Synthesis of zwitterionic selenonium and sulfonium sulfates from D-mannose as potential glycosidase inhibitors

Article abstract of DOI:10.1139/V06-027

Four chain-extended analogues of the naturally occurring glycosidase inhibitor salacinol were synthesized for structure-activity studies with different glycosidase enzymes. The syntheses involved the reaction of isopropylidene-protected 1,4-thio- and 1,4-

Full text of DOI:10.1139/V06-027

497
Synthesis of zwitterionic selenonium and
sulfonium sulfates from D-mannose as potential
glycosidase inhibitors1
Hui Liu and B. Mario Pinto
Abstract: Four chain-extended analogues of the naturally occurring glycosidase inhibitor salacinol were synthesized for
structure–activity studies with different glycosidase enzymes. The syntheses involved the reaction of isopropylidene-
protected 1,4-thio- and 1,4-seleno-D-talitols and 1,5-thio- and 1,5-seleno-L-gulitols, derived from D-mannose, with a
benzylidene- and isopropylidene-protected 1,3-cyclic sulfate, also derived from D-mannose. Deprotection of the products
afforded the novel selenonium and sulfonium sulfates composed of heterocyclic five- and six-membered ring core struc-
tures with pendant polyhydroxylated, acyclic chains of six carbon atoms.
Key words: glycosidase inhibitors, zwitterionic selenonium and sulfonium sulfates, cyclic sulfate.
Résumé : Afin de pouvoir procéder à des études de structure–activité avec divers enzymes de glycosidase, on a synthé-
tisé quatre analogues à chaîne allongée du salacinol, un inhibiteur de la glycosidase qu’on retrouve à l’état naturel. Ces
synthèses ont impliquées les réactions de dérivés isopropylidènes de 1,4-thio et 1,4-séléno-D-talitols ainsi que de 1,5-
thio- et 1,5-séléno-L-gulitols obtenus à partir du D-mannose avec des dérivés benzylidènes et isopropylidènes de sulfates
cycliques-1,3 aussi obtenus à partir du D-mannose. La déprotection des produits a permis d’obtenir de nouveaux sulfa-
tes de sélénonium et de sulfonium formés structures à cycle central formé d’hétérocycles à cinq et à six chaînons por-
tant des chaînes pendantes polyhydroxylées de six atomes de carbone.
Mots clés : inhibiteurs de glycosidase, sulfates de sélénonium et de sulfonium zwitterioniques, sulfate cyclique.
[Traduit par la Rédaction] Liu and Pinto 505
Introduction
of the heptitol side chain of kotalanol has yet to be deter-
mined. However, kotalanol has shown more potent
glucosidase inhibitory activity towards sucrase than
salacinol (6). It is believed that the inhibitory activities of
salacinol and kotalanol come from their ability to mimic
both the shape and charge of the oxacarbenium-ion-like
transition state involved in the enzymatic reactions (7–9).
However, the details of the mechanism of action of these
compounds are yet to be elucidated.
In our current research program, we have undertaken a
limited structure–activity study of salacinol and related com-
pounds. The synthesis of salacinol and its ammonium and
selenonium analogues have been reported by us and others
(10–14). We also have synthesized analogues containing six-
membered heterocyclic rings and chain-extended analogues
of salacinol, some of which have shown inhibitory activity
in the micromolar range of recombinant human maltase
glucoamylase, a key intestinal glucosidase (15–18). These
studies have revealed an interesting variation in the inhibi-
tory power of these compounds against glycosidase enzymes
of different origin (11–14). The molecular basis for this se-
lectivity is being investigated through structural studies of
the enzyme-bound inhibitors using molecular modeling in
conjunction with NMR techniques (19) and X-ray crystal-
lography (20). To further understand this selectivity, addi-
tional examples of analogues of salacinol that differ in
stereochemistry on both the heterocyclic ring and the side
chain, in chain length of the acyclic chain, and in size of the
heterocyclic ring are required.
The controlled inhibition of glycosidase enzymes plays
important roles in the biochemical processing of
biopolymers containing carbohydrates (1, 2). Recently, a
new class of glycosidase inhibitors, namely salacinol (1) and
kotalanol (2), with an intriguing inner-salt sulfonium sulfate
structure was isolated from the roots and stems of the plant
Salacia reticulata. These compounds have been found to be
potent inhibitors of intestinal glucosidase enzymes (3, 4).
Salacinol (1) and kotalanol (2) presumbly compete for sub-
strate binding in the active site, thus preventing glucose oli-
gosaccharides from being processed and thereby inhibiting a
surge in blood glucose levels after a meal rich in carbohy-
drates (Chart 1). Hence, they have potential as therapeutics
in the management of blood glucose levels for patients suf-
fering from type II diabetes (5). The absolute configuration
Received 31 August 2005. Published on the NRC Research
Press Web site at http://canjchem.nrc.ca on 6 April 2006.
This work is dedicated with respect and affection to Walter
A. Szarek, an inspiring teacher and mentor, in celebration of
his 65th birthday.
H. Liu and M. Pinto.2 Department of Chemistry, Simon
Fraser University, Burnaby, BC V5A 1S6, Canada.
1This article is part of a Special Issue dedicated to Professor
Walter A. Szarek.
2Corresponding author (e-mail: bpinto@sfu.ca).
Can. J. Chem. 84: 497–505 (2006)
doi:10.1139/V06-027
© 2006 NRC Canada

498
Can. J. Chem. Vol. 84, 2006
Scheme 1.
OH OH
OSO3
OP OP
OH
H
H
X
OH
X
OP
RO
O
O
OP
HO
S
OR
OH
OROR
O
O
OHOH
R, P = protecting groups
X = Se, S
OH OH
OP OP
OH
OH
X
OSO3
OH
X
OP
HO
HO
RO
RO
O
O
OP
S
OR
O
O
OH
OR
X = Se, S
R, P = protecting groups
Chart 1.
Chart 2.
