Synthesis of C-5-thioglycopyranosides and their sulfonium derivatives from 1-C-(2′-oxoalkyl)-5-S-acetylglycofuranosides

Article abstract of DOI:10.1016/j.carres.2004.11.014

1-C-(2′-oxoalkyl)-5-S-acetylglycofuranosides of l-arabinose, d-ribose, and d-xylose were converted to 1-C-(2′-oxoalkyl)-5- thioglycopyranosides by base treatment. The transformation was achieved through β-elimination to an acyclic α,β-conjugated aldehyde (ketone or ester), followed by an intramolecular hetero-Michael addition by the 5-thiol group. The cycloaddition was highly stereoselective in favor of an equatorial 1-C-substitution. The resultant C-5-thioglycopyranosides were further converted to the sulfonium salts by treatment with cyclic sulfate and methyl iodide. Two sulfonium isomers were obtained due to the presence of both S-axial and S-equatorial substitutions. We observed that the chemical shifts of both C-1 and C-5 in the S-axial substituted sulfonium sugars are always shifted up-field (5-10 ppm) in comparison to those in the S-equatorial substitutions (δ_C 49-53 ppm vs 42-45 ppm at C-1 and 37-42 ppm vs 32-35 ppm at C-5), which provides an easy way for determination of the stereochemistry. Crown Copyright

Full text of DOI:10.1016/j.carres.2004.11.014

Carbohydrate
RESEARCH
Carbohydrate Research 340 (2005) 235–244
Synthesis of C-5-thioglycopyranosides and their sulfonium
derivatives from 1-C-(20-oxoalkyl)-5-S-acetylglycofuranosides
Tian Yi,a Shih-Hsiung Wub and Wei Zoua,*
aInstitute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario, Canada K1A 0R6
bInstitute of Biological Chemistry, Academia Sinica, Taipei 115, Taiwan
Received 13 September 2004; accepted 18 November 2004
Available online 18 December 2004
Abstract—1-C-(20-oxoalkyl)-5-S-acetylglycofuranosides of L-arabinose, D-ribose, and D-xylose were converted to 1-C-(20-oxoalkyl)-
5-thioglycopyranosides by base treatment. The transformation was achieved through b-elimination to an acyclic a,b-conjugated
aldehyde (ketone or ester), followed by an intramolecular hetero-Michael addition by the 5-thiol group. The cycloaddition was
highly stereoselective in favor of an equatorial 1-C-substitution. The resultant C-5-thioglycopyranosides were further converted
to the sulfonium salts by treatment with cyclic sulfate and methyl iodide. Two sulfonium isomers were obtained due to the presence
of both S-axial and S-equatorial substitutions. We observed that the chemical shifts of both C-1 and C-5 in the S-axial substituted
sulfonium sugars are always shifted up-field (5–10 ppm) in comparison to those in the S-equatorial substitutions (dC 49–53 ppm vs
42–45 ppm at C-1 and 37–42 ppm vs 32–35 ppm at C-5), which provides an easy way for determination of the stereochemistry.
Crown Copyright ꢀ 2004 Published by Elsevier Ltd. All rights reserved.
Keywords: Synthesis; Thiosugar; C-Glycoside; Sulfonium; Inhibitor; NMR spectroscopy
1. Introduction
metabolic instability.8 On the other hand, metabolically
stable C-glycosides can mimic the O-glycosides in terms
of their binding to natural ligands and the solution con-
formation.9 Hence, the C-glycosyl compounds were
designed as possible enzyme inhibitors.10 It is therefore
reasonable to propose that the C-5-thioglycosides may
be potentially better gylcosyl receptors and/or glycosi-
dase inhibitors. Thus far, synthetic methods to C-5-thio-
glycosides are very limited. Praly and co-workers
reported an electrophilic C-glycosylation using trichlo-
roacetamide of thioxylopyranoside,11 and Hashimoto
and co-workers prepared C-5-thioglycosides by a thio-
glycosyl radical addition.12 More recently, Grignard
and Wittig reactions to thiosugars were used for the
C-5-thioglycoside synthesis.8 In a preliminary report,13
we have described the synthesis of C-5-thioglycosides
from 1-C-(20-oxoalkyl)-4/5-S-acetylglycosides as illus-
trated in Scheme 1. Here, we report the synthesis of C-
5-thioglycosides from D-ribose and D-xylose and the
further transformation of these thiosugars into their
sulfonium derivatives.
Thiosugars are important intermediates to some nucleo-
tide-based antiviral and anticancer agents, and numer-
ous methods for their synthesis have been developed in
the last two decades.1 Although thiosugars are less
potent glycosidase inhibitors than iminosugars,2 the
sulfonium salts of thiosugars such as salacinol3 and
kotalanol4 are potent glucosidase inhibitors that have
traditionally been used for the treatment of diabetes in
India and Sri Lanka.5 The synthesis of those sulfonium
salts and their analogs has attracted considerable atten-
tion in the last few years.6 Thiosugars have also been
used as competitive glycosyl receptors instead of the
enzyme inhibitors, for example, 1,5-dithio-b-D-xylopyr-
anoside is used for the treatment of thrombosis as a
competitive substrate in glycosaminoglycan biosynthe-
sis.7 One of the drawbacks of this compound is its
*
Corresponding author. Tel.: +1 613 991 0855; fax: +1 613 952 9092;
e-mail: wei.zou@nrc-cnrc.gc.ca
0008-6215/$ - see front matter Crown Copyright ꢀ 2004 Published by Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2004.11.014

236
T. Yi et al. / Carbohydrate Research 340 (2005) 235–244
OH
BnO
R
OBn
OBn
HO
S
O
SH
ref.13
O
L-arabinose
O
O
AcS
OBn
OBn
OBn
R = H, Me
R
R
Scheme 1.
2. Results and discussion
namically stable b anomers as the major products and
the a-C-glycosides as the minor products,16 which were
inseparable by silica gel chromatography. According
to HNMR analysis, the ratio of two isomers was esti-
mated to be b:a > 10:1 (Scheme 2).
Methyl tri-O-benzyl-a/b-glycofuranosides 1 and 214 ob-
tained from D-ribose and D-xylose were converted to
respective C-allyl glycosides 3 and 4 by treatment with
allyltrimethylsilane–TMSOTf,15 which were further sub-
jected to selective 5-O-acetolysis using 0.2% H2SO4–
Ac2O to afford 5 and 6 in 60–80% yield. Removal of
the acetyl group from the 5-position of 5 and 6 was fol-
lowed by 5-O-mesylation (MsCl–Et3N) and 5-AcS
substitution (KSAc–DMF) to give 1-C-allyl-5-S-acetyl-
furanosides 7 and 8 in 40–60% overall yield. 20-
Aldehydes 9 and 10 were then derived from 7 and 8
by ozonolysis (O3 and Zn–HOAc) in 70–80% yield.
