 3926–3937
6
in aqueous solution. When the oxidation of 15 was tried
HO
HO
HO
O
4
O
Ph
a
b
O 1
OH
under the conventional conditions, the yield of the cyclic
sulfate 13 ended up to be low or moderate (ca. < 65%).
Addition of sodium bicarbonate to the reaction mixture
was found to be effective, and substantial improvement
of the yield of the cyclic sulfate 13 up to around 90–
95% from the diol 14 was achieved. No noticeable sig-
nals due to side products other than to the desired oxi-
dated product 13 were observed in its 13C NMR
spectrum, supporting that 13 was pure enough for the
next reaction (see Fig. 5). The cyclic sulfate 13 thus ob-
tained was labile on storing even in a freezer, and puri-
fication by column chromatography was needed to keep
this compound for a few months. The yield after column
chromatography was around 78–83%.
OH
OH
O
OH
HO
OH
D-glucose
19
1
O
HO3
e
Ph
O
Ph
O
O
O
O
O
S
20
22
c
f
RO
RO
O
O
O
Ph
O
O
O
S
O
S
e
O
21 : R = benzylidene
14 : R = H
23
d
Gallienne and co-workers5h also described that the yield
of the cyclic sulfination of another diol 20 was moderate,
and the reported yield (82%)4c of 2,4-O-benzylidene-D-
erythritol-1,3-cyclic sulfite (22) was irreproducible after
their numerous attempts. The condensation of 20 with
thionyl chloride proceeded without the formation of side
products and gave reproducibly and almost quantita-
tively the cyclic sulfite 22 as reported by Ghavami
et al.4c Its 13C NMR spectrum suggested that the crude
product of this reaction was also pure enough for the
next reaction (see Fig. 6). The crude product was then
subjected to the modified oxidation conditions used
for the preparation of the sulfate 13 to give the practi-
cally pure cyclic sulfate, 2,4-O-benzylidene-D-erythri-
tol-1,3-cyclic sulfate (23), in around 92% yield from
the diol 20 (see Fig. 7). The yield of 23 after column
O
O
S
f
O
O
O
O
O
O
O
O
O
15
13
Scheme 2. Reagents and conditions: (a) PhCH(OCH3)2, p-TsOH,
DMF, 50–60 °C; (b) NaIO4, NaHCO3, H2O, THF, rt, then NaBH4, rt;
(c) CH3(CH3O)C@CH2, p-TsOH, DMF, 0–5 °C; (d) H2, Pd–C, EtOH,
rt; (e) SOCl2, Et3N, CH2Cl2, 0 °C; (f) NaIO4, RuCl3, NaHCO3, CCl4,
CH3CN, H2O, 0 °C to rt.
Figure 4. 13C NMR spectrum (67.5 MHz, CDCl3) of the crude sulfite
15.
resulted in the reduction of the yield of the cyclic sulfite
15. The formation of these undesired products would be
attributable to the facile hydrolysis of the isopropylidene
moiety of 15, although triethylamine was added to trap
the hydrogen chloride formed during the reaction.
Moreover, quenching the reaction with water caused
formation of considerable amount of highly polar and
water-soluble materials, the yield of the cyclic sulfite
15 being reduced to ca. <60%. Rapid quenching of the
reaction with excess ice-cooled aqueous sodium bicar-
bonate under vigorous stirring was needed to prevent
the hydrolysis of the product 15. When the quenching
with aqueous sodium bicarbonate failed, the yields of
15 varied irregularly (ca. 75–90%).
Figure 5. 13C NMR spectrum (67.5 MHz, CDCl3) of 13.
The crude cyclic sulfite 15 was immediately oxidized to
the cyclic sulfate 13 because of its instability even at
room temperature. This oxidation stage was also prob-
lematic due probably to the acidity of sodium periodate
Figure 6. 13C NMR spectrum (67.5 MHz, CDCl3) of the crude 22.

G. Tanabe et al. / Bioorg. Med. Chem. 15 (2007) 3926–3937
3929
Finally, the monomethyl sulfate anion of 10a was ex-
changed to the chloride anion by the treatment with
ion exchange resin IRA-400J (Clꢀ form) to give 10b in
96% yield. The FAB mass spectrum of 10a run in the po-
sitive mode showed a peak at m/z 255 due to the sulfo-
nium cation structure, and one in the negative mode
showed a peak at m/z 111 due to methyl sulfate anion
moiety, supporting the desired structure. Observed
downfield shift signals [dH 3.86 (H-1), 3.73 (H-10a),
3.85 (H-10b) and 4.02 (H-4)] corresponding to a-protons
of the sulfur in its 1H NMR spectrum supported the sul-
fonium ion structure of 10a. The 13C NMR spectro-
scopic properties of 10a were similar to those of 1a
except for the signal due to C-30 methine carbon (dC
75.3), which is significantly shifted upfield in comparison
with that of 1a (dC 80.61b), supporting the depicted
de-O-sulfonated structure. The relative stereochemistry
of the side chain on the sulfur atom was detected on
the basis of nuclear Overhauser effect spectroscopy
(NOESY) experiments, as shown in Scheme 3. The
observed NOE correlations between the ring proton
(H-4) a to the sulfur atom and methylene protons on
C-10 suggested the depicted configuration of the side
chain. The corresponding chloride 10b showed very sim-
Figure 7. 13C NMR spectrum (67.5 MHz, CDCl3) of the crude 23.
chromatography was slightly superior to that of 13 and
was around 88% from the diol 20.
2.2. Sulfonium salts (10, 11, and 12)
The coupling reactions were carried out by Sharpless’s
ring-opening method,13 which was applied for the syn-
thesis of salacinol (1a) by Yuasa4a and Ghavami4b,c
(Scheme 3). The reaction of the thiosugars D- and L-
16b with the cyclic sulfate 13 in DMF proceeded at
45 °C to give the coupled products 24 or 25 in 65%
and 58% yield, respectively. The coupled products 24
and 25 were then subjected to acid-catalyzed deprotec-
tion to give 1a and the diastereomer 11 in 74% and
89% yield, respectively. The specific rotation of 11
([a]D +35.5) implied that 11 was the antipode of the
levorotatory isomer 3a ([a]D ꢀ35.6) reported.4c The cou-
pling reaction of the perbenzylated thiosugar D-18 with
13 was performed in gently refluxed 1,1,1,3,3,3-hexaflu-
oroisopropanol (HFIP) according to the lit.4d to give the
desired product 26 quantitatively. Hydrogenolysis of 26
with palladium on carbon in 90% acetic acid proceeded
smoothly to give 1a in 82% yield. De-O-sulfonation of
salacinol (1a) and the diastereomer 11 with methanolic
hydrogen chloride gave the desired sulfonium salts 10a
and 12a in 86% and 79% yield, respectively.
1
ilar H and 13C NMR spectral properties to those of
10a. Disappearance of the peak at m/z 111 in the FAB
mass spectrum of 10a run in the negative mode also sup-
ported the exchange of the methyl sulfate anion into the
chloride. Compound 12a also displayed similar 1H spec-
troscopic properties to those of 10a, with deshielded sig-
nals of five protons a to the sulfonium ion. The relative
stereochemistry of the side chain on the sulfur atom of
12a was also confirmed by means of NOESY
experiments.
