Synthesis of a unique trisaccharide having an acetal linkage between open-chain and cyclic sugar found in the cell wall of Proteus

Article abstract of DOI:10.1016/j.tetasy.2008.12.006

The first stereoselective synthesis of a unique trisaccharide containing an open-chain glycosyl cyclic acetal moiety found in the cell wall of Proteus has been successfully achieved. Most of the intermediate steps are high yielding and highly reproducible. The acetal linkage of the open-chain d-galactosamine moiety with an (S)-configuration was formed exclusively.

Full text of DOI:10.1016/j.tetasy.2008.12.006

Tetrahedron: Asymmetry 19 (2008) 2746–2751
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Synthesis of a unique trisaccharide having an acetal linkage between
open-chain and cyclic sugar found in the cell wall of Proteus q
*
Chinmoy Mukherjee, Anup Kumar Misra
Medicinal and Process Chemistry Division, Central Drug Research Institute, Chattar Manzil Palace, Lucknow 226 001, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The first stereoselective synthesis of a unique trisaccharide containing an open-chain glycosyl cyclic ace-
tal moiety found in the cell wall of Proteus has been successfully achieved. Most of the intermediate steps
are high yielding and highly reproducible. The acetal linkage of the open-chain D-galactosamine moiety
with an (S)-configuration was formed exclusively.
Received 27 November 2008
Accepted 9 December 2008
Available online 10 January 2009
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
Open Chain
OH
OH
HO
NHAc
Proteus mirabilis is one of the most common gram-negative
pathogens encountered in clinical specimens belonging to ‘Entero-
bacteriaceae’ and can cause a variety of community or hospital-ac-
quired illnesses, including urinary tract, wound, and bloodstream
infections (BSI).1 Proteus mirabilis is a common cause of urinary
tract infection (UTI) in catheterized patients and those with uri-
nary tract abnormalities and occurs with significant frequency in
hospitals.2 It shows a preference for the upper urinary tract where
it can cause serious kidney damage, acute pyelonephritis, bladder
or renal stones, fever, and bacteriemia.3 The mechanism of patho-
genesis is unclear, but several virulence properties have been cited
in the literature,4 which include uroepithelial cell adhesin, fimb-
riae, hemolysin production, the ability to invade kidney epithe-
lium, and the production of urease.
O
HO
HO
O
C-1
OH
HO
O
O
O
Pyranose
H
O
NH2
Acetal Linkage
HO
Figure 1. A unique trisaccharide found in the core lipopolysaccharide of the cell
wall of Proteus mirabilis O27.
accepted and well-supported mechanism for the biosynthesis of
polysaccharides, it is believed that a glycosyltransferase enzyme
stereospecifically joins a cyclic pyranose or furanose sugar to an-
other sugar residue using required cyclic sugar nucleotides.8 In
contrast to the generally accepted knowledge, the formation of
such types of glycosidic linkage found in the cell wall lipopolysac-
charide of Proteus probably takes place via a new, yet unknown,
biosynthetic pathway.9 After the discovery of such a new type of
glycosylidine glycoside in the cell wall of Proteus, it is essential
to establish whether this type of glycosides has any role in impor-
tant biological function or can function as a cellwall antigen or act
as a virulence factor. The existence of this new type of glycoside
certainly indicated the existence of a new class of enzymes for
their biosynthesis, which are different from the existing glycosyl-
transferases as they use cyclic sugar nucleotides as substrates.
For a detailed study on the biological role of this unique trisaccha-
ride, it is essential to synthesize it chemically, as the natural source
cannot provide it in large quantity. Due to the unique structural
features of this trisaccharide, it poses some extra challenges to
the synthetic chemist.
In 1999, for the first time, Vinogardov and Bock5 discovered a
trisaccharide found in the core lipopolysaccharide (LPS) of the cell
wall of two serotypes of Proteus, in which an open-chain monosac-
charide moiety is linked to a cyclic monosaccharide through an
acetal linkage (Fig. 1). Afterwards, a number of oligosaccharides
of similar structures have been found in other strains of Gram-neg-
ative bacteria.6 Generally, in the naturally occurring glycosides,
monosaccharide units exist in the cyclic form (pyranose or fura-
nose) and are joined together through O-glycosidic and sometimes
through C-glycosidic bonds. Several biosynthetic pathways for the
formation of naturally occurring glycoconjugates have been dem-
onstrated by considering the involvement of several glycosyltrans-
ferase enzymes in their biosynthesis.7 According to the generally
q
C.D.R.I. Communication No. 7615.
* Corresponding author at present address. Division of Molecular Medicine,
Bose Institute, P-1/12, C.I.T. Scheme VII-M, Kolkata 700 054, India. Tel.: +91 33
25693240; fax: +91 33 2355 3886.
In the present scenario, the preparation of carbohydrate-de-
rived molecules of biological importance becomes an important
area in medicinal chemistry. Herein, we report a concise chemical
E-mail address: akmisra69@rediffmail.com (A.K. Misra).
0957-4166/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2008.12.006

C. Mukherjee, A. K. Misra / Tetrahedron: Asymmetry 19 (2008) 2746–2751
2747
synthesis of the unique trisaccharide found in the core lipopoly-
AcO
AcO
OAc
O
saccharide of Proteus mirabilis O27 (Fig. 2). A number of reports10
have already appeared in the literature for the syntheses and
isolations of oligosaccharides containing acetal linkages between
two cyclic monosaccharides. Recently, the formation of glycosy-
lidene acetals and their selective reduction toward the formation
of 6,60-ether-linked disaccharide natural product, coyolosa has
been reported.11 Very recently, Yu et al.12 also reported the syn-
thesis of a natural product containing such a type of acyclic gly-
cosylidene linkage.
AcO
AcO
OAc
O
Three steps
OAc
N3
2
3
Ph
O
OAc
O
AcO
AcO
O
a
b, c
O
HO
N3
N3
OPMP
OPMP
4
5
OH
OH
Ph
OH
NHAc
O
OH
O
HO
BzO
O
HO
e
O
C
O
d
B
O
O
O
HO
BzO
HO
OH
O
OPMP
NHAc
H
N3
N3
OPMP
A
OPMP
7
1
6
HO
Scheme 1. Reagents and conditions: (a) 4-Methoxy phenol, BF3ꢀEt2O, CH2Cl2,
0 °C?15 °C, 3 h, 70%; (b) CH3ONa, CH3OH, room temperature, 3 h; (c) benzaldehyde
dimethylacetal, p-TsOH, CH3CN, room temperature, 2 h, 88% over two steps; (d)
benzoyl chloride, pyridine, room temperature, 2 h, 95%; (e) HClO4–SiO2, CH3CN–
H2O (20:1, v/v) 20 min, room temperature, 85%.