OH OH
OH OH
3'
OH
OH OH
5'
5'
OH
1'
3'
OH
6'
OH
OSO3
2'
4'
1'
6
OH
6'
2'
4'
OSO3 OH
X
5 1
OSO3 OH
S
OSO3OH
S
H
5
HO
HO
X
4
HO
HO
HO
6
1
2
3
HO
OH
4
2
HO
OH
OH
3
OHOH
OH
OH
salacinol (1)
kotalanol (2)
5 X = S
6
3 X = S
4
X = Se
X = Se
Herein, we report the synthesis of two series of
selenonium and sulfonium sulfates (3–6) based on seleno-
and thio-anhydroalditols derived from D-mannose (Chart 2).
started from D-mannose (12, Scheme 2). D-Mannose was
first treated with 2,2-dimethoxypropane in dry acetone with
p-toluenesulfonic acid as a catalyst to give 2,3,5,6-di-O-
isopropylidene-D-mannose (13) (21). Compound 13 was sub-
sequently subjected to reduction with sodium borohydride to
afford the corresponding diol 14. The diol was then con-
verted to the corresponding dimesylate 15 in 80% yield by
treatment with methanesulfonyl chloride and pyridine. The
isopropylidene-protected 1,4-anhydro-1-thio-D-talitol (7)
was prepared in 92% yield by treatment of the dimesylate 15
with sodium sulfide in DMF in 92% yield. When the
dimesylate 15 was reacted with selenium and sodium
borohydride in EtOH at 60–65 °C, the isopropylidene-
protected 1,4-anhydro-1-seleno-D-talitol (8) was obtained in
a 60% yield (Scheme 2).
With D-mannose as a starting material, the isopropylidene-
protected 1,5-anhydro-1-thio-L-gulitol (9) and 1,5-anhydro-
1-seleno-L-gulitol (10) were also synthesized (Scheme 3). D-
Mannose (12) was treated with 2-methoxypropene in dry
DMF with p-toluenesulfonic acid as a catalyst to give the
kinetically controlled product, 2,3,4,6-di-O-isopropylidene-
D-mannose (16) (22). Compound 16 was subsequently sub-
jected to sodium borohydride reduction to afford the corre-
sponding diol 17. The diol 17 was then converted to the
corresponding dimesylate 18 in 90% yield by treatment with
methanesulfonyl chloride and pyridine. The isopropylidene-
protected 1,5-anhydro-1-thio-L-gulitol (9) was prepared in
85% yield by treatment of the dimesylate 18 with sodium
sulfide in DMF. Reaction of dimesylate 18 with selenium
Results and discussion
Retrosynthetic analysis indicated that the analogues 3–6
could be synthesized by alkylation of the protected anhydro-
heteroalditols at the ring heteroatom with a terminal 1,3-
cyclic sulfate derived from D-mannose (Scheme 1).
The choice of protecting groups for the seleno- and thio-
anhydroalditols and the cyclic sulfate, however, merited
careful consideration, especially in the case of the selenon-
ium analogues. Our previous work suggested that hydro-
genolysis and strongly basic conditions as deprotection steps
were problematic for the selenonium analogues (12–14).
Therefore, we envisioned the use of only isopropylidene and
benzylidene acetals as the protecting groups for the seleno-
and thio-anhydroalditols (7–10) and the cyclic sulfate (11),
since these acetals would be subject to acidic hydrolysis
(Chart 3).
Our previous work also suggested that the release of ring
strain in the opening of a cyclic sulfate was beneficial (11–
14). Therefore, the benzylidene acetal at the 2,4-positions of
the cyclic sulfate 11 played a dual role as both a protecting
group and also as a facilitator of the coupling reactions with
the heterocyclic ethers 7–10. After the coupling reactions,
the products could then be readily deprotected by simple
treatment with trifluoroacetic acid.
The synthesis of the isopropylidene-protected 1,4-anhydro-
1-thio-D-talitol (7) and 1,4-anhydro-1-seleno-D-talitol (8)
© 2006 NRC Canada

Liu and Pinto
499
Chart 3.
Ph
O
H
H
S
Se
O
S
O
S
Se
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
10
7
8
9
11
Scheme 2.
OH
O
OH
MeO OMe
O
O
O
OH
OH
NaBH4, MeOH
OH
HO
HO
O
O
H
O
O
Acetone, p-TSA
O
O
OH
14
12
13, 87%
H
S
O
Na2S, DMF
90 °C
O
O
O
OMs
O
OMs
MsCl, pyr.
CH2Cl2
7, 88%
O
O
O
H
Se
O
Se, NaBH4
15
, 78%
in two steps
O
O
O
70 °C, EtOH
8
, 60%
Scheme 3.
O
OH
OH
O
O
O
O
OH
NaBH4, MeOH
HO
HO
12
OMe
DMF, p-TSA
O
O
O
OH
OH
O
O
OH
17
16
, 71%
S
O
Na2S, DMF
9, 85%
O
O
O
OMs
O
90 °C
O
O
MsCl, pyr.
CH2Cl2
O
Se
O
OMs O
Se, NaBH4
70 °C, EtOH
18, 75%,
two steps
O
10, 62%
O
and sodium borohydride in EtOH at 60–65 °C gave
isopropylidene-protected 10 in 62% yield (Scheme 3).
The coupling reactions of protected 7 and 8 were then in-
vestigated (Scheme 4). The solvent chosen for the coupling
reactions was the unusual solvent 1,1,1,3,3,3-hexafluoro-
isopropanol (HFIP), which was demonstrated in our earlier
work to offer significant advantage in analogous reactions.
Cyclic sulfate (11), prepared by a method developed in our
earlier work (16), was used as the coupling partner. 11 was
reacted with isopropylidene-protected 7 and 8 to give the
corresponding protected sulfonium and selenonium com-
pounds 19 and 20, respectively (Scheme 4).
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Can. J. Chem. Vol. 84, 2006
Scheme 4.
Ph
O
O
O
Ph
O
O
H
X
HFIP, K2CO3
O
S
O
H
O
+
O
X
OSO3
O
60-65 °C, X = Se
70-75 °C, X = S
O
O
O
O
O
O
O
O
O
O
19
X = S, 85%
20 X = Se, 73%
7 X = S
8
11
X = Se
Scheme 5.
Ph
O
O
Ph
O
O
O
S
O
O
X
OSO3
O
X
HFIP, K2CO3
O
O
+
O
80-85 oC, X =Se
90-95 oC, X =S
O
O
O
O
O
O
O
O
O
21 X = S, 90%
22
X = Se, 77%
9 X = S
10
11
X = Se
In analogous fashion, the coupling reactions of protected
9 and 10 with 11 afforded the protected sulfonium and
selenonium compounds 21 and 22, respectively (Scheme 5).
Fig. 1. NOE correlations observed in the 1D-NOE spectrum of 20.
Ph
O
O
O
The reactivities of 7, 8, 9, and 10 with 11 varied slightly.
