Synthesis of a dithio analogue of n-propyl kojibioside as a potential glucosidase I inhibitor

Article abstract of DOI:10.1016/S0008-6215(98)00165-7

Procedures for the preparation of 3,4,6-protected 2-thio-α-D-glucopyranoside derivatives by thiolate nucleophilic displacement of the 2-O-triflate of α-D-mannopyranoside derivatives were investigated. A synthesis of n-propyl 3,4,6-tri-O-benzyl-2-thio-β-D-glucopyranoside was developed. Glycosylation of this derivative with 2,3,4,6-tetra-O-acetyl-5-thio-α-D-glucopyranosyl trichloroacetimidate gave an α/β mixture of protected n-propyl β-dithiokojibioside and β-dithiosophoroside. Deprotection of the mixture by standard methods and separation by chromatography gave n-propyl β-dithiokojibioside (1) which is a potential enzyme inhibitor of glucosidase I. Copyright (C) 1998 Elsevier Science Ltd.

Full text of DOI:10.1016/S0008-6215(98)00165-7

Carbohydrate Research 310 (1998) 27±33
Synthesis of a dithio analogue of n-propyl
kojibioside as a potential glucosidase I inhibitor
John S. Andrews, Blair D. Johnston, B. Mario Pinto *
Department of Chemistry and Protein Engineering Network of Centres of Excellence, Simon Fraser
University, Burnaby, B.C., Canada V5A 1S6
Received 1 February 1998; accepted 1 May 1998
Abstract
Procedures for the preparation of 3,4,6-protected 2-thio-ꢀ-d-glucopyranoside derivatives by
thiolate nucleophilic displacement of the 2-O-tri¯ate of ꢀ-d-mannopyranoside derivatives were
investigated. A synthesis of n-propyl 3,4,6-tri-O-benzyl-2-thio-ꢁ-d-glucopyranoside was developed.
Glycosylation of this derivative with 2,3,4,6-tetra-O-acetyl-5-thio-ꢀ-d-glucopyranosyl trichloro-
acetimidate gave an ꢀ=ꢁ mixture of protected n-propyl ꢁ-dithiokojibioside and ꢁ-dithiosophoroside.
Deprotection of the mixture by standard methods and separation by chromatography gave n-
propyl ꢁ-dithiokojibioside (1) which is a potential enzyme inhibitor of glucosidase I. # 1998
Elsevier Science Ltd. All rights reserved
Keywords: 5-Thio-ꢀ-d-glucopyranosyl trichloroacetimidate; Thio sugars; n-Propyl kojibioside dithio analo-
gue; Glucosidase inhibitor
1. Introduction
action of mannosidase II enzymes and the addition
of speci®c sugar residues by the corresponding
glycosyl transferases. Certain complex structures
have been linked to the propagation of tumors and
the infectivity of HIV [4]. Interference with the
trimming process by glucosidase or mannosidase
inhibitors might constitute, therefore, an e€ective
therapeutic strategy.
Thus far, we have reported the synthesis of het-
eroanalogues of disaccharides, Glc-ꢀ-(1!2)-Glc-
OR, in which the ring and/or glycosidic oxygen
atoms have been O/S [5], S/O [6], and S/N [7].
Previous studies [7±14] have shown that disac-
charides with sulfur in the non-reducing sugar
ring or with sulfur in the glycosidic linkage are
weak to moderately-strong inhibitors of glyco-
sidase enzymes. Thus, it is of interest to investigate
The major biosynthetic pathway to complex N-
linked oligosaccharides in higher eukaryotes occurs
by processing of oligosaccharides via the trimming
pathway [1±3]. In the initial events, the trimming of
the high mannose structure, Glc3Man9(GlcNAc)2
by ꢀ-glucosidases I and II removes the three glu-
cose residues, and a collection of processing man-
nosidases then removes the four ꢀ-1,2-mannose
residues to yield Man5(GlcNAc)2. A wide variety
of more complex bi-, tri- and tetra-antennary struc-
tures may then be obtained through the trimming
* Corresponding author. Tel.: 604-291-4327; Fax: 604-
291-3765; e-mail: bpinti@sfu.ca
0008-6215/98/$Ðsee front matter # 1998 Elsevier Science Ltd. All rights reserved
PII S0008-6215(98)00165-7

28
J.S. Andrews et al./Carbohydrate Research 310 (1998) 27±33
whether these e€ects are synergistic when sulfur is
present in both locations. We now report the synth-
esis of this type of disaccharide, heteroanalogue 1, as
a potential inhibitor of Glucosidase I.
2. Results and discussion
Initial attempts at the synthesis of the dithio-
kojibioside 1 were made using the reaction of
2,3,4,6-tetra-O-acetyl-5-thio-ꢀ-d-glucopyranosyl tri-
chloroacetimidate (2) [6] with allyl 3,4,6-tri-O-ben-
zyl-2-thio-ꢁ-d-glucopyranoside (3) [5]. In contrast
to ordinary trichloracetimidate glycosyl donors, 5-
thio trichloroacetimidate donors with ester pro-
tecting groups at the 2-position generally give good
yields of ꢀ-glycosides [6,12]. However, in glycosy-
lation reactions of 3 using triethylsilyl tri¯ate as the
catalyst, a complex inseparable mixture was pro-
1
duced, whose H NMR spectrum suggested a mix-
ture of at least three di€erent products of
undetermined structure. It was therefore decided
that a thiol glycosyl acceptor with ester protecting
groups instead of benzyl ethers might simplify the
reaction by increasing the proportion of the ꢀ-dis-
accharide formed in the glycosylation reaction due
to the expected lower reactivity of the ester-pro-
tected thiol. This approach was also expected to
simplify the deprotection of the disaccharide, based
on our previous experience [5].
