Stereoselective synthesis of 2-S-ethyl(phenyl)-2-thio-β-glucopyranosides via 1,2-migration and concurrent glycosidation of ethyl(phenyl) 2,3-orthoester-1-thio-α-mannopyranosides

Article abstract of DOI:10.1016/S0008-6215(01)00124-0

1,2-Migration and concurrent glycosidation of ethyl(phenyl) 2,3-orthoester-1-thio-α-D- and L-mannopyranosides under the action of TMSOTf readily afforded the corresponding 2-S-ethyl(phenyl)-2-thio-β-glucopyranosides, ready precursors to 2-deoxy-arabino-hexopyranosides (2-deoxy-β-glucopyranosides).

Full text of DOI:10.1016/S0008-6215(01)00124-0

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Carbohydrate Research 333 (2001) 105–114
Stereoselective synthesis of
2-S-ethyl(phenyl)-2-thio-b-glucopyranosides via
1,2-migration and concurrent glycosidation of
ethyl(phenyl) 2,3-orthoester-1-thio-a-mannopyranosides
Zunyi Yang, Biao Yu*
State Key Laboratory of Bio-organic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, People’s Republic of China
Received 14 February 2001; accepted 24 April 2001
Abstract
1,2-Migration and concurrent glycosidation of ethyl(phenyl) 2,3-orthoester-1-thio-a-D- and L-mannopyranosides
under the action of TMSOTf readily afforded the corresponding 2-S-ethyl(phenyl)-2-thio-b-glucopyranosides, ready
precursors to 2-deoxy-arabino-hexopyranosides (2-deoxy-b-glucopyranosides). © 2001 Elsevier Science Ltd. All
rights reserved.
Keywords: 1,2-Migration; Glycosidation; 2,3-Orthoester; 2-Thio-b-glucopyranoside
1. Introduction
ergy,1,2 and indeed, experimental results of
producing the anomeric isomers have also
been reported.3a The ‘pull’ has been installed
by means of a mesyl group,3 a hydroxyl group
(under the action of Mitsunobu conditions4 or
by means of the DAST reagent5), or a phe-
noxythiocarbonyl group6 (upon subjection to
NIS–TfOH). Incidentally, Bundle and Auzan-
neau have observed 1,2-migration during the
1,2-Migration of 1-thioglycosides to give 2-
thioglycosides is well known in carbohydrate
chemistry, which is facilitated by a ‘pull’ from
the C-2 initiated by the departure of a leaving
group and a ‘push’ from the ring oxygen’s
lone pair of electrons, providing the groups
involved are in trans configuration.1–8 As out-
lined in Scheme 1, the migration has been
believed to be mainly involved in the forma-
tion of a 1,2-episulfonium (A), therefore re-
sulting in the stereoselective formation of
1,2-trans glycosides; however, calculations us-
ing both MNDO semiempirical and high-level
ab initio methods argued the oxacarbenium
ions (B) were likely to be of the lower en-
* Corresponding author. Tel.: +86-21-64163300; fax: +
86-21-64166128.
E-mail address: byu@pub.sioc.ac.cn (B. Yu).
Scheme 1.
0008-6215/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0008-6215(01)00124-0

106
Z. Yang, B. Yu / Carbohydrate Research 333 (2001) 105–114
Scheme 2.
Scheme 3.
attempted preparation of ethyl 2,3-orthoester-
1-thio-a- -rhamnopyranoside
derivatives.7
product 3 in 64% yield.13 Surprisingly, when
using TMSOTf (0.15 equiv) as a promoter,
little of starting 1 was consumed under
analogous conditions, and disaccharide 4 was
isolated as the major product (70%) upon
raising the reaction temperature to −10 °C
(Scheme 2).
L
Ziegler and Herold reported 1,2-migration
triggered by a remote 3,4-O-benzyldioxonium
cation, which finished with an intramolecular
glycosidation leading to 1,6-anhydropyranosyl
compounds.8 2-Thioglycosides thus produced
are valuable precursors to 2-deoxy-glycosides
which exit as important structural components
in many antibiotics (e.g., macrolides, anthra-
cyclines, aureolic acids, and enediynes),9 car-
diac glycosides,10 and pregnane glycosides.11
We report herewith a full account of prepara-
tion of 2-S-ethyl(phenyl)-2-thio-glucopyrano-
sides by using ethyl(phenyl) 2,3-O-ethoxy-
We envisaged that the production of 4
should conceivably involve the glycosylation
of 1 with 1,2-episulfonium A, which was re-
sulted from the cation D, and D from 2,3-or-
thoester C (Scheme 3). This ‘pull–push’
mechanistic process is in accordance with that
known for the 1,2-migration and consecutive
glycosidation of thioglycosides,1–8 in particu-
lar in accordance with the 1,2-migration pro-
cess observed incidentally by Bundle and
Auzanneau during the attempted preparation
ethylidene-1-thio-a-
D
- and
L
-mannopyrano-
sides as donors through 1,2-migration and
consecutive glycosidation processes.12
of ethyl 2,3-orthoester-1-thio-a- -rhamnopy-
L
ranoside derivatives.7
2. Results and discussion
As expected on mechanistic grounds, in the
absence of the trichloroacetimidate 2, the 1,2-
migrated self-coupled product 4 was still pro-
duced in comparable yield (64%) under similar
conditions. When diosgenin (as a nucleophile,
1.5 equiv) was added to the reaction, glycoside
5 formed by capture of the episulfonium A
Glycosylation of ethyl 2-O-acetyl-4-O-ben-
zoyl-1-thio-a- -rhamnopyranoside (1) with
L
trichloroacetimidate 2 under the promotion of
BF3·OEt2 (0.1 equiv) at low temperature
(−78 °C) produced the desired coupling

Z. Yang, B. Yu / Carbohydrate Research 333 (2001) 105–114
107
good donors for the preparation of 2-
thioglycosides.