The five-membered-ring anhydroalditols 7 and 8 were more
reactive than their six-membered-ring counterparts, 9 and
10, as illustrated by the higher temperatures required for the
coupling reactions in the latter cases. Compounds 7 and 8
reacted readily with 11 at 70–75 °C and 60–65 °C, respec-
tively, while compounds 9 and 10 reacted very slowly and
gave low yields of the coupling products at these tempera-
tures. When the temperature was increased to 90–95 °C and
80–85 °C, respectively, compounds 9 and 10 reacted readily
with 11. Within the same series, the selenoalditols were
found to be slightly more reactive than their sulfur counter-
parts. Selectivity for the attack at the primary center of 11
over possible alternative attack at the secondary center by
compounds 7–10 was invariably excellent and in no case
were isolable quantities of the regioisomers detected. In the
case of the coupling reaction of 8 with 11, there was a small
amount (<10%) of the diastereomer formed resulting from
electrophilic attack on the β-face of compound 8. However,
diastereoisomers at the stereogenic heteroatom centers were
not detected in all other cases.
1'
H2C
O
O
Se
4
OSO3
H
O
O
O
20
rinsing away the cleaved protecting groups with dichloro-
methane, the resulting residues were purified by flash
chromatography to yield compounds 3–6 as amorphous, hy-
groscopic solids. These compounds were characterized by
spectroscopic methods.
Conclusions
Two series of selenonium and sulfonium sulfates were
synthesized from D-mannose. The analogues contained ex-
tended acyclic chains of six carbon atoms, as well as ring
heteroatom substitution (S, Se) and five- and six-membered
heterocyclic rings. These syntheses utilized a 1,3-cyclic sul-
fate, also derived from D-mannose, in four steps. The
isopropylidene acetal and benzylidene acetal protecting
groups on the coupled products ensured facile deprotection
with TFA to yield the final compounds (3–6). These com-
pounds are being tested for their enzymatic activities.
The absolute stereochemistry at the heteroatom centre of
compounds 19–22 was established by 1D-NOE NMR spec-
troscopy (Fig. 1). Thus, for example, the 1D NOE spectra of
compound 20 indicated an H-4 to H-1′b correlation, imply-
ing that these hydrogens are syn-facial, and consequently, C-
1′ of the side chain must be anti to C-5 of the heterocyclic
moiety.
Deprotection of the coupled products 19–22 was carried
out by treatment with trifluoroacetic acid (Scheme 6). After
© 2006 NRC Canada

Liu and Pinto
501
Scheme 6.
Ph
O
O
O
OH OH
OSO3
OH
O
OH
TFA
H
O
H
O
OH
X
OSO3
X
O
HO
HO
O
HO
19 X = S
20
X = Se
3 X = S, 59%
4
X = Se, 47%
Ph
O
O
OH OH
O
OH
TFA
X
OSO3 O
O
OH
X
OSO3
OH
O
HO
HO
O
O
OH
21 X = S
22
5
X = S, 65%
6 X = Se, 55%
X = Se
ing material, the reaction mixture was poured into ice water,
extracted with CH2Cl2 (3 × 100 mL), washed with brine
(50 mL), and dried over Na2SO4. Purification by column
chromatography (hexane–EtOAc, 2:1) yielded compound 15
Experimental section
General
Optical rotations were measured at 23°. H and 13C NMR
spectra were recorded at 500 and 125 MHz, respectively. All
assignments were confirmed with the aid of two-dimensional
1
as a colorless syrup (25 g, 78%). [α]22 +18.0° (c 0.5,
D
1
CH2Cl2). H NMR ((CD3)2O) δ: 4.86 (1H, dd, J3,4 = 6.8,
1
1
1H, H (COSYDFTP), or H, 13C (INVBTP) experiments us-
ing standard Bruker pulse programs. Column chromatogra-
phy was performed with Merck Silica gel 60 (230–400
mesh). MALDI mass spectra were obtained on a PerSeptive
Biosystems, Voyager DE time-of-flight spectrometer for
samples dispersed in a 2,5-dihydroxybenzoic acid matrix.
High-resolution mass spectra were obtained by the
electrospray ionization (ESI) technique, using a ZabSpec
oaTOF mass spectrometer at 10 000 RP.
J4,5 = 6.5, H-4), 4.55–4.50 (3H, m, H-2, H-3, H-1b), 4.47
(1H, dd, J1a,1b = 11.1, J1a,2 = 7.6, H-1a), 4.29 (1H, ddd,
J4,5 = 6.5, H-5), 4.16 (1H, dd, J5,6b = 6.4, J6a,6b = 8.5, H-6b),
3.99 (1H, dd, J5,6a = 7.5, J6a,6b = 8.5, H-6a), 3.22 and 3.16
(6H, 2 s, 2OSO2CH3), 1.53, 1.43, 1.38, and 1.33 (12H, 4 s, 4
CH3). 13C NMR ((CD3)2O) δ: 109.97, 109.44 ((CH3)2C(OR)2),
78.72 (C-4), 76.79 (C-3), 75.11 (C-5), 75.02 (C-2), 68.92
(C-1), 66.43 (C-6), 38.93, 36.75 (2 SO2CH3), 26.89, 25.68,
25.34, 24.82 (4CH3). Anal. calcd. for C14H26O10S2: C 40.18,
H 6.26; found: C 40.45, H 6.14.
2,3,5,6-Di-O-isopropylidene-1,4-di-O-methanesulfonyl-D-
mannitol (15)
2,3,4,6-Di-O-isopropylidene-1,5-di-O-methanesulfonyl-D-
2,3,5,6-Di-O-isopropylidene-D-mannose (13) was pre-
pared by the literature method (23). To a solution of 13
(20 g, 77 mmol) in MeOH (200 mL), NaBH4 (5.8 g, 0.15
mol) was added portionwise at 0 °C. The progress of the re-
action was followed by TLC analysis of the aliquots (devel-
oping solvent, hexane–EtOAc, 1:1). When starting material
13 had been essentially consumed, the solvent was evapo-
rated under reduced pressure. The residue was redissolved in
EtOAc (150 mL), washed with satd. NH4Cl solution
(200 mL) and brine (50 mL), and dried over Na2SO4. After
evaporating the solvent, the crude diol (14) was used without
further purification. Diol 14 was dissolved in CH2Cl2
(50 mL) and then added dropwise to a mixture of pyridine
(100 mL) and methanesulfonyl chloride (26 mL, 0.34 mol)
cooled to 0 °C. The reaction mixture was stirred at 0 °C for
30 min, then allowed to rise to room temperature for 6 h.