Upon treatment of compounds 9 and 10 with 2%
NaOMe in MeOHat 0 ꢁC to room temperature for
4 h, 1-C-(20-carbonylmethyl)-5-thio-b-D-glycopyrano-
sides 11 and 12 were obtained, respectively, in ca. 70%
yield. As expected, the reactions provided thermody-
1
We expect the same chemistry also applicable to 1-
C-(methoxycarbonylmethyl)-5-S-acetylglycosides. Thus,
we prepared ester 13 from C-allyl glycoside 6 (38%) in
three steps: (1) oxidation of the allyl group to the alde-
hyde by ozonolysis; (2) further oxidation of the aldehyde
with KMnO4 in acetone–water to a carboxylic acid;17
and (3) esterification with MeI in NaHCO3–DMF.
The 5-O-Ac group of 13 was then transformed to 5-S-
Ac to give 14 following the same procedures as de-
scribed for the preparation of 7 and 8. Finally, treatment
of 14 with 4% NaOMe in MeOHat room temperature
overnight provided the desired 15 stereospecifically in
54% yield (see Scheme 3). Although both the Wittig
reaction to the lactol and the b-elimination of 14 pro-
R1
R1
R1
BnO
BnO
AcO
O
O
O
OMe
b
a
OBn
OBn
OBn
R2
R2
R2
1 R1 = H, R2 = OBn
2 R1 = OBn, R2 = H
3 R1 = H, R2 = OBn (α only)
4 R1 = OBn, R2 = H
5 R1 = H, R2 = OBn (α only)
6 R1 = OBn, R2 = H
S
R1
HO
AcS
R1
AcS
c,d,e
R1
O
O
g
O
f
OBn
O
R2
β/α > 10:1
OBn
R2
OBn
R2
7 R1 = H, R2 = OBn (α only)
9 R1 = H, R2 = OBn (α only)
10 R1 = OBn, R2 = H
11 R1 = H, R2 = OBn
12 R1 = OBn, R2 = H
8 R1 = OBn, R2 = H
Scheme 2. Reagents and conditions: (a) allyl-SiMe3–TMSOTf in MeCN, ꢀ40 ꢁC to room temperature, 80%; (b) 0.2% H2SO4–Ac2O, room
temperature, overnight, 60–80%; (c) 0.4% MeONa–MeOH, room temperature, 2 h; (d) MsCl–Et3N in CH2Cl2, 0 ꢁC to room temperature, overnight,
86%; (e) KSAc in DMF, 80 ꢁC, overnight, 74%; (f) O3 in CH2Cl2, ꢀ78 ꢁC, 30 min, then, Zn–HOAc, 2 h, room temperature, 70%; (g) 2% MeONa–
MeOH, 0 ꢁC to room temperature, 4 h, 71%.
OBn
OBn
AcO
AcS
S
O
O
HO
BnO
d,e
a,b,c
f
6
CO2Me
CO2Me
CO2Me
OBn
OBn
OBn
15 (β only)
14
13
Scheme 3. Reagents and conditions: (a) O3 in CH2Cl2, then, Zn–HOAc, 67%; (b) KMnO4 in 1:1 acetone–H2O, 92%; (c) MeI–NaHCO3 in DMF,
61%; (d) 2% NaOMe–MeOH, then, MsCl–Et3N in CH2Cl2, 77%; (e) KSAc in DMF, 80 ꢁC, 74%; (f) 4% MeONa–MeOH, overnight, 54%.

T. Yi et al. / Carbohydrate Research 340 (2005) 235–244
237
-
ation to give 18 and 19 in ca. 60% yield. The respective
sulfonium inner salts were then prepared by coupling 18
and 19 with 2,4-O-benzylidene-D-erythritol-1,3-cyclic
sulfate (see Scheme 5) in 1,1,1,3,3,3-hexafluoro-2-propan-
ol (HFIP) using the method of Pinto and co-workers6d
to afford 20 and 21 in 75–85% yield. The polar solvent
HFIP was critical to the coupling reaction. Pinto and
co-workers have proposed that the increased reactivity
was due to better solvation by HFIP of the polar transi-
tion states.6 Unlike the trans-selectivity obtained in the
coupling reaction between the cyclic sulfate and 4-thio-
glycofuranosides,6 sulfonium salts 20 and 21 from 5-
thioglycopyranosides were obtained as a mixture of
two isomers in a ratio of about 1:1 based on NMR analy-
sis.20 One was axially substituted at the S-atom, and
the other was equatorially substituted. We were able
to obtain one pure compound, 20-ax, by chromatogra-
phy and determine its stereochemistry by NOE analysis
as illustrated in Figure 1. Catalytic hydrogenation of 20
and 21 produced 22 and 23 in 61% and 45% yield,
respectively.
In addition to the sulfonium inner salts, the methyl
sulfonium salts of thiosugars also inhibit some glycosi-
dases.19a Thus, we prepared methyl sulfonium salts (24
and 25) by treatment of thiosugars (18 and 19) with
MeI–AgClO4 (see Scheme 6) in excellent yield. Surpris-
ingly, both reactions were stereoselective, and only one
isomer (24 and 25) was formed, respectively, in each
case. However, NOE analysis (see Fig. 1) indicated the
methyl group in 24 is equatorial, while methyl group
in 25 was axially oriented. After removal of benzyl
groups by catalytic hydrogenation, the sulfonium salts
26 and 27 were obtained as a mixture of two diastereo-
mers with both axial and equatorial substitutions of
methyl group presented. The low-recovery yields (ca.
20%) for 26 and 27 in the catalytic hydrogenation were
OSO3
S
BnO
BnO
S
BnO
BnO
R
O
OBn
OBn
c
a
S
BnO
BnO
OBn
S
BnO
BnO
b
O
OBn
SO2
OBn
BnO
BnO
Scheme 4. Reagents and conditions: (a) Ph3P+CH3Brꢀ–t-BuOK in
ether, ꢀ78 to 0 ꢁC, 62%; (b) m-CPBA in CH2Cl2, 0 ꢁC; (c) Me3S+Iꢀ–
n-BuLi in THF, ꢀ78 to 0 ꢁC.
duce the similar a,b-conjugated ester as an intermediate
prior to a hetero-Michael addition to form C-glycosides,
the transition state under two conditions must be very
different because poor stereoselectivity is often observed
in the Wittig reaction (b:a ca. 1:1).8,18
The sulfonium salts of the thiosugars are better glyco-
sidase inhibitors because they are able to mimic the tran-
sition state.19 With the thiosugars in hand we turned our
attention to the synthesis of the sulfonium salts of the
5-thiosugars. Initially, we attempted to synthesize the
bicyclic sulfonium inner salts as illustrated in Scheme
4. However, the reaction of the 20-aldehyde to a sulfur
ylide did not provide the desired epoxide intermediate,
nor did the oxidation of the double bond because the
oxidation of the thioether to sulfone occurred more
rapidly.