OAc
AcO
AcO
OAc
O
O
AcO
AcO
AcO
CCl3
NH
O
fied to use protected acyclic 2-amino-2-deoxy-galactitol derivative
for the preparation of the target trisaccharide derivative.
2
8
Using 3,4,6-tri-O-acetyl-
2-azido-3,4,6-tri-O-benzyl-2-deoxy-
D
-galactal
2
D
as
a starting material,
a,b-
-galactopyranose 917 was
Figure 2. Structure of the synthesized trisaccharide as its 4-methoxyphenyl
prepared in three steps following literature-reported reaction
conditions. Compound 9 was converted to linear galactitol deriva-
tive 10 via sodium borohydride reduction18 in 86% yield. Selective
protection of the primary hydroxy group19 of compound 10 using
tert-butyldimethylchlorosilane furnished the linear galactitol
acceptor 11 in 90% yield. Glycosylation of compound 11 with
glycoside and its precursors.
2. Results and discussion
The synthesis of the target trisaccharide 1 as its 4-methoxy-
phenyl glycoside has been achieved from
intermediates in a minimum number of steps. 1,3,4,6-Tetra-O-
acetyl-2-azido-2-deoxy- ,b-
-galactopyranose 313 was prepared
from 3,4,6-tri-O-acetyl- -galactal 2 under azido-nitration condi-
tion reported earlier. Compound 3 was reacted with 4-methoxy-
phenol in the presence of borontrifluoride14 to give compound 4
in 70% yield. Deacetylation followed by benzylidenation of
compound 4 furnished compound 5 in 88% overall yield. Conven-
tional benzoylation of compound 5 followed by removal of the
benzylidene acetal using perchloric acid supported over silica gel
D
-galactal-derived
2,3,4,6-tetra-O-acetyl-a-D
-glucopyranosyl trichloroacetimidate 820
in the presence of trimethylsilyl trifluoromethanesulfonate
(TMSOTf)21 afforded disaccharide derivative 12 in 82% yield. Sig-
nals at d 99.3 (C-1C) and 71.5 (C-1B) in the 13C NMR spectra sup-
ported the formation of compound 12. Removal of the silyl
protection of compound 12 under acidic conditions22 gave
compound 13 in 86% yield. Oxidation of the primary hydroxy
group of compound 13 using the Dess–Martin periodinane fol-
lowed by acetal formation12 with compound 7 in the presence of
TMSOTf furnished trisaccharide derivative 14 in 69% overall yield.
Signals at d 5.69 (d, J = 3.3 Hz, H-1A), 5.39 (d, J = 5.4 Hz, H-1B), 4.88
(d, J = 8.1 Hz, H-1C) in the 1H NMR and at d 99.6 (C-1C), 97.5 (C-1A),
95.9 (C-1B) in the 13C NMR spectra supported the formation of
compound 14. Compound 14 has a new stereogenic center which
a
D
D
(HClO4–SiO2)15 furnished compound
(Scheme 1).
Initially, it was planned to use an acyclic glycosyl dithioacetal
derivative as the precursor of acyclic galactosamine moiety to form
glycosylidene acetal using our earlier reported reaction condition.16
For this purpose, treatment of the 3,4,6-tri-O-acetyl-2-deoxy-2-
7
in excellent yield
is C-1B of acyclic D-galactosamine moiety. It is noteworthy that
compound 14 was formed only as a single stereoisomer, which
was confirmed from its 2D NOESY NMR spectrum. In the NOESY
spectrum of compound 14 cross peaks appeared between the H-
1B and H-4A and H-6A, which is possible only if H-1B is present in
an axial orientation having (S)-configuration. Reduction of the azi-
do group and removal of benzyl protection under a recently re-
ported reduction conditions23 using triethylsilane over 10% Pd–C
followed by N-acetylation furnished the target trisaccharide 1 as
its 4-methoxyphenyl glycoside in 82% overall yield. Signals at d
5.48 (d, J = 3.4 Hz, H-1A), 5.12 (d, J = 5.7 Hz, H-1B), 4.54 (d,
J = 7.7 Hz, H-1C) in the 1H NMR and at d 103.4 (C-1C), 98.9 (C-1A),
96.6 (C-1B) in the 13C NMR spectra confirmed the structure of com-
pound 1 (Scheme 2).
phthalimido-
presence of conc. HCl furnished only ethyl 3,4,6-tri-O-acetyl-2-
deoxy-2-phthalimido-b- -galactopyranoside instead of giving
dithioacetal derivative. Alternatively, the reaction of the 3,4,6-tri-
O-acetyl-2-azido-2-deoxy- -galactopyranose derivative with etha-
D-galactosamine derivative with ethanethiol in the
D
D
nethiol in the presence of borontrifluoride also did not furnish the
required dithioacetal derivative. We presumed that the azido group
may be reduced in the presence of ethanethiol and borontrifluoride
diethyletherate leading to the formation of an uncharacterized
product. Prompted by a recent report,12 in which a suitably pro-
tected acyclic glycosyl aldehyde has been used for the preparation
of glycosylidene derivative, the synthetic strategy has been modi-

2748
C. Mukherjee, A. K. Misra / Tetrahedron: Asymmetry 19 (2008) 2746–2751
N3
OBn
BnO
BnO
OBn
O
a
OH
Three steps
BnO
2
OBn
10
OH
OH
N3
9
BnO
OAc
N3
OBn
O
AcO
AcO
c
C
O
OTBDMS
b
AcO
BnO
OBn
N3
BnO
OBn
OH
B
12
11
OTBDMS
BnO
BnO
OAc
O
OAc
AcO
AcO
O
C
AcO
AcO
O
O
C
AcO
OBn
N3
d
OBn
N3
e, f
OAc
BnO
BnO
B
B
O
O
H
13
H
OH
14
H
BzO
O
A
N3
g, h, i
OPMP
1
PMP: 4-methoxyphenyl
Scheme 2. Reagents and conditions: (a) Sodium borohydride, CH3OH, room temperature, 2 h, 86%; (b) tert-butyldimethylchlorosilane, pyridine, DMF, room temperature, 5 h,
90%; (c) 8, TMSOTf, CH2Cl2, ꢃ20 °C, 1 h, 82%; (d) 80% aq AcOH, 60 °C, 2 h, 86%; (e) Dess–Martin periodinane, CH2Cl2, room temperature, 2 h; (f) 7, TMSOTf, CH2Cl2, ꢃ20 °C, 1 h,
69% in two steps; (g) 10% Pd-C, Et3SiH, CH3OH–CHCl3 (5:1), room temperature, 6 h; (h) acetic anhydride, pyridine, room temperature, 12 h; (i) CH3ONa, CH3OH, room
temperature, 12 h, 82% in three steps.