When TLC analysis of the aliquots (developing solvent,
hexane–EtOAc, 1:1) showed total consumption of the start-
mannitol (18)
2,3,4,6-Di-O-isopropylidene-D-mannose (16) was pre-
pared by the literature method (24). To a solution of 16
(20 g, 77 mmol) in MeOH (200 mL), NaBH4 (5.8 g,
0.15 mol) was added portionwise at 0 °C. The progress of
the reaction was followed by TLC analysis of the aliquots
(developing solvent, hexane–EtOAc, 1:1). When starting ma-
terial 13 had been essentially consumed, the solvent was
evaporated under reduced pressure. The residue was
redissolved in EtOAc (150 mL), washed with satd. NH4Cl
solution (200 mL) and brine (50 mL), and dried over
Na2SO4. After evaporating the solvent, the crude diol (17)
was used without further purification. Diol 17 was dissolved
in CH2Cl2 (50 mL) and then added dropwise to a mixture of
pyridine (100 mL) and methanesulfonyl chloride (26 mL,
0.34 mol) cooled to 0 °C. The reaction mixture was stirred at
0 °C for 30 min, then allowed to rise to room temperature
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Can. J. Chem. Vol. 84, 2006
for 6 h. When TLC analysis of the aliquots (developing sol-
vent, hexane–EtOAc, 1:1) showed total consumption of the
starting material, the reaction mixture was poured into ice
water, extracted with CH2Cl2 (3 × 100 mL), washed with
brine (50 mL), and dried over Na2SO4. Purification by col-
umn chromatography (hexane–EtOAc, 2:1) yielded com-
109.16 ((CH3)2C(OR)2), 88.44 (C-3), 85.37 (C-2), 78.42 (C-
5), 68.97 (C-6), 51.34 (C-4), 29.17 (C-1), 26.73, 26.06,
25.37, 24.31 (4 CH3). Anal. calcd. for C12H20O4Se: C 46.91,
H 6.56; found: C 46.71, H 6.62.
2,3,4,6-Di-O-isopropylidene-1,5-anhydro-1-thio-L-gulitol
(9)
pound 18 as a colorless syrup (24 g, 75%). [α]22 +2.4°
D
1
(c 0.5, CH2Cl2). H NMR (CDCl3) δ: 4.82 (1H, ddd, J5,6a
=
To a solution of dimesylate 18 (6.0 g, 14.3 mmol) in DMF
(100 mL), Na2S·9H2O (4.1 g, 18.2 mmol) was added and the
reaction mixture was heated at 100 °C for 12 h. The reaction
mixture was poured into water (100 mL), extracted with
Et2O (4 × 50 mL), washed with water (10 × 20 mL), and
dried over Na2SO4. After evaporating the solvent, the crude
product was purified by column chromatography (hexane–
7.3, J5,6b = 5.1, J4,5 = 8.8, H-5), 4.54 (1H, ddd, J1a,2 = 4.1,
J1b,2 = 7.5, J2,3 = 6.3, H-2), 4.50 (1H, dd, J1a,1b = 10.3,
J1b,2 = 7.5, H-1b), 4.40 (1H, dd, J3,4 = 1.1, H-3), 4.38 (1H,
dd, H-1a), 4.14 (1H, dd, J6a,6b = 12.0, H-6b), 3.89 (1H, dd,
H-6a), 3.82 (1H, dd, H-4), 3.09 and 3.08 (6H, 2 s,
2OSO2CH3), 1.52, 1.49, 1.41, and 1.37 (12H, 4 s, 4CH3).
13C NMR (CDCl3) δ: 110.55, 100.03 ((CH3)2C(OR)2), 74.94
(C-2), 73.85 (C-3), 72.22 (C-5), 69.58 (C-4), 68.13 (C-1),
62.64 (C-6), 38.11, 38.04 (2SO2CH3), 27.45, 26.83 25.82,
20.37 (four CH3). Anal. calcd. for C14H26O10S2: C 40.18, H
6.26; found: C 39.99, H 6.02.
EtOAc, 3:1) to give 9 as a colorless oil (3.5 g, 93%). [α]22
D
1
–41° (c 0.5, CH2Cl2). H NMR ((CD3)2O) δ: 4.51 (1H, ddd,
J2,3 = 2.9, J1b,2 = 4.2, H-2), 4.30–4.24 (2H, m, H-4, H-6b),
4.06 (1H, dd, J3,4 = 6.2, J5,6b = 6.2, H-3), 3.63 (1H, dd,
J5,6a = 1.9, J6a,6b = 12.5, H-6a), 2.95 (1H, dd, J1a,1b = 13.5,
H-1b), 2.92 (1H, m, H-5), 2.57 (1H, dd, J1b,2 = 7.2, H-1a),
1.45, 1.39, 1.32, and 1.25 (12H, 4 s, 4CH3). 13C NMR
((CD3)2O) δ: 112.52, 103.61 ((CH3)2C(OR)2), 79.65 (C-3),
75.26 (C-4), 71.63 (C-2), 68.40 (C-6), 39.94 (C-5), 33.77
(C-1), 31.53, 29.55, 29.49, 23.22 (4CH3). Anal. calcd. for
C12H20O4S: C 55.36, H 7.74; found: C 55.43, H 7.70.
2,3,5,6-Di-O-isopropylidene-1,4-anhydro-1-thio-D-talitol
(7)
To a solution of dimesylate 15 (4.0 g, 9.6 mmol) in DMF
(80 mL), Na2S·9H2O (2.8 g, 11.5 mmol) was added and the
reaction mixture was heated at 90 °C for 12 h. The reaction
mixture was poured into water (100 mL), extracted with
Et2O (4 × 50 mL), washed with water (10 × 20 mL), and
dried over Na2SO4. After evaporating the solvent, the crude
product was purified by column chromatography (hexane–
2,3,4,6-Di-O-isopropylidene-1,5-anhydro-1-seleno-L-
gulitol (10)
To a suspension of Se powder (1.6 g, 20.2 mmol) and
95% EtOH (100 mL), NaBH4 was added portionwise until
the black selenium color disappeared. To this mixture a solu-
tion of dimesylate 18 (6.0 g, 14.3 mmol) in THF (10 mL)
was added and the reaction mixture was heated at 70 °C for
12 h. The solvent of the reaction mixture was evaporated un-
der reduced pressure, redissolved in EtOAc, washed with
water (20 mL) and brine (20 mL), and dried over Na2SO4.