We therefore prepared several ethyl(phenyl)
2,3-O-ethoxyethylidene-1-thio-glycosides (9,
10, 19, and 24) bearing the
L
- and
D
-manno
configuration (see Schemes 5 and 6, respec-
tively). Ethyl 4-O-benzoyl-2,3-orthoacetyl-1-
Scheme 4. Reagents and conditions: TMSOTf (0.15 equiv),
CH2Cl2, 4A MS, 0 °C–rt.
thio-a-
L
-rhamnopyranoside (9) was readily
-rhamnopyran-
,
obtained from ethyl 1-thio-a-
L
oside (6) by employing two routes. Route 1
involved two steps, i.e., selective 2,3-or-
thoester formation7 and 4-OH benzoylation,
and produced 9 in ꢀ46% yield. Route 2
employed four steps, i.e., blocking of the
2,3-OH groups with an isopropylidene group,
4-OH benzoylation, removal of 2,3-O-iso-
propylidene group, and 2,3-orthoester forma-
tion, affording 9 in overall ꢀ89% yield. Since
there was no need for purification of the inter-
mediate products, route 2 was preferred, and
it was used in the preparation of phenyl
derivative 10 (in overall ꢀ89% yield). Ethyl
4,6-O-benzylidene-2,3-orthoacetyl-1-thio-a-
mannopyranoside (19) was prepared from
-man-
nopyranoside (17) in three steps and overall
89% yield, i.e., removal of acetates, formation
of the 4,6-O-benzylidene derivatives,14 and
2,3-orthoacetate generation. Treatment of
D
-
Scheme 5. Reagents and conditions: (a) CH3C(OEt)3, p-
TsOH·H2O (ca.), DMF, rt; (b) BzCl, pyridine, 0 °C–rt; (c)
CH3C(OMe)2CH3, p-TsOH·H2O (ca.), CH2Cl2, rt; (d) 80%
HOAc, 75 °C, 3 h (46% for Route 1, ꢀ89% for Route 2).
ethyl 2,3,4,6-tetra-O-acetyl-1-thio-a-
D
was isolated in 19% yield, whereas the self-
coupled product, 4 turned out to be the major
‘byproduct’ (Scheme 4). Accordingly, 2,3-or-
thoester-1-thio-glycosides were expected to be
ethyl 1-thio-a-
D
-mannopyranoside with 2,2-di-
methoxypropane and a catalytic amount of p-
Scheme 6. Reagents and conditions: (a) NaOMe, HOMe, rt; (b) PhCH(OMe)2, p-TsOH·H2O (cat), DMF 30 °C; (c) CH3C(OEt)3,
p-TsOH·H2O (ca.), DMF, rt; 89% for 17“19; (d) CH3C(OMe)2CH3, p-TsOH·H2O (cat.), acetone, rt, then H2O, 33% (for 20),
63% (for 21); (e) 25% HOAc, rt, 70%; (f) Ac2O, pyridine, rt; (g) 80% HOAc, 50 °C, 86%; (h) the same as (c); 100%.

108
Z. Yang, B. Yu / Carbohydrate Research 333 (2001) 105–114
Table 1
amount (0.15 equiv) of TMSOTf to a solution
of an alcohol acceptor (1.2 equiv) in
dichloromethane at room temperature, fol-
lowed by the addition of the 2,3-orthoacetate
(1.0 equiv). The results are listed in the
Table 1.
Glycosylation with ethyl(phenyl) 2,3-orthoester-1-thio-
mannopyranoside donors (9, 10, 19, and 24) a,b
Entry
Donor
Acceptor
Product (yield) c
1
2
3
4
5
6
7
8
9
10
11
12 b
13 b
9
9
9
9
9
10
10
19
19
24
24
24
24
cyclohexanol
diosgenin
cholesterol
11
25
11
26 (44%)
5 (54%)
27 (20%)
27 (20%)
27 (25%)
27 (45%)
27 (53%)
32 (38%)
32 (38%)
35 (28%)
35 (24%)
38 (28%)
38 (18%)
38 (40%)
38 (29%)
The reaction of ethyl 2,3-orthoacetyl-1-thio-
28 (68%)
29 (48%)
30 (39%)
31 (53%)
33 (43%)
34 (40%)
36 (70%)
37 (40%)
39 (39%)
39 (68%)
40 (87%)
a- -rhamnopyranoside 9 with alcohols (cyclo-
L
hexanol, diosgenin, cholesterol, as well as
sugar alcohols 11 and 25) produced the ex-
25
pected 2-S-ethyl-2-thio-b- -glucopyranosides
L
cholesterol
cyclohexanol
cholesterol
25
(26, 5, 28–30) in moderate to good yields
(39–68%); the corresponding a anomers had
not previously been isolated by careful chro-
matography (entries 1–5). The anomeric
ethylthio ether on acceptor 11 was unaffected
(entry 4). However, the resulting ꢀOEt from
the 2,3-orthoacetate of donor 9 competed con-
siderably with the alcohol acceptors for the
glycosidation reactions, producing the corre-
sponding ethyl-3-O-acetyl-4-O-benzoyl-6-de-
25
cyclohexanol
a Conditions: donor (1.0 equiv), acceptor (1.2 equiv) (except
in entries 12 and 13), TMSOTf (0.15 equiv), CH2Cl2, 4 A MS,
,
0 °C–rt.
b Donor (1.2 equiv), acceptor (1.0 equiv).
c Isolated yields based on donors, except in entries 12 and
13, whereupon yields for 39 and 40 were based on acceptors.
oxy-2-S-ethyl-2-thio-b- -glucopyranoside (27)
L
in 19–53% yields. The reaction of the phenyl
1-thio-rhamnopyranoside 10 with sugar alco-
hols 11 and 25 gave similar results, providing
the expected products 31 and 33 stereoselec-
tively and in 53 and 43% yields, with the
byproduct ethyl glycoside 32 in 32 and 38%
yields, respectively (entries 6 and 7). Raney
nickel-mediated desulfurization of the SPh
derivative to produce the corresponding 2-de-
oxy-glycoside is known to be more facile than
that of the corresponding SEt derivative.6 In
contrast, the reaction of 4,6-O-benzylidene-
TsOH in acetone, followed by treatment with
water afforded 2,3-O-isopropylidene 2115 as
the major product (63%) and 2,3;4,6-di-O-iso-
propylidene 20 in minor amount (33%).16
Compound 20 could be readily converted to
21 in 70% yield upon treatment with 25%
HOAc at room temperature. 4,6-Diol 21 was
then acetylated to give 22, which was sub-
jected to 80% HOAc at 50 °C to give 2,3-diol
23 in 86% yield. Treatment of 23 with triethyl
orthoacetate afforded 2,3-orthoacetate 24
quantitatively. 1H NMR analyses demon-
strated that ethyl 2,3-orthoacetates 9, 10, and
24 were all mixtures of the two stereoisomers,
with the ethoxy group being either exo or
endo and in nearly equal amounts. However,
ethyl 2,3-orthoacetate 19 was a single com-
pound, conceivably with its ethoxy group in
the exo configuration due to the steric hin-
drance of the endo face produced by the 4,6-
O-benzylidene ring.