4.2. 4-Methoxyphenyl 3,4,6-tri-O-acetyl-2-azido-2-deoxy-a-D-
3. Conclusion
galactopyranoside 4
In conclusion, an expedient approach for the synthesis of a
unique trisaccharide containing open-chain cyclic acetal linkage
has been developed. The stereoselective formation of the acetal
To a solution of compound 3 (570 mg, 1.53 mmol) and 4-
methoxyphenol (230 mg, 1.83 mmol) in dry CH2Cl2 (8 mL) was
added BF3ꢀOEt2 (390
ll, 3.06 mmol) at 0 °C and stirred at 15 °C
linkage of the acyclic D-galactosamine moiety has been achieved
for 3 h. The reaction mixture was diluted with CH2Cl2 (15 mL),
and the organic layer was washed in succession with water
(2 ꢁ 10 mL) and satd. NaHCO3 solution (2 ꢁ 10 mL). The organic
layer was dried over Na2SO4, filtered, and concentrated. The crude
product was purified over SiO2 using hexane–EtOAc (3:1) as eluant
to give pure compound 4 (470 mg, 70%) as a colorless oil;
for the first time leading to the synthesis of uncommon trisac-
charide present in Proteus mirabilis O27. This will certainly open
up an avenue for the large-scale preparation of this class of
compounds for their potential use in the preparation of
therapeutics.
½
a 2D5
ꢂ
¼ þ146 (c 1.0, CHCl3); IR (neat): 3021, 2360, 2112, 1750,
1216, 761, 670 cmꢃ1 1H NMR (CDCl3, 300 MHz): d 7.04 (d,
;
4. Experimental
J = 9.1 Hz, 2H, Ar-H), 6.83 (d, J = 9.1 Hz, 2H, Ar-H), 5.55 (dd,
J = 11.1, 3.2 Hz, 1H, H-3), 5.50 (d, J = 3.2 Hz, 1H, H-1), 5.50 (br s,
1H, H-4), 4.43–4.37 (m, 1H, H-5), 4.16–4.03 (m, 2H, H-6ab), 3.78
(s, 3 H, OCH3), 3.74 (dd, J = 11.3, 3.6 Hz, 1H, H-2), 2.17, 2.09, 1.99
(3s, 9 H, 3 COCH3); 13C NMR (CDCl3, 75 MHz): d 170.0, 169.7,
169.5 (3C, 3 COCH3), 155.6 (Ar-C), 150.2 (Ar-C), 118.2 (2C, Ar-C),
114.6 (2C, Ar-C), 98.0 (C-1), 68.1 (C-4), 67.4 (C-6), 67.3 (C-3),
61.3 (C-5), 57.3 (OCH3), 55.5 (C-2), 20.6 (3C, 3 COCH3); ESI-MS:
m/z 460.3 [M+Na]+; Anal. Calcd for C19H23N3O9 (437.1): C, 52.17;
H, 5.30. Found: C, 52.0; H, 5.50.
4.1. General methods
All the reactions were monitored by thin layer chromatogra-
phy over silica gel-coated TLC plates. The spots on TLC were
visualized by warming ceric sulfate (2% Ce(SO4)2 in 2 N
H2SO4)-sprayed plates in hot plate. Silica gel 230–400 mesh
was used for column chromatography. 1H and 13C NMR, 2D
COSY, HSQC, and NOESY spectra were recorded on Brucker Ad-
vance DPX 300 MHz using CDCl3 and D2O as solvents and TMS
as internal reference unless stated otherwise. Chemical shift val-
ues are expressed in d ppm. ESI-MS were recorded on a MICRO-
MASS QUTTRO II triple quadrupole mass spectrometer.
Elementary analysis was carried out on Carlo ERBA-1108 ana-
lyzer. Optical rotations were measured at 25 °C on a Rudolf
Autopol III polarimeter. Commercially available grades of organic
solvents of adequate purity are used in many reactions.
4.3. 4-Methoxyphenyl 2-azido-4,6-O-benzylidine-2-deoxy-a-D-
galactopyranoside 5
To a solution of compound 4 (430 mg, 0.98 mmol) in anhyd
MeOH (10 mL) was added solid sodium methoxide until the pH
of the solution reached to ꢄ10. The reaction mixture was allowed

C. Mukherjee, A. K. Misra / Tetrahedron: Asymmetry 19 (2008) 2746–2751
2749
to stir at room temperature for 3 h, neutralized with Dowex-50W
X-8 (H+), filtered, and evaporated to dryness. To a solution of the
deacetylated product in dry acetonitrile (6 mL) were added benzal-
1H, H-5), 4.08 (dd, J = 11.0, 3.5 Hz, 1H, H-2), 3.98–3.86 (m, 2H,
H-6ab), 3.78 (s, 3H, OCH3); 13C NMR (CDCl3, 75 MHz): d 165.9–
114.6 (12C, Ar-C), 98.2 (C-1), 71.5 (C-4), 70.2 (C-6), 67.8 (C-5),
61.9 (C-3), 57.5 (C-2), 55.5 (OCH3); ESI-MS: m/z 438.4 [M+Na]+;
Anal. Calcd for C20H21N3O7 (415.1): C, 57.83; H, 5.10. Found: C,
57.66; H, 5.30.
dehyde dimethylacetal (220 ll, 1.47 mmol) and p-TsOH (50 mg),
and the reaction mixture was allowed to stir at room temperature
for 2 h. The reaction mixture was quenched with triethylamine
(0.1 mL), and the solvents were removed under reduced pressure.