The alcohol 4 [15] was acetylated using acetic
anhydride in pyridine to give 5. Simultaneous
debenzylation and hydrogenation of the allyl to the
propyl aglycon, with hydrogen and activated palla-
dium on carbon gave the triol 6. Benzoylation of 6
using benzoyl chloride in pyridine gave the propyl
glycoside 7 in an 85% overall yield from 4. Selective
deprotection of the 2-acetate group was best
achieved using anhydrous 1% HCl in MeOH to give
the desired 2-alcohol 8 in 89% yield. The selective
deprotection of acetate esters in the presence of
benzoate esters is normally achieved using 3% HCl
in MeOH [16]. However, at this concentration, sub-
stantial removal of the 6-benzoate was observed.
Quantitative formation of the 2-tri¯ate 9 was
achieved by a reaction analogous to the known pro-
cedure [17] for the tri¯ation of 1,3,4,6-tetra-O-acetyl-
ꢁ-d-mannopyranose using tri¯uoromethanesulfonic
anhydride in CH2Cl2 containing pyridine.
The route to a suitable thiol precursor was
examined next. The 2-thioacetyl glucopyranoside
10 was synthesized in 74% yield by stirring the
crude tri¯ate with potassium thioacetate in DMF
for 1 h. Selective deprotection of the 2-thioacetate
of 10 in the presence of the benzoate esters was
complicated due to the fact that S-acetates are
more stable towards acid hydrolysis than O-acetates.
In order to hydrolyze the S-acetate, anhydrous,

J.S. Andrews et al./Carbohydrate Research 310 (1998) 27±33
29
oxygen-free, 2% HCl in MeOH±CH2Cl2 was
ꢀ
using a 50% excess of the thiol 11. A signi®cant
reduction in the quantity of molecular sieves (4 A)
was also made, since it was assumed that an excess
of sieves was slowing the glycosylation reaction,
resulting in incomplete reactions and elimination
reactions with the disaccharide to give 15. Indeed,
when the glycosylation reaction was performed
using 0.2 equiv. of triethylsilyl tri¯ate and a 50%
excess of the thiol, an ꢀ=ꢁ mixture (1.6:1) of the
disaccharides was isolated in 72% yield. A reduc-
tion in the yield (11%) of 15 was also observed. No
corresponding orthoesters [5] were observed or
isolated due to the substantial concentration of
triethylsilyl tri¯ate used in the reaction and the
temperature to which the reaction mixture was
warmed (22 ꢀC) before quenching with base.
required, with heating to 40 C. However, under
these conditions, the simultaneous hydrolysis of
the 6-benzoate was observed if the hydrolysis of
the S-acetate was allowed to reach completion. At
room temperature, the reaction was slow [after 16 h
the reaction was approximately 50% complete (by
TLC)]. Quenching the reaction with ice after heat-
ing the reaction mixture at 40 ꢀC for 3 h resulted in
the isolation of the desired thiol 11 in 64% yield
(74% based on unrecovered thioacetate 10).
Degassed solvents were used in these reactions to
avoid oxidation of the thiol to the disul®de,
although this occurs less readily in acidic rather
than basic solutions. Nevertheless, small amounts
of the disul®de were detected by TLC, although the
thiol 11 was far more stable towards oxidation
than the benzyl ether-protected thiol 3. Selective
deprotection was also attempted using cysteamine
in acetonitrile [18] and diethylamine in DMF [19],
but these methods were unsuccessful. The corre-
sponding thiocyanate 12 was also synthesized in
order to circumvent the problem of selective
deprotection of the thioacetate 10. This was
achieved in approximately the same yield (77%) as
the thioacetate by heating a crude mixture of the
tri¯ate with potassium thiocyanate in DMF at
1
The H NMR spectrum of a mixture of the ꢀ-
and ꢁ-disaccharides 13 and 14 was well resolved,
permitting the proof of anomeric con®guration by
3
0
0
observation of JH1 ,H2 (4.5 Hz for the ꢀ- and
10.5 Hz for the ꢁ-thioglycosidic linkage). Pure
samples of the ꢁ-anomer 14 were obtained by
fractional crystallization of the anomeric mixture
of disaccharides from Et2O±CH2Cl2-hexanes, but
successive crystallizations did not yield the pure ꢀ-
anomer. The structural assignment of the bypro-
1
duct disaccharide 15 was made on the basis of H
3
ꢀ
0
0
70 C for 3 h. Attempted reduction of the thiocya-
NMR and COSY spectra. The value of JH1 ,H2
nate using sodium borohydride in oxygen-free
THF±EtOH gave rise to a mixture of products
including the desired thiol, as judged by compar-
ison of TLC standards. This approach was dis-
continued in favor of the thioacetate route.