2,3-orthoacetyl-1-thio-a- -mannopyranoside
D
(19) with cholesterol and cyclohexanol pro-
duced the desired 2-S-ethyl-glucopyranosides
(34, 36) as their anomeric mixtures (a:b=1:4
and 2:3, respectively), which were clearly indi-
1
cated by H NMR spectral analyses (entries 8
and 9). Nevertheless, the reaction of 4,6-di-O-
acetyl-2,3-orthoacetyl-1-thio-a- -mannopy-
D
ranoside (24), gave only the b anomeric
products (entries 10–13). It should be con-
cluded that the fused 4,6-O-benzylidene ring
made the pyranose ring more rigid and fa-
vored the transformation of episulphonium
(A) into oxycabenium (B) (Scheme 1); capture
of the oxycabenium (B) by alcohols generated
the a anomers favorably due to the anomeric
Employing ethyl(phenyl) 2,3-orthoacetyl-1-
thio-a-mannopyranosides (9, 10, 19, and 24)
as donors to prepare the corresponding
2-S-ethyl(phenyl)-2-thio-b-glucopyranosides
through 1,2-migration and consecutive gly-
cosidation was examined. A typical reaction
procedure involved the addition of a catalytic

Z. Yang, B. Yu / Carbohydrate Research 333 (2001) 105–114
109
effect. The effects of fused-ring protection on
the reactivity of the pyranose donors have
been well observed in many studies.17 Herein,
it is difficult to interpret the results that only
ethyl b-glycoside 35 was isolated along with
the anomeric isomers of 34 and 36 (entries 8
and 9).
12 and 13, using an excess amount (1.2 equiv)
of the 2,3-orthoacetate donor 24 greatly in-
creased the yields of the desired products (68%
for 39, 87% for 40). The yields calculated on
the consumed acceptors should be reasonable
providing the aglycone was more precious.
The expected 2-S-ethyl(phenyl)-2-thio-gly-
cosides were produced in only moderate to
good yields due to the OEt transfer side reac-
tion in this protocol. However, it should be
noted that the yields for the expected gly-
cosides were calculated based on the 2,3-or-
thoester donors added (1.0 equiv). The yields
would be reasonably improved on the sacrifice
of the amount of donors. As shown in entries
3. Conclusions
Ethyl(phenyl) 2,3-orthoester-1-thio-a-man-
nopyranosides, which are easily accessible,
were demonstrated to be good donors for the
stereoselective synthesis of the corresponding
2-S-ethyl(phenyl)-2-thio-b-glucopyranosides,
ready precursors to 2-deoxy-b-glucopyran-

110
Z. Yang, B. Yu / Carbohydrate Research 333 (2001) 105–114
1
osides. The reaction proceeded through the
glycosidation of the 1,2-episulfonium inter-
mediates. Structural variation of the 2,3-
orthoacetate donors (e.g., 4,6-O-benzylidene
protection) would facilitate the transformation
of 1,2-episulfonium to oxycarbenium, hence
resulting in the absence of the stereoselectiv-
ity. One major drawback of the present proto-
col is the competing glycosidation of the
nascent OEt from the ethyl orthoacetate moi-
ety of the donors, leading to only moderate to
good yields for the desired products. Never-
theless, using excess amounts of the 2,3-or-
thoester donors reasonably improved the
yields.
1729 (Bz) cm−1. H NMR (CDCl3): l 8.11–
7.39 (m, 10 H), 5.43 (dd, 1 H, J 3.2, 1.6 Hz,
H-2), 5.37 (t, 1 H, J 9.8 Hz, H-4), 5.31 (d, 1
H, J 1.1 Hz, H-1), 5.03 (dd, 1 H, J 11.6, 9.3
Hz, H-3%), 4.81 (t, 1 H, J 9.5 Hz, H-4%), 4.45
(d, 1 H, J 8.7 Hz, H-1%), 4.38–4.27 (m, 2 H,
H-3, H-5), 3.54–3.45 (m, 1 H, H-5%), 2.78–
2.49 (m, 3 H, H-2%, SCH2), 2.18 (s, 3 H, Ac),
1.89 (s, 3 H, Ac), 1.36–0.88 (m, 12 H). EIMS
(m/z, %): 672 ([M+ −water], 0.5), 629 ([M+
−water−Ac], 3.7), 105 (Bz, 100). Anal.
Calcd for C34H42O11S2: C, 59.11; H, 6.13.
Found: C, 59.32; H, 6.38.
Diosgenyl 3-O-acetyl-4-O-benzoyl-6-deoxy-
2-S-ethyl-2-thio-i- -glucopyranoside (5).—To
L
a stirred solution of diosgenin (85 mg, 0.21
,
mmol) and 4 A MS (120 mg) in anhyd CH2Cl2
(2 mL) at rt under Ar, was added a solution of
TMSOTf in CH2Cl2 (0.1 M, 0.07 mmol), fol-
lowed by addition of a solution of 1 (50 mg,
0.14 mmol) in CH2Cl2 (0.5 mL). After being
stirred for 1 h, the reaction mixture was
quenched with Et3N, and then filtered through
a pad of Celite. The filtrates were concen-
trated. The residue was applied to a silica gel
column (8:1 petroleum ether–EtOAc) to give
5 (14 mg, 19%) as a white amorphous solid:
[h]D −35.7° (c 1.4, CHCl3). IR (film):
4. Experimental
General methods.—TLC was performed on
precoated plates of Silica Gel HF254 (0.5 mm,
Yantai, Shandong, China). Flash-column
chromatography was performed on Silica Gel
H (10–40 mm, Yantai, Shandong, China). Op-
tical rotations were determined with a
Perkin–Elmer model 241 MC polarimeter,
and [h]D values are on units of 10−1 deg
cm2/g. NMR spectra were recorded on a
Bruker AM 300 spectra with Me4Si as the
internal standard. J values are given in Hz.