The residue was diluted with CH2Cl2 (15 mL) and the organic layer
was washed with water (2 ꢁ 8 mL) and satd NaHCO3 (2 ꢁ 8 mL)
successively. The organic layer was dried over Na2SO4, filtered,
and concentrated under reduced pressure. The crude product was
purified over SiO2 using hexane–EtOAc (7:2) as eluant to give pure
4.6. 2-Azido-3,4,6-tri-O-benzyl-2-deoxy-D-galactitol 10
To a solution of compound 9 (465 mg, 0.98 mmol) in dry meth-
anol (8 mL) was added NaBH4 (75 mg, 1.96 mmol) at 0 °C under ar-
gon. The reaction mixture was allowed to stir at room temperature
for 2 h. The reaction mixture was cooled to 0 °C and was quenched
by the addition of glacial AcOH (2 mL). After removal of the sol-
vents under reduced pressure, the crude product was dissolved
in CH2Cl2 (15 mL) and the organic layer was washed with water
(2 ꢁ 8 mL) and brine (2 ꢁ 8 mL) successively. The organic layer
was dried over Na2SO4, filtered, and concentrated under reduced
pressure. The crude product was purified over SiO2 using hex-
ane–EtOAc (1:1) as eluant to give pure compound 10 (400 mg,
compound 5 (345 mg, 88%) as a white solid; mp 73 °C; ½a D25
¼ ꢃ22
ꢂ
(c 1.0, CHCl3); IR (KBr): 2935, 2362, 2104, 1508, 1452, 1249, 1218,
1103, 1041, 999, 827, 796, 755, 701 cmꢃ1
;
1H NMR (CDCl3,
300 MHz): d 7.50–7.45 (m, 2H, Ar-H), 7.38–7.34 (m, 3 H, Ar-H),
7.0 (d, J = 9.1 Hz, 2H, Ar-H), 6.80 (d, J = 9.1 Hz, 2H, Ar-H), 5.54 (s,
1H, PhCH), 5.51 (d, J = 3.2 Hz, 1H, H-1), 4.38–4.27 (m, 2H, H-3
and H-5), 4.22 (dd, J = 12.7, 1.1 Hz, 1H, H-6a), 4.00 (dd, J = 12.5,
1.4 Hz, 1H, H-6b), 3.82 (br s, 1H, H-4), 3.75 (s, 3H, OCH3), 3.62
(dd, J = 10.3, 3.2 Hz, 1H, H-2), 2.66 (d, J = 10.4 Hz, 1H, OH); 13C
NMR (CDCl3, 75 MHz): d 155.3–114.7 (12C, Ar-C), 101.2 (PhCH),
98.3 (C-1), 75.4 (C-4), 69.1 (C-6), 67.3 (C-3), 63.4 (C-5), 60.4 (C-
2), 55.5 (OCH3); ESI-MS: m/z 422.4 [M+Na]+; Anal. Calcd for
C20H21N3O6 (399.1): C, 60.14; H, 5.30. Found: C, 59.93; H, 5.52.
86%) as a white solid; mp 55 °C; ½a D25
ꢂ
¼ ꢃ245 (c 1.0, CHCl3); IR
(KBr): 3020, 2360, 2110, 1216, 1100, 928, 760, 670 cmꢃ1
;
1H
NMR (CDCl3, 300 MHz): d 7.32–7.21 (m, 15 H, Ar-H), 4.72 (d,
J = 11.4 Hz, 1H, PhCH2), 4.63 (d, J = 11.1 Hz, 1H, PhCH2), 4.58 (d,
J = 11.4 Hz, 1H, PhCH2), 4.50 (d, J = 10.8 Hz, 1H, PhCH2), 4.44 (d,
J = 11.9 Hz, 1H, PhCH2), 4.40 (d, J = 11.0 Hz, 1H, PhCH2), 4.01–3.97
(m, 1H, H-5), 3.86 (dd, J = 7.4, 3.0 Hz, 1H, H-1a), 3.78 (dd, J = 7.4,
1.4 Hz, 1H, H-1b), 3.73 (dd, J = 8.0, 3.6 Hz, 1H, H-6a), 3.64 (dd,
J = 11.1, 5.8 Hz, 1H, H-6b), 3.55–3.43 (m, 3H, H-2, H-3 and H-4);
13C NMR (CDCl3, 75 MHz): d 137.6–127.9 (18C, Ar-C), 77.9 (C-4),
77.6 (C-3), 74.5 (2C, PhCH2), 73.4 (PhCH2), 71.1 (C-1), 69.2 (C-5),
62.8 (C-2), 61.8 (C-6); ESI-MS: m/z 500.3 [M+Na]+; Anal. Calcd for
C27H31N3O5 (477.2): C, 67.91; H, 6.54. Found: C, 67.74; H, 6.75.
4.4. 4-Methoxyphenyl 2-azido-3-O-benzoyl-4,6-O-benzylidine-
2-deoxy-a-D-galactopyranoside 6
To a solution of compound 5 (300 mg, 0.75 mmol) in dry pyri-
dine (5 mL) was added benzoyl chloride (130 l, 1.12 mmol), and
l
the reaction mixture was stirred at room temperature for 2 h.
The solvents were removed under reduced pressure, and the crude
material was purified over SiO2 using hexane–EtOAc (6:1) as elu-
ant to give pure compound 6 (360 mg, 95%) as a white solid; mp
4.7. 2-Azido-3,4,6-tri-O-benzyl-1-O-tert-butyldimethylsilyl-2-
deoxy-D-galactitol 11
70 °C; ½a 2D5
ꢂ
¼ þ117 (c 1.0, CHCl3); IR (KBr): 3021, 2359, 2113,
1723, 1596, 1216, 1039, 760, 671 cmꢃ1
;
1H NMR (CDCl3,
300 MHz): d 8.14–8.07 (m, 2H, Ar-H), 7.59–7.54 (m, 1H, Ar-H),
7.47–7.41 (m, 4H, Ar-H), 7.35–7.30 (m, 3H, Ar-H), 7.05 (d,
J = 9.1 Hz, 2H, Ar-H), 6.81 (d, J = 9.1 Hz, 2H, Ar-H), 5.76 (dd,
J = 11.1, 3.4 Hz, 1H, H-3), 5.67 (d, J = 3.2 Hz, 1H, H-1), 5.52 (s, 1H,
PhCH), 4.65 (d, J = 3.1 Hz, 1H, H-4), 4.28–4.22 (m, 1H, H-6a), 4.19
(dd, J = 11.1, 3.3 Hz, 1H, H-2), 4.06–4.01 (m, 1H, H-6b), 3.95 (br s,
1H, H-5), 3.75 (s, 3H, OCH3); 13C NMR (CDCl3, 75 MHz): d 165.8–
114.7 (18C, Ar-C), 100.6 (PhCH), 98.1 (C-1), 73.5 (C-4), 69.8 (C-3),
69.0 (C-6), 63.2 (C-5), 57.5 (C-2), 55.5 (OCH3); ESI-MS: m/z 526.3
[M+Na]+; Anal. Calcd for C27H25N3O7 (503.2): C, 64.41; H, 5.00.
Found: C, 64.22; H, 5.25.