(<1 Hz) and long-range coupling between H-20
and H-40 led to the assignment of the structure of
the unsaturated ring. The anomeric con®guration
1
0
0
was assigned as ꢁ by comparison of JC1 ,H1
(156 Hz) to that for 14 (156 Hz).
The glycosylation of the thiol 11 with the tri-
chloroacetimidate 2 was ®rst attempted using a 1:1
mixture of 2 and 11 and 0.25 equiv of triethylsilyl
Deprotection of a 1.6:1 mixture of the ꢀ- and
ꢁ-disaccharides 13 and 14 was achieved in 85%
yield using 0.1 M NaOMe in MeOH. Propyl 2,50-
dithio-ꢁ-kojibioside 1 and propyl 2,50-dithio-ꢁ-
sophoroside 16 were partially separable by careful
chromatography using 2:1 CH2Cl2±MeOH as
eluent (Rf 0.38±0.55). The stereochemical integ-
rity of the two dithiodisaccharides was con®rmed
ꢀ
tri¯ate at 50 to +20 C. Chromatographic pur-
i®cation of the crude product mixture was success-
ful in separating a byproduct, the unsaturated
disaccharide 15 (27%), but did not result in reso-
lution of the ꢀ- and ꢁ-disaccharides 13 and 14 (1:1
mixture, 35%). These two products appeared as a
single spot in TLC analysis using a variety of
development solvents. Reduction of the amount of
triethylsilyl tri¯ate while retaining the same ratio of
2 and 11 gave less 15 (15%), although the isolated
yield of the ꢀ- and ꢁ-disaccharides (ꢁ1:1) was
38%, or 78% based on recovered thiol. Based on
observations of glycosylation reactions with similar
systems, in which the use of an excess of the
acceptor led to increased yields of the desired
products [14], the above reactions were repeated
3
1
0
0
0
0
by JH1 ,H2 and JC1 ,H1 values (4.5 and 159 Hz,
respectively, for 1, and 10.5 and 156 Hz,
respectively, for 16). It should be noted that the
1
di€erences in the JC,H coupling constants for ꢀ=ꢁ
pairs is not as pronounced with these S,S-acetals as
compared to O,O-acetals [20] and, in certain cases,
may be too small to provide reliable evidence for
assignment of anomeric con®guration.
In conclusion, the synthesis of a dithio analogue
of n-propyl ꢁ-d-kojibioside, for evaluation as an
inhibitor of glucosidase I, has been described.

30
J.S. Andrews et al./Carbohydrate Research 310 (1998) 27±33
3. Experimental
MeOH (25 mL) containing dry CH2Cl2 (5 mL), and
ꢀ
the mixture was stirred at 22 C under nitrogen.
For general experimental methods see [5].
TLC (3:1 hexanes±EtOAc) after 16 h indicated that
the reaction was complete. The reaction mixture
was diluted with CH2Cl2, made basic with solid
NaHCO3, and washed consecutively with H2O and
saturated aq NaCl. After drying with Na2SO4, the
solvent was evaporated and the resulting syrup was
crystallized from MeOH to give 8 (2.05 g, 89%):
Allyl 2-O-acetyl-3,4,6-tri-O-benzyl-b-d-manno-
pyranoside (5).ÐAcetylation of allyl 3,4,6-tri-O-
benzyl-ꢁ-d-mannopyranoside [14] by the standard
acetic anhydride/pyridine method gave a quantita-
tive yield of syrupy 5, which was used without fur-
ther puri®cation in the preparation of 7.
mp 164±165 ꢀC; [ꢀ]d
54.4ꢀ (c 1.03, CH2Cl2); H
22
1
Propyl 2-O-acetyl-3,4,6-tri-O-benzoyl-b-d-manno-
pyranoside (7).ÐTo a solution of 5 (0.567 g,
1.06 mmol) in 5:3 MeOH-80% aq HOAc (8 mL)
was added dry 10% palladium on carbon (0.250 g)
and the mixture was stirred under hydrogen at a
pressure of 50 p.s.i. for 24 h. The mixture was ®l-
tered through Celite and concentrated, and the
acetic acid removed by repeated codistillation with
100% EtOH. The resulting syrupy 6 was dissolved
NMR (400 MHz, CDCl3):