3. a-Glucosidase inhibitory activity
The glycosidase inhibitory activities of synthesized com-
pounds 10a, 10b, 11, and 12a were tested for the intesti-
nal a-glucosidase in vitro14 and compared with that of
salacinol (1a), as shown in Table 1. It is noteworthy that
desulfonated compounds (10a and 10b) maintained
O
O
a
d
O
-
SO3
S+
HO
HO
HO
4'
3'
O
HO
HO
2'
OH
HO
H
H
H
HO
O
HO
O
OH
CH3OSO3
OH
O
O
H
H
H
NOE
HO
-
b
f
d
f
1'
-
24
-
Y-
1
SO3
1a
SO3
13
NOE
HO
S+
S+
S+
S+
HO
HO
4
O
2
5
HO
3
OH
HO
OH
OH
HO
12a
OH
HO
O
-
25
11
10a : Y = CH3OSO3
10b : Y = Cl-
-
c
e
SO3
g
S+
BnO
OBn
BnO
26
Scheme 3. Reagents and conditions: (a) D-16, DMF, Na2CO3, 45 °C; (b) L-16, DMF, Na2CO3, 45 °C; (c) D-18, HFIP, K2CO3, reflux; (d) 0.2% aq
HCl, 40 °C; (e) H2, Pd–C, 90% aq AcOH, 50 °C; (f) 5% methanolic HCl, 45 °C; (g) IRA-400J (Clꢀ form), MeOH–H2O, rt.

3930
G. Tanabe et al. / Bioorg. Med. Chem. 15 (2007) 3926–3937
Table 1. IC50 values (lM) of compounds 1a, 10a, 10b, 11, and 12a
against disaccharidase
washed with benzene), benzyl bromide (8.4 ml,
70.7 mmol), and DMF (100 ml) at 0 °C. After being
stirred at 0 °C for 30 min, the mixture was poured
into ice-water (1 L) and extracted with diethyl ether.
The extract was washed with brine and evaporated
to give a colorless oil (15.5 g), which on column
chromatography (n-hexane/ethyl acetate, 10:1) gave
Entry
Compound
Maltase
Sucrase
1
2
3
4
5
1a
9.6
15.6
2.5
3.7
10a
10b
11
14.0
>1197 (18)a
>1092b
3.5
>1197 (21)a
>1092 (48)a
12a
the title compound D-18 (13.1 g, 90%) as a colorless
20
a Values in parentheses indicate inhibition (%) at 400 lg/ml (11,
1197 lM; 12a, 1092 lM).
oil, bp 221–224 °C/1 mmHg; ½aꢁ
+6.03 (c = 1.44,
D
CHCl3) lit.4c +5 (c = 1.6, CHCl3). The spectral proper-
ties of D-18 were in accord with those reported.4c
b Compound 12a showed no inhibition at 1092 lM.
4.2. 1,4-Dideoxy–1,4-epithio-L-arabinitol (D-16)
almost equal activities to salacinol (1a), irrespective of
species of the counteranion. Thus, characteristic spirobi-
cyclic structure of 1a is found no longer to be essential
for the potent a-glucosidase activity.
A solution of 2,3,5-tri-O-benzyl-1,4-dideoxy-1,4-epithio-
L-arabinitol9 (L-18, 7.05 g, 16.8 mmol) in THF (50 ml)
was treated with a solution of sodium (1.54 g, 67 mg-
atom) in liquid ammonia (ca. 140 ml) at ꢀ60 °C for
1 h. After addition of a mixture of methanol (5 ml)
and THF (15 ml) to the mixture, ammonia was gradu-
ally removed by increasing the temperature of the mix-
ture and neutralized with concd hydrochloric acid. The
resulting precipitates were filtered off and washed with
methanol. The combined filtrate and washings were
evaporated to give a pale yellow oil (3.5 g), which on
column chromatography (CHCl3/EtOH, 5:1) gave the
Upon substitution of the thiosugar moiety (D-form) of
1a to its enantiomer (L-form, 11), the inhibitory activi-
ties against both enzymes were reduced to a large extent.
Same tendency had been observed with respect to
aza-analogs of 1a, where aza-isomer composed of L-aza-
sugar showed less activity than the one composed of
D-azasugar (1b, X = NH+).7b
title compound L-16 (2.14 g, 85%) as a pale yellow oil,
The de-O-sulfonated version (12a) of 11 showed no
inhibitory activity against maltase, though 12a sustained
modest activity against sucrase (48% inhibition at ca.
1.1 mM, entry 5). Further structure–activity relationship
studies on the strong a-glucosidase inhibitory activity of
1a and selectivity to glycosidases are in progress.
22
D
½aꢁ ꢀ41.8 (c = 1.2, MeOH). The spectral properties of
L-16 were in accord with those of the corresponding
D-isomer D-16 reported.10
4.3. 4,6-O-Benzylidene-D-glucose (19)
According to the method reported by Barili et al.11 tosic
acid catalyzed transacetalation of D-glucose (15 g,
83.3 mmol) with benzaldehyde dimethyl acetal
(13.8 ml, 91.7 mmol) in DMF (70 ml) was carried out.
Work-up in a manner similar to that described in the
lit.11 gave a viscous syrup, which was triturated with a
mixture of diethyl ether (40 ml) and water (40 ml). The
deposited solid was collected by filtration, and then
washed with diethyl ether and water to give the title
compound 19 (13 g, 58%, a/b = ca. 2/1) as colorless nee-
dles. The combined filtrate and washings were sepa-
rated, and organic layer was extracted with water.
Deposited solid during evaporation of the water layer
was collected by filtration to give 19 (1.9 g, 9%) as color-
less needles. The filtrate was evaporated again, and the
residue was extracted with hot ethyl acetate to give 19
(3.4 g, 15%) as a colorless solid. Mp 181–183 °C, lit.11
178–179 °C. The spectral properties of 19 were in accord
with those reported.11 Compound 19 was used in the
next step without further purification.
4. Experimental
Mps were determined on a Yanagimoto MP-3S micro-
melting point apparatus, and mps and bps are uncor-
rected. IR spectra were measured on either
a
Shimadzu IR-435 grating spectrophotometer or a Shi-
madzu FTIR-8600PC spectrophotometer. NMR spectra
were recorded on a JEOL JNM-GSX 270 (270 MHz 1H,
67.5 MHz 13C), a JEOL JNM- ECA 500 (500 MHz H,
1
125 MHz 13C) or a JEOL JNM-ECA 600 (600 MHz 1H,
150 MHz 13C) spectrometer. Chemical shifts (d) and
coupling constants (J) are given in parts per million
and Hertz, respectively. Low-resolution and high-reso-
lution mass spectra (electron impact) were recorded on
either a Shimadzu QP 1000EX spectrometer or a JEOL
JMS-HX 100 spectrometer. Optical rotations were
determined with a JASCODIP-370 digital polarimeter.
Column chromatography was effected over Merck Kie-
selgel 60 (70–230 mesh). All the organic extracts were
dried over either anhydrous magnesium sulfate or anhy-
drous sodium sulfate prior to evaporation.
4.4. 1,3-O-Benzylidene-L-erythritol (20)
A mixture of 19 (6.0 g, 22.4 mmol), sodium metaperio-
date (9.8 g, 45.9 mmol), sodium hydrogen carbonate
(5.0 g, 60 mmol), water (160 ml), and THF (70 ml) was
stirred at room temperature for 1 h. The mixture was
cooled to 0 °C, and sodium borohydride (1.74 g,
45.9 mmol) was added, and the resulting mixture was
stirred for another 1 h. The precipitates were filtered
4.1. 2,3,5-Tri-O-benzyl-1,4-dideoxy-1,4-epithio-D-arabin-
itol (D-18)
A
solution of 3-O-benzyl-1,4-dideoxy-1,4-epithio-D-
arabinitol7a,8 (D-17, 8.27 g, 34.5 mmol) in DMF
(100 ml) was added dropwise to a mixture of sodium
hydride (3.2 g, 80 mmol, 60% in liquid paraffin,

G. Tanabe et al. / Bioorg. Med. Chem. 15 (2007) 3926–3937
3931
Table 2. 1H NMR data of 20 in CD3OD
d observed (500 MHz)
d lit.4c (400 MHz)
H-1ax
H-1eq
H-2
3.58 (dd, J = 10.0, 10.0)
4.20 (dd, J = 10.0, 4.0)
3.55-3.67 (m)
4.20 (m)
3.60–3.66 (m)
3.60–3.66 (m)
3.55–3.67 (m)
3.55–3.67 (m)
H-3
H-4a
H-4b
Others
3.74 (dd, J = 12.0, 5.5)
3.91 (dd, J = 12.0, 2.0)
5.52 (1H, s, PhCH), 7.27–7.35 (3H, m, arom.), 7.45–7.51 (2H, m, arom.)