Consequently, 11 and 12 were reduced using NaBH4
to 1-C-(20-hydroxyethyl)-5-thioglycosides 16 and 17,
and the resultant diols were in turn protected by benzyl-
S
S
BnO
HO
R1
11
12
R1
a
b
OBn
OH
OBn
OBn
R2
R2
16 R1 = H, R2 = OBn
18 R1 = H, R2 = OBn
17 R1 = OBn, R2 = H
19 R1 = OBn, R2 = H
OH
O
-
Ph
OSO3
OH
O
c
d
-
+
S
OSO3
+
HO
R1
S
BnO
R1
OH
OH
R2
OBn
OBn
R2
20 R1 = H, R2 = OBn
21 R1 = OBn, R2 = H
22 R1 = H, R2 = OH
23 R1 = OH, R2 = H
Scheme 5. Reagents and conditions: (a) NaBH4–MeOH, 30 min, 87% for 16, 85% for 17; (b) BnBr–NaHin DMF, 0 ꢁC to room temperature,
2.5 h, 57% for 18, 65% for 19; (c) 2,4-O-benzylidene-D-erythritol-1,3-cyclic sulfate and K2CO3–HFIP, 70 ꢁC, overnight, 75% for 20, 85% for 21;
(d) 10% Pd–C/H2, 61% for 22, 45% for 23.

238
T. Yi et al. / Carbohydrate Research 340 (2005) 235–244
-
mixtures, we were able to assign the chemical shifts for
O3SO
NOE
O
the protons and carbons using various NMR techniques
(COSY, TOCSY, HMQC, and ROESY). The data are
summarized in Tables 1 and 2.
-
+
H
ClO4
O
NOE
H
Ph
H
S
+
Me
S
BnO
HO
BnO
HO
OBn
H
The configurations of the sulfonium salts of C-5-thio-
glycopyranosides were established primarily by NOE
analysis. However, the 13C NMR analysis indicates that
the stereochemistry of S-substitution can also be as-
signed directly based on the chemical shifts of adjacent
S-connected carbons (C-1 and C-5). The chemical shifts
of C-1 and C-5 with an equatorial S-alkyl substitution
are always downfield (5–10 ppm) in comparison to those
with an axial substitution (see Table 2 and Fig. 2). This
conclusion is supported by the data available in the
literature.21
OBn
OBn
H
BnO
OBn
OBn
20-ax
24
NOE
H
Me
-
NOE
ClO4
-
ClO4
+
Me
+
S
S
H
HO
HO
OH
OH
OH
27-eq
H
OH
H
27-ax
Figure 1. NOE analysis of compounds 20, 24, 24-ax, and 27-eq.
In summary, we have developed a new method for the
synthesis of C-5-thioglycopyranosides by a tandem b-
elimination and intramolecular hetero-Michael addition
from 1-C-(20-oxoalkyl)-5-S-Ac-glycofuranosides. These
C-5-thiopyranosides were further transformed to their
sulfonium derivatives as potential glycosidase inhibitors.
likely due to the absorption of those compounds by acti-
vated charcoal.
The sulfonium salts 20–27 were characterized by spec-
troscopic analysis. Although 20–23, 26, and 27 were
Me
+
-
ClO4
+
-
ClO4
S
S
Me
HO
BnO
b
a
18
19
OH
OBn
OBn
OH
OBn
OH
OBn
24
26 (eq:ax 3:1)
Me
-
ClO4
+
Me
S
BnO
a
+
b
-
S
ClO4
BnO
HO
OBn
25
HO
OH
27 (eq:ax 1:2)
OH
Scheme 6. Reagents and conditions: (a) CH3I–AgClO4 in MeCN, room temperature, overnight, 95% for 24, 87% for 25; (b) 10% Pd–C/H2, 18%
for 26, 22% for 27.
Table 1. NMR data for C-5-thioglycopyranosides (11, 12, and 15–19)a
Compd
Atom
Chemical shifts (ppm)b,c
5
1
2
3
4
10
20
OMe
11
12
15
16
17
18
19
1H3.70
13C
3.44
34.1
3.71
35.1
3.51
37.4
3.47
37.5
3.68
38.7
3.29
37.4
3.85
38.5
4.07
83.6
3.52
78.2
3.80
77.3
4.02
84.2
3.57
79.8
4.09
83.9
3.47
82.5
3.76
77.1
3.85
76.8
3.84
78.7
3.76
77.7
3.85
69.1
3.60
75.4
3.67
83.6
2.43, 2.92
71.2
2.58, 3.05
68.5
2.61, 2.98
69.4
2.44, 2.85
71.3
2.58, 2.94
72.9
2.68, 3.13
80.5
2.59–2.63
82.3
2.34, 2.76
9.66
9.63
29.6
30.4
30.0
29.7
32.1
26.3
26.4
44.5
43.9
34.4
33.2
29.9
30.5
26.0
198.5
199.6
1H3.56
13C
2.62, 2.79
2.55, 2.80
1.51, 2.26
1.75, 1.94
1.55, 2.38
1.68, 2.41
1H3.60
13C
3.65
171.9
61.1
60.6
68.2
67.7
52.0
1H3.29
13C
3.76
3.74
3.60
3.67
1H3.25
13C
1H3.38
13C
1H3.14
13C
a Recorded in CDCl3 at 25 ꢁC.
b Obtained from HMQC experiments.
c Chemical shifts of benzyl groups not included.