ꢂ
0.93 (t, 3H,
OCH2CH2CH3), 1.67 (m, 2H OCH2CH2CH3), 2.45
(br s, 1H, OH), 3.57 (m, 1H, OCHaHbCH2CH3),
3.92 (m, 1H, OCHaHbCH2CH3), 4.03 (ddd, 1H,
J4,5 9.5, J5,6a 3.5, J5,6b 5.5 Hz, H-5), 4.38 (dd, 1H,
J1,2 1.0, J2,3 3.0 Hz, H-2), 4.51 (dd, 1H, J6a,6b
12.0 Hz, H-6b), 4.63 (dd, 1H, H-6a), 4.78 (d, 1H,
H-1), 5.38 (dd, 1H, J3,4 9.5 Hz, H-3), 5.95 (t, 1H,
H-4), 7.31±8.04 (m, 15H, aromatic); 13C NMR
(100 MHz, CDCl3): ꢂ 10.3 (OCH2CH2CH3), 22.7
(OCH2CH2CH3), 63.7 (C-6), 67.4 (C-4), 69.3 (C-2),
71.6, 72.4, 73.9 (C-3, C-5, OCH2CH2CH3), 99.5
(C-1), 128.3±133.3 (Ph), 165.4, 166.0, 166.2
(3COPh). Anal. Calcd for C30H30O9: C, 67.41; H,
5.66. Found: C, 67.19; H, 5.61.
ꢀ
in pyridine (5 mL) and cooled to 0 C. Benzoyl
chloride (0.65 mL, 5.60 mmol) was added dropwise
to the stirred mixture which was then heated to
ꢀ
60 C. After 1 h, TLC (3:1 hexanes-EtOAc) indi-
cated that the reaction was complete. Ice was added
to the stirred solution to hydrolyze excess benzoyl
chloride and the mixture was stirred for a further
20 min. Pyridine was removed by codistillation with
toluene to yield a yellow syrup that was dissolved in
CH2Cl2 and washed consecutively with H2O, 10%
aq HCl, aq NaHCO3 and H2O. The organic layer
was dried (Na2SO4) and the solvent evaporated.
The resulting syrup was chromatographed using
3:1 hexanes-EtOAc as eluent (Rf 0.35) to yield 7
Propyl 3,4,6-tri-O-benzoyl-2-S-acetyl-2-thio-b-d-
glucopyranoside (10).ÐTo a stirred solution of 8
(1.635 g, 3.06 mmol) in dry CH2Cl2 (20 mL) con-
ꢀ
taining pyridine (0.57 mL, 7.04 mmol) at 15 C
under nitrogen was added over a period of 1 h, via
a dropping funnel, tri¯ic anhydride (1.03 mL,
6.18 mmol) in CH2Cl2 (15 mL). The reaction was
brought to room temperature and after 1 h TLC
(3:1 hexanes: EtOAc) indicated that the reaction
was complete. The reaction mixture was diluted
with CH2Cl2 and extracted consecutively with ice
cold H2O, saturated aq NaHCO3, H2O, and satu-
rated aq NaCl, and dried with Na2SO4 to yield,
after removal of solvent, a light yellow foam 9; the
compound was pure by TLC and was used imme-
diately in the following reaction.
To the tri¯ate 9 (0.40 g, 0.60 mmol) in dry DMF
(5 mL) was added potassium thioacetate (0.089 g,
0.78 mmol) and the mixture was stirred at room
temperature for 1 h. TLC (3:1 hexanes±EtOAc)
indicated that the reaction was complete. The
DMF was removed in vacuo and the resulting
orange syrup was diluted with CH2Cl2 and extrac-
ted consecutively with H2O (x2) and saturated aq
NaCl, and dried over Na2SO4. After removal of
the solvent, the syrup was chromatographed using
4:1 hexanes±EtOAc as the eluent (Rf 0.35) to yield
(0.486 g, 85%). The pure syrup was crystallized
from MeOH: mp 125±127 ꢀC; [ꢀ]d
58.5ꢀ (c 1.06,
22
1
CH2Cl2); H NMR (400 MHz, CDCl3): ꢂ 0.90 (t,
3H, OCH2CH2CH3), 1.62 (m, 2H OCH2CH2CH3),
2.19 (3H, s, COCH3), 3.53 (1H, m, OCHaHbCH2
CH3), 3.88 (1H, m, OCHaHb CH2CH3), 4.08 (ddd,
1H, J4,5 9.8, J5,6a 3.5, J5,6b 6.0 Hz, H-5), 4.53 (dd,
1H, J6a,6b 12.0 Hz, H-6b), 4.65 (dd, 1H, H-6a), 4.85
(d, 1H, J1,2 1.0 Hz, H-1), 5.50 (dd, 1H, J2,3 3.2, J3,4
10.0 Hz, H-3), 5.73 (dd, 1H, H-2), 5.82 (t, 1H, H-4),
7.32±8.04 (m, 15H, aromatic); 13C NMR (100 MHz,
CDCl3): ꢂ 10.3 (OCH2CH2CH3), 20.7 (COCH3),
22.7 (OCH2CH2CH3), 63.8 (C-6), 67.7 (C-4), 69.2
(C-2), 71.9 (C-3, OCH2CH2CH3), 72.5 (C-5), 98.9
(C-1), 128.3-133.4 (Ph), 165.5, 166.1 (3COPh),
169.9 (COCH3). Anal. Calcd for C32H32O10: C,
66.66; H, 5.59. Found: C, 66.68; H, 5.55.