Mass spectra were obtained on a HP5989A or
a VG Quatro mass spectrometer. Elemental
analyses were performed on a Perkin–Elmer
model 2400 instrument. Petroleum ether refers
to the fraction with distillation range 60–
90 °C.
1
1751(Ac), 1726 (Bz) cm−1. H NMR (CDCl3):
l 7.99–7.41 (m, 5 H), 5.39 (d, 1 H, J 4.9 Hz,
H-6), 5.10 (t, 1 H, J 9.3 Hz, H-3%), 5.02 (t, 1
H, J 9.3 Hz, H-4%), 4.56 (d, 1 H, J 8.7 Hz,
H-1%), 4.42 (m, 1 H, H-16), 3.67–3.60 (m, 2 H,
H-3, H-5%), 3.46–3.38 (m, 2 H, H-26), 2.80–
2.68 (m, 3 H, H-2%, SCH2), 2.50–2.30 (m, 2
H), 1.96 (s, 3 H, Ac). EIMS (m/z, %): 750
([M+], 0.7), 397 (49.6), 105 (Bz, 100). Anal.
Calcd for C44H62O8S·H2O: C, 68.72; H, 8.39.
Found: C, 68.46; H, 8.12.
Ethyl 3-O-acetyl-4-O-benzoyl-6-deoxy-2-S-
ethyl-2-thio-i-
L
-glucopyranosyl-(1“3)-2-O-
-rhamnopyran-
acetyl-4-O-benzoyl-1-thio-h-
L
Ethyl 4-O-benzoyl-2,3-O-ethoxyethylidene-
oside (4).—To a mixture of 1 (110 mg, 0.31
1-thio-h- -rhamnopyranoside (9).—Route 1:
L
,
mmol) and 4 A MS (100 mg) in anhyd CH2Cl2
To a stirred solution of ethyl 2,3,4-tri-O-ace-
tyl-1-thio-a- -rhamnopyranoside (3.15 g, 9.43
(1 mL) at −8 °C under Ar, was added a
solution of TMSOTf in CH2Cl2 (0.05 M, 0.031
mmol). After being stirred for 30 min, the
mixture was quenched with Et3N, and then
filtered through a pad of Celite. The filtrates
were concentrated. The residue was purified
by a silica gel-column chromatography (6:1–
4:1, petroleum ether–EtOAc) to give 4 (68
mg, 64%) as a white amorphous solid: [h]D
+20.8° (c 1.8, CHCl3). IR (film): 1750 (Ac),
L
mmol) in MeOH (15 mL), was added a cata-
lytic amount of NaOMe (84 mg). After being
stirred at rt for 1 h, the reaction mixture was
neutralized with Dowex-50WX8 (H+ form),
and then filtered, and concentrated in vacuo.
The residue 6 was dissolved in dry DMF (15
mL), and triethyl orthoacetate (5.0 mL, 27.0
mmol) was added, followed by a catalytic
amount of p-TsOH·H2O (20 mg, 0.11 mmol).

Z. Yang, B. Yu / Carbohydrate Research 333 (2001) 105–114
111
was purified by flash-column chromatography
(20:1 petroleum ether–EtOAc) to give 9 (29.5
g, 89%) as a colorless syrup. Compound 9 was
a mixture of the two endo/exo stereoisomers:
1H NMR (CDCl3): l 8.07–7.45 (m, 5 H), 5.62,
5.60 (2×s, 1 H, H-1), 5.48, 5.12 (2×dd, 1 H,
J 7.4, 10.2 Hz, H-4), 4.47–4.20 (m, 3 H, H-2,
H-3, H-5), 3.78, 3.55 (2×q, 2 H, OCH2),
2.71–2.55 (m, 2 H, SCH2), 1.73, 1.54 (2×s, 3
H, CH3CO3), 1.35–1.14 (m, 9 H, H-6,
OCH2CH3, SCH2CH3). EIMS (m/z, %): 337
([M+ −OEt], 3.6), 321 ([M+ −SEt], 31.2), 105
(Bz, 100). Anal. Calcd for C19H26O6S: C,
59.67; H, 6.85. Found: C, 60.02; H, 7.32.
Phenyl 4-O-benzoyl-2,3-O-ethoxyethylidene-
After being stirred at 0 °C for 1 h, the reaction
mixture was quenched with Et3N, and then
diluted with EtOAc. The organic layer, washed
with water and brine, respectively, was dried
over MgSO4, and then filtered and concen-
trated in vacuo. The residue 8 was dissolved in
dry pyridine (10 mL), and BzCl (1.5 mL) was
added. After being stirred at rt for 1 h, the
reaction mixture was quenched with Et3N, and
diluted with EtOAc. The organic layer was
washed with brine, dried over anhyd MgSO4,
and then filtered and concentrated in vacuo.
The residue was purified by flash chromatogra-
phy (15:1 petroleum ether–EtOAc) to give 9
(1.66 g, 46% for three steps) as a colorless
syrup.
1-thio-h- -rhamnopyranoside (10).—A proce-
L
Route 2: To a stirred solution of ethyl
dure similar to Route 2 for the preparation of
9 was employed (89% overall yield). Com-
pound 10, as a colorless syrup, was a mixture
2,3,4-tri-O-acetyl-1-thio-a- -rhamnopyrano-
L
side (29.0 g, 86.7 mmol) in MeOH (100 mL),
was added a catalytic amount of NaOMe (380
mg). After being stirred at rt for 5 h, the
reaction mixture was neutralized with Dowex-
50WX8 (H+ form), and then filtered, and
concentrated in vacuo. The residue 6 was dis-
solved in dry CH2Cl2 (20 mL), and 2,2-
dimethoxy propane (35 mL, 285 mmol) was
added, followed by a catalytic amount of p-
TsOH·H2O (420 mg). After being stirred at rt
for 3 h, the reaction mixture was quenched
with Et3N, and then concentrated in vacuo.