Table 2. NMR data for sulfonium salts of C-5-thioglycopyranosides (20–27)a
Compd
Atom
Chemical shifts (ppm)b,c
20 10 0
2.55, 3.04 4.47, 4.67
64.4 40.5
3.30, 3.45 3.94, 4.66
66.6 42.2
2.64, 3.09 4.40, 4.66
64.5 40.3
3.26, 3.45 3.75, 4.03
66.3 42.1
3.93, 4.08 4.20, 4.20
59.6 40.5
3.93, 4.08 3.80, 3.90
59.6 42.7
3.81, 4.05 4.09, 4.16
59.6 43.9
3.81, 4.05 3.84, 3.92
59.6 44.7
3.35, 3.42
65.3
3.63, 3.64
66.6
3.80–3.84
57.5
3.85, 3.87
57.3
3.94–3.98
57.8
1
2
3
4
5
10
1.60, 1.94
29.4
2.20, 2.33
27.0
1.67, 1.97
29.3
2.15, 2.28
27.0
2.27, 2.35
29.9
2.12, 2.31
28.4
2.15–2.28
29.4
2.15–2.28
28.4
2.05, 2.33
26.4
2.00, 2.22
28.7
2.20–2.32
27.9
2.20–2.30
29.4
2.15, 2.27
28.6
20 0
4.50
75.2
4.55
75.8
4.50
75.2
4.50
75.3
4.35
69.3
4.40
67.9
4.42
67.1
4.36
72.6
30 0
40 0
CHPh
Me
20-ax
20-eq
21-ax
21-eq
22-ax
22-eq
23-ax
23-eq
24-eq
25-ax
26-eq
27-ax
27-eq
1H3.78
13C
3.59
44.4
3.66
52.4
3.58
44.7
3.86
52.5
4.35
44.4
4.35
50.7
4.44
43.9
4.49
49.7
3.76
50.9
3.79
44.2
3.89
49.4
4.25
42.3
4.35
52.0
3.87
75.0
3.90
73.9
3.86
74.7
4.02
70.8
4.02
67.1
4.35
66.6
4.17
64.6
4.09
68.6
4.11
75.8
4.00
74.7
4.19
68.3
4.23
69.3
4.10
68.6
3.94
68.7
3.75
68.7
4.06
68.5
4.48
71.3
4.35
69.0
4.46
68.6
4.59
69.3
4.48
69.0
4.06
73.9
4.07
68.7
4.21
71.4
4.36
67.9
4.39
68.4
3.27, 4.55
4.01
4.11
4.06
4.40
4.22
4.20
4.30
4.39
4.64, 3.71
5.45
5.50
5.00
5.45
69.4
33.8
65.6
4.66
67.1
69.3
101.0
101.6
101.1
101.5
1H3.97
13C
3.57, 4.59
71.5
69.4
39.3
69.4
1H3.87
13C
4.44, 4.52
4.61, 4.63
33.9
66.0
69.1
60.1
58.1
57.6
1H4.04
13C
3.55, 3.68
3.76, 4.06
67.5
39.9
59.2
3.85
80.7
3.82
1H4.10
13C
3.75, 3.90
65.9
35.7
1H4.10
13C
3.75, 3.90
64.8
39.1
80.3
1H3.99
13C
3.58, 3.68
3.75, 3.92
59.6
32.1
80.3
57.6
58.2
1H4.07
13C
3.52, 3.70
3.75, 3.92
63.5
36.2
80.6
1H3.66
13C
3.26, 4.05
2.90
73.7
37.4
25.4
20.4
23.9
19.8
21.8
1H3.95
13C
3.66, 3.91
3.16
3.12
3.28
3.06
69.9
32.3
1H3.72
13C
3.41, 3.56
65.3
37.5
1H3.99
13C
3.51, 3.79
65.5
34.8
1H3.97
13C
3.72, 3.72
66.4
41.7
a Recorded in CDCl3 (20, 21, 24, and 25) and in D2O (22, 23, 26, and 27) at 25 ꢁC.
b Obtained from HMQC experiments.
c Chemical shifts of benzyl groups not included.

240
T. Yi et al. / Carbohydrate Research 340 (2005) 235–244
@CH2), 4.85 (d, 1H, J 11.6 Hz, PhCH2), 4.68 (d, 1H, J
37-42 ppm
+
32-35 ppm
R
S-axial
12.0 Hz, PhCH2), 4.62 (d, 1H, J 11.6 Hz, PhCH2), 4.51
(d, 1H, J 12.0 Hz, PhCH2), 4.27 (m, 1H, H-5), 4.24
(m, 1H, H-2), 4.22 (m, 1H, H-5), 4.04 (m, 1H, H-4),
3.98 (m, 1H, H-1), 3.93 (m, 1H, H-3), 2.52 (dd, 2H,
J 6.8 Hz, CH2CH@CH2), 1.99 (s, 3H, CH3CO); 13C
NMR (CDCl3): d 170.8 (C@O), 138.2 (Ph), 137.5 (Ph),
134.5 (@CH), 128.5–127.7 (Ph), 117.1 (@CH2), 80.3
(C-4), 80.1 (C-3), 77.4 (C-2), 77.0 (C-1), 73.5 (PhCH2),
73.8 (PhCH2), 64.5 (C-5), 34.2 (CH2CH@CH2), 20.9
(CH3CO); HRFABMS: Calcd for C24H29O5 (M+H),
m/z 397.2015; found, m/z 397.2450.
S-equarorial
+
S
R
S
PO
PO
49-53 ppm
42-45 ppm
P = Protecting group, H
Figure 2. 13C chemical shifts correlate to sulfonium conformations.
In addition, a simple 13C NMR-based method was pro-
posed to determine the stereochemistry of the sulfonium
salts.
3.3. 3-C-(5-O-Acetyl-2,3-di-O-benzyl-a,b-D-xylofuranos-
yl)propene (6)
3. Experimental
The same procedures as described above were used for
the preparation of 6 (79% in two steps) as a mixture
1
3.1. General method
of a/b (ca. 1:1) anomers; HNMR (CDCl ): d 7.39–
3
7.24 (m, 10H, Ph), 5.78 (m, 1H, @CH), 5.06 (m, 2H,
@CH2), 4.57–4.41 (m, 4H, PhCH2), 4.32 (m, 1H, H-5),
4.26 (m, 0.5H, H-3b), 4.21–4.16 (m, 2H, H-1b, H-2b,
H-5), 4.01 (d, 0.5H, J 4.0 Hz, H-4b), 3.96 (m, 1H, H-
1a, H-2a), 3.93 (d, 0.5H, J 3.2 Hz, H-4a), 3.79 (d,
0.5H, J 2.8 Hz, H-3a), 2.48 (m, 2H, CH2CH@CH2),
2.07 and 2.03 (s and s, 3H, CH3CO); 13C NMR (CDCl3):
d 170.9 (C@O), 137.7 (Ph), 137.5 (Ph), 134.7–134.2
(@CH), 128.5–127.7 (Ph), 117.5–117.1 (@CH2), 85.0
(C-3a), 83.6 (C-1a), 82.9 (C-2a), 81.4 (C-4a), 81.3
(C-4b), 80.2 (C-1b), 78.8 (C-2b), 77.7 (C-3b), 72.3–
71.6 (PhCH2), 63.7 (C-5a), 63.5 (C-5b), 38.4 (CH2-
CH@CH2-a), 33.5 (CH2CH@CH2-b), 21.2 (CH3CO);
HRFABMS: Calcd for C24H29O5 (M+H), m/z
397.2015; found, m/z 397.2019.