Propyl 3,4,6-tri-O-benzoyl-b-d-mannopyranoside
(8).ÐCompound 7 (2.5 g, 4.34 mmol) was dis-
solved in an anhydrous solution of 1% HCl in

J.S. Andrews et al./Carbohydrate Research 310 (1998) 27±33
10 (0.261 g, 74%), which was crystallized from the
31
(10 mL) was added potassium thiocyanate (0.164 g,
ꢀ
chromatography solvent: mp 142±143 ꢀC; [ꢀ]d
1.688 mmol) and the mixture was heated at 70 C
22
49ꢀ (c 0.54, CH2Cl2); 1H NMR (400 MHz,
CDCl3): ꢂ 0.40 (t, 3H, OCH2CH2CH3), 1.61 (m,
2H OCH2CH2CH3), 2.25 (3H, s, SCOCH3), 3.50
(m, 1H, OCHaHbCH2CH3), 3.85 (m, 1H, OCHaHb
CH2CH3), 3.88 (dd, 1H, J1,2 9.0, J2,3 11.2 Hz, H-2),
4.08 (ddd, 1H, J4,5 9.5, J5,6a 3.5, J5,6b 5.5 Hz, H-5),
4.48 (dd, 1H, J6a,6b 12.0 Hz, H-6b), 4.59 (dd, 1H,
H-6a), 4.79 (d, 1H, H-1), 5.57 (t, 1H, J3,4 9.5 Hz,
H-4), 5.76 (dd, 1H, H-3), 7.03±8.04 (m, 15H, aro-
matic); 13C NMR (100 MHz, CDCl3): ꢂ 10.3
(OCH2CH2CH3), 22.8 (OCH2CH2CH3), 30.6
(SCOCH3), 49.1 (C-2), 63.5 (C-6), 71.2, 71.9, 72.0,
72.1 (C-3, C-4, C-5, OCH2CH2CH3), 101.2 (C-1),
128.3±133.3 (Ph), 163.5 (3COPh), 193.2 (SCOCH3).
Anal. Calcd for C32H32O9S: C, 64.85; H, 5.44.
Found: C, 64.49; H, 5.39.
for 3 h, after which time TLC (3:1 hexanes-EtOAc)
indicated that the reaction was complete. The
DMF was removed in vacuo and the resulting
syrup diluted with CH2Cl2, extracted consecutively
with H2O (x2) and saturated aq NaCl, and dried
over Na2SO4. After removal of the solvent the
syrup was chromatographed using 3:1 hexanes±
EtOAc as the eluent (Rf 0.43) to yield 12 (0.496 g,
1
77%): H NMR (400 MHz, CDCl3): ꢂ 0.98 (t, 3H,
OCH2CH2CH3), 1.70 (m, 2H OCH2CH2CH3), 3.31
(dd, 1H, J1,2 9.0, J2,3 11.5 Hz, H-2), 3.65, 3.95 (2H,
2m, OCH2CH2CH3), 4.11 (m, 1H, H-5), 4.48 (dd,
1H, J5,6b 5.5, J6a,6b 12.0 Hz, H-6b), 4.60 (dd, 1H,
J5,6a 3.5 Hz, H-6a), 4.81 (d, 1H, J1,2 9.0 Hz, H-1),
5.59 (t, 1H, J3,4=J4,5=9.5 Hz, H-4), 5.77 (dd, 1H,
H-3), 7.03±8.00 (m, 15H, aromatic).
Propyl 3,4,6-tri-O-benzoyl-2-thio-b-d-glucopyr-
anoside (11).ÐA solution of 10 (0.45 g, 0.76 mmol)
in anhydrous 2% HCl in MeOH (4 mL, oxygen-
free) containing CH2Cl2 (1.5 mL) was prepared at
Propyl 2-S-(20,30,40,60-tetra-O-acetyl-50-thio-a-d-
glucopyranosyl)-3,4,6-tri-O-benzoyl-2-thio-b-d-gluco-
pyranoside (13) and 2-S-(20,30,40,60-tetra-O-acetyl-
50-thio-b-d-glucopyranosyl)-3,4,6-tri-O-benzoyl-2-
thio-b-d-glucopyranoside (14).ÐThe thiol 11
(0.200 g, 0.363 mmol) and O-(2,3,4,6-tetra-O-ace-
tyl-5-thio-ꢀ-d-glucopyranosyl)-trichloroacetimidate
(2) (0.123 g, 0.242 mmol) [6] were dissolved in dry
CH2Cl2 (2.5 mL) containing activated 4A molecular
sieves (0.135 g) in a Schlenk tube under nitrogen.
Trimethylsilyl tri¯ate (10.9 ꢃL, 0.048 mmol) was
ꢀ
0 C and stirred under nitrogen at room tempera-
ture. After 16 h TLC (3:1 hexanes±EtOAc) indi-
cated that the reaction was approximately 60%
ꢀ
complete. The reaction was heated to 40 C and
after 3 h TLC indicated that a small amount of the
starting thioacetate was unreacted. The reaction
was quenched with ice and extracted with CH2Cl2
(x3). The organic layer was washed with cold aq
NaCl and dried over MgSO4, and the solvent evap-
orated to yield a light yellow syrup. Chromatog-
raphy with 6:1 hexanes±EtOAc as eluent (Rf 0.36)
yielded 11 (0.261 g, 64%) (74% based on recovered
ꢀ
added to the stirred solution at 78 C. The reac-
tion mixture was stirred at 78 ꢀC for 1 h and then
ꢀ
warmed to 0 C over 2 h at which time TLC (3:2
hexanes±EtOAc) indicated that the reaction was
complete. The reaction was warmed to room tem-
22
ꢀ
10) and 10 (0.063 g). 11: [ꢀ]d
34ꢀ (c 0.87,
perature for 20 min and then quenched at 78 C
1
CH2Cl2); H NMR (400 MHz, CDCl3): ꢂ 0.45 (t,
3H, OCH2CH2CH3), 1.68 (m, 2H OCH2CH2CH3),
1.92 (d, 1H, J2,SH 4.8Hz, SH), 3.31 (ddd, 1H, J1,2 8.5,
J2,3 9.8 Hz, H-2), 3.57 (m, 1H, OCHaHbCH2CH3),
3.90 (m, 1H, OCHaHbCH2CH3), 4.07 (ddd, 1H,
J4,5 9.0 Hz, J5,6a 3.5 Hz, J5,6b 5.5 Hz, H-5), 4.47 (dd,
1H, J6a,6b 12.0 Hz, H-6b), 4.56 (d, 1H, H-1), 4.58
(dd, 1H, H-6a), 5.53 (m, 2H, H-3, H-4), 7.30±8.00
(m, 15H, aromatic); 13C NMR (100 MHz, CDCl3): ꢂ
10.5 (OCH2CH2CH3), 22.8 (OCH2CH2CH3), 45.1
(C-2), 63.5 (C-6), 71.0 (C-4), 72.2 (C-5, OCH2
CH2CH3), 74.9 (C-3), 104.2 (C-1), 128.3-133.2 (Ph),
165.4, 165.9 (3COPh). Anal. Calcd for C30H30O8S:
C, 65.44; H, 5.49. Found: C, 65.25; H, 5.48.
