First synthesis of a pentasaccharide repeating unit of the O-antigenic polysaccharide from enterohaemorrhagic Escherichia coli O48:H21

Article abstract of DOI:10.1016/j.tetasy.2009.05.026

A concise synthesis of a pentasaccharide as its 4-methoxyphenyl glycoside, found in the O-antigenic polysaccharide of enterohaemorrhagic Escherichia coli O48:H21 has been achieved for the first time in excellent yield. Most of the intermediate steps are h

Full text of DOI:10.1016/j.tetasy.2009.05.026

Tetrahedron: Asymmetry 20 (2009) 1550–1555
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Tetrahedron: Asymmetry
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First synthesis of a pentasaccharide repeating unit of the O-antigenic
polysaccharide from enterohaemorrhagic Escherichia coli O48:H21
*
Rajib Panchadhayee, Anup Kumar Misra
Bose Institute, Division of Molecular Medicine, P-1/12, C.I.T. Scheme VII-M, Kolkata 700 054, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A concise synthesis of a pentasaccharide as its 4-methoxyphenyl glycoside, found in the O-antigenic poly-
saccharide of enterohaemorrhagic Escherichia coli O48:H21 has been achieved for the first time in excel-
lent yield. Most of the intermediate steps are high yielding and the stereooutcome of each glycosylation
step was excellent. Stereoselective glycosylation and removal of the 4-methoxybenzyl group were
achieved in one-pot by tuning the reaction conditions. A late-stage TEMPO-mediated oxidation strategy
has been adopted for the oxidation of a primary hydroxyl group to carboxylic acid.
Received 18 May 2009
Accepted 26 May 2009
Available online 24 June 2009
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
tinal infections and is associated with several outbreaks of the dis-
ease in the Europe, America and Japan.5–8 In addition to E. coli
Escherichia coli (E. coli) is a facultative Gram-negative bacterium
present predominantly in the colonic flora of animals and human.
The species is divided into different serotypes based on the immu-
nogenicity of the surface oligosaccharide structures. In general, the
strains are described as O:K:H serotypes, where O stands for O-
antigen, that is, the polysaccharide portion of the lipopolysaccha-
ride; K is the capsular polysaccharide, and H is the flagella antigen.
To date, more than 170 different O-antigens and over 100 capsular
polysaccharides have been identified within the species.1 In gen-
eral, pathogenic E. coli strains cause three common infections, for
example, (i) enteric/diarrhoeal; (ii) urinary tract infections; and
(iii) septicaemia/meningitis.2 Virulent E. coli strains causing diar-
rhoeal diseases are classified in six classes, which are recognized
as (i) enteropathogenic E. coli (EPEC); (ii) enteroinvasive E. coli
(EIEC); (iii) enterotoxigenic E. coli (ETEC); (iv) enteroaggregative
E. coli (EAEC); (v) diffusely adherent E. coli (DAEC); and (vi) entero-
haemorrhagic E. coli (EHEC).3
Enterohaemorrhagic E. coli (EHEC) is mostly responsible for
diarrhoea with life threatening complications, for example, haem-
orrhagic colitis (HC) and haemolytic–uraemic syndrome (HUS).3
EHEC strains are also called ‘verotoxigenic E. coli’ (VTEC) because
of their toxic effect on cultured Vero cells. They also produce a bac-
teriophage-mediated Shiga-like toxin and are termed as ‘Shiga tox-
in-producing E. coli’ (STEC).4 The pathological symptoms due to the
HC and HUS are the result of the action of Shiga toxin (Stx) on
endothelial cells. The best-known Shigatoxin producing EHEC
strain is E. coli O157:H7, which is the frequent cause of fatal intes-
O157:H7, several other E. coli serotypes have been reported to be
associated with the STEC category.9 Recent structural analysis of
the O-antigen of enterohaemorrhagic E. coli (EHEC) O48:H21
showed that it contains a pentasaccharide repeating unit with a
D
-galactouronic acid at the non-reducing terminal through an
a
-linkage (Fig. 1).10 It has been well established that the immuno-
chemical activities of the glyco-vaccines depend on the bacterial
O-antigens, which make them attractive targets for the develop-
ment of glycoconjugate vaccine candidates.11 Recently, several
reports have appeared in the literature for the synthesis and
evaluation of glycoconjugate vaccines against bacterial infec-
tions.11 In order to understand the antigenicity of the O-antigen
and its role in the pathogenicity on a molecular level it is necessary
to have a considerable amount of the pentasaccharide in hand. As
the natural source cannot provide the required quantity of the
oligosaccharides for their biological evaluation, development of a
chemical synthetic strategy for the preparation of the target penta-
saccharide is always useful. For the immunochemical studies, it is
often required to conjugate the oligosaccharide moiety with a
OH
COONa
HO
O
O
HO
O
OH
HO
HO
A
OH
E
OMP
NHAc
O
O
HO
O
C
HO
D
O
O
B
HO
NHAc
O
HO OH
1
Figure 1. Structure of the synthesized pentasaccharide repeating unit of the
O-antigenic polysaccharide of enterohaemorrhagic Escherichia coli O48:H21 as its
4-methoxyphenyl (MP) glycoside.
* Corresponding author. Tel.: +91 33 25693240; fax: +91 33 23553886.
E-mail address: akmisra69@rediffmail.com (A.K. Misra).
0957-4166/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2009.05.026