3.74 (dd, J = 12.1, 5.7)
3.92 (dd, J = 12.1, 1.7)
5.53 (1H, s, PhCH), 7.28–7.53 (5H, m, arom.)
Compound 20 was named as 2,4-O-benzylidene-D-erythritol in the literature.4c
Table 3. 13C NMR data of 20 in CD3OD
off, and the filtrate was extracted with ethyl acetate. The
extract was washed with aqueous sodium thiosulfate–so-
dium hydrogen carbonate, and evaporated to give the ti-
tle compound 20 (4.41 g, 94%) as a colorless solid, which
was pure enough for further reaction. For analytical
purpose a small portion was recrystallized from a mix-
ture of dichloromethane and methanol.
d observed (125 MHz)
d lit.4c (100 MHz)
C-1
C-2
C-3
C-4
72.2
62.6
84.2
62.8
72.21
84.22
62.59
62.76
Others 102.4 [PhCH], 127.5/129.0/ 102.36 [PhCH],
129.8 (d, arom.),
139.5 (s, arom.)
127.49/128.99/129.77
(d, arom.), 139.52 (s, arom.)
Compound 20. Colorless needles; Mp 133–134 °C, lit.4c
19
mp 138–139 °C. ½aꢁ ꢀ46.8 (c = 1.0, CH3OH), lit.4c
Compound 20 was named as 2,4-O-benzylidene-D-erythritol in the
literature.4c
D
[a]D ꢀ44.0 (c = 1.0, CH3OH).
Although H and 13C NMR spectroscopic properties of
1
1
Although H and 13C NMR spectroscopic properties of
20 were in good accordance with those reported,4c in
which assigned signals due to C-2 and C-3 carbons4c
were found to be interchanged with each by two-dimen-
sional spectroscopic studies. All the signals were unam-
biguously assigned as shown in Tables 2 and 3.
21 were in good accordance with those reported,5h there
appeared some incorrect assignments in the lit.5h On the
basis of two-dimensional spectroscopic studies, all the
signals were unambiguously assigned as shown in Tables
4 and 5.
Long-range correlation was detected between the signals
due to the benzylidene methine ptoton (dH 5.52) and C-3
methine carbon (dC 84.2), and no correlation between
the signal due to C-2 methine carbon (dC 62.6) and that
due to the benzylidene methine proton (dH 5.52) as
shown below.
Long-range correlations were detected with the benzyli-
dene methine proton (dH 5.61) between both C-1 (dC
69.6) and C-3 (dC 75.0) carbons in HMBC experiments.
Between the signals due to the equatorial protons (dH
4.23) on C-1 and the tertiary carbon (dC 102.0) of the
Table 4. 1H NMR data of21 in CDCl3
d observed (600 MHz)
d lit.5h (400 MHz)
1
O
2
Ph
OH
OH
H-1ax 3.77 (dd, J = 10.1, 9.8)
H-1eq 4.23 (dd, J = 10.1, 4.6)
3.95–4.01 (m)
3.95–4.01 (m)
3.73–3.80 (m)
3
O
HMBC
4
H-2
H-3
3.98 (ddd, J = 9.8, 9.2, 4.6)
20
3.76 (ddd, J = 10.1, 9.2, 5.2) 3.88–3.93 (m)
H-4ax 3.90 (dd, J = 10.6, 10.1)
H-4eq 3.96 (dd, J = 10.6, 5.2)
3.73–3.80 (m) as H-4b
4.23 (dd J = 10.3, 4.0)
as H-4a
4.5. 1,3-O-Benzylidene-2,4-O-isopropylidene-L-erythritol
(21)
Others 1.43/1.56 [s, (CH3)2C], 5.61
(s, PhCH), 7.33–7.39
(3H, m, arom.),
1.57/1.43 [s, (CH3)2C], 5.62
(s, PhCH), 7.35–7.38
(3H, m, arom.),
A mixture of 20 (3.0 g, 14.3 mmol), 2-methoxypropene
(2.07 g, 28.8 mmol), tosic acid (30 mg, 0.17 mmol), and
DMF (60 ml) was stirred at 0–5 °C for 12 h. The reac-
tion mixture was neutralized by the addition of sodium
carbonate (700 mg), and the resulting mixture was fil-
tered. The filtrate was poured into water (300 ml) and
extracted with n-hexane. The extract was washed with
brine, and evaporated to give quantitatively 21 (3.6 g)
as a colorless solid, which was pure enough for further
reaction. For analytical purpose a small portion was
recrystallized from ethanol to give colorless needles.
7.46–7.49 (2H, m, arom.)
7.47–7.80 (2H, m, arom.)
Table 5. 13C NMR data of 21 in CDCl3
d observed (150 MHz)
d lit.5h (100 MHz)
C-1
C-2
C-3
C-4
69.6
66.6
75.0
62.3
62.3
75.0
66.6
69.6
Others 19.3/29.1 [(CH3)2C],
100.0 [(CH3)2C], 102.0
19.3/29.1 [(CH3)2C], 100.0
[(CH3)2C], 102.0 [PhCH],
[PhCH], 126.1/128.3/129.1 126.1/128.3/129.2
(d, arom.), 137.2
(s, arom.)
22
Compound 21. Mp 76.5–78 °C. ½aꢁ +3.1 (c = 1.0,
(d, arom.), 137.2 (s, arom.)
D
CHCl3), lit.5h [a]D +2 (c = 1.2, CHCl3).

3932
G. Tanabe et al. / Bioorg. Med. Chem. 15 (2007) 3926–3937
Table 6. 1H NMR data of 14 in CDCl3
d observed (500 MHz)
benzylidene moiety were also observed. Furthermore,
the equatorial proton (dH 3.96) on C-4 also correlated
with the quaternary carbon (dC 100.0) of the isopropy-
lidene moiety.
d lit.5h (400 MHz)
H-1a
H-1b
H-2
3.59 (dd, J = 11.5, 6.0)
3.77 (dd, J = 11.5, 2.3)
3.76–3.82 (m)
3.57–3.69 (m)
3.66 (ddd, J = 9.5, 6.0, 2.3) 3.48 (td, J = 9.2, 9.2, 5.6)
3.47 (ddd, J = 9.5, 9.5, 5.5) 3.57–3.69 (m)
1
H-3
O
2
Ph
O
H-4ax 3.60 (dd, J = 11.5, 9.5)
H-4eq 3.79 (1dd, J = 11.5, 5.5)
Others 1.34/1.46 [s, (CH3)2C]
3.57–3.69 (m) as H-4b
3.76–3.82 (m) as H-4a
1.35/1.48 [s, (CH3)2C]
3
O
O
4
HMBC
21
4.6. 2,4-O-Isopropylidene-L-erythritol (14)
Table 7. 13C NMR data of 14 in CDCl3
d observed (125 MHz)
A suspension of 10% palladium-on-carbon (1.0 g) in eth-
anol (25 ml) was pre-equilibrated with hydrogen. To the
d lit.5h (100 MHz)
suspension was added
a solution of 21 (2.08 g,
C-1
C-2
63.2
76.5
65.5
64.0
8.3 mmol) in ethanol (50 ml), and hydrogenation was
continued at room temperature under atmospheric pres-
sure for 6 days. The catalyst was filtered off, and the fil-
trate was evaporated to give an oil (1.41 g), which was
triturated with n-hexane to give the title compound 14
(1.33 g, 99%) as a colorless oil. A mixture of the oil
and a small amount of dichloromethane solidified on
keeping in a refrigerator to give colorless needles.