with triethylamine (20 ꢃL). The reaction mixture
was ®ltered and the solvent evaporated, and the
resulting syrup puri®ed by chromatography using
3:2 hexanes±EtOAc as eluent (Rf 0.33) to yield a
mixture of 13 and 14 (one spot on TLC) (0.156 g,
72%) and 15 (0.023 g, 11%) and unreacted thiol
1
(0.05 g). The ratio of 13:14 was determined by H
NMR spectroscopy to be 1.6:1. Fractional crystal-
lization of the mixture of 13 and 14 yielded pure
14; pure fractions of the ꢀ-anomer 13 were not
obtained due to the preferential crystallization of 14.
1
13: H NMR (400 MHz, CDCl3): ꢂ 1.00 (t, 3H,
OCH2CH2CH3), 1.61 (m, 2H OCH2CH2CH3),
1.82, 1.94, 2.03 (12H, 3s, 4COCH3), 3.09 (m, 1H,
H-50), 3.45 (dd, 1H, J1,2 8.8, J2,3 11.2 Hz, H-2), 3.51
Propyl 3,4,6-tri-O-benzoyl-2-deoxy-2-thiocyan-
ato-b-d-glucopyranoside (12).ÐTo a solution of
the tri¯ate 9 (0.750 g, 1.125 mmol) in dry DMF
0
(m, 1H, OCHaHbCH2CH3), 3.52 (dd, 1H, J5 ,6 a
0
2.4, J6 a,6 b 12.0 Hz, H-60a), 3.81 (m, 1H, OCHa
0
0

32
J.S. Andrews et al./Carbohydrate Research 310 (1998) 27±33
HbCH2CH3; 3.81 (dd, 1H, J5 ,6 b 4.0 Hz, H-60b),
4.03 (ddd, 1H, J4,5 9.5, J5,6a 5.5, J5,6b 3.5 Hz, H-5),
4.48 (dd, 1H, J6a,6b 12.0 Hz, H-6a), 4.58 (dd, 1H,
7.03±8.00 (m, 15H, 3COPh); 13C NMR (100 MHz,
0
0
CDCl3):
ꢂ 10.4 (OCH2CH2CH3), 20.5, 20.7
(3COCH3), 22.8 (OCH2CH2CH3), 37.7 (C-500), 48.1
0
[1JC1 ,H1 156 Hz (C-1 )], 52.2 (C-2), 61.1 (C-6 ), 63.4
(C-6), 68.5 (C-4), 71.1 (C-40,C-5), 72.0, 72.1 (C-3,
OCH2CH2CH3), 105.0 [1JC1,H1 163 Hz (C-1)], 119.7
(C-20), 128.3±133.4 (Ph), 146.7 (C-30), 165.3, 165.6,
166.1 (3COPh), 168.0, 170.0, 170.3 (4COCH3).
Propyl 2-thio-2-S-(50-thio-a-d-glucopyranosyl)-
b-d-glucopyranoside (1) and propyl 2-thio-2-S-(50-
thio-b-d-glucopyranosyl)-b-d-glucopyranoside (16).Ð
A 1.6:1 mixture of 13:14 (0.098 g, 0.109 mmol) in
0.1 M NaOMe was stirred under nitrogen. After
12 h the reaction mixture was diluted with MeOH
(ꢁ10 mL) and neutralized with Rexyn 101 (H+)
resin. After washing the resin with MeOH, the sol-
vent was removed and the syrupy residue was pur-
i®ed by column chromatography using 2:1
CH2Cl2±MeOH as the eluent (Rf 0.38±0.55). Frac-
tions were analyzed by TLC, with multiple devel-
opment, using 1:1:1:0.4 EtOAc±CH2Cl2±MeOH±
H2O as the eluent. A total of 0.039 g (85%) of 1/16
was obtained of which 0.011 g was the pure, less-
polar ꢁ-isomer 16 and 0.008 g was the pure, more-
polar ꢀ-isomer 1.