1Hand 13C NMR spectra were recorded at 400 and
100 MHz, respectively, with a Varian instrument at
293 K. Chemical shifts are given in ppm downfield from
the signal of internal TMS and are assigned on the basis
1
of 2D HCOSY, TOCSY and 1H–13C chemical-shift
correlated experiments. High-resolution fast-atom bom-
bardment mass spectrometry (HRFABMS) was carried
out on a JEOL JMS-AX505Hmass spectrometer using
a 6 kV xenon beam at an accelerating voltage of 3 kV.
m-Nitrobenzyl alcohol (m-NBA) was used as the matrix,
and polyethylene glycol (PEG) was the internal cali-
brant. All chemicals were purchased from Aldrich
Chemical Co. and used without further purification.
3.2. 3-C-(5-O-Acetyl-2,3-di-O-benzyl-a-D-ribofuranos-
yl)propene (5)
3.4. 3-C-(5-S-Acetyl-2,3-di-O-benzyl-a-D-ribofuranos-
yl)propene (7)
To a solution of 1 (8.69 g, 20 mmol) and allyl-SiMe3
(3.42 g, 30 mmol) in 150 mL of MeCN was added
TMSOTf (2.7 g, 12 mmol) at ꢀ40 ꢁC. The mixture was
stirred overnight while the temperature was allowed to
rise from ꢀ40 ꢁC to room temperature. The reaction
was quenched by the addition of water, and the aqueous
solution was extracted with EtOAc (2 · 150 mL). The
combined organic extract was washed with water and
brine, dried, and concentrated. Purification by silica
gel column chromatography (8:1 hexanes–EtOAc) gave
3 (7.1 g) as a syrup. A solution of 3 (7.1 g) in 40 mL
of 0.2% (v/v) H2SO4–Ac2O solution was stirred over-
night at room temperature, and then diluted with
EtOAc (200 mL). The resulting solution was washed
with water and satd NaHCO3, dried, and concentrated
to a residue. Purification by chromatography (8:1 hex-
To the solution of 5 (5 g, 12.6 mmol) in MeOH(100 mL)
was added 4% NaOMe–MeOH(10 mL). The mixture
was stirred for 2 h, neutralized by the addition of solid
NH4Cl (5 g), and evaporated to a residue. The residue
was partitioned between EtOAc and water. The water
layer was extracted with EtOAc twice, and the combined
organic extract was washed with water, brine, dried, and
concentrated to a residue (4.5 g). To a solution of above
residue in 1:10 Et3N–CH2Cl2 (100 mL) was slowly
added at 0 ꢁC a solution MsCl (1.95 g, 17.05 mmol) in
CH2Cl2 (5 mL). The mixture was stirred overnight at
room temperature, then diluted with EtOAc, washed
with water, and brine, dried, and concentrated. Purifica-
tion by chromatography (2:1 hexanes–EtOAc) gave the
5-O-Ms product (4.2 g). A mixture of above product
(4.2 g, 9.72 mmol) and KSAc (2.2 g, 19 mmol) in DMF
(30 mL) was stirred at 80 ꢁC overnight, then diluted with
EtOAc. The solution was washed with water and brine,
anes–EtOAc) gave 5 as a syrup (4.5 g, 58% in two steps):
1
[a]D +44.5 (c 4.2, CHCl3); HNMR (CDCl ): d 7.39–
3
7.24 (m, 10H, Ph), 5.82 (m, 1H, @CH), 5.12 (m, 2H,

T. Yi et al. / Carbohydrate Research 340 (2005) 235–244
241
dried, and concentrated to a residue. Purification by
chromatography (2:1 hexanes–EtOAc) gave 7 (2.93 g,
63% in three steps): [a]D +18.4 (c 0.8, CHCl3); 1H
NMR (CDCl3): d 7.35–7.25 (m, 10H, Ph), 5.80 (m,
1H, @CH), 5.11 (m, 2H, @CH2), 4.81 (d, 1H, J
11.6 Hz, PhCH2), 4.65 (d, 1H, J 11.6 Hz, PhCH2), 4.58
(d, 1H, J 11.2 Hz, PhCH2), 4.57 (d, 1H, J 12.0 Hz,
PhCH2), 4.28 (m, 1H, H-4), 4.04 (m, 1H, H-1), 3.81
(dd, 1H, J 7.2, 4.4 Hz, H-3), 3.2 (m, 2H, H-5a, 5b),
2.48 (dd, 2H, J 6.8 Hz, CH2CH@CH2), 2.31 (s, 3H,
CH3CO); 13C NMR (CDCl3): d 194.4 (C@O), 137.8,
137.2 (Ph), 134.3 (@CH), 128.1–127.3 (Ph), 116.7
(@CH2), 82.5 (C-3), 80.3 (C-1), 78.1 (C-4), 77.5 (C-2),
73.5 (PhCH2), 73.0 (PhCH2), 34.6 (CH2CH@CH2),
32.7 (C-5), 31.0 (CH3CO); HRFABMS: Calcd for
C24H29O4S (M+H), m/z 413.1787; found, m/z 413.1760.
11.6 Hz, PhCH2), 4.24 (dd, 1H, J 6.5, 5.6 Hz, H-4),
4.12 (dd, 1H, J 4.4 Hz, H-2), 3.81 (dd, 1H, J 2.0,
4.4 Hz, H-3), 3.18 (dd, 1H, J 13.6, 4.8 Hz, H-5), 3.12
(dd, 1H, J 14.0, 5.2 Hz, H-5), 2.90 (dd, 1H, J 17.6,
6.4 Hz, CH2CH@CH2), 2.81 (dd, 1H, J 17.6, 6.4 Hz,
CH2CH@CH2), 2.31 (s, 3H, CH3CO); 13C NMR
(CDCl3): d 200.4 (CH3C@O), 194.8 (CHO), 137.6
(Ph), 137.3 (Ph), 127.7–127.8 (Ph), 81.8 (C-3), 78.6 (C-
4), 77.5 (C-2), 75.4 (C-1), 73.5 (PhCH2), 73.0 (PhCH2),
44.6 (CH2CH@CH2), 32.1 (C-5), 30.8 (CH3CO);
HRFABMS: Calcd for C23H27O5S (M+H), m/z
415.1578; found, m/z 415.1078.
3.7. 2-C-(5-S-Acetyl-2,3-di-O-benzyl-a,b-D-xylofuranos-
yl)acetaldehyde (10)
Compound 10 was prepared from 8 by the same proce-
dure as those used for 9 (80%) as a mixture of a/b (ca.