C-3
C-4
64.0
65.5
76.5
63.3
Others
19.6/28.9 [(CH3)2C],
99.8 [(CH3)2C]
19.7/28.9 [(CH3)2C],
99.9 [(CH3)2C]
ethylamine (1.74 ml, 12.6 mmol), and dichloromethane
(25 ml) at 0 °C. After being stirred at 0 °C for 10 min,
the mixture was poured into ice-cooled and vigorously
stirred aqueous sodium hydrogen carbonate (50 ml),
and extracted with dichloromethane. The extract was
washed with brine, and evaporated to give 15 (1.05 g)
as a pale yellow oil, whose 13C NMR spectrum sug-
gested that the crude product was pure enough for the
next reaction (Fig. 4). The crude mixture was immedi-
ately used in the next step without purification.
The hydrogenation of 21 was very slow, and 4 days was
also taken up to complete the reduction when the hydrog-
enolysis was preformed at 50 °C. When reaction progress
is hardly recognized by TLC analysis, replacement of the
used catalyst to new one was effective to complete the
hydrogenation. Significant improvement of reaction effi-
ciency was also not observed under 4.5 atm pressure.
Compound 14. Mp 41–42 °C. Bp 138–140 °C/2 mmHg.
22
½aꢁ +46.6 (c = 1.0, CH3OH), lit.5h [a]D +45 (c = 1.1,
D
CH3OH).
A mixture of the sulfite 15: FABMS m/z: 209 [M+H]+
(pos.), FABHRMS m/z: 209.0491 (C7H13O5S requires
1
1
Although H and 13C NMR spectroscopic properties of
209.0483), H NMR (600 MHz, CDCl3) d: 1.40 [3H, s,
(CH3)2C], 1.54 [1.8H, s, (CH3)2C], 1.55 [1.2H, s,
(CH3)2C], 3.83 (0.4H, dd, J = 10.8, 5.8 Hz, H-b4eq),
3.86 (0.4H, dd, J = 10.8, 10.0 Hz, H-b4ax), 3.890
(0.6H, dd, J = 11.0, 10.5 Hz, H-a4ax), 3.892 (0.4H, dd,
J = 10.0, 4.6 Hz, H-b1eq), 3.97 (0.6H, dd, J = 11.0,
5.3 Hz, H-a4eq), 4.13 (0.6H, dd, J = 10.5, 8.6 Hz, H-
a1ax), 4.16 (0.6H, ddd, J = 10.5, 9.6, 5.3 Hz, H-a3),
4.18 (0.4H, ddd, J = 10.3, 10.0, 4.6 Hz, H-b2), 4.44
(0.6H, ddd, J = 9.6, 8.6, 5.8, H-a2), 4.47 (0.6H, dd,
J = 10.5, 5.8 Hz, H-a1eq), 4.67 (0.4H, dd, J = 10.3,
10.0 Hz, H-b1ax), 4.89 (0.4H, ddd, J = 10.0, 10.0,
5.8 Hz, H-b3), 13C NMR (150 MHz, CDCl3, a/b) d:
65.6/60.4 (C-1), 61.6/61.1 (C-4), 69.8/64.7 (C-3), 64.9/
66.2 (C-2), 100.4/100.5 [(CH3)2C].
14 were in good accordance with those reported, there
appeared some incorrect assignments in the lit.5h On
the basis of two-dimensional spectroscopic studies, all
the signals were unambiguously assigned as shown in
Tables 6 and 7.
Long-range correlations, between the signals due to
both methylene protons (dH 3.60 and 3.79) on C-4 and
the quaternary carbon (dC 99.8) of the isopropylidene
moiety were detected in HMBC experiments.
1
HO 3
HO
2
O
O
4
HMBC
14
4.8. 2,4-O-Isopropylidene-L-erythritol 1,3-cyclic sulfate
(13)
To a well-stirred mixture of the crude 15 (1.05 g), so-
dium hydrogen carbonate (1.39 g mg, 16.5 mmol), car-
bon tetrachloride (20 ml), acetonitrile (20 ml), and
water (10 ml) was added dropwise a brown mixture of
sodium metaperiodate (3.21 g, 15 mmol), ruthenium
chloride n-hydrate (70 mg), and water (20 ml) at 0 °C.
After being stirred at room temperature for 30 min,
4.7. 2,4-O-Isopropylidene-L-erythritol 1,3-cyclic sulfite
(15)
A solution of freshly distilled thionyl chloride (476 ll,
6.55 mmol) in dichloromethane (20 ml) was added drop-
wise to a stirred mixture of 14 (810 mg, 5.0 mmol), tri-

G. Tanabe et al. / Bioorg. Med. Chem. 15 (2007) 3926–3937
3933
Table 9. 13C NMR data of 13 in CDCl3
d observed (125 MHz)
the reaction was quenched by the addition of aqueous
d lit.5h (100 MHz)
sodium thiosulfate–sodium hydrogen carbonate
(20 ml). The resulting purple mixture was filtered off,
and the filtrate was extracted with diethyl ether. The ex-
tract was washed with brine, and evaporated to give a
colorless solid (1.1 g), to which was added successively
diethyl ether and n-hexane, and the deposited solid
was filtered off. The filtrate was evaporated to give the
title compound 13 (1.06 g, 95%) as a colorless solid,
which was pure enough for further reaction. This was
supported by the 13C NMR spectrum of the solid
(Fig. 5). Compound 13 decomposed gradually on
keeping even in a freezer. Column chromatography
(n-hexane/acetone, 5:1, n-hexane/ethyl acetate, 7:1 or
n-hexane/dichloromethane, 1:2) gave 13 in around
78–83%, and pure 13 could be kept in a freezer for few
months.
C-1
C-2
73.3
64.6
60.8
76.6
64.7
73.3
C-3
C-4
76.6
60.8
Others
18.8/28.5 [(CH3)2C],
101.1 [(CH3)2C]
18.9/28.5 [(CH3)2C],
101.1 [(CH3)2C]
pylidene moiety was also observed in the HMBC
experimental.
O
1
S
O
3
2
O
O
O
O
4
HMBC
Compound 13. Colorless prisms. Mp 91–92.5 °C (dec).
24
13
The value of the specific rotation for 13 was ½aꢁ +2.2
D
(c = 1.15, CHCl3), being inconsistent with that reported
[lit.5h [a]D = ꢀ4 (c = 1.1, CHCl3)]. In order to reconfirm
the [a]D value of 13, the enantiomer of 13, 2,4-O-isopro-
pylidene-D-erythritol-1,3-cyclic sulfate (28) was synthe-
sized as follows (Scheme 4). According to the modified
method used for the preparation of the cyclic sulfate
13, 2,4-O-isopropylidene-D-erythritol15 (27, 1.0 g,
6.17 mmol) was converted to 284a,b (1.1 g, 80%), the spe-
4.9. 2,4-O-Benzylidene-D-erythritol 1,3-cyclic sulfite (22)
Following the method used for the preparation of 15,
the diol 20 (1.6 g, 7.6 mmol) was treated with thionyl
chloride (0.7 ml, 9.6 mmol) in dichloromethane
(54 ml). Work-up gave a practical pure crude mixture
of cyclic sulfite 22 (1.96 g, a/b = ca. 1/1.6) quantitatively.