0
H-6b), 4.69 (d, 1H, H-1), 4.91 (d, 1H, J1 ,2 4.5 Hz,
H-10), 5.12 (m, 2H H-30, H-40), 5.26 (dd, 1H, J2 ,3
0
0
0
0
0
9.8 Hz, H-20), 5.52 (dd, 1H, J3,4 9.5 Hz, H-3), 5.59
(t, 1H, H-4); 13C NMR (100 MHz, CDCl3): ꢂ 10.4
(OCH2CH2CH3), 20.5±20.6 (4COCH3), 22.6
(OCH2CH2CH3), 39.0 (C-50), 49.9 (C-2), 50.9 (C-
10), 60.3 (C-60), 63.3 (C-6), 70.9 (C-4), 71.1 (C-3),
71.2, 71.5 (C-30, C-40), 71.9 (C-5), 72.2 (OCH2
CH2CH3), 73.9 (C-20), 104.9 (C-1), 128.3±133.4
(Ph), 165.3±166.1 (3COPh), 169.2±170.4 (4COCH3).
Anal. Calcd for C44H48O16S2: C, 58.92; H, 5.39.
Found (ꢀ=ꢁ mixture): C, 58.99; H, 5.31.
ꢀ
14: mp 164±165 C; [ꢀ]d
14ꢀ (c 0.9, CH2Cl2);
19
1H NMR (400 MHz, CDCl3): ꢂ 1.00 (t, 3H,
OCH2CH2CH3), 1.68, 1.89, 1.98, 2.07 (12H, 4s,
4COCH3), 1.72 (m, 2H, OCH2CH2CH3), 3.16
(ddd, 1H, J4 ,5 10.5, J5 ,6 a 3.5, J5 ,6 b 5.5 Hz , H-50),
3.35 (dd, 1H, J1,2 8.5, J2,3 10.8 Hz, H-2), 3.61, 3.91
(2H, 2m, OCH2CH2CH3), 4.02 (ddd, 1H, J4,5
9.5 Hz, J5,6a 3.5 Hz, J5,6b 5.5 Hz, H-5), 4.10 (dd,
1H, J6 a,6 b 12.0 Hz, H-60a), 4.19 (dd, 1H, H-60b),
4.29 (d, 1H, J1 ,2 10.8 Hz, H-10), 4.48 (dd, 1H,
0
0
0
0
0
0
0
0
0
0
19
J6a,6b 12.0 Hz, H-6b), 4.58 (dd, 1H, H-6a), 4.59 (0d,
1: [ꢀ]d +231ꢀ (c 0.52, MeOH); 1H NMR
0
0
0
0
1H, H-1), 4.78 (t, 1H, J2 ,3 =J3 ,4 =9.5 Hz, H-3 ),
0
(400 MHz, CDCl3): ꢂ 0.86 (t, 3H, OCH2CH2CH3),
1.60 (m, 2H, OCH2CH2CH3), 2.96 (t, 1H,
J1,2=J2,3=9.0 Hz, H-2), 3.32 (m, 1H, H-50), 3.39
(m, 1H, H-4), 3.40 (m, 2H, H-3, H-5), 3.57 (m, 2H,
H-30, H-40), 3.60 (m, 1H, OCHaHbCH2CH3), 3.68
(dd, 1H, J5,6a 4.8, J6a,6b 12.0 Hz, H-6a), 3.85 (m,
1H, OCHaHbCH2CH3), 3.88 (3H, m, H-6b, H-60a,
H-60b), 4.04 (m, 1H, H-20), 4.63 (d, 1H, J1,2 9.0 Hz,
5.04 (dd, 1H, H-20), 5.17 (dd, 1H, J3 ,4 9.5 Hz, H-
40), 5.45 (dd, 1H, J3,4 9.5 Hz, H-3), 5.55 (t, 1H, H-
0
4); 13C NMR (100 MHz, CDCl3):
ꢂ
10.6
(OCH2CH2CH3), 20.1, 20.3, 20.4, 20.5 (4COCH3),
22.9 (OCH2CH2CH3), 44.9 (C-50), 48.0 [1JC1,H1
156 Hz (C-10)], 52.0 (C-2), 61.4 (C-60), 63.4 (C-6),
70.8 (C-4), 71.9 (C-40), 72.0 (C-5), 72.5
(OCH2CH2CH3), 72.9 (C-3), 74.6 (C-30), 74.9 (C-
20), 104.1 [1JC1,H1 164 Hz (C-1)], 128.3±133.4 (Ph),
165.4, 165.8, 166.1 (3COPh), 168.8, 169.2, 169.4,
170.3 (4COCH3). Anal. Calcd for C44H48O16S2: C,
58.92; H, 5.39. Found: C, 58.83; H, 5.38.
H-1), 4.68 (d, 1H, J1 ,2 4.5 Hz, H-10); 13C NMR
(100 MHz, CDCl3): ꢂ 12.7 (OCH2CH2CH3), 25.0
(OCH2CH2CH3), 46.5 (C-50), 54.3 (C-2), 55.2
0
0
[1JC1 ,H1 159 Hz, (C-10)], 62.8 (C-60), 63.8 (C-6),
73.7 (C-4), 75.4 (C-5, OCH2CH2CH3), 76.5, 77.2
(C-30, C-40), 77.5 (C-20), 78.4 (C-3), 107.2 [1JC1,H1
161 Hz, (C-1)]. Anal. Calcd for C15H28O9S2: C,
43.26; H, 6.78. Found: C, 43.63; H, 6.37.