To a solution of compound 10 (370 mg, 0.77 mmol) in dry DMF
(2 mL) was added pyridine (1 mL) followed by tert-butyldimethyl-
chlorosilane (130 mg, 0.85 mmol) at 0 °C under argon. The reaction
mixture was stirred at room temperature for 5 h. After removal of
the solvents under reduced pressure, the crude material was puri-
fied over SiO2 using hexane–EtOAc (4:1) as eluant to afford pure
compound 11 (410 mg, 90%) as a colorless oil; ½a D25
¼ ꢃ2 (c 1.0,
ꢂ
CHCl3); IR (neat): 3020, 2360, 2105, 1596, 1216, 1107, 840, 761,
670 cmꢃ1 1H NMR (CDCl3, 300 MHz): d 7.40–7.22 (m, 15 H, Ar-
;
H), 4.73 (d, J = 11.4 Hz, 1H, PhCH2), 4.64 (d, J = 11.1 Hz, 1H, PhCH2),
4.58 (d, J = 11.5 Hz, 1H, PhCH2), 4.53 (d, J = 11.8 Hz, 1H, PhCH2),
4.51 (d, J = 11.3 Hz, 1H, PhCH2), 4.46 (d, J = 11.9 Hz, 1H, PhCH2),
4.08–3.97 (m, 1H, H-5), 3.89–3.76 (m, 3H, H-3, H-4 and H-6a),
3.67 (dd, J = 10.3, 5.5 Hz, 1H, H-6b), 3.61–3.45 (m, 3H, H-2 and H-
6ab), 2.40 (d, J = 7.4 Hz, 1H, OH), 0.90 (s, 9H, C(CH3)3), 0.04, 0.03
(2s, 6H, 2CH3); 13C NMR (CDCl3, 75 MHz): d 137.8–127.8 (18C,
Ar-C), 77.9 (C-4), 77.2 (C-3), 74.6 (2C, 2 PhCH2), 73.4 (PhCH2),
71.3 (C-1), 69.1 (C-5), 63.2 (C-6), 63.0 (C-2), 25.9 (3C, C(CH3)3),
18.2 (C(CH3)3), ꢃ5.4 (2C, 2CH3); ESI-MS: m/z 615.2 [M+Na]+; Anal.
Calcd for C33H45N3O5Si (591.3): C, 66.97; H, 7.66. Found: C, 66.80;
H, 7.85.
4.5. 4-Methoxyphenyl 2-azido-3-O-benzoyl-2-deoxy-a-D-
galactopyranoside 7
To a solution of compound 6 (315 mg, 0.63 mmol) in CH3CN–
H2O (8 mL, 20:1, v/v) was added HClO4–SiO2 (100 mg), and the
reaction mixture was allowed to stir at room temperature for
20 min. The reaction mixture was filtered through a CeliteÒ bed
and was washed with CH2Cl2 (20 mL). Solvents were evaporated
and co-evaporated with toluene (3 ꢁ 5 mL), and the crude prod-
uct was purified over SiO2 using hexane–EtOAc (1:1) as eluant
to give pure compound 7 (220 mg, 85%) as a white solid. Mp
4.8. 2-Azido-5-O-[(2,3,4,6-tetra-O-acetyl-b-D-glucopyranosyl)]-
3,4,6-tri-O-benzyl-1-O-tert-butyldimethylsilyl-2-deoxy-D-
galactitol 12
145 °C; ½a 2D5
ꢂ
¼ þ205 (c 1.0, CH3CN); IR (KBr): 3021, 2928, 2359,
2112, 1724, 1597, 1430, 1216, 760, 671 cmꢃ1
;
1H NMR (CDCl3,
300 MHz): d 8.14–8.10 (m, 2H, Ar-H), 7.64–7.58 (m, 1H, Ar-H),
7.50–7.44 (m, 2H, Ar-H), 7.06 (d, J = 9.1 Hz, 2H, Ar-H), 6.84 (d,
J = 9.1 Hz, 2H, Ar-H), 5.68 (dd, J = 11.0, 2.9 Hz, 1H, H-3), 5.60 (d,
J = 3.5 Hz, 1H, H-1), 4.52 (d, J = 2.3 Hz, 1H, H-4), 4.16–4.11 (m,
To a solution of compound 11 (370 mg, 0.63 mmol) and com-
pound 8 (370 mg, 0.75 mmol) in dry CH2Cl2 (8 mL) was added acti-
vated MS 4 Å (200 mg), and the reaction mixture was allowed to

2750
C. Mukherjee, A. K. Misra / Tetrahedron: Asymmetry 19 (2008) 2746–2751
stir under argon at room temperature for 1 h. After cooling the
reaction mixture to ꢃ20 °C, TMSOTf (5 l) was added to it and
out further purification. To a solution of crude aldehyde (285 mg,
0.35 mmol) and compound 7 (165 mg, 0.39 mmol) in anhyd
CH2Cl2–CH3CN (6 mL, 5:1, v/v) was added activated MS 4 Å
(150 mg), and the reaction mixture was allowed to stir under argon
at room temperature for 1 h. After cooling the reaction mixture to
l
the reaction mixture was allowed to stir at ꢃ20 °C for 1 h. The reac-
tion mixture was filtered through a CeliteÒ bed and washed with
CH2Cl2 (3 ꢁ 10 mL). The organic layer was washed successively
with water (2 ꢁ 10 mL) and satd. aq. NaHCO3 (2 ꢁ 10 mL), dried
over Na2SO4, and concentrated under reduced pressure. The crude
material was purified over SiO2 using hexane–EtOAc (3:1) as elu-
ant to afford pure compound 12 (475 mg, 82%) as colorless oil;
ꢃ40 °C, TMSOTf (60
lL, 0.35 mmol) was added to it and the reac-
tion mixture was allowed to stir at ꢃ20 °C for 1 h. The reaction
mixture was quenched with triethylamine (0.1 mL), filtered
through a CeliteÒ bed, and washed with CH2Cl2 (3 ꢁ 10 mL). The
organic layer was washed successively with water (2 ꢁ 10 mL)
and brine (2 ꢁ 10 mL), dried over Na2SO4, and concentrated under
reduced pressure. The crude product was purified over SiO2 using
toluene–EtOAc (7:2) as eluant to afford the title compound 14
½
a 2D5
ꢂ
¼ ꢃ12 (c 1.0, CHCl3); IR (neat): 3021, 2931, 2360, 2105,
1751, 1371, 1216, 1040, 761, 670 cmꢃ1 1H NMR (CDCl3,
;
300 MHz): d 7.45–7.21 (m, 15H, Ar-H), 5.22–5.09 (m, 1H, H-3C),
5.07–4.91 (m, 3H, H-1C, H-2C and H-4C), 4.81 (d, J = 11.6 Hz, 1H,
PhCH2), 4.68 (d, J = 11.6 Hz, 1H, PhCH2), 4.54 (d, J = 10.7 Hz, 1H,
PhCH2), 4.51 (d, J = 10.9 Hz, 1H, PhCH2), 4.43 (br s, 1H, PhCH2),
4.39–4.31 (m, 1H, H-5B), 4.10 (dd, J = 12.3, 3.7 Hz, 1H, H-6aC),
3.98–3.88 (m, 2H, H-3B and H-6bC), 3.86–3.63 (m, 5H, H-1abB, H-
4B and H-6abB), 3.62–3.49 (m, 2H, H-2B and H-5C), 2.02, 1.88, 1.85
(3s, 12H, 4COCH3), 0.9 (s, 9H, C(CH3)3), 0.04, 0.04 (2s, 6H, 2CH3);