The crude 22 was immediately used in the next step
without further purification. The 1H and 13C NMR
spectra of the minor isomer 22a were in good accor-
dance with those of less polar isomer reported.4c The
downfield shift of signals due to H-1ax and H-3 of 22a
arising from anisotropy effect by the S ! O bond sug-
gested the a orientation of the oxygen in S ! O group.16
cific rotation of which is lacking in the lit.4a,b The specific
27
D
rotation of enantiomer 28 was ½aꢁ ꢀ2.43 (c = 1.25,
CHCl3), indicating that the value of the specific rotation
reported by Gallienne et al.5h was incorrect.
1
Although H and 13C NMR spectroscopic properties of
13 were in good accordance with those reported, there
appeared some incorrect assignments in the lit.5h On
the basis of two-dimensional spectroscopic studies, all
the signals were unambiguously assigned as shown in
Tables 8 and 9.
1
A mixture of the sulfite 22: H NMR (CDCl3) d: 3.88
(0.38H, dd, J = 10.6, 10.3 Hz, H-4aax), 3.91 (0.62H,
dd, J = 10.6, 10.3 Hz, H-4bax), 4.05 (0.38H, dd,
J = 10.3, 4.9 Hz, H-1aeq), 4.16 (0.38H, ddd, J = 10.9,
9.6, 4.9 Hz, H-a2), 4.26 (0.38H, dd, J = 10.6, 4.9 Hz,
H-4aeq), 4.27 (0.62H, dd, J = 11.0, 9.0 Hz, H-b1ax),
4.32 (0.62H, ddd, J = 10.3, 9.8, 4.9 Hz, H-b3), 4.39
(0.62H, dd, J = 10.6, 4.9 Hz, H-b4eq), 4.47 (0.62H,
ddd, J = 9.8, 9.0, 6.0, H-b2), 4.63 (0.62H, dd, J = 11.0,
6.0 Hz, H-b1eq), 4.83 (0.38H, dd, J = 10.9, 10.3 Hz, H-
a1ax), 5.07 (0.38H, ddd, J = 10.3, 9.6, 4.9 Hz, H-a3),
5.62, (0.62H, s, PhCHb), 5.67 (0.38H, s, PhCH-a),
7.36–7.48 (5H, m, arom.). 13C NMR (CDCl3, a/b)
d: 59.7/64.4 (C-1), 63.4/68.5 (C-3), 67.8/68.3 (C-4),
Following long-range correlation between signals due to
both methylene protons (dH 3.92 and 4.03) on C-4 and
that of the quaternary carbon (dC 101.1) of the isopro-
a,b
O
O
O
OH
O
O
O
O
S
HO
O
28
27
Scheme 4. Reagents and conditions: (a) SOCl2, Et3N, CH2Cl2, 0 °C;
(b) NaIO4, RuCl3, NaHCO3, CCl4, CH3CN, H2O, 0 °C to rt.
Table 8. 1H NMR data of 13 in CDCl3
d observed (500 MHz)
d lit.5h (400 MHz)
H-1ax
H-1eq
H-2
4.61 (dd, J = 10.6, 10.3),
4.47 (dd, J = 10.3, 4.9)
4.22 (ddd, J = 10.6, 10.1, 4.9),
4.66 (ddd, J = 10.6, 10.1, 5.2)
3.92 (dd, J = 10.9, 10.6)
4.03 (dd, J = 10.9, 5.2)
1.43/1.55 [(CH3)2C]
3.92 (dd, J = 10.3, 10.3) as H-1b
4.03 (dd, J = 10.3, 5.4) as H-1a
4.66 (td, J = 10.3, 5.4)
H-3
4.22 (td, J = 10.3, 4.8)
H-4ax
H-4eq
Others
4.61 (dd, J = 10.3, 10.3) as H-4a
4.46 (dd, J = 10.3, 4.8) as H-4b
1.43/1.55 [(CH3)2C]

3934
G. Tanabe et al. / Bioorg. Med. Chem. 15 (2007) 3926–3937
72.1/ 73.3 (C-2), 102.0/102.5 (PhCH2), 126.0/126.1/
128.4/129.5 (d, arom.), 136.2/136.3 (s, arom.).
H-20), 4.41 (1H, br s-like, H-3), 4.63 (1H, br s-like, H-
2). 13C NMR (CD3OD) d: 19.7/28.4 [(CH3)2C], 49.5
(C-10), 51.4 (C-1), 60.9 (C-5), 63.3 (C-40), 70.4 (C-20),
71.1 (C-30), 74.0 (C-4), 79.3 (C-2), 79.9 (C-3),
101.4 [(CH3)2C]. FABMS m/z: 375 [M+H]+ (pos.),
FABHRMS m/z: 375.0767 (C12H23O9S2 requires
375.0783).
4.10. 2,4-O-Benzylidene-D-erythritol 1,3-cyclic sulfate
(23)
Following the method used for the preparation of 13,
the crude 22 (1.96 g) was oxidized with ruthenium
tetroxide generated in situ from sodium metaperiodate
(4.8 g, 22.4 mmol) and ruthenium chloride n-hydrate
(80 mg) in the presence of sodium bicarbonate (1.9 g,
22.6 mmol). Work-up in a manner similar to that used
for the preparation of 13 gave the title compound 23
as a colorless solid (1.9 g, 92%), which was pure enough
for further reaction. This was supported by the 13C
NMR spectrum of the crude 23 as shown in Figure 7.
Purification of the crude 23 on column chromatography
(n-hexane/CH2Cl2, 1:2) gave 23 (1.82 g, 88%) as a color-
less solid. The 1H and 13C NMR spectroscopic
properties of 23 were in good accordance with those
reported.4c
Following the method A, a mixture of L-16 (150 mg,
1.0 mmol), 13 (336 mg, 1.5 mmol), sodium carbonate
(318 mg, 2.8 mmol), and DMF (500 ll) was stirred at
45 °C for 60 h. Work-up gave a pale brown oil
(501 mg), which on column chromatography (AcOEt/
MeOH, 4:1 to 2:1) gave 1,4-dideoxy-1,4-{(R)-[(2S,3S)-
2,4-O-isopropylidene-3-(sulfooxy)butyl]episulfoniumy-
lidene}-L-arabinitol inner salt (25, 218 mg, 58%).
24
Compound 25. Pale yellow oil. ½aꢁ +64.9 (c = 1.0,
D
CH3OH). IR (neat): 3364, 1651, 1223, 1163, 1081,
1
1005 cmꢀ1. H NMR (CD3OD) d: 1.41/1.53 [each 3H,
s, (CH3)2C], 3.81 (1H, dd, J = 12.9, 3.5 Hz, H-1a), 3.84
(1H, dd, J = 12.9, 2.3 Hz, H-1b), 3.85 (1H, dd,
J = 11.8, 9.2 Hz, H-40a), 3.90 (1H, dd, J = 13.5,
6.6 Hz, H-10a), 3.97 (1H, dd, J = 11.8, 8.0 Hz, H-5a),
3.98 (1H, dd, J = 13.5, 3.5 Hz, H-10b), 4.01 (1H, dd,
J = 11.8, 5.7 Hz, H-5b), 4.07 (1H, br dd, J = 8.0,
5.7 Hz, H-4), 4.09 (1H, dd, J = 11.8, 5.5 Hz, H-40b),
4.24 (1H, ddd, J = 9.5, 9.2, 5.5 Hz, H-30), 4.35 (1H,
ddd, J = 9.5, 6.6, 3.5 Hz, H-20), 4.44 (1H, dd, J = 2.6,
1.7 Hz, H-3), 4.63 (1H, ddd, J = 3.5, 2.6, 2.3, H-2). 13C
NMR (CD3OD) d: 19.7/28.4 [(CH3)2C], 49.3 (C-10),
51.7 (C-1), 60.8 (C-5), 63.3 (C-40), 70.7 (C-20), 71.2 (C-
30), 73.0 (C-4), 79.4 (C-2), 79.9 (C-3), 101.4 [(CH3)2C].