The residue 11 was dissolved in dry pyridine
(50 mL), and BzCl (12 mL) was added. After
being stirred at rt for 2 h, the reaction mixture
was quenched with MeOH, and diluted with
EtOAc. The organic layer was washed with
brine and then concentrated in vacuo. The
resulting residue 13 was dissolved in 80%
HOAc (400 mL). After being stirred at 80 °C
for 3 h, the solution was concentrated in
vacuo. The residue was purified by flash-
column chromatography (2:1 petroleum
ether–EtOAc) to give 15 as a white solid. To
a solution of 15 in dry DMF (40 mL) was
added triethyl orthoacetate (30 mL, 162
mmol), followed by a catalytic amount of
p-TsOH·H2O (80 mg). After being stirred at rt
for 2 h, the mixture was quenched with Et3N
and then diluted with EtOAc. The organic
layer, washed with water and brine, respec-
tively, was dried over dry MgSO4, and then
filtered and concentrated in vacuo. The residue
1
of the two endo/exo stereoisomers: H NMR
(CDCl3): l 8.08–7.31 (m, 10 H), 5.82, 5.80
(2×s, 1 H, H-1), 5.53–5.47, 5.14 (m, dd, 1 H,
J 7.4, 9.8 Hz, H-4), 4.62–4.38 (m, 2 H, H-2,
H-3), 4.38–4.28 (m, 1 H, H-5), 3.80–3.72,
3.60–3.52 (2×m, 2 H, OCH2), 1.71, 1.55
(2×s, 3 H, CH3CO3), 1.26–1.15 (m, 6 H, H-6,
OCH2CH3). EIMS (m/z, %): 385 ([M+−OEt],
1.4), 321 ([M+ −SPh], 41.0), 105 (Bz, 100).
Anal. Calcd for C23H26O6S: C, 64.17; H, 6.09.
Found: C, 64.30; H, 6.24.
Ethyl 4,6-O-benzylidene-2,3-O-ethoxyethyli-
dene-1-thio-h- -mannopyranoside (19).—To a
D
stirred solution of 18 (3.44 g, 11.02 mmol) in
dry DMF (5 mL) was added triethyl orthoac-
etate (4.0 mL, 22.04 mmol), followed by a
catalytic amount of p-TsOH·H2O (100 mg).
After being stirred at rt for 20 min, the mixture
was quenched with Et3N and then diluted with
EtOAc. The organic layer, washed with water
and brine, respectively, was dried over MgSO4,
and then filtered and concentrated in vacuo.
The residue was purified by a flash-column
chromatography (10:1 petroleum ether–
EtOAc) to give 19 (3.73 g, 89%) as a colorless
1
syrup. H NMR (CDCl3): l 7.50–7.34 (m, 5
H), 5.60 (s, 1 H, H-1), 5.56 (s, 1 H, PhCH),
4.47–4.39 (m, 2 H, H-3, H-4), 4.28–4.08 (m,
2 H, H-6), 3.80–3.67 (m, 2 H, H-2, H-5), 3.50
(q, 2 H, OCH2CH3), 2.71–2.51 (m, 2 H,
SCH2CH3), 1.70 (s, 3 H, CH3CO3), 1.30 (m, 3
H, OCH2CH3), 1.17 (m, 3 H, SCH2CH3).

112
Z. Yang, B. Yu / Carbohydrate Research 333 (2001) 105–114
([M+ −OEt], 1.2), 105 (Bz, 100). Anal. Calcd
Ethyl
dene-1-thio-h-
procedure similar to that for the preparation
of 19 from 18 was employed to prepare 24
from 23 (100%). H NMR (CDCl3): l 5.62
4,6-di-O-acetyl-2,3-O-ethoxyethyli-
-mannopyranoside
for C19H26O6S: C, 59.67; H, 6.85. Found: C,
59.33; H, 7.31.
D
(24).—A
Cholesteryl 3-O-acetyl-4-O-benzoyl-6-de-
1
oxy - 2 - S - ethyl - 2 - thio - i - - glucopyranoside
L
1
(28).—[h]D −21.1° (c 1.4, CHCl3); H NMR
(CDCl3): l 7.99–7.41 (m, 5 H), 5.38 (d, 1 H, J
4.9 Hz, H-6), 5.08 (t, 1 H, J 10.1 Hz, H-3%),
5.01 (t, 1 H, J 9.2 Hz, H-4%), 4.55 (d, 1 H, J
8.8 Hz, H-1%), 3.65–3.60 (m, 2 H, H-3%, H-5),
2.80–2.60 (m, 3 H, H-2, SCH2), 2.48–2.30 (m,
2 H), 1.94 (s, 3 H, Ac). EIMS (m/z, %): 369
(100), 105 (Bz, 93.4). Anal. Calcd for
C44H66O6S: C, 73.09; H, 9.20. Found: C,
72.81; H, 9.10.
(2×s, 1 H, H-1), 5.08 (m, 1 H, H-4), 4.38 (m,
2 H, H-2, H-3), 4.24 (m, 2 H, H-6), 4.50 (m, 1
H, H-5), 3.75–3.56 (2×m, 2 H, OCH2), 2.62
(m, 2 H, SCH2), 2.04 (m, 6 H, 2 Ac), 1.69,
1.55 (2×s, 3 H, CH3CO3), 1.22 (m, 6 H,
SCH2CH3, OCH2CH3). Anal. Calcd for
C16H26O8S: C, 50.78; H, 6.82. Found: C,
50.80; H, 7.04.