1:1) anomers: 1HNMR (CDCl 3): d 9.77 (ds, 1H, CHO),
7.38–7.21 (m, 10H, Ph), 4.59 (m, 0.5H, H-1a), 4.53–4.33
(m, 3H, PhCH2), 4.45 (d, 1H, J 12.0 Hz, PhCH2), 40.38
(m, 0.5H, H-1b), 4.22 (dt, 0.5H, J 3.6 Hz, 7.2 Hz, H-
4b), 4.13 (dt, 0.5H, J 3.2, 6.8 Hz, H-4a), 4.02 (d, 0.5H, J
4.0 Hz, H-3b), 3.94 (d, 0.5H, J 4.0 Hz, H-2b), 3.91 (d,
0.5H, J 4.0 Hz, H-3a), 3.80 (d, 0.5H, J 2.8 Hz, H-2a),
3.23 (dd, 1H, J 6.8, 14.0 Hz, H-5a), 3.15 (dd, 1H, J 6.8,
13.6 Hz, H-5b), 2.81 (m, 1H, CH2CH@CH2-a), 2.70
(dd, 1H, J 6.4, 16.8 Hz, CH2CH@CH2-b), 2.33 (s, 3H,
CH3CO); 13C NMR (CDCl3): d 200.4 (CH3C@O),
195.1 (CHO-a), 195.0 (CHO-b), 137.3 (Ph), 137.2 (Ph),
128.4–127.6 (Ph), 85.5 (C-2a), 82.7 (C-3a), 81.7 (C-2b),
81.6 (C-2b), 80.3 (C-4), 79.0 (C-1b), 75.8 (C-1a), 72.5,
72.3, 72.171.8 (2 · PhCH2-a, -b), 48.0 (CH2CH@CH2-
a), 43.8 (CH2CH@CH2-b), 30.7 (CH3CO), 28.3 (C-5b),
28.1 (C-5a); HRFABMS: Calcd for C23H27O5S (M+H),
m/z 415.1578; found, m/z 415.1410.
3.5. 3-C-(5-S-Acetyl-2,3-di-O-benzyl-a,b-D-xylofuranos-
yl)propene (8)
The same procedures as described above were used for
the preparation of 8 (41% in three steps) as a mixture
1
of a/b (ca. 1:1) anomers; HNMR (CDCl ): d 7.35–
3
7.25 (m, 10H, Ph), 5.79 (m, 1H, @CH), 5.09 (m, 2H,
@CH2), 4.57–4.42 (m, 4H, PhCH2), 4.26 (m, 0.5H, H-
4a), 4.14 (m, 0.5H, H-4b), 4.05 (m, 0.5H, H-1a), 3.95
(d, 0.5H, J 4.4 Hz, H-2a), 3.90 (m, 1H, H-1b, H-3a),
3.84 (d, 0.5H, J 4.0 Hz, H-2b), 3.77 (d, 0.5H, J 4.0 Hz,
H-3b), 3.23 (m, 1H, H-10), 3.12 (dd, 1H, J 13.2,
6.8 Hz, H-5), 2.46 (m, 1H, H-5), 2.36 (m, 1H,
CH2CH@CH2), 2.37 and 2.31 (s and s, 3H, CH3CO);
13C NMR (CDCl3): d 195.5 (C@O), 137.8–137.7 (Ph),
134.9, 134.3 (@CH-a, -b), 128.5–127.7 (Ph), 117.4,
117.0 (@CH2-a, -b), 85.3 (C-3b), 83.5 (C-4a), 83.2 (C-
3a), 81.7 (C-2b), 81.5 (C-2a), 80.1 (C-1a), 79.8 (C-1b),
78.8 (C-4b), 72.4, 72.1, 71.77, 71.70 (2 · PhCH2-a, b),
38.4 (CH2CH@CH2-a), 33.5 (CH2CH@CH2-b), 30.6
(CH3CO), 28.4, 28.1 (C-5a, b); HRFABMS: Calcd for
C24H29O4S (M+H), m/z 413.1787; found, m/z 413.1997.
3.8. 2-C-(2,3-Di-O-benzyl-5-thio-b-D-ribopyranosyl)acet-
aldehyde (11)
3.6. 2-C-(5-S-Acetyl-2,3-di-O-benzyl-a-D-ribofuranos-
yl)acetaldehyde (9)
To a solution of 9 (1.1 g, 2.65 mmol) in MeOH(20 mL)
was added 4% NaOMe–MeOH(40 mL). After stirring
at 0 ꢁC to room temperature for 5 h, solid NH4Cl (5 g)
was added, and the solvent was evaporated. The residue
was extracted with EtOAc, and the organic extract was
washed with water. Purification by chromatography
(2:1 hexanes–EtOAc) gave 11 as colorless syrup (0.7 g,
71%): [a]D ꢀ0.08 (c 1.27, CHCl3); HRFABMS: Calcd
for C21H25O4S (M+H), m/z 373.1473; found, m/z
373.1444. For NMR data see Table 1.
A solution of 7 (2.51 g, 5.44 mmol) in CH2Cl2 (80 mL)
was bubbled with ozone at ꢀ78 ꢁC for 1 h and then con-
centrated to a residue. To a solution of above residue in
AcOH(20 mL) was added zinc dust (1 g), and the mix-
ture was stirred at room temperature for 2 h and filtered.
The filtrate was diluted with EtOAc, and the solution
was washed with water, satd NaHCO3 solution and
brine, dried, and concentrated. Purification by chroma-
tography (2:1 hexane–EtOAc) gave 9 (1.6 g, 70%): [a]D
3.9. 2-C-(2,3-Di-O-benzyl-5-thio-b-D-xylopyranosyl)acet-
aldehyde (12)
1
+9.1 (c 2.0, CHCl3); HNMR (CDCl ): d 9.72 (s, 1H,
3
CHO), 7.38–7.21 (m, 10H, Ph), 4.75 (d, 1H, J 11.6 Hz,
PhCH2), 4.64 (d, 1H, J 12.0 Hz, PhCH2), 4.59 (d, 1H,
J 11.6 Hz, PhCH2), 4.53 (m, 1H, H-1), 4.47 (d, 1H, J
Compound 12 was prepared from 10 by the same proce-
dure as that used for 11 (67%): [a]D ꢀ0.02 (c 0.5,

242
T. Yi et al. / Carbohydrate Research 340 (2005) 235–244
CHCl3); HRFABMS: Calcd for C21H25O4S (M+H),
m/z 373.1473; found, m/z 373.1656. For NMR data see
Table 1.