R. Panchadhayee, A. K. Misra / Tetrahedron: Asymmetry 20 (2009) 1550–1555
1551
carrier protein through a spacer linker. Therefore, synthesis of an
11 + 12
oligosaccharide moiety with a temporary protecting group at the
reducing end would be useful for its ready removal whenever nec-
essary.12 In this direction, for the first time we herein report an effi-
cient chemical synthesis of the pentasaccharide repeating unit of
the O-antigenic polysaccharide from enterohaemorrhagic E. coli
O48:H21 as its 4-methoxyphenyl glycoside using a block synthetic
approach.
a
Ph
Ph
BnO
BnO
OAc
Ph
B
O
O
O
O
O
O
O
O
A
E
OMP
O
O
O
C
NPhth
BnO
D
O
O
O
BnO
NPhth
O
AcO
OAc
13
b, c
Ph
2. Results and discussion
The synthesis of the pentasaccharide 1 as its 4-methoxyphenyl
glycoside (Fig. 1) was achieved using a block synthetic strategy, in
which, a trisaccharide derivative 11 was stereoselectively coupled
with a disaccharide thioglycoside derivative 12 under iodonium-
mediated thioglycoside activation conditions to furnish the penta-
saccharide derivative 13 (Schemes 1 and 2). The pentasaccharide
derivative 13 was transformed to the target pentasaccharide 1
using a late-stage TEMPO-mediated oxidation of a primary hydro-
xyl group followed by deprotection of functional groups (Scheme
2). For this purpose, trisaccharide glycosyl acceptor 11 and disac-
charide thioglycoside donor 12 were prepared from the suitably
protected monosaccharide derivatives (Fig. 2, Scheme 3) derived
from the commercially available reducing sugars following a se-
quence of reactions reported in the literature. 4-Methoxyphenyl
Ph
BnO
BnO
ONa
O
O
Ph
B
O
O
O
O
O
NPhth
O
O
E
O
A
OMP
O
O
C
BnO
D
O
O
O
BnO
NPhth
O
HO
OH
14
d, e
Phth: Phthalimido
MP: 4-Methoxyphenyl
MBn: 4-Methoxybenzyl
1
Scheme 2. Reagents and conditions: (a) NIS, TMSOTf, CH2Cl2, ꢀ20 °C, 1 h, 75%; (b)
CH3ONa, CH3OH, room temperature, 40 min; (c) (i) NaBr, CH2Cl2, H2O, TBAB,
TEMPO, NaHCO3, NaOCl, 0–5 °C, 3 h ; (ii) tert-butanol, 2-methyl-but-2-ene, NaClO2,
NaH2PO4, room temperature, 3 h, 78%; (d) (i) ethylene diamine, n-butanol, 105 °C,
8 h; (ii) acetic anhydride, pyridine, room temperature, 6 h; (iii) CH3ONa, CH3OH,
room temperature, 5 h; (e) H2, 20% Pd(OH)2–C, room temperature, 24 h, 71%.
4,6-O-benzylidene-2-deoxy-2-N-phthalimido-b-
213 was prepared from
-glucosamine hydrochloride using
reported reaction conditions. Ethyl 2,3-O-isopropylidene-1-thio-
-rhamnopyranoside 7,14 prepared from
-rhamnose in four
steps was transformed into ethyl 2,3-di-O-acetyl-4-O-allyl-1-
thio- -rhamnopyranoside 3 following a sequence of reactions
D-glucopyranoside
D
a-
L
L
Ph
a-D
SC2H5
O
O
Ph
O
consisting of allylation, removal of the isopropylidene ketal and
O
O
O
O
OMP
AllO
SC2H5
acetylation in overall 90% yield. Ethyl 4,6-O-benzylidene-1-thio-
HO
MBnO
AcO
b-D D-galactose in four steps
-galactopyranoside 8,15 prepared from
NPhth
OAc
BnO
2
3
4
was subjected to a set of reaction sequences involving selective
Ph
OAc
BnO
BnO
O
O
O
O
2 + 3
SC2H5
HO
BnO
OC(NH)CCl3
NPhth
a
6
5
Ph
B
O
O
O
Figure 2. Suitably functionalized monosaccharide intermediates used for the
construction of the pentasaccharide 1.
A
OMP
O
NPhth
O
RO
AcO
OAc
4-methoxybenzylation followed by benzylation to furnish ethyl 2-
9: R = Allyl
10:
b
R = H
4 c
O-benzyl-4,6-O-benzylidene-3-O-(4-methoxybenzylidene)-1-thio-b-
D
-galactopyranoside 4 in 88% overall yield. Compounds 516 and 617
were prepared following earlier literature reports (Scheme 3).
Stereoselective glycosylation of compound 2 with thioglycoside
derivative 3 in the presence of N-iodosuccinimide (NIS) and tri-
methylsilyl trifluoromethanesulfonate (TMSOTf)18 furnished disac-
charide derivative 9 in 91% yield, which was confirmed from its
spectroscopic analysis. The allyl ether was removed from the disac-
charide derivative 9 by the reaction of palladium chloride in acetic
acid–sodium acetate buffer19 to give compound 10 in 79% yield. A
one-pot 1,2-cis directing glycosylation of compound 10 with thio-
glycoside derivative 4 followed by the removal of the 4-methoxy-
benzyl ether protection20 from the trisaccharide derivative formed
in situ was achieved in the presence of a NIS-TMSOTf combination
by tuning the reaction condition to furnish trisaccharide derivative
11 in 78% yield. The presence of signals at d 5.76 (d, J = 8.4 Hz, 1H,
H-1A), 5.60 (s, 1H, PhCH), 5.52 (s, 1H, PhCH), 4.91 (d, J = 3.1 Hz, 1H,
H-1C), 4.69–4.52 (m, H-1B and other protons) in 1H NMR and d
101.9 (PhCH), 100.8 (PhCH), 99.8 (C-1C), 98.1 (C-1A), 97.1 (C-1B)
in the 13C NMR spectra confirmed the exclusive formation of
Ph
Ph
O
O
C
O
O
O
A
OMP
O
O
NPhth
HO
B
O
BnO
O
AcO
11
OAc
Ph
BnO OAc
O
O
d
O
E
5 + 6
BnO
O
BnO
D
SC2H5
NPhth
O
Phth: Phthalimido
MP: 4-Methoxyphenyl
MBn: 4-Methoxybenzyl
12
Scheme 1. Reagents and conditions: (a) N-iodosuccinimide (NIS), TMSOTf, CH2Cl2,
ꢀ20 °C, 45 min, 91%; (b) PdCl2, NaOAcꢁ3H2O, AcOH–H2O, room temperature, 12 h,
79%; (c) NIS, TMSOTf, CH2Cl2, ꢀ50 °C, 45 min, then 0 °C for 30 min, 78%; (d) TfOH,
CH2Cl2, ꢀ20 °C, 2 h, 85%.