Typical procedure for the reaction of the
2,3-orthoacetates (9, 10, 19, and 24) with alco-
hol acceptors.—To a stirred solution of an
alcohol acceptor (70–110 mg, 1.2 equiv) and 4
Ethyl 3-O-acetyl-4-O-benzoyl-6-deoxy-2-S-
ethyl-2-thio-i-
L
-glucopyranosyl-(1“4)-2,3-
-rhamnopyranoside
O-isopropylidene-1-thio-h-
L
,
A MS (200 mg) in anhyd CH2Cl2 (2 mL) at rt
1
(29).—[h]D −46.2° (c 0.7, CHCl3); H NMR
(CDCl3): l 7.99–7.41 (m, 5 H), 5.52 (s, 1 H,
H-1%), 5.17–5.08 (m, 2 H, H-3, H-4), 4.65 (d, 1
H, J 8.9 Hz, H-1), 4.24–4.18 (m, 2 H, H-2%,
H-3%), 4.09–4.04 (m, 1 H, H-4%), 3.68–3.58 (m,
2 H, H-5%, H-5), 2.88–2.52 (m, 5 H, H-2,
2×SCH2), 1.94 (s, 3 H, Ac), 1.63, 1.56 (2×s,
6 H, (CH3)2C). EIMS (m/z, %): 584 ([M+],
0.5), 523 ([M+ −SEt], 9.5), 155 (100). Anal.
Calcd for C28H48O9S2: C, 57.51; H, 6.90.
Found: C, 57.33; H, 7.08.
under Ar was added a solution of TMSOTf in
CH2Cl2 (0.1 M, 0.15 equiv), followed by the
addition of a solution of an orthoacetate
donor (1.0 equiv) in CH2Cl2 (0.5 mL). After
being stirred for 1 h, the mixture was
quenched with Et3N and then filtered through
a pad of Celite. The filtrates were concen-
trated. The residue was applied to a silica
gel-column chromatography with petroleum
ether–EtOAc as eluent to give the corre-
sponding 2-thioglycosides as white amorphous
solids.
3-O-Acetyl-4-O-benzoyl-6-deoxy-2-S-ethyl-
2-thio-i-
L
-glucopyranosyl-(1“6)-1,2;3,4-di-
Cyclohexanyl 3-O-acetyl-4-O-benzoyl-6-de-
O-isopropylidene-h-
D
-galactopyranoside (30).
oxy - 2 - S - ethyl - 2 - thio - i - - glucopyranoside
L
—[h]D −5.6° (c 1.0, CHCl3); 1H NMR
(CDCl3): l 7.98–7.40 (m, 5 H), 5.54 (d, 1 H, J
5.1 Hz, H-1), 5.12 (dd, 1 H, J 9.4, 9.3 Hz,
H-3%), 5.02 (t, 1 H, J 9.3 Hz, H-4%), 4.63 (dd, 1
H, J 8.0, 2.3 Hz, H-3), 4.48 (d, 1 H, J 8.7 Hz,
H-1%), 4.33 (m, 2 H, H-2, H-4), 4.05 (m, 2 H,
H-6), 3.82 (m, 1 H, H-5), 3.64 (m, 1 H, H-5%),
2.76 (m, 3 H, H-2%, SCH2), 1.97 (s, 3 H, Ac),
1.53, 1.46 (2×s, 6 H, (CH3)2C), 1.35, 1.33
(2×s, 6 H, (CH3)2C), 1.26 (d, 3 H, J 6.3 Hz),
1.22 (t, 3 H, J 7.2 Hz, SCH2CH3). EIMS (m/z,
%): 581 ([M+ −Me], 0.2), 337 ([M+−
galacto], 1.4), 115 (28.6), 105 (Bz, 100). Anal.
Calcd for C29H40O11S: C, 58.37; H, 6.76.
Found: C, 58.33; H, 6.84.
1
(26).—[h]D +44.5° (c 1.3, CHCl3); H NMR
(CDCl3): l 7.98–7.40 (m, 5 H), 5.09 (t, 1 H, J
10.2 Hz, H-3), 5.02 (t, 1 H, J 9.1 Hz, H-4),
4.55 (d, 1 H, J 8.8 Hz, H-1), 3.74–3.58 (m, 2
H, H-5, OCH(CH2)5), 2.80–2.60 (m, 3 H, H-2,
SCH2), 1.94 (s, 3 H, Ac), 1.80–1.70 (m, 2 H),
1.60–1.16 (m, 14 H). EIMS (m/z, %): 436
([M+], 0.1), 337 ([M+], 26.3), 155 (100). Anal.
Calcd for C23H32O6S: C, 63.28; H, 7.39.
Found: C, 63.30; H, 7.53.
Ethyl 3-O-acetyl-4-O-benzoyl-6-deoxy-2-S-
ethyl-2-thio-i- -glucopyranoside (27).—[h]D
L
1
+43.3° (c 1.0, CHCl3); H NMR (CDCl3):
7.98–7.42 (m, 5 H), 5.10 (dd, 1 H, J 11.0, 9.2
Hz, H-3), 5.02 (dd, 1 H, J 9.5, 9.2 Hz, H-4),
4.55 (d, 1 H, J 8.8 Hz, H-1), 3.99 (m, 1 H,
H-5), 3.68–3.61(m, 2 H, OCH2), 2.80–2.61
(m, 3 H, H-2, SCH2CH3), 1.92 (s, 3 H, Ac),
1.30–1.20 (m, 9 H). EIMS (m/z, %): 337
Ethyl 3-O-acetyl-4-O-benzoyl-6-deoxy-2-S-
phenyl-2-thio-i-
L
-glucopyranosyl-(1“4)-2,3-
-rhamnopyranoside
O-isopropylidene-1-thio-h-
L
1
(31).—[h]D −9.4° (c 1.1, CHCl3); H NMR
(CDCl3): 7.96–7.26 (m, 10 H), 5.48 (s, 1 H,

Z. Yang, B. Yu / Carbohydrate Research 333 (2001) 105–114
113
Anal. Calcd for C44H64O6S: C, 73.29; H, 8.95.
Found: C, 73.11; H, 9.24.
H-1%), 5.33 (dd, 1 H, J 11.3, 9.3 Hz), 5.09 (t, 1
H, J 9.3 Hz), 4.70 (d, 1 H, J 9.0 Hz, H-1),
4.19–4.13 (m, 2 H, H-2%, H-3%), 4.00–3.92 (dd,
1 H, J 10.2, 6.3 Hz, H-4%), 3.68–3.54 (m, 2 H,
H-5%, H-5), 3.38 (dd, 1 H, J 11.3, 8.8 Hz, H-2),
2.66–2.44 (m, 2 H, SCH2), 1.83 (s, 3 H, Ac),
1.53, (s, 6 H, (CH3)2C), 1.36–1.25 (m, 9 H).