13C NMR (CDCl3, 75 MHz): d 170.2, 170.0, 169.2, 169.0 (4C,
4COCH3), 138.3–127.2 (18C, Ar-C), 99.3 (C-1C), 79.0 (C-4B), 77.1
(C-3B), 76.0 (C-5B), 74.3 (PhCH2), 73.7 (PhCH2), 73.5 (PhCH2), 72.8
(C-3C), 71.9 (C-5C), 71.5 (2C, C-2C and C-1B), 68.4 (C-4C), 63.5 (C-
6B), 63.4 (C-2B), 61.7 (C-6C), 25.9 (3C, C(CH3)3), 20.6, 20.5, 20.4
(4C, 4COCH3), 18.2 (C(CH3)3), ꢃ5.4 (2C, 2CH3); ESI-MS: m/z 938.9
[M+NH4]+; Anal. Calcd for C47H63N3O14Si (921.4): C, 61.22; H,
6.89. Found: C, 61.05; H, 7.10.
(315 mg, 69%) as a colorless oil; ½a D25
¼ þ96 (c 1.0, CHCl3); IR
ꢂ
(neat): 3020, 2361, 2338, 2112, 1755, 1507, 1368, 1216, 1041,
760, 669 cmꢃ1 1H NMR (CDCl3, 300 MHz): d 8.18 (d, J = 7.2 Hz,
;
2H, Ar-H), 7.63 (t, J = 7.4 Hz, 1H, Ar-H), 7.47 (t, J = 7.8 Hz, 2H, Ar-
H), 7.39–7.22 (m, 15H, Ar-H), 7.07 (d, J = 9.1 Hz, 2H, Ar-H), 6.86
(d, J = 9.1 Hz, 2H, Ar-H), 5.77 (dd, J = 7.9, 3.0 Hz, 1H, H-3A), 5.69
(d, J = 3.3 Hz, 1H, H-1A), 5.39 (d, J = 5.4 Hz, 1H, H-1B), 5.15 (t,
J = 9.4 Hz, 1H, H-3C), 5.00–4.92 (m, 2H, H-2C and H-4C), 4.88 (d,
J = 8.1 Hz, 1H, H-1C), 4.78–4.60 (m, 4H, H-6abC and PhCH2), 4.59–
4.38 (m, 5H, H-4A and 2 PhCH2), 4.32–4.27 (m, 1H, H-5B), 4.26–
4.01 (m, 4H, H-2A, H-6aA, H-4B and H-6aB), 3.98–3.88 (m, 2H, H-
6bA and H-2B), 3.78 (s, 3H, OCH3), 3.85–3.70 (m, 3H, H-5A, H-3B
and H-6bB), 3.58–3.50 (m, 1H, H-5C), 2.03, 2.02, 1.98, 1.97 (4s,
12H, 4COCH3); 13C NMR (CDCl3, 75 MHz): d 170.1, 170.0, 169.4,
168.8 (4C, 4COCH3), 165.6 (COPh), 155.3–114.7 (30C, Ar-C), 99.6
(C-1C), 97.5 (C-1A), 95.9 (C-1B), 78.6 (C-3B), 77.4 (C-5A), 76.8 (C-
5B), 74.8 (PhCH2), 73.4 (PhCH2), 72.9 (2C, C-3C and PhCH2), 71.8
(C-5C), 71.5 (C-6C), 71.3 (C-4C), 69.2 (C-3A), 68.3 (C-2C), 66.9 (C-
4A), 65.8 (C-6B), 64.4 (C-4B), 62.1 (C-2B), 61.9 (C-6A), 57.5 (C-2A),
55.6 (OCH3), 20.5 (4C, 4COCH3); ESI-MS: m/z 1219.9 [M+NH4]+;
Anal. Calcd for C61H66N6O20 (1202.4): C, 60.89; H, 5.53. Found: C,
60.71; H, 5.75.
4.9. 5-[O-(2,3,4,6-Tetra-O-acetyl-b-
D-glucopyranosyl)]-2-azido-
3,4,6-tri-O-benzyl-2-deoxy- -galactose 13
D
A solution of 12 (440 mg, 0.48 mmol) in 80% aq AcOH (12 mL)
was allowed to stir at 60 °C for 2 h, and the solvents were removed
under reduced pressure. The crude product was purified over SiO2
using hexane–EtOAc (3:2) as eluant to give pure compound 13
(330 mg, 86%) as colorless oil; ½a D25
¼ ꢃ14 (c 1.0, CHCl3); IR (neat):
ꢂ
3021, 2917, 2361, 2108, 1751, 1631, 1428, 1372, 1216, 1040, 762,
4.11. 4-Methoxyphenyl 2-acetamido-2-deoxy-4,6-O-(1S)-[5-O-
670 cmꢃ1
;
1H NMR (CDCl3, 300 MHz): d 7.40–7.22 (m, 15H, Ar-H),
(b-D
-glucopyranosyl)-2-acetamido-2-deoxy]-
D-galactosylidene-
5.15 (t, J = 9.1 Hz, 1H, H-3C), 5.02 (t, J = 9.6 Hz, 1H, H-4C), 4.97–4.87
(m, 2H, H-1C and H-2C), 4.78 (d, J = 11.1 Hz, 1H, PhCH2), 4.68 (d,
J = 11.7 Hz, 1H, PhCH2), 4.59 (d, J = 10.9 Hz, 1H, PhCH2), 4.56 (d,
J = 11.6 Hz, 1H, PhCH2), 4.42 (br s, 2H, PhCH2), 4.30–4.22 (m, 1H,
H-5B), 4.11 (dd, J = 12.4, 4.3 Hz, 1H, H-6aC), 4.02 (dd, J = 12.3,
2.1 Hz, 1H, H-6bC), 3.88–3.78 (m, 2H, H-3B and H-4B), 3.77–3.67
(m, 4H, H-1abB and H-6abB), 3.66–3.60 (m, 1H, H-2B), 3.59–3.51
(m, 1H, H-5C), 2.02, 2.01, 1.98, 1.97 (4s, 12H, 4COCH3); 13C NMR
(CDCl3, 75 MHz): d 170.4, 170.0, 169.3, 169.2 (4C, 4COCH3),
138.1–127.5 (18C, Ar-C), 99.6 (C-1C), 78.7 (C-4B), 78.6 (C-5B), 77.0
(C-3B), 74.6 (PhCH2), 73.5 (2PhCH2), 72.6 (C-3C), 71.9 (C-5C), 71.4
(2C, C-1B and C-2C), 68.3 (C-4C), 64.2 (C-6B), 62.3 (C-2B), 61.5 (C-
6C), 20.5 (4C, 4COCH3); ESI-MS: m/z 830.2 [M+Na]+; Anal. Calcd
for C41H49N3O14 (807.3): C, 60.96; H, 6.11. Found: C, 60.78; H, 6.30.