After evaporating the solvent, the crude product was purified
by column chromatography (hexane–EtOAc, 3:1) to give 10
EtOAc, 3:1) to give 7 as a colorless oil (2.2 g, 88%). [α]22
D
1
–47° (c 0.5, CH2Cl2). H NMR ((CD3)2O) δ: 4.93 (1H, ddd,
J2,3 = 5.7, J1a,2 = 1.3, J1b,2 = 5.1, H-2), 4.75 (1H, dd, J3,4
=
1.6, J2,3 = 5.7, H-3), 4.06 (1H, dd, J6a,6b = 7.7, J5,6b = 6.2, H-
6b), 3.72 (1H, dd, J5,6a = 7.4, H-6a), 3.34 (1H, dd, H-4),
3.17 (1H, dd, J1a,1b = 12.2, H-1b), 2.74 (1H, dd, H-1a), 1.43,
1.38, 1.29, and 1.28 (12H, 4 s, 4CH3). 13C NMR ((CD3)2O)
δ: 110.85, 109.27 ((CH3)2C(OR)2), 87.33 (C-3), 84.09 (C-2),
78.25 (C-5), 68.03 (C-6), 56.34 (C-4), 38.47 (C-1), 26.45,
25.93, 25.38, 24.24 (4CH3). Anal. calcd. for C12H20O4S: C
55.36, H 7.74; found: C 55.62, H 7.73.
as a colorless oil (2.7 g, 62%). [α]22 –32° (c 0.5, CH2Cl2).
D
1H NMR ((CD3)2O) δ: 4.97 (1H, ddd, J2,3 = 5.8, J1a,2 = 2.4,
J1b,2 = 5.4, H-2), 4.71 (1H, dd, J3,4 = 2.9, H-3), 4.28 (1H,
ddd, J4,5 = 5.1, J5,6a = 7.9, J5,6b = 6.1, H-5), 4.09 (1H, dd,
J6a,6b = 8.0, H-6b), 3.69 (1H, dd, H-6a), 3.61 (1H, dd, H-4),
3.23 (1H, dd, J1a,1b = 11.4, H-1b), 2.87 (1H, dd, H-1a), 1.45,
1.39, 1.28, and 1.26 (12H, 4 s, 4CH3). 13C NMR ((CD3)2O)
δ: 110.64, 109.13 ((CH3)2C(OR)2), 88.46 (C-3), 85.42 (C-4),
78.46 (C-5), 68.93 (C-6), 51.34 (C-4), 26.71 (C-1), 26.06,
25.38, 25.23, 24.43 (4CH3). Anal. calcd. for C12H20O4Se: C
46.91, H 6.56; found: C 46.67, H 6.28.
2,3,5,6-Di-O-isopropylidene-1,4-andydro-1-seleno-D-
talitol (8)
To a suspension of Se (1.6 g, 20.2 mmol) and 95% EtOH
(100 mL), NaBH4 (1.5 g, 40.4 mmol) was added portionwise
until the black selenium color disappeared. To this mixture a
solution of dimesylate 15 (6.0 g, 14.3 mmol) in THF
(10 mL) was added and the reaction mixture was heated at
70 °C for 12 h. The solvent of the reaction mixture was
evaporated under reduced pressure, redissolved in EtOAc,
washed with water (20 mL) and brine (20 mL), and dried
over Na2SO4. After evaporating the solvent, the crude prod-
uct was purified by column chromatography (hexane–
General procedure for the preparation of sulfonium
and selenium sulfates (19–22)
A mixture of 2,3,5,6-di-O-isopropylidene-1,4-anhydro-1-
thio-D-talitol (7), 2,3,4,6-di-O-isopropylidene-1,5-anhydro-1-
thio-L-gulitol (9), 2,3,5,6-di-O-isopropylidene-1,4-anhydro-
1-seleno-D-talitol (8), or 2,3,4,6-di-O-isopropylidene-1,5-
anhydro-1-seleno-L-gulitol (10) and cyclic sulfate 11 in
HFIP were placed in a reaction vessel and K2CO3 (20 mg)
was added. The stirred reaction mixture was heated in a
sealed tube at the indicated temperature for the indicated
time, as given in the following. The progress of the reaction
EtOAc, 3:1) to give 8 as a colorless oil (3.1 g, 71%). [α]22
D
1
–40° (c 1, CH2Cl2). H NMR ((CD3)2O) δ: 4.97 (1H, ddd,
J2,3 = 5.7, J1a,2 = 2.4, J1b,2 = 5.5, H-2), 4.71 (1H, dd, J3,4
=
2.9, J2,3 = 5.7, H-3), 4.28 (1H, ddd, J5,6a = 7.4, J5,6b = 6.1,
H-5), 4.09 (1H, dd, J6a,6b = 8.1, H-6b), 3.69 (1H, dd, J5,6a
=
7.4, H-6a), 3.61 (1H, dd, J4,5 = 5.1, H-4), 3.23 (1H, dd,
J1a,1b = 11.3, H-1b), 2.87 (1H, dd, H-1a), 1.43, 1.38, 1.29,
and 1.27 (12H, 4 s, 4CH3). 13C NMR ((CD3)2O) δ: 110.59,
© 2006 NRC Canada

Liu and Pinto
503
was followed by TLC analysis of the aliquots (developing
solvent, EtOAc–MeOH, 10:1). When the limiting reagent
had been essentially consumed, the mixture was cooled, then
diluted with CH2Cl2 and evaporated to give a syrupy resi-
due. Purification by column chromatography (EtOAc to
EtOAc–MeOH, 10:1) gave the purified and sulfonium salts
19 and 21 and selenonium salts 20 and 22.