EIMS (m/z, %): 571 ([M+−SEt], 1.1), 385
([M+−Rhamno], 5.7), 203 (95.2), 105 (Bz,
100). Anal. Calcd for C32H40O9S2: C, 60.74; H,
6.37. Found: C, 61.01; H, 6.57.
Ethyl 3-O-acetyl-4,6-O-benzylidene-2-S-
ethyl-2-thio-i-
D
-glucopyranoside
(35).—1H
NMR (CDCl3): l 7.44–7.32 (m, 5 H), 5.49 (s,
1 H, CHPh), 5.08 (dd, 1 H, J 11.0, 9.5 Hz,
H-3), 4.52 (d, 1 H, J 8.8 Hz, H-1), 4.32 (dd, 1
H, J 10.3, 5.1 Hz, H-4), 3.97 (m, 1 H), 3.78 (t,
1 H, J 10.3 Hz, H-6), 3.66 (m, 1 H), 3.62 (t, 1
H, J 9.5 Hz, H-6%), 3.46 (dt, 1 H, J 9.5, 5.1 Hz,
H-5), 2.79–2.60 (m, 3 H, H-2, SCH2), 2.11 (s,
3 H, Ac), 1.25–1.20 (m, 6 H).
Ethyl 3-O-acetyl-4-O-benzoyl-6-deoxy-2-S-
Cyclohexanyl 3-O-acetyl-4,6-O-benzylidene-
phenyl-2-thio-i- -glucopyranoside (32).—[h]D
L
1
2-S-ethyl-2-thio-h/i- -glucopyranoside (36).
D
+61.2° (c 1.0, CHCl3); H NMR (CDCl3): l
7.99–7.27 (m, 10 H), 5.28 (dd, 1 H, J 11.3, 9.3
Hz, H-3), 5.02 (t, 1 H, J 9.5 Hz, H-4), 4.34 (d,
1 H, J 8.8 Hz, H-1), 3.99–3.88 (m, 1 H, H-5),
3.64–3.52 (m, 2 H, OCH2), 3.17 (dd, 1 H, J
11.3, 8.8 Hz, H-2), 1.89 (s, 3 H, Ac), 1.23 (m,
6 H). EIMS (m/z, %): 430 ([M+], 0.6), 105
(Bz, 100). Anal. Calcd for C28H26O6S: C,
64.17; H, 6.09. Found: C, 64.47; H, 6.32.
3-O-Acetyl-4-O-benzoyl-6-deoxy-2-S-phenyl-
1
—(a:b=2:3). H NMR (CDCl3): l 7.44–7.32
(m, 5 H), 5.52–5.50 (m, 1.4 H, PhCH, H-1a),
5.12–5.05 (m, 1 H, H-3), 4.63 (d, 0.6 H, J 8.8
Hz, H-1b), 4.62 (dd, 0.6 H, J 10.6, 4.9 Hz,
H-4b), 4.50 (dd, 0.4 H, J 10.2, 4.9 Hz, H-4a),
4.15–4.02 (m, 0.4 H, H-5a), 3.83–3.55 (2×m,
3 H, H-6, OCH(CH2)5), 3.50–3.42 (m, 3 H,
SCH2CH3).
Cholesteryl 3,4,6-tri-O-acetyl-2-S-ethyl-2-
thio-i- -glucopyranoside (37).—[h]D −4.8°
D
2-thio-i-
L
-glucopyranosyl-(1“6)-1,2;3,4-di-
-galactopyranoside (33).
1
(c 0.4, CHCl3); H NMR (CDCl3): l 5.39 (m,
1 H, H-6), 5.01 (t, 1 H, J 9.3 Hz), 4.93 (t, 1 H,
J 9.9 Hz), 4.54 (d, 1 H, J 8.8 Hz, H-1%), 4.30
(dd, 1 H, J 11.9, 4.8 Hz, H-6%), 4.08 (dd, 1 H,
J 12.1, 2.2 Hz, H-6%), 3.66–3.54 (m, 2 H, H-5%,
H-3), 2.80–2.60 (m, 3 H, H-2%, SCH2), 2.44–
2.22 (m, 2 H), 2.12, (s, 6 H, 2×Ac), 2.02 (s, 3
H, Ac). EIMS (m/z, %): 703 ([M+−Me], 0.2),
659 ([M+−SEt], 0.3), 369 ([M+−Man], 100).
Anal. Calcd for C41H66O8S: C, 68.48; H, 9.25.
Found: C, 68.28; H, 9.27.
O-isopropylidene-h-
D
—[h]D −10.0° (c 0.9, CHCl3); 1H NMR
(CDCl3): l 7.98–7.22 (m, 10 H), 5.54 (d, 1 H,
J 4.9 Hz, H-1), 5.27 (dd, 1 H, J 11.2, 9.3 Hz,
H-3%), 5.02 (t, 1 H, J 9.5 Hz, H-4%), 4.58 (dd, 1
H, J 8.0, 2.2 Hz, H-3), 4.42 (d, 1 H, J 8.8 Hz,
H-1%), 4.34–4.29 (m, 2 H, H-2, H-4), 4.01–
3.97 (m, 2 H, H-6), 3.81–3.74 (m, 1 H, H-5),
3.61–3.56 (m, 1 H, H-5%), 3.18 (dd, 1 H, J
11.3, 8.8 Hz, H-2%), 1.92 (s, 3 H, Ac), 1.49 (s,
6 H), 1.36, 1.34 (2×s, 2×3 H), 1.24 (d, 3 H,
J 6.2 Hz). EIMS (m/z, %): 644 ([M+], 0.2),
203 (23.8), 152 (43.6), 105 (Bz, 100). Anal.
Calcd for C33H40O11S: C, 61.48; H, 6.25.
Found: C, 61.41; H, 6.40.