a-D-galactopyranoside 1
To a solution of compound 14 (280 mg, 0.23 mmol) in CH3OH–
CHCl3 (6 mL, 5:1, v/v) was added 10% Pd-C (100 mg) and Et3SiH
(560 L, 3.5 mmol) under argon, and the reaction mixture was
stirred at room temperature for 2 h. Another portion of Et3SiH
(250 L) was added to the reaction mixture and it was allowed
l
l
to stir at room temperature for 4 h. The reaction mixture was fil-
tered through a CeliteÒ bed and washed with CH3OH (3 ꢁ 10 mL).
The solvents were removed under reduced pressure, and a solu-
tion of the crude mass in pyridine and acetic anhydride (5 mL,
3:2, v/v) was kept at room temperature for 12 h. The reaction
mixture was evaporated to dryness and co-evaporated with tolu-
ene (3 ꢁ 5 mL). A solution of the crude product in 0.1 M CH3ONa
in CH3OH (5 mL) was allowed to stir at room temperature for
12 h and was neutralized with Dowex-50W X8 (H+). The reaction
mixture was filtered and evaporated to dryness to give pure com-
4.10. 4-Methoxyphenyl 2-azido-3-O-benzoyl-2-deoxy-4,6-O-
(1S)-[5-O-(2,3,4,6-tetra-O-acetyl-b-
D
-glucopyranosyl)-2-azido-
3,4,6-tri-O-benzyl-2-deoxy]-
D
-galactosylidene– -galactopy-
D
pound 1 (130 mg, 82%) as a white powder; ½a D25
¼ þ91 (c 1.0,
ꢂ
ranoside 14
H2O); IR (KBr): 3020, 2362, 1653, 1367, 1216, 763, 669 cmꢃ1
;
1H NMR (D2O, 300 MHz): d 7.01 (d, J = 9.2 Hz, 2H, Ar-H), 6.88
(d, J = 9.2 Hz, 2H, Ar-H), 5.48 (d, J = 3.4 Hz, 1H, H-1A), 5.12 (d,
J = 5.7 Hz, 1H, H-1B), 5.03 (br s, 1H, H-2B), 4.54 (d, J = 7.7 Hz, 1H,
H-1C), 4.37 (dd, J = 11.0, 3.4 Hz, 1H, H-2A), 4.30 (d, J = 2.8 Hz, 1H,
H-4A), 4.22–4.12 (m, 2H, H-3A and H-6aB), 4.11–4.00 (m, 2H,
H-5A and H-4C), 3.95 (br s, 1H, H-4B), 3.73 (s, 3H, OCH3), 3.88–
3.64 (m, 5H, H-6abA, H-6bB and H-6abC), 3.47–3.21 (m, 5H, H-3B,
H-5B, H-2C, H-3C and H-5C), 1.98 (s, 6H, 2NHCOCH3); 13C NMR
To a solution of compound 13 (305 mg, 0.38 mmol) in dry
CH2Cl2 (5 mL) was added Dess–Martin periodinane (240 mg,
0.57 mmol), and the reaction mixture was stirred at room temper-
ature for 2 h. The reaction mixture was diluted with CH2Cl2 (5 mL)
and the organic layer was washed with 10% aq Na2S2O3 (3 mL) and
satd NaHCO3 (3 mL). The organic layer was dried over Na2SO4, fil-
tered, and concentrated under reduced pressure to give the crude
aldehyde as a colorless oil, which was used in the next step with-
(DMSO-d6, 75 MHz):
d 173.9 (2C, 2NHCOCH3), 155.9 (Ar-C),

C. Mukherjee, A. K. Misra / Tetrahedron: Asymmetry 19 (2008) 2746–2751
2751
1997; (c) Michael, F. S.; Brisson, J. R.; Larocque, S.; Monteiro, M.; Li, J. J.; Jacques,
M.; Perry, M. B.; Cox, A. D. Carbohydr. Res. 2004, 339, 1973–1984; (d) Moule, A.
L.; Galbraith, L.; Cox, A. D.; Wilkinson, S. G. Carbohydr. Res. 2004, 339, 1185–
1188.
151.8 (Ar-C), 119.9 (2C, Ar-C), 116.0 (2C, Ar-C), 103.4 (C-1C), 98.9
(C-1A), 96.6 (C-1B), 78.6 (C-5A), 77.1 (C-4B), 76.9 (C-5C), 74.4 (C-
5B), 71.0 (C-2C), 70.1 (C-3C), 68.4 (C-4C), 68.3 (C-4A), 66.6 (C-3A),
64.6 (C-3B), 63.7 (C-6B), 62.3 (C-6C), 62.0 (C-6A), 56.7 (OCH3),
50.4 (C-2A), 46.2 (C-2B), 23.4 (2C, 2NHCOCH3); ESI-MS: m/z
715.3 [M+Na]+; Anal. Calcd for C29H44N2O17 (692.3): C, 50.29; H,
6.40. Found: C, 50.10; H, 6.65.
7. (a) Ichikawa, Y.; Look, G. C.; Wong, C.-H. Anal. Biochem. 1992, 202, 215–
238; (b) Palcic, M. M. Methods Enzymol. 1994, 230, 300–316; (c) Toone, E.
J.; Simon, E. S.; Bednarski, M. D.; Whitesides, G. M. Tetrahedron 1989, 45,
5365–5422; (d) Look, G. C.; Ichikawa, Y.; Shen, G. J.; Cheng, P. W.; Wong,
C.-H. J. Org. Chem. 1993, 58, 4326–4330; (e) Herrmann, G. F.; Ichikawa, Y.;
Wandrey, C.; Gaeta, F. C. A.; Paulson, J. C.; Wong, C.-H. Tetrahedron Lett.