1,5-Anhydro-2,3,4,6-di-O-isopropylidene-1-[(S)-
[(2′R,3′S,4′R,5′R)-2′,4′-benzylidenedioxy-5′,6′-
isopropylidenedioxy-3′-(sulfooxy)hexyl]sulfonio]-L-gulitol
inner salt (21)
Reaction of compound 9 (500 mg, 1.92 mmol) with 11
(860 mg, 2.30 mmol) in HFIP (2.0 mL) for 12 h at 90–95 °C
gave compound 21 as a colorless, amorphous solid (1.12 g,
90% based on 9). [α]22 –52 ° (c 0.5, CH2Cl2). H NMR
1
((CD3)2O) δ: 7.62–7.38D(5H, m, Ar), 5.88 (1H, s, CHPh),
4.94 (1H, ddd, J2,3 = 3.0, J1a,2 = 2.4, J1b,2 = 3.0, H-2), 4.85
(1H, ddd, J2′,3′ = 1.8, J1′a,2′ = 6.1, J1′b,2′ = 3.1, H-2′), 4.60
1,4-Anhydro-2,3,5,6-di-O-isopropylidene-1-[(S)-
[(2′R,3′S,4′R,5′R)-2′,4′-benzylidenedioxy-5′,6′-
isopropylidenedioxy-3′-(sulfooxy)hexyl]sulfonio]-D-talitol
inner salt (19)
Reaction of compound 7 (400 mg, 1.53 mmol) with 11
(740 mg, 1.99 mmol) in HFIP (2.0 mL) for 12 h at 70–75 °C
(1H, dd, J3,4 = 3.0, H-4), 4.55 (1H, ddd, J4′,5′ = 2.0, J5′,6′a
=
7.7, J5′,6′b = 6.7, H-5′), 4.52 (1H, dd, J3′,4′ = 1.9, H-3′),
4.44 (1H, dd, J1′a,1′b = 14.2, H-1′b), 4.43 (1H, m, H-4′),
4.39 (1H, dd, J6′a,6′b = 8.5, H-6′b), 4.35 (1H, dd, H-3), 4.33
gave compound 19 as a colorless, amorphous solid (820 mg,
(1H, dd, H-1′a), 4.26 (1H, dd, H-6′a), 4.18 (1H, dd, J1a,1b
=
1
85% based on 7). [α]22 –40° (c 0.5, CH2Cl2). H NMR
D
13.6, H-1b), 4.14 (1H, m, H-6b), 3.93 (1H, dd, J6a,6b = 13.3,
J5,6a = 1.6, H-6a), 3.80 (1H, dd, H-1a), 3.68 (1H, m, H-5),
1.62, 1.48, 1.40, 1.36, 1.35, and 1.29 (18H, 6 s, 6CH3). 13C
NMR ((CD3)2O) δ: 138.12, 129.26, 128.46, 126.52 (4 CAr),
109.73, 107.42, 100.73 (3(CH3)2C(OR)2), 100.46 (CHPh),
79.03 (C-4′), 76.84 (C-5′), 74.24 (C-2), 71.66 (C-3), 69.95
(C-3′), 67.16 (C-4), 65.71 (C-4), 64.66 (C-6′), 61.52 (C-6),
49.18 (C-1′), 48.93 (C-5), 33.77 (C-1), 28.73, 25.92, 25.74,
25.67, 22.72, 18.23 (6CH3). Anal. calcd. for C28H40O12S2: C
53.15, H 6.37; found: C 52.95, H 6.14.
(CD2Cl2) δ: 7.48–7.30 (5H, m, Ar), 5.68 (1H, s, CHPh),
5.15 (1H, ddd, J2,3 = 5.6, J1a,2 = 1.9, J1b,2 = 5.6, H-2), 4.98
(1H, dd, H-3), 4.55–4.51 (2H, m, H-4, H-2′), 4.46 (1H, ddd,
J4,5 = 4.1, J5,6 a = 6.3, J5,6b = 6.3, H-5), 4.40 (1H, dd, J1a,1b
=
13.4, J1b,2 = 5.6, H-1b), 4.18 (2H, dd, H-6a, H-6b), 4.16–
4.04 (4H, m, H-1a, H-3′, H-4′, H-5), 3.76 (2H, dd, H-1a, H-
1b), 3.35 (1H, dd, J6a,6b = 9.5, J5,6b = 7.6, H-6b), 3.16 (1H,
dd, J5,6a = 6.4, H-6a), 1.52, 1.33, 1.31, 1.28, 1.26, and 1.16
(18H, 6 s, 6CH3). 13C NMR (CD2Cl2) δ: 137.28, 129.65,
128.63, 126.37 (4CAr), 112.85, 111.37, 108.64 (three
(CH3)2C(OR)2), 100.87 (CHPh), 89.77 (C-3), 84.24 (C-2),
79.32 (C-3′), 75.48 (C-5′), 75.33 (C-5), 74.36 (C-4), 70.47
(C-2′), 67.92 (C-4′), 67.05 (C-6), 65.18 (C-6′), 50.12 (C-1),
44.42 (C-1′) 26.56, 26.15, 25.62, 25.57, 25.03, 22.86
(6CH3). Anal. calcd. for C28H40O12S2: C 53.15, H 6.37;
found: C 52.92, H 6.17.
1,5-Anhydro-2,3,4,6-di-O-isopropylidene-1-[(S)-
[(2′R,3′S,4′R,5′R)-2′,4′-benzylidenedioxy-5′,6′-
isopropylidenedioxy-3′-(sulfooxy)hexyl]selenonio]-L-gulitol
inner salt (22)
Reaction of compound 10 (500 mg, 1.63 mmol) with 11
(780 mg, 2.09 mmol) in HFIP (2.0 mL) for 12 h at 80–85 °C
gave compound 22 as a colorless, amorphous solid (850 mg,
1
77% based on 10). [α]22 –31° (c 0.5, CH2Cl2). H NMR
1,4-Anhydro-2,3,5,6-di-O-isopropylidene-1-[(S)-
[(2′R,3′S,4′R,5′R)-2′,4′-benzylidenedioxy-5′,6′-
isopropylidenedioxy-3′-(sulfooxy)hexyl]selenonio]-D-talitol
inner salt (20)
Reaction of compound 8 (500 mg, 1.63 mmol) with 11
(780 mg, 2.09 mmol) in HFIP (2.0 mL) for 12 h at 60–65 °C
gave compound 20 and a minor product (<10%) as a color-
less, amorphous solid (810 mg, 73% based on 8). The major
product (20): [α]22 –46° (c 0.5, CH2Cl2). 1H NMR
((CD3)2O) δ: 7.62–7D.38 (5H, m, Ar), 5.92 (1H, s, CHPh),
5.47 (1H, ddd, J2,3 = 5.6, J1a,2 = 1.3, J1b,2 = 5.9, H-2), 5.35
D
((CD3)2O) δ: 7.62–7.40 (5H, m, Ar), 5.92 (1H, s, CHPh),
5.46 (1H, ddd, J2,3 = 5.6, J1a,2 = 1.2, J1b,2 = 5.9, H-2), 5.37
(1H, dd, H-3), 4.85 (1H, m, H-2′), 4.62 (1H, dd, J1′b,2′ = 6.5,
J1′a,1 ′b = 11.3, H-1′b), 4.60 (1H, m, H-3′), 4.55 (1H, ddd,
J4,5 = 1.3, J5,6a = 6.6, J5,6b = 6.8, H-5), 4.47 (1H, ddd, J4′,5′
=
2.4, J5′,6′a = 7.4, J5′,6′b = 6.6, H-5′), 4.39 (2H, m, H-4, H-
4′)), 4.35 (1H, dd, J6′a,6′b = 8.5, H-6′b), 4.24 (1H, dd, H-
6′a), 4.09 (1H, dd, J1′a,2′ = 1.4, H-1 a), 3.90 (1H, dd, J1a,1b
=
14.2, H-1b), 3.84 (1H, dd, H-1a), 3.70 (1H, dd, J6a,6b = 9.4,
H-6b), 3.32 (1H, dd, H-6a), 1.59, 1.38, 1.35, 1.31, 1.30, and
1.24 (18H, 6 s, 6CH3). 13C NMR ((CD3)2O) δ: 138.23,
129.22, 128.47, 126.45 (4CAr), 110.43, 110.75, 107.67
(3(CH3)2C(OR)2), 100.45 (CHPh), 91.58 (C-3), 85.89 (C-2),
78.93 (C-4), 76.55 (C-5′), 75.42 (C-5), 74.16 (C-2′), 70.95
(C-3′), 68.03 (C-6), 67.56 (C-4), 64.86 (C-6′), 46.23 (C-1),
41.60 (C-1′), 26.03, 25.85, 25.62, 25.34, 23.99, 22.72
(6CH3). Anal. calcd. for C28H40O12SSe: C 49.48, H 5.93;
found: C 49.71, H 6.10.