Ethyl 3,4,6-tri-O-acetyl-2-S-ethyl-2-thio-i-
D
-glucopyranoside (38).—[h]D +22.2° (c 1.1,
1
CHCl3); H NMR (CDCl3): l 5.03 (t, 1 H, J
9.1 Hz), 4.94 (dd, 1 H, J 11.0, 9.1 Hz), 4.42 (d,
1 H, J 8.8 Hz, H-1), 4.30 (dd, 1 H, J 12.4, 4.9
Hz, H-6), 4.12 (dd, 1 H, J 12.1, 2.2 Hz, H-6),
4.04–3.94 (m, 1 H, H-5), 3.71–3.59 (m, 2 H,
OCH2), 2.82–2.60 (m, 3 H, H-2, SCH2), 2.09,
2.08, 2.02 (3×s, 9 H, 3×Ac), 1.28–1.23 (m,
6 H, SCH2CH3, OCH2CH3). EIMS (m/z, %):
377 ([M++1], 0.8), 333 ([M+ −OEt], 2.4).
Anal. Calcd for C16H26O8S: C, 50.78; H, 6.82.
Found: C, 50.63; H, 6.83.
Cholesteryl 3-O-acetyl-4,6-O-benzylidene-2-
S-ethyl-2-thio-h/i- -glucopyranoside (34).—
D
1
(a:b=1:4). H NMR (CDCl3): l 7.44–7.32
(m, 5 H), 5.51–5.49 (m, 1.2 H, PhCH, 0.2
H-1a), 5.40 (m, 0.8 H, H-6%), 5.34 (m, 0.2 H,
b
H-6%), 5.12–5.05 (m, 1 H, H-3), 4,63 (d, 0.8 H,
a
J 8.7 Hz, H-1b), 4.32–4.23 (m, 1 H, H-4),
4.14–4.04 (m, 0.2 H, H-5a), 3.82–3.56 (2×m,
3 H, H-6, H-3%), 3.50–3.45 (m, 0.8 H, H-5b),
2.82–2.61 (m, 3 H, H-2, SCH2), 2.48–2.22
(2×m, 2 H), 2.10 (s, 3 H, Ac). EIMS (m/z,
%): 721 ([M+], 4.1), 369 ([M+−Gluco], 100).
3,4,6-Tri-O-acetyl-2-S-ethyl-2-thio-i-
glucopyranosyl-(1“6)-1,2;3,4-di-O-isoprop-
ylidene-h- -galactopyranoside (39).—[h]D
33.4° (c 1.0, CHCl3); H NMR (CDCl3): l
D
-
D
−
1

114
Z. Yang, B. Yu / Carbohydrate Research 333 (2001) 105–114
2. Dudley, T. J.; Smoliakova, I. P.; Hoffmann, M. R. J.
Org. Chem. 1999, 64, 1247–1253.
3. (a) Johnston, B. D.; Pinto, B. M. J. Org. Chem. 2000, 65,
4607–4617;
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5.53 (d, 1 H, J 4.9 Hz, H-1%), 5.03 (t, 1 H, J
9.5 Hz), 4.97 (dd, 1 H, J 11.3, 9.1 Hz), 4.63
(dd, J 7.7, 2.5 Hz, H-6), 4.52 (d, 1 H, J 8.5
Hz, H-1), 4.46–4.24 (m, 3 H), 4.13–4.00 (m, 3
H), 3.74 (dd, 1 H, J 10.7, 7.1 Hz), 3.65 (m, 1
H), 2.87–2.66 (m, 3 H, H-2, SCH2), 2.09, 2.08,
2.02 (3×s, 9 H, 3×Ac), 1.51, 1.46 (2×s, 6
H, (CH3)2CO2), 1.34 (s, 6 H, (CH3)2CO2), 1.22
(m, 3 H, SCH2CH3). EIMS (m/z, %): 577
([M+−Me], 10.7), 213 (100). Anal. Calcd for
C26H40O13S: C, 52.69; H, 6.80. Found: C,
52.55; H, 6.88.
(b) Zuurmond, H. M.; van der Klein, P. A. M.; van der
Marel, G. A.; van Boom, J. H. Tetrahedron 1993, 49,
6501–6514.
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Fortschritte der Chemie Organischer Naturstoffe; Herz,
W.; Kirby, G. W.; Moore, R. E.; Steglich, W.; Tamm,
Ch., Eds. Cardiac glycosides.; Springer–Verlag: Wien,
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11. Deepak, D.; Srivastav, S.; Khare, A. In Fortschritte der
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13. (a) Yu, B.; Yu, H.; Hui, Y.; Han, X. Synlett 1999,
753–755;
2 - thio - i -
D
- glucopyranoside (40).—[h]D
1
+24.7° (c 1.0, CHCl3); H NMR (CDCl3): l
5.18 (t, 1 H, J 9.3 Hz), 4.92 (dd, 1 H, J 10.7,
9.3 Hz), 4.51 (d, 1 H, J 8.8 Hz, H-1), 4.30 (dd,
1 H, J 12.1, 4.9 Hz, H-6), 4.09 (dd, 1 H, J
12.1, 2.2 Hz, H-6), 3.79–3.59 (m, 2 H, H-5,
OCH), 2.80–2.60 (m, 3 H, H-2, SCH2), 2.09
(s, 6 H, 2×Ac), 2.03 (s, 3 H, Ac), 2.00–1.84
(m, 2 H), 1.80–1.66 (m, 2 H), 1.58–1.36 (m, 3
H), 1.36–1.19 (m, 6 H). EIMS (m/z, %): 415
([M+−OH], 1.3), 333 ([M+−(CH2)5], 9.8),
213 (100). Anal. Calcd for C20H32O8S: C,
55.54; H, 7.46. Found: C, 55.02; H, 7.33.
(b) Yu, H.; Yu, B.; Wu, X.; Hui, Y.; Han, X. J. Chem.
Soc., Perkin Trans. 1 2000, 1445–1453.
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Acknowledgements
We thank the Ministry of Science and Tech-
nology of China and the National Natural
Science Foundation of China (29925203) for
financial support.
(b) Crich, D.; Sun, S. J. Am. Chem. Soc. 1998, 120,
435–436;
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