1993, 34, 3091–3094.
8. (a) Crawley, S. C.; Palcic, M. M. In Modern Methods in Carbohydrate Chemistry;
Khan, S. H., O’Neil, R. A., Eds.; Harwood Academic: Amsterdam, 1995; pp 492–
517; (b) Palcic, M. M.; Hindsgaul, O. Trends Glycosci. Glycotechnol. 1996, 8, 37–
49. and references cited therein; (c) Schachter, H. In Molecular Glycobiology;
Fukuda, M., Hindsgaul, O., Eds.; Oxford: IRL, 1994; pp 88–162.
9. Hindsgaul, O. Nature 1999, 399, 644–645.
10. (a) Nicolaou, K. C.; Mitchell, H. J.; Fylaktakidou, K. C.; Suzuki, H.; Rodriguez, R.
M. Angew. Chem., Int. Ed. Engl. 2000, 39, 1089–1093; (b) Ohtake, H.; Ichiba, N.;
Shiro, M.; Ikegami, S. J. Org. Chem. 2000, 65, 8164–8170; (c) Ohtake, H.; Ichiba,
N.; Ikegami, S. J. Org. Chem. 2000, 65, 8171–8179; (d) Hada, N.; Ohtsuka, I.;
Sugita, M.; Takeda, T. Tetrahedron Lett. 2000, 41, 9065–9068; (e) Jaurand, G.;
Beau, J.-M.; Sinay, P. Chem. Commun. 1982, 701–703.
Acknowledgments
Instrumentation facilities from SAIF, CDRI, are gratefully
acknowledged. C.M. thanks CSIR, New Delhi, for providing a Senior
Research Fellowship. This work was supported by Ramanna Fel-
lowship (AKM), Department of Science and Technology, New Delhi
(SR/S1/RFPC-06/2006).
References
11. Takashi, H.; Fukuda, T.; Mitsuzuka, H.; Namme, R.; Miyamoto, H.; Ohkura, Y.;
Ikegami, S. Angew. Chem., Int. Ed. Engl. 2003, 42, 5069–5071.
12. Sun, J.; Han, X.; Yu, B. Org. Lett. 2005, 7, 1935–1938.
1. (a) O’Hara, C. M.; Brenner, F. W.; Miller, J. M. Clin. Microbiol. Rev. 2000, 13, 534–
546; (b) Rozalski, A.; Sidorczyk, Z.; Kotelko, K. Microbiol. Mol. Biol. Rev. 1997, 61,
65–89.
2. (a) Fowler, E. J.; Stamey, T. A. J. Urol. 1978, 120, 315–318; (b) Mobley, H. L. T.;
Warren, J. W. J. Clin. Microbiol. 1987, 25, 2216–2217; (c) Warren, J. W.; Tenney, J.
H.; Hoopes, J. M.; Muncie, H. L.; Anthony, W. C. J. Infect. Dis. 1982, 146, 719–723.
3. Zunino, P.; Geymonat, L.; Allen, A. G.; Preston, A.; Sosa, V.; Maskell, D. J. FEMS
Immunol. Med. Microbiol. 2001, 31, 113–120.
4. (a) Peerbooms, P. G.; Verweij, A. M. J. J.; MacLaren, D. M. J. Med. Microbiol. 1985,
19, 55–60; (b) Warren, J. W.; Damron, D.; Tenney, J. H.; Hoopes, J. M.; Deforge,
B., ; Muncie, H. L., Jr. J. Infect. Dis. 1987, 155, 1151–1158; (c) Wray, S. K.; Hull, S.
I.; Cook, R. G.; Barrish, J.; Hull, R. A. Infect. Immun. 1986, 54, 43–49; (d)
Adegbola, R. A.; Old, D. C.; Senior, B. W. J. Med. Microbiol. 1983, 16, 427–431; (e)
Silverblatt, F. J. J. Exp. Med. 1974, 140, 1696–1711; (f) Svanborg-Eden, C.;
Larsson, P.; Lomberg, H. Infect. Immun. 1980, 27, 804–807.
5. (a) Vinogradov, E.; Bock, K. Angew. Chem., Int. Ed. 1999, 38, 671–674; (b)
Vinogradov, E.; Bock, K. Carbohydr. Res. 1999, 319, 92–101; (c) Vinogradov, E.;
Bock, K. Carbohydr. Res. 1999, 320, 239–243.
13. Alper, P. B.; Hung, S.-C.; Wong, C.-H. Tetrahedron Lett. 1996, 37, 6029–6032.
14. Zhang, Z.; Magnusson, G. Carbohydr. Res. 1996, 295, 41–55.
15. (a) Misra, A. K.; Agnihotri, G. Tetrahedron Lett. 2006, 47, 3653–3658;
Preparation of HClO4–SiO2: (b) Gulhane, R.; Chakraborti, A. K. Chem.
Commun. 2003, 1896–1897.
16. Madhusudan, S. K.; Misra, A. K. Eur. J. Org. Chem. 2005, 3196–3205.
17. Koto, S.; Asami, K.; Hirooka, M.; Nagura, K.; Takizawa, M.; Yamamoto, S.;
Okamoto, N.; Sato, M.; Tajima, H.; Yoshida, T.; Nonaka, N.; Sato, T.; Zen, S.;
Yago, K.; Tomonaga, F. Bull. Chem. Soc. Jpn. 1999, 72, 765–778.
18. Villalobos, A.; Danishefsky, S. J. J. Org. Chem. 1990, 55, 2776–2786.
19. Clode, D. M.; Laurie, W. A.; McHale, D.; Sheridan, J. B. Carbohydr. Res. 1985, 139,
161–183.
20. Schmidt, R. R.; Jung, K. H. In Preparative Carbohydrate Chemistry; Hanessian, S.,
Ed.; Marcel Dekker: New York, 1997; pp 283–312.
21. Schmidt, R. R. Angew. Chem., Int. Ed. Engl. 1986, 25, 212–236.
22. Corey, E. J.; Venkateswarlu, A. J. Am. Chem. Soc. 1972, 94, 6190–6191.
23. Mandal, P. K.; McMurray, J. S. J. Org. Chem. 2007, 72, 6599–6601.
6. (a) Vinogradov, E.; Sidorczyk, Z. Carbohydr. Res. 2001, 330, 537–540; (b)
Vinogradov, E.; Korenevsky, A.; Beveridge, T. J. Carbohydr. Res. 2003, 338, 1991–