FABMS m/z: 375 [M+H]+ (pos.), FABHRMS m/z:
375.0757 (C12H23O9S2 requires 375.0783).
Compound 23. Colorless prisms. Mp 129–130 °C (dec).
22
Lit.4c 115–125 °C (dec). ½aꢁ +6.4 (c = 1.14, CHCl3),
D
lit.4c [a]D +4 (c = 1.0, CHCl3). 1H NMR (CDCl3) d:
3.96 (1H, dd, J = 10.5, 10.0 Hz, H-4ax), 4.22 (1H, ddd,
J = 10.5, 9.5, 5.0 Hz, H-2), 4.45 (1H, dd, J = 10.5,
5.0 Hz, H-4eq), 4.62 (1H, dd, J = 10.5, 5.0 Hz, H-1eq),
4.76 (1H, dd, J = 10.5, 10.5 Hz, H-1ax), 4.85 (1H, ddd,
J = 10.0, 9.5, 5.0 Hz, H-3), 5.63 (1H, s, PhCH2), 7.36–
7.47 (5H, m, arom.). 13C NMR (CDCl3) d: 67.3 (C-4),
71.5 (C-2), 72.5 (C-1), 75.1 (C-3), 102.7 (PhCH2),
126.2/128.5/ 129.8 (d, arom.), 135.6 (s, arom.).
4.11. Coupling reaction between cyclic sulfate and
thiosugars
4.11.2. Method B.
A mixture of D-18 (840 mg,
According to the literature, the cyclic sulfate 13 was
treated with thiosugars D-16, L-16, and L-18 in
either DMF4a or 1,1,1,3,3,3-hexafluoroisopropanol4b,c
(HFIP).
2.0 mmol), 13 (672 mg, 3 mmol), potassium carbonate
(55 mg, 0.4 mmol), and HFIP (2 ml) was heated under
reflux for 6 h. After removal of the solvent in vacuo,
the residue (20 mg) was purified on column chromatog-
raphy (CHCl3/EtOH, 20:1) to give 2,3,5-tri-O-benzyl-
1,4-dideoxy-1,4-{(S)-[(2S,3S)-2,4-O-isopropylidene-3-
(sulfooxy)butyl]episulfoniumylidene}-D-arabinitol inner
salt (26, 1.27 g, 99%).
4.11.1. Method A.
A mixture of D-16 (100 mg,
0.67 mmol), 13 (224 mg, 1.0 mmol), sodium carbonate
(212 mg, 2.0 mmol), and DMF (300 ll) was stirred at
45 °C for 63 h. The reaction mixture was diluted with
methanol (10 ml), and solid material was filtered off.
The filtrate was concentrated in vacuo, and the residue
was triturated with diethyl ether to give a pale brown
oil (310 mg), which on column chromatography
(AcOEt/MeOH/H2O, 20:4:1) gave 1,4-dideoxy-1,4-{(S)-
[(2S,3S)-2,4-O-isopropylidene-3-(sulfooxy)butyl]epis-
ulfoniumylidene}-D-arabinitol inner salt (24, 163 mg,
65%).
24
Compound 26. Amorphous solid. ½aꢁ ꢀ16.3 (c = 1.56,
D
1
CHCl3). IR (CHCl3): 1215, 1092, 1018 cmꢀ1. H NMR
(CDCl3, 500 MHz) d: 1.26/1.45 (each 3H, s, C(CH3)2),
3.68 (1H, dd, J = 9.8, 8.3 Hz, H-5a), 3.73 (1H, dd,
J = 9.8, 6.9 Hz, H-5b), 3.78 (1H, dd, J = 11.5, 10.0 Hz,
H-40a), 3.90 (2H, br dd-like, J = ca. 13.0, 3.4 Hz, H-
1a, H-10a), 3.99 (1H, br dd, J = 8.3, 6.9 Hz, H-4), 4.04
(1H, dd, J = 13.0, 1.5 Hz, H-1b), 4.14 (1H, dd,
J = 11.5, 5.8 Hz, H-40b), 4.28 (ddd, 1H, J = 10.0, 3.4,
2.3 Hz, H-20), 4.33 (1H, dd, J = 13.0, 2.3 Hz, H-10b),
4.34 (1H, br s, H-3), 4.41 (1H, d, J = 11.8 Hz, PhCH2),
4.44 (1H, d, J = 12.0 Hz, PhCH2), 4.49 (1H, td, J = 10.0,
5.8 Hz, H-30), 4.50 (1H, d, J = 11.8 Hz, PhCH2), 4.52
(1H, d, J = 12.0 Hz, PhCH2), 4.55 (1H, dd,
J = 12.0 Hz, PhCH2), 4.63 (1H br s, H-2), 4.65 (1H,
dd, J = 12.0 Hz, PhCH2), 7.14–7.38 (15H, m, arom.)
13C NMR (CDCl3, 125 MHz) d: 19.0/28.3 [C(CH3)2],
20
Compound 24. Pale yellow oil. ½aꢁ +28.1 (c = 3.37,
D
CH3OH). IR (neat): 3499, 3225, 1381, 1281, 1200,
1161, 1126, 1087, 1007 cmꢀ1 1H NMR (CD3OD) d:
.
1.41/1.52 [each 3H, s, (CH3)2C], 3.76–3.89 (4H, m, H-
1a, H-1b, H-10a, H-40a), 3.93 (1H, dd, J = 9.5, 7.7 Hz,
H-5a), 3.96–4.06 (3H, m, H-4, H-5b, H-10b), 4.08 (1H,
dd, J = 11.5, 5.5 Hz, H-40b), 4.28 (1H, ddd, J = 8.9,
8.9, 5.5 Hz, H-30), 4.33 (1H, ddd, J = 8.9, 6.3, 3.2 Hz,

G. Tanabe et al. / Bioorg. Med. Chem. 15 (2007) 3926–3937
3935
47.4 (C-1), 49.7 (C-10), 62.3 (C-40), 65.4 (C-4), 66.6 (C-
4.14. De-O-sulfonation of salacinol (1a) and the Diaste-
reomer (11)
5), 67.2 (C-30), 69.7 (C-20), 72.1/72.3/73.6 (PhCH2),
82.3 (C-2), 83.1 (C-3), 99.7 [C(CH3)2], 127.9/128.0/
128.2/128.3/128.4/128.5/128.58/128.63/128.7 (d, arom.),
136.05/136.14/136.5 (s, arom.). FABMS m/z: 645
[M+H]+ (pos.). FABHRMS m/z: 645.2220 (C33H41
O9S2 requires 645.2192).
A mixture of salacinol (1a, 28 mg, 0.08 mmol) and 5%
methanolic hydrogen chloride (0.6 ml) was stirred at
45 °C for 3 h. After removal of the solvent, the residue
(29 mg) was purified on column chromatography
(AcOEt/MeOH/H2O, 10:4:1) to give 1,4-dideoxy-1,4-
{(R)-[(2S,3S)-2,3,4-trihydroxybutyl]episulfoniumyl-idene}-
D-arabinitol methyl sulfate (10a, 26.5 mg, 86%) as a
colorless oil.
4.12. 1,4-Dideoxy-1,4-{(S)-[(2S,3S)-2,4-dihydroxy-3-
(sulfooxy)butyl]episulfoniumylidene}-D-arabinitol inner
salt (salacinol 1a)
20
Compound 10a Colorless oil. ½aꢁ +3.6 (c = 1.08,
.
1042, 1007 cmꢀ1 1H NMR (CD3OD) d: 3.59–3.62
D
CH3OH). IR (neat): 3360, 1651, 1420, 1207, 1072,
4.12.1. Method A. A solution of 24 (77 mg, 0.2 mmol)
and 0.2% hydrochloric acid (1 ml) was stirred at 40 °C
for 4 h. After neutralization of the reaction mixture with
ion exchange resin (IRA-67), the resin was filtered off.