0
0
1
15: H NMR (400 MHz, CDCl3): ꢂ 0.92 (t, 3H,
OCH2CH2CH3), 1.44 (m, 2H OCH2CH2CH3),
1.96, 2.02, 2.13 (9H, 3s, 3COCH3), 3.13 (1H, dt,
J4 ,5 10.5, J5 ,6 a=J5 ,6 b 3.0 Hz, H-50), 3.35 (dd, 1H,
J1,2 9.0, J2,3 11.5 Hz, H-2), 3.55 (m, 1H,
OCHaHbCH2CH3), 3.58 (dd, 1H, J6 a,6 b 12.0 Hz,
H-60b), 3.87 (m, 1H, OCHaHbCH2CH3), 3.97 (dd,
1H, H-60a), 4.02 (ddd, 1H, J4,5 9.8, J5,6a 3.5, J5,6b
5.5 Hz, H-5), 4.48 (dd, 1H, J6a,6b 12.0 Hz, H-6b),
4.59 (dd, 1H, H-6a), 4.73 (d, 1H, J1,2 9.0 Hz, H-1),
16: [ꢀ]d +26ꢀ (c 0.73, MeOH). 1H NMR
19
0
0
0
0
0
0
(400 MHz, CDCl3): ꢂ 0.89 (t, 3H, OCH2CH2CH3),
1.63 (m, 2H OCH2CH2CH3), 2.84 (dd, 1H, J1,2 9.0,
0
0
0
0
0
0
J2,3 10.5 Hz, H-2), 2.98 (ddd, 1H, J4 ,5 10.5, J5 ,6 a
3.0, J5 ,6 b 6.0 Hz0, H-50), 3.25 (t, 1H, J2 ,3
0
0
0
0
=
J3 ,4 =9.0 Hz, H-3 ), 3.34 (dd, 1H, J3,4 8.5, J4,5
0
0
0
0
9.5 Hz, H-4), 3.40 (m, 1H, H-5), 3.45 (dd, 1H, J1 ,2
4.97 (broad s, 1H, H-10), 5.44 (d, 1H, J2 ,4 2.5 Hz,
H-20), 5.47 (dd, 1H, J3,4 9.0 Hz, H-3), 5.58 (1H,
obscured m, H-40), 5.59 (1H, obscured m, H-4),
10.5 Hz, H-20), 3.46 (dd, 1H, H-3), 3.53 (dd, 1H,
H-40), 3.62 (m, 1H, OCHaHbCH2CH3), 3.67 (dd,
1H, J5,6a 4.5, J6a,6b 12.5 Hz, H-6a), 3.67 (dd, 1H,
0
0

J.S. Andrews et al./Carbohydrate Research 310 (1998) 27±33
33
J6 a,6 b 12.0 Hz, H-60a), 3.83±3.89 (3H, m, H-6b, H-
60b, OCHaHbCH2CH3), 4.08 (d, H-10), 4.52 (d, 1H,
H-1); 13C NMR (100 MHz, CDCl3): ꢂ 12.6
R.J. Batchelor, F.W.B. Einstein, and B.M. Pinto,
Tetrahedron: Asymmetry, 5 (1994) 2367±2396.
[7] J.S. Andrews, T. Weimar, T.P. Frandsen,
B. Svensson, and B.M. Pinto, J. Am. Chem. Soc.,
117 (1995) 10799±10804.
[8] H. Hashimoto, T. Fujimori, and H. Yuasa, J.
Carbohydr. Chem., 9 (1990) 683±694.
[9] H. Hashimoto, K. Shimada, and S. Horito, Tetra-
hedron: Asymmetry, 5 (1994) 2351±2366.
[10] H. Hashimoto, M. Kawanishi, and H. Yuasa,
Carbohydr. Res., 282 (1996) 207±221.
0
0
(OCH2CH2CH3), 25.0 (OCH2CH2CH3), 51.6 (C-
0
5 ), 51.7 [1JC1 ,H1 156 Hz, (C-10)], 55.4 (C-2), 63.0
(C-60), 63.7 (C-6), 73.5 (C-4), 75.3 (OCH2
CH2CH3), 75.8 (C-40), 77.3 (C-3), 78.4 (C-5), 79.6
(C-20), 80.5 (C-30), 105.2 [1JC1,H1 161 Hz, (C-1)].
Anal. Calcd for C15H28O9S2: C, 43.26; H, 6.78.
Found: C, 43.71; H, 6.41.
0
0
[11] H. Hashimoto, M. Kawanishi, and H. Yuasa,
Chem. Eur. J., 2 (1996) 556±560.
[12] M. Izumi, O. Tsuruta, S. Harayama, and
H. Hashimoto, J. Org. Chem., 62 (1997) 992±998.
[13] Y.L. Merrer, M. Fuzier, I. Dosbaa, M.-J. Foglietti,
and J.-C. Depezay, Tetrahedron, 53 (1997) 16731±
16746.
[14] S. Mehta, J.S. Andrews, B.D. Johnston, B. Svensson,
and B.M. Pinto, J. Am. Chem. Soc., 117 (1995)
9783±9790.
Acknowledgements
The authors thank the Natural Sciences and
Engineering Research Council of Canada and the
Protein Engineering Network of Centres of Excel-
lence for ®nancial support.
[15] V.K. Srivastava and C. Schuerch, Tetrahedron
Lett., (1979) 3269±3272.
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