(1H, dd, H-3), 4.92 (1H, ddd, H-2′), 4.60 (1H, dd, J1 ′b,2 ′
=
6.4, J1 ′a,1 ′b = 12.3, H-1′b), 4.57 (1H, m, H-4), 4.55 (1H,
ddd, J5,6b = 6.9, J5,6a = 6.6, J4,5 = 1.5, H-5), 4.48 (1H, ddd,
J5 ′,6 ′b = 6.7, J5 ′,6 ′a = 7.4, J4 ′,5 ′ = 2.5, H-5′), 4.42–4.34
(3H, m, H-3′, H-6′b, H-4), 4.24 (1H, dd, J6 ′a,6 ′b = 8.1, H-
6′a), 4.09 (1H, dd, J1 ′a,2 ′ = 1.5, H-1′a), 3.89 (1H, dd, J1a,1b
=
14.1, H-1b), 3.84 (1H, dd, H-1a), 3.70 (1H, dd, J6a,6b = 9.4,
H-6b), 3.34 (1H, dd, H-6a),1.59, 1.38, 1.35, 1.30, 1.29, and
1.24 (18H, 6 s, 6CH3). 13C NMR ((CD3)2O) δ: 138.21,
129.24, 128.42, 126.48 (4CAr), 111.32, 107.67, 100.47
(3(CH3)2C(OR)2), 100.41 (CHPh), 91.54 (C-3), 85.82 (C-2),
78.92 (C-3′), 76.67 (C-5), 75.54 (C-5), 74.18 (C-2), 70.82
(C-4′), 67.97 (C-6), 67.45 (C-4), 64.74 (C-6′), 46.24 (C-1),
41.78 (C-1) 26.02, 25.85, 25.67, 25.44, 24.02, 22.75 (6CH3).
Anal. calcd. for C28H40O12SSe: C 49.48, H 5.93; found: C
49.16, H 6.09.
General procedure for the deprotection of the coupling
products to yield the final compounds (3–6)
The protected coupling products 19–22 were dissolved in
CH2Cl2 (2 mL), TFA (10 mL) was then added, and the mix-
ture was stirred for 6–8 h at room temperature. The progress
of the reaction was followed by TLC analysis of the aliquots
(developing solvent, EtOAc–MeOH–H2O, 7:3:1). When the
© 2006 NRC Canada

504
Can. J. Chem. Vol. 84, 2006
starting material had been consumed, the TFA and CH2Cl2
were removed under reduced pressure. The residue was
rinsed with CH2Cl2 (4 × 2 mL) and the CH2Cl2 was de-
canted to remove the cleaved protecting groups. The remain-
ing gum was dissolved in MeOH and purified by column
chromatography (EtOAc and EtOAc–MeOH, 2:1) to give
the purified compounds 3–6 as colorless, amorphous, and
hygroscopic solids.
ddd, J4,5 = 4.5, J5,6b = 6.3, H-5), 4.07 (1H, dd, J1′b,2′ = 3.3,
J1′a,1 ′b = 10.8, H-1′b), 4.06–4.02 (2H, m, H-4′, H-6′b), 3.98
(1H, dd, J6′a,6′b = 11.9, J5′,6′a = 7.4, H-6′a), 3.94 (1H, dd,
J3,4 = 2.4, J4,5 = 4.5, H-4), 3.86–3.83 (1H, m, H-5), 3.73
(1H, dd, J5,6b = 2.6, J6a,6b = 11.8, H-6b), 3.69 (1H, dd,
J1′a,2 ′ = 4.4, H-1′a), 3.58 (1H, dd, J1b,2 = 5.5, J1a,1b = 11.4,
H-1b), 3.56 (1H, dd, J5,6a = 5.8, H-6a), 3.46 (1H, dd, H-1a).
13C NMR (D2O) δ: 77.63 (C-2′), 70.53 (C-2), 69.57 (C-3),
69.04 (C-4), 68.84 (C-5′), 67.42 (C-3′), 63.55 (C-5), 62.73
(C-6), 59.60 (C-6′), 54.03 (C-4′), 45.56 (C-1′), 37.34 (C-1).
HRMS calcd. for C12H24O12S2Na: 447.0601 (M + Na);
found: 447.0601.
1,4-Anhydro-1-[(S)-[(2′R,3′S,4′R,5′R)-2′,4′,5′,6′-
tetrahydroxy-3′-(sulfooxy)hexyl]sulfonio]-D-talitol inner
salt (3)
To a solution of 19 (400 mg, 0.63 mmol) in CH2Cl2
(2 mL) was added TFA (10 mL) to yield compound 3 as a
colorless, amorphous, and hygroscopic solid (150 mg, 59%).