The filtrate was concentrated in vacuo. The residue
(67 mg) was purified on column chromatography
(AcOEt/MeOH/H2O, 20:4:1) to give salacinol (1a,
50 mg, 74%) as a colorless solid.
(1H, m, H-30), 3.62 (1H, dd, J = 13.4, 5.2 Hz, H-40a),
3.68 [3 H, s, ðCH3OSO3ꢀ)], 3.69 (1H, dd, J = 13.4,
3.8 Hz, H-40b), 3.73 (1H, dd, J = 13.1, 8.9 Hz, H-10a),
3.85 (1H, dd, J = 13.1, 3.4 Hz, H-10b), 3.86 (2H, m, H-
1a, H-1b), 3.93 (1H, dd, J = 11.0, 8.9 Hz, H-5a), 4.02
(1H, br dd, J = 8.9, 5.2 Hz, H-4), 4.05 (1H, dd,
J = 11.0, 5.2 Hz, H-5b), 4.09 (1H, ddd, J = 8.9, 6.5,
3.4 Hz, H-20), 4.38 (1H, dd, J = 2.4, 1.4 Hz, H-3), 4.63
(1H, ddd-like, J = ca. 2.4, 2.4, 2.4 Hz, H-2). 13C NMR
(CD3OD) d: 51.8 (C-10), 52.0 (C-1), 55.2 ðCH3OSO3ꢀÞ,
61.0 (C-5), 64.0 (C-40), 69.6 (C-20), 73.6 (C-4), 75.3 (C-
30), 79.4 (C-2), 79.5 (C-3). FABMS m/z: 255
[MꢀCH3OSO3]+ (pos.), 111 [CH3OSO3]ꢀ (neg.). FAB-
HRMS m/z: 255.0912 (C9H19O6S requires 255.0902).
4.12.2. Method B. A suspension of 10% palladium-on-
carbon (100 mg) in 90% aqueous acetic acid (6 ml)
was pre-equilibrated with hydrogen. To the suspen-
sion was added a solution of 26 (200 mg, 0.31 mmol)
in 90% aqueous acetic acid (8 ml), and the mixture
was hydrogenated at 50 °C for 5 h. The catalyst
was filtered off, and the filtrate was evaporated to
give a colorless oil (118 mg), which on column chro-
matography (CHCl3/MeOH/H2O, 12:8:1) gave 1a
(84 mg, 82%).
Following the method used for de-O-sulfonation of sal-
acinol (1a), a mixture of 11 (30 mg, 0.09 mmol) and 5%
methanolic hydrogen chloride (0.6 ml) was stirred at
40 °C for 4 h. Work-up gave a pale brown oil (34 mg),
which on column chromatography (AcOEt/MeOH/
H2O, 10:4:1) gave 1,4-dideoxy-1,4-{(S)-[(2S,3S)-2,3,4-
trihydroxybutyl]episulfoniumylidene}-L-arabinitol methyl
sulfate (12a, 26 mg, 79%) as a colorless oil.
4.13. 1,4-Dideoxy-1,4-{(R)-[(2S,3S)-2,4-dihydroxy-3-
(sulfooxy)butyl]episulfoniumylidene}-L-arabinitol inner
salt (11)
Compound 25 (120 mg, 0.32 mmol) was treated in a
manner similar to that used for hydrolysis of 24.
Work-up gave a colorless oil (117 mg), which on column
chromatography (AcOEt/MeOH/H2O, 20:4:1) gave 11
(95 mg, 89%) as a colorless solid.
23
Compound 12a. Colorless oil. ½aꢁ +62.5 (c = 1.0,
D
CH3OH). IR (neat): 3199, 1651, 1421, 1204, 1051,
1
1003 cmꢀ1. H NMR (CD3OD) d: 3.60–3.65 (2H, m,
H-30, H-40a), 3.68 [3H, s, ðCH3OSO3ꢀÞ], 3.69 (1H, dd,
J = 12.7, 5.5 Hz, H-40b), 3.77–3.82 (2H, br d-like,
J = ca. 5.8 Hz, H-10a, H-10b), 3.82 (2H, d-like,
J = 2.8 Hz, H-1a, H-1b), 3.95 (1H, dd, J = 11.7,
8.9 Hz, H-5a), 4.03 (1H, dd, J = 11.7, 5.8 Hz, H-5b),
4.05–4.13 (2H, m, H-4, H-20), 4.40 (1H, dd, J = 2.4,
1.4 Hz, H-3), 4.62 (1H, ddd-like, J = ca. 2.4, 2.4,
2.4 Hz, H-2). 13C NMR (CD3OD) d: 50.8 (C-1), 51.4
(C-10), 55.1 ðCH3OSO3ꢀÞ, 61.1 (C-5), 64.0 (C-40), 69.5
(C-20), 73.5 (C-4), 75.1 (C-30), 79.4 (C-2), 79.7 (C-3).
FABMS m/z: 255 [MꢀCH3OSO3]+ (pos.), 111
[CH3OSO3]ꢀ (neg.). FABHRMS m/z: 255.0891
(C9H19O6S requires 255.0902).
Compound 11. Colorless plates. Mp 150–152 °C (from
24
aq MeOH). ½aꢁ +35.5 (c = 1.0, MeOH), lit.4a ½aꢁ
24
D
24
D
ꢀ25.2 (c =1.17, MeOH for the enantiomer), lit.4c½aꢁ
D
ꢀ35.6 (c = 0.86, MeOH for the enantiomer). IR
(KBr): 3348, 1265, 1215, 1080, 1049, 1018 cmꢀ1. FAB-
MS m/z: 335 [M+H]+ (pos.). FABHRMS m/z:
335.0466 (C9H19O9S2 requires 355.0451). 1H NMR
spectroscopic properties of compound 11 were in ac-
cord with those of the corresponding emantiomer re-
ported.4a,c The two close signals at dc 79.2 (C-30) and
79.3 (C-3) observed in the 13C NMR (150 MHz) spec-
trum of 13a were unambiguously assigned on the basis
of two-dimensional NMR spectroscopic studies, and
the reported assignments4c for signals due to two
methine carbons [dc 79.38 (C-3) and 79.46 (C-30)] of
the corresponding enantiomer were found interchanged
with each other. 13C NMR (pyridine-d5) d: 51.0 (C-1),
52.7 (C-10), 60.2 (C-5), 62.0 (C-40), 67.4 (C-20), 71.9 (C-
4), 79.0 (C-2), 79.2 (C-30), 79.3 (C-3).
4.15. 1,4-Dideoxy-1,4-{(R)-[(2S,3S)-2,3,4-trihydroxy
butyl]episulfoniumylidene}-D-arabinitol chloride (10b)
A mixture of 10a (16 mg, 0.04 mmol), ion exchange resin
IRA-400J (Clꢀ form, 290 mg), methanol (0.3 ml), and
water (0.5 ml) was stirred at room temperature for
12 h. The resin was filtered off, and the filtrate was

3936
G. Tanabe et al. / Bioorg. Med. Chem. 15 (2007) 3926–3937
3. Yoshikawa, M.; Murakami, T.; Yashiro, K.; Matsuda, H.
Chem. Pharm. Bull. 1998, 46, 1339.
evaporated to give a pale yellow oil (15 mg), which on
column chromatography (AcOEt/MeOH/H2O, 6:4:1)
gave 10b (12.2 mg, 96%).
4. (a) Yuasa, H.; Takada, J.; Hashimoto, H. Tetrahedron
Lett. 2000, 41, 6615; (b) Hashimoto, H.; Yuasa, H.;
Takada, J. 2002, JP 2002179673. Chem. Abstr. 2002, 137,
63418; (c) Ghavami, A.; Johnston, B. D.; Pinto, B. M.