60 ꢁC overnight. Usual workup and chromatography
(2:1 hexanes–EtOAc) gave 14 (0.4 g, 57% in two steps)
1
as a mixture of a/b (1:4) anomers: HNMR (CDCl ):
3
d 7.41–7.22 (m, 10H, Ph), 4.57–4.47 (m, 4H, PhCH2),
4.33 (m, 1H, H-1), 4.19–4.12 (m, 1H, H-4), 3.92–3.65
(m, 2H, H-2, 3), 3.67 and 3.62 (s and s, 3H, OCH3),
3.23–3.13 (m, 2H, H-5a, 5b), 2.73–2.57 (m, 2H,
CH2CO2CH3), 2.32 (s, 3H, CH3CO); 13C NMR
(CDCl3): d 195.4 (CH3C@O), 171.4 (O@COCH3),
128.6-127.7 (Ph), 85.0 (C-3), 82.9 (C-2), 81.6 (C-1),
80.2 (C-4), 72.1 (PhCH2), 71.6 (PhCH2), 51.8 (OCH3),
38.9 (CH2CO2CH3), 30.6 (CH3CO), 28.1 (C-5);
HRFABMS: Calcd for C24H29O6S (M+H), m/z
445.1684; found, m/z 445.1731.
3.10. Methyl 2-C-(5-O-acetyl-2,3-di-O-benzyl-a,b-D-
xylofuranosyl)acetate (13)
Compound 6 (1.5 g, 3.79 mmol) was subjected to ozon-
olysis to give the 20-aldehyde (1.0 g) after chromatogra-
phy (2:1 hexane–EtOAc). The aldehyde was then
dissolved in 1:1 H2O–acetone (100 mL), and KMnO4
(0.6 g) and H2SO4 (concd 0.2 mL) were added. After
stirring for 4 h at room temperature, the suspension
was filtered. The filtrate was evaporated to remove ace-
tone, and the aqueous solution was extracted with
EtOAc. The organic solution was dried and concen-
trated to give 0.96 g of crude carboxylic acid. To a solu-
tion of the carboxylic acid in DMF (30 mL) was added
MeI (0.49 g, 3.45 mmol) and NaHCO3 (0.19 g,
2.3 mmol). The mixture was stirred overnight and di-
luted with Et2O, washed with water and brine, dried,
and concentrated. Purification by chromatography (2:1
3.12. Methyl 2-C-(2,3-di-O-benzyl-5-thio-b-D-xylopyr-
anosyl)acetate (15)
A solution of 14 (0.4 g, 0.9 mmol) in 4% NaOMe–
MeOH(20 mL) was stirred overnight. Solid NH 4Cl
(2 g) was then added, and the solvent was evaporated.
Usual workup and chromatography (2:1 hexanes–
EtOAc) gave 15 (0.2 g, 54%) as a syrup: [a]D ꢀ0.03 (c
0.6, CHCl3); HRFABMS: Calcd for C22H27O5S
(M+H), m/z 403.1579; found, m/z 403.1624. For NMR
data see Table 1.
hexanes–EtOAc) gave 13 (0.6 g, 38% in three steps) as
1
a mixture of a/b (1:4) anomers: HNMR (CDCl ): d
3
7.40–7.20 (m, 10H, Ph), 4.85 (m, 1H, PhCH2), 4.55
(m, 3H, PhCH2), 4.38 (m, 3H, H-1, 2 · H-5), 4.27 (m,
1H, H-4), 4.18–4.05 (m, 1H, H-2), 3.94 (m, 1H, H-3),
3.67 and 3.62 (s and s, 3H, OCH3), 2.85–2.59 (m, 2H,
CH2CO2CH3), 2.03 (s, 3H, CH3CO); 13C NMR
(CDCl3): d 171.2 (C@O), 170.9 (C@O), 128.5–127.6
(Ph), 84.8 (C-3), 84.6 (C-3), 82.5 (C-1), 81.3 (C-1), 80.1
(C-2), 79.0 (C-4), 77.7 (C-2), 76.7 (C-4), 72.3–71.5
(PhCH2), 63.4 (C-5), 63.3 (C-5), 51.6 (OCH3), 38.8
(CH2CO2CH3-a), 34.0 (CH2CO2CH3-b), 20.9 (CH3CO);
HRFABMS: Calcd for C24H29O7 (M+H), m/z 429.1913;
found, m/z 429.2068.
3.13. 2-C-(2,3-Di-O-benzyl-5-thio-b-D-ribopyranosyl)eth-
anol (16)
To a solution of 11 (0.65 g, 1.75 mmol) in MeOH
(20 mL) was added NaBH4 (0.13 g, 3.5 mmol) at 0 ꢁC.
The mixture was stirred for 0.5 h, and solid NH4Cl
(2.0 g) was added. Usual workup and chromatography
gave 16 (0.57 g, 87%) as a syrup: [a]D ꢀ69.0 (c 0.2,
CHCl3); HRFABMS: Calcd for C21H27O4S (M+H),
m/z 375.1630; found, m/z 375.1531. For NMR data see
Table 1.
3.11. Methyl 2-C-(5-S-acetyl-2,3-di-O-benzyl-a/b-D-
xylofuranosyl)acetate (14)
3.14. 2-C-(2,3-Di-O-benzyl-5-thio-b-D-xylopyranos-
yl)ethanol (17)
To a solution of 13 (0.6 g, 1.4 mmol) in MeOH(10 mL)
was added 4% NaOMe–MeOH(5 mL). After stirring
for 15 min, the solution was neutralized by the addition
of solid NH4Cl (2 g), and the solvent was evaporated.
The residue was partitioned between EtOAc and water.
The organic solution was washed with water and brine,
dried and concentrated to a residue. To a solution of
above residue and Et3N (0.7 mL) in CH2Cl2 (20 mL)
was added at 0 ꢁC a solution of MsCl (0.25 g, 2.1 mmol)
in CH2Cl2 (1 mL). The mixture was stirred overnight at
room temperature and then diluted with EtOAc, washed
with water and brine, dried and concentrated. Purifica-
tion by chromatography (2:1 hexanes–EtOAc) gave the
5-O-Ms product (0.5 g) as a syrup. To a solution of
the 5-O-Ms product (0.5 g) in DMF (10 mL) was added
KSAc (0.4 g, 3.5 mmol), and the mixture was stirred at
Compound 17 was obtained from 12 by the same proce-
dure (85%); [a]D +25.2 (c 1.5, CHCl3); HRFABMS:
Calcd for C21H27O4S (M+H), m/z 375.1630; found,
m/z 375.1630. For NMR data see Table 1.
3.15. 1-Benzyloxy-2-C-(2,3,4-tri-O-benzyl-5-thio-b-D-
ribopyranosyl)ethane (18)
To a solution of 16 (0.57 g, 1.52 mmol) in dry DMF
(60 mL) was added NaH(209 mg, 5.19 mmol). After
0.5 h, BnBr (0.64 g, 3.8 mmol) was added to the mixture.