[α]22D –29° (c 0.1, H2O). 1H NMR (D2O) δ: 4.60 (1H, m, H-
2), 4.56 (1H, dd, J3 ′,4 ′ = 1.1, J2 ′,3 ′ = 5.0, H-3′), 4.50 (1H,
1,5-Anhydro-1-[(S)-[(2′R,3′S,4′R,5′R)-2′,4′,5′,6′-
tetrahydroxy-3′-(sulfooxy)hexyl]selenonio]-L-gulitol inner
salt (6)
To a solution of 22 (400 mg, 0.59 mmol) in CH2Cl2
(2 mL) was added TFA (10 mL) to yield compound 6 as a
colorless, amorphous, and hygroscopic solid (150 mg, 55%).
[α]22D –68° (c 0.1, H2O). 1H NMR (D2O) δ: 4.74 (1H, m, H-
2), 4.55 (1H, dd, J3′,4′ = 1.1, J2′,3′ = 5.0, H-3′), 4.49 (1H,
ddd, J1 ′b,2 ′ = 10.5, J1 ′a,2 ′ = 2.8, H-2′), 4.32 (1H, dd, J2,3
=
9.6, J3,4 = 2.8, H-3), 4.17 (1H, ddd, H-5), 4.00 (1H, dd,
J1 ′a,1 ′b = 13.2, H-1′b), 3.92 (1H, dd, J4,5 = 9.5, H-4), 3.91
(1H, dd, H-1′a), 3.80 (1H, dd, J4 ′,5 ′ = 9.0, H-4′), 3.78 (1H,
ddd, J1′b,2′ = 10.3, H-2′), 4.23 (1H, dd, J2,3 = 3.1, J3,4
=
dd, J6a,6b = 12.2, J5,6b = 3.5, H-6b), 3.73 (1H, dd, J5 ′,6 ′b
=
10.2, H-3), 4.15 (1H, m, H-5), 3.98 (1H, dd, J1′a,1′b = 12.3,
H-1′b), 3.94 (1H, dd, J1′a,2′ = 3.7, H-1′a), 3.86 (1H, dd,
J4,5 = 1.7, H-4), 3.81–3.75 (2H, m, H-4′, H-6b), 3.73 (1H,
dd, J5′,6′b = 2.8, J6′a,6′b = 11.7, H-6′b), 3.69 (1H, ddd, H-5′),
3.61 (1H, dd, J5,6a = 3.3, J6a,6b = 8.7, H-6a), 3.55 (1H, dd,
J5′,6′a = 11.7, H-6′a), 3.41 (1H, dd, J1b,2 = 3.2, J1a,1b = 13.4,
H-1b), 3.37 (1H, dd, H-1a). 13C NMR (D2O) δ: 78.35 (C-
3′), 77.22 (C-3), 73.54 (C-2), 70.54 (C-5′), 69.28 (C-4′),
67.92 (C-2′), 67.15 (C-5), 65.04 (C-6), 63.78 (C-4), 62.74
(C-6′), 46.63 (C-1′), 40.68 (C-1). HRMS calcd. for
C12H24O12SSeNa: 495.0046 (M + Na); found: 495.0045.
2.7, J6 ′a,6 ′b = 11.8, H-6′b), 3.69 (1H, ddd, J5 ′,6 ′a = 6.1,
H-5′), 3.66 (1H, dd, J5,6a = 4.1, H-6a), 3.56 (1H, dd, J1b,2
=
7.6, J1a,1b = 11.4, H-1b), 3.55 (1H, dd, J1a,2 = 5.8, H-1a),
3.54 (1H, m, H-6′a). 13C NMR (D2O) δ: 77.81 (C-3′), 76.26
(C-3), 72.93 (C-2), 70.52 (C-5′), 68.98 (C-4′), 67.91 (C-2′),
67.55 (C-5), 64.62 (C-6), 64.53 (C-4), 62.85 (C-6′), 49.41
(C-1′), 44.57 (C-1). HRMS calcd. for C12H24O12S2Na:
447.0601 (M + Na); found: 447.0604.
1,4-Anhydro-1-[(S)-[(2′R,3′S,4′R,5′R)-2′,4′,5′,6′-
tetrahydroxy-3′-(sulfooxy)hexyl]selenonio]-D-talitol inner
salt (4)
To a solution of 20 (400 mg, 0.59 mmol) in CH2Cl2
(2 mL) was added TFA (10 mL) to yield compound 4 as a
colorless, amorphous, and hygroscopic solid (132 mg, 47%).
[α]22D –50° (c 0.1, H2O). 1H NMR (D2O) δ: 4.74 (1H, m, H-
2), 4.54 (1H, dd, J3′,4 ′ = 1.1, J2 ′,3 ′ = 5.0, H-3′), 4.47 (1H,
ddd, H-2), 4.22′ (1H, dd, J2,3 = 10.0, J3,4 = 2.9, H-3), 4.14
(1H, m, H-5), 3.96 (1H, dd, J1 ′b,2 ′ = 10.3, H-1′b), 3.92 (1H,
Acknowledgements
We are grateful to the Natural Sciences and Engineering
Research Council of Canada (NSERC) for financial support
and to B.D. Johnston for helpful discussions. We are also
grateful to D.R. Bundle for the high-resolution mass spectra.
dd, J1 ′a,2 ′ = 3.7, J1 ′a,1 ′b = 12.3, H-1′a), 3.85 (1H, dd, J4,5
=
References
1.9, H-4), 3.77 (1H, dd, J5,6b = 2.6, J6a,6b = 12.2, H-6b), 3.71
(1H, dd, J6 ′a,6 ′b = 11.8, J5 ′,6 ′b = 2.4, H-6′b), 3.70–3.63
(2H, m, H-4′, H-5′), 3.60 (1H, dd, J5,6a = 3.5, H-6a), 3.55
(1H, dd, J5 ′,6 ′a = 9.1, H-6′a), 3.41 (1H, dd, J1b,2 = 3.2,
J1a,1b = 13.2, H-1b), 3.36 (1H, dd, H-1a). 13C NMR (D2O) δ:
78.44 (C-3′), 77.28 (C-3), 73.62 (C-2), 70.50 (C-5′), 69.13
(C-4′), 67.96 (C-2′), 67.22 (C-5), 65.06 (C-6), 63.69 (C-4),
62.73 (C-6), 46.84 (C-1′), 40.99 (C-1). HRMS calcd. for
C12H24O12SSeNa: 495.0046 (M + Na); found: 495.0044.
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