J. Org. Chem. 2001, 66, 2312; (d) Ghavami, A.; Sadala-
pure, K. S.; Johnston, B. D.; Lobera, M.; Snider, B. B.;
Pinto, B. M. Synlett 2003, 1259.
20
D
Compound 10b. Colorless oil. ½aꢁ
+5.9 (c = 0.8,
CH3OH). IR (neat): 3325, 1651, 1420, 1261, 1209,
1076 cmꢀ1. H NMR (CD3OD) d: 3.58–3.62 (1H, m,
1
H-30), 3.62 (1H, dd, J = 12.9, 5.2 Hz, H-40a), 3.68 (1H,
dd, J = 12.9, 5.7 Hz, H-40b), 3.73 (1H, dd, J = 13.2,
8.9 Hz, H-10a), 3.85 (1H, dd, J = 13.2, 3.2 Hz, H-10b),
3.86 (2H, m, H-1a, H-1b), 3.92 (1H, dd, J = 10.3,
8.6 Hz, H-5a), 4.02 (1H, br dd, J = 8.6, 5.5 Hz, H-4),
4.05 (1H, dd, J = 10.3, 5.5 Hz, H-5b), 4.09 (1H, ddd,
J = 8.9, 6.3, 3.2 Hz, H-20), 4.37 (1H, d-like, J = ca.
1.5 Hz, H-3), 4.62 (1H, br d-like, J = ca. 2.3 Hz, H-2).
13C NMR (CD3OD) d: 51.8 (C-10), 52.1 (C-1), 61.0
(C-5), 64.0 (C-40), 69.6 (C-20), 73.7 (C-4), 75.3 (C-30),
79.4 (C-2), 79.5 (C-3). FABMS m/z: 255 [MꢀCl]+
(pos.). FABHRMS m/z: 255.0915 (C9H19O6S requires
255.0902).
5. (a) Muraoka, O.; Ying, S.; Yoshikai, K.; Matsuura, Y.;
Yamada, E.; Minematsu, T.; Tanabe, G.; Matsuda, H.;
Yoshikawa, M. Chem. Pharm. Bull. 2001, 49, 1503; (b)
Yuasa, H.; Takada, J.; Hashimoto, H. Bioorg. Med.
Chem. Lett. 2001, 11, 1137; (c) Ghavami, A.; Johnston,
B. D.; Jensen, M. T.; Svensson, B.; Pinto, B. M. J. Am.
Chem. Soc. 2001, 123, 6268; (d) Yuasa, H.; Izumi, M.;
Hashimoto, H. Yuki Gosei Kagaku Kyokaishi 2002, 60,
774, Chem. Abstr. 2002, 138, 122763; (e) Johnston, B.
D.; Ghavami, A.; Jensen, M. T.; Svensson, B.; Pinto, B.
M. J. Am. Chem. Soc. 2002, 124, 8245; (f) Ghavami, A.;
Johnston, B. D.; Maddess, M. D.; Chinapoo, S. M.;
Jensen, M. T.; Svensson, B.; Pinto, B. M. Can. J. Chem.
2002, 80, 937; (g) Szczepina, M. G.; Johnston, B. D.;
Yuan, Y.; Svensson, B.; Pinto, B. M. J. Am. Chem. Soc.
2004, 126, 12458; (h) Gallienne, E.; Benazza, M.;
Demailly, G.; Bolte, J.; Lemaire, M. Tetrahedron 2005,
61, 4557; (i) Kuntz, D. A.; Ghavami, A.; Johnston, B.
D.; Pinto, B. M.; Rose, D. R. Tetrahedron: Asymmetry.
2005, 16, 25; (j) Liu, H.; Pinto, B. M. J. Org. Chem.
2005, 70, 753; (k) Kumar, N. S.; Pinto, B. M.
Carbohydr. Res. 2005, 340, 2612; (l) Gallienne, E.;
Gefflaut, T.; Bolte, J.; Lemaire, M. J. Org. Chem. 2006,
71, 894; (m) Johnston, B. D.; Jensen, H. H.; Pinto, B.
M. J. Org. Chem. 2006, 71, 1111; (n) Liu, H.; Sim, L.;
Rose, D. R.; Pinto, B. M. J. Org. Chem. 2006, 71, 3007;
(o) Choubdar, N.; Pinto, B. M. J. Org. Chem. 2006, 71,
4671; (p) Liu, H.; Pinto, B. M. Can. J. Chem. 2006, 84,
497.
4.16. Enzyme inhibition assays
Rat small intestinal brush border membrane vesicles
were prepared and its suspension in 0.1 M maleate
buffer (pH 6.0) was used as small intestinal a-glucosi-
dase of maltase and sucrase. Test compound was dis-
solved in dimethylsulfoxide DMSO, and the resulting
solution was diluted with 0.1 M maleate buffer to pre-
pare the test compound solution (concentration of
DMSO: 10%). The substrate solution in the maleate
buffer (maltose, 74 mM; sucrose, 74 mM, 100 ll), test
compound solution (50 ll), and the enzyme solution
(50 ll) were mixed and incubated at 37 °C for
30 min. After incubation, the solution was mixed with
water (0.8 ml) and was immediately heated by boiling
water for 2 min to stop the reaction. Glucose concen-
tration was then determined by the glucose-oxidase
method. Final concentration of DMSO in test solution
was 2.5% and no influence of DMSO was detected on
the inhibitory activity.
6. Krasikov, V. V.; Karelov, D. V.; Firsov, L. M. Biochem-
istry (Moscow) 2001, 66, 267; Knapp, S.; Choe, Y. H.;
Reilly, E. Tetrahedron Lett. 1993, 34, 4443.
7. (a) Muraoka, O.; Yoshikai, K.; Takahashi, H.; Minem-
atsu, T.; Lu, G.; Tanabe, G.; Wang, T.; Matsuda, H.;
Yoshikawa, M. Bioorg. Med. Chem. 2006, 14, 500; (b)
Matsuda, H.; Yoshikawa, M.; Morikawa, T.; Tanabe,
G.; Muraoka, O. J. Trad. Med 2005, 22(suppl. 1), 145,
Part of this work has been patented; Muraoka, O.;
Yoshikawa, M.; Tanabe, G.; Matsuda, H. JP
2003167786; WO 2004111028. Chem. Abstr. 2004,
142:74438.
Acknowledgments
This study was supported in part by a Grant-in-Aid for
Scientific Research from the Japan Society of the Pro-
motion of Science. The authors also thank Pharmaceu-
tical Research and Technology Institute of Kinki
University for financial support.
8. Yoshimura, Y.; Kitano, K.; Yamada, K.; Satoh, H.;
Watanabe, M.; Miura, S.; Sakata, S.; Sasaki, T.;
Matsuda, A. J. Org. Chem. 1997, 62, 3140; Yoshimura,
Y.; Kitano, K.; Satoh, H.; Watanabe, M.; Miura, S.;
Sakata, S.; Sasaki, T.; Matsuda, A. J. Org. Chem. 1996,
61, 882.
9. Satoh, H.; Yoshimura, Y.; Sakata, S.; Miura, S.; Machida,
H.; Matsuda, A. Bioorg. Med. Chem. Lett. 1998, 8, 989.
10. Yuasa, H.; Kajimoto, T.; Wong, H. C. Tetrahedron Lett.
1994, 35, 8243.
References and notes
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Chem. 2002, 10, 1547.
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3937
Lett. 1989, 30, 566–658; Lohray, B. B. Synthesis 1992,
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14. a-Glucosidase inhibitory activities of 10a, 10b, 11 and 12a
were measured according to the method described in the
literature.1,7a
15. Wolfrom, M. L.; Diwadkar, A. B.; Gelas, J.; Horton, D.
Carbohydr. Res. 1974, 35, 87; Kiso, M.; Hasegawa, A.
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