The reaction was quenched after 2 h by the addition of
water, and the mixture was extracted with ether. Usual
workup and chromatography (5:1 hexanes–EtOAc) gave

T. Yi et al. / Carbohydrate Research 340 (2005) 235–244
243
18 (0.57 g, 57%) as a syrup: [a]D ꢀ18.8 (c 1.8, CHCl3);
HRFABMS: Calcd for C35H39O4S (M+H), m/z
555.2569; found, m/z 555.2527. For NMR data see
Table 1.
Calcd for C11H23O10S2 (M+H), m/z 379.0733; found,
m/z 379.0710. For NMR data see Table 2.
3.21. 1-Benzyloxy-2-C-(2,3,4-tri-O-benzyl-5-methylsulfo-
niumylidene-b-D-ribopyranosyl)ethane perchlorate salt
(24)
3.16. 1-Benzyloxy-2-C-(2,3,4-tri-O-benzyl-5-thio-b-D-
xylopyranosyl)ethane (19)
To a solution of 18 (200 mg, 0.36 mmol) in MeCN
(5 mL) was added MeI (200 mg, 1.4 mmol) and AgClO4
(110 mg, 0.54 mmol). The mixture was stirred overnight
at room temperature. The solvent was removed, and the
residue was partitioned between EtOAc (100 mL) and
water (30 mL). The organic phase was dried and concen-
trated to a residue. Purification by silica gel column chro-
matography (10:1 EtOAc–MeOH) yielded 24 (230 mg,
95%) as a colorless foam: [a]D ꢀ27.7 (c 1.45, CHCl3);
HRFABMS: Calcd for C36H41O4S (M), m/z 569.2725;
found, m/z 569.2838. For NMR data see Table 2.
Compound 19 was obtained from 17 by the same proce-
dure (65%); [a]D +55.5 (c 2.0, CHCl3); HRFABMS:
Calcd for C35H39O4S (M+H), m/z 555.2569; found,
m/z 555.2238. For NMR data see Table 1.
3.17. 1-Benzyloxy-2-C-{2,3,4-tri-O-benzyl-5-[(2r,3r)-2,4-
O-benzylidene-3-(sulfooxy)butyl]sulfoniumylidene-b-D-
ribopyranosyl}ethane inner salt (20)
To a solution of 18 (120 mg, 0.22 mmol) in HFIP (1 mL)
was added 2,4-O-benzylidene-D-erythritol-1,3-cyclic sul-
fate (100 mg, 0.36 mmol) and K2CO3 (10 mg). The mix-
ture was stirred at 70 ꢁC overnight. The crude product
was purified by chromatography (20:1 CH2Cl2–MeOH)
to get 20 (0.19 g, 75%) as a mixture of two isomers (1:1):
[a]D ꢀ30.6 (c 0.7, CHCl3); HRFABMS: Calcd for
C46H51O10S2 (M+H), m/z 827.2924; found, m/z
827.4528. For NMR data see Table 2.
3.22. 1-Benzyloxy-2-C-(2,3,4-tri-O-benzyl-5-methylsulfo-
niumylidene-b-D-xylopyranosyl)ethane perchlorate salt
(25)
Compound 25 was obtained from 19 (87%) by the same
procedure: [a]D ꢀ2.5 (c 0.5, CHCl3); HRFABMS: Calcd
for C36H41O4S (M), m/z 569.2725; found, 569.2875. For
NMR data see Table 2.
3.18. 1-Benzyloxy-2-C-{2,3,4-tri-O-benzyl-5-[(2r,3r)-2,4-
O-benzylidene-3-(sulfooxy)butyl]sulfoniumylidene-b-D-
xylopyranosyl}ethane inner salt (21)
3.23. 2-C-(5-methylsulfoniumylidene-b-D-ribopyranos-
yl)ethanol perchlorate salt (26)
The same procedure as those for 20 was used to afford
21 (85%) as a mixture of two isomers (1:1): [a]D ꢀ30.6
(c 3.5, CHCl3); HRFABMS: Calcd for C46H51O10S2
(M+H), m/z 827.2924; found, m/z 827.2896. For NMR
data see Table 2.
Compound 24 (239 mg, 0.34 mmol) was subjected to
catalytic hydrogenation (50 psi) with 10% Pd–C
(50 mg) three times, respectively, in 5:1 EtOAc–EtOH
(20 mL), 10:1 MeOH–HOAc (20 mL), and 5:1 HOAc–
H2O (20 mL). The filtrate was concentrated and purified
through an LH-20 column, eluted with 2:1 H2O–MeOH
to yield 26 (19 mg, 18%) as a mixture of two isomers (1:3
ax:eq): [a]D +2.2 (c 1.0, H2O); HRFABMS: Calcd for
C8H17O4S (M), m/z 209.0847; found, (M) m/z
209.0862. For NMR data see Table 2.
3.19. 2-C-{5-[(2r,3r)-2,4-dihydroxy-3-(sulfooxy)butyl]sul-
foniumylidene-b-D-ribopyranosyl}ethanol inner salt (22)
Compound 20 (83 mg, 0.1 mmol) was subjected to cata-
lytic hydrogenation (50 psi) with 10% Pd–C (50 mg) first
in 1:1 MeOH–HOAc (10 mL) and then in 1:1 HOAc–
H2O (10 mL) overnight. The filtrate was concentrated
to a residue, which was purified by silica gel column
chromatography (10:2:1 EtOAc–MeOH–H2O) to yield
22 (16 mg, 61%) as a white foam: [a]D ꢀ3.1 (c 0.3,
H2O); HRFABMS: Calcd for C11H23O10S2 (M+H),
m/z 379.0733; found, m/z 379.0799. For NMR data see
Table 2.
3.24. 2-C-(5-methylsulfoniumylidene-b-D-xylopyranos-
yl)ethanol perchlorate salt (27)
Compound 27 was obtained from 25 by catalytic hydro-
genation (22%) as a mixture of two isomers (2:1 ax:eq):
[a]D +0.02 (c 0.4, H2O); HRFABMS: Calcd for
C8H17O4S (M), m/z 209.0847; found (M), m/z
209.0797. For NMR data see Table 2.
3.20. 2-C-{5-[(2r,3r)-2,4-dihydroxy-3-(sulfooxy)butyl]sul-
foniumylidene]-b-D-xylopyranosyl}ethanol inner salt (23)
Acknowledgements
Compound 23 was obtained from 21 (45%) as a 1:1 mix-
ture of two isomers: [a]D ꢀ2.3 (c 0.2, H2O); HRFABMS:
This is NRCC publication no. 42495. We are grateful to
Lisa Morrison for the mass spectroscopic analysis.

244
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