1552
R. Panchadhayee, A. K. Misra / Tetrahedron: Asymmetry 20 (2009) 1550–1555
SC2H5 SC2H5
a, b, c
O
O
L-Rhamnose
AllO
HO
AcO
O
O
OAc
3
7
Ph
Ph
O
O
O
O
O
O
d, e
D-Galactose
SC2H5
SC2H5
MBnO
HO
BnO
OH
4
8
Scheme 3. Reagents and conditions: (a) allyl bromide, NaOH, TBAB, THF, room temperature, 6 h; (b) 80% aq AcOH, 80 °C, 1.5 h; (c) acetic anhydride, pyridine, room
temperature, 2 h, overall 90%; (d) Bu2SnO, CH3OH, 80 °C, 3 h; (ii) 4-methoxybenzyl chloride, DMF, 80 °C, 10 h; (e) benzyl bromide, NaOH, TBAB, THF, room temperature, 4 h,
overall 88%.
compound 11. In this case, an exclusive formation of the
side was achieved using a non-participating benzyl group at the
C-2 position of -galactosyl thioglycoside donor 4 in the first step
a-glyco-
4. Experimental
D
4.1. General methods
of the one-pot reaction (Scheme 1).
In another experiment, disaccharide thioglycoside derivative 12
All the reactions were monitored by thin layer chromatography
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 a hot plate. Silica gel 230–400 mesh was used for column chro-
matography. 1H and 13C NMR, 2D COSY, HSQC, NOESY spectra were
recorded on Brucker Advance DPX 300 MHz using CDCl3 and D2O
as solvents and TMS as an internal reference unless stated other-
wise. Chemical shift value is expressed in d ppm. ESI-MS was re-
corded on a MICROMASS QUTTRO II triple quadrupole mass
spectrometer. Elementary analysis was carried out on Carlo
ERBA-1108 analyzer. 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.
was synthesized by acid-catalyzed21 stereoselective coupling of
thioglycoside derivative 5 with D-galactose derived trichloroace-
timidate derivative 6 in 85% yield, which was characterized from
its spectral analysis [d 5.24 (s, PhCH), 5.21 (d, J = 10 Hz, H-1D),
4.97 (d, J = 3.1 Hz, H-1E) in the 1H NMR and d 100.9 (PhCH), 98.3
(C-1E), 80.3 (C-1D) in the 13C NMR spectra] (Scheme 1). With trisac-
charide glycosyl acceptor 11 and disaccharide thioglycoside donor
12, the iodonium ion-mediated stereoselective glycosylation of
compound 11 with compound 12 in the presence of NIS-TMSOTf18
furnished desired pentasaccharide derivative 14 in 75% yield. The
formation of pentasaccharide derivative 13 was confirmed from
its spectral analysis [d 101.5 (PhCH), 100.9 (PhCH), 100.3 (PhCH),
100.1 (C-1C), 99.1 (C-1A), 98.2 (C-1D), 98.1 (C-1E), 97.6 (C-1B) in
the 13C NMR spectra]. Compound 13 was transformed into penta-
saccharide acid derivative 14 in 78% overall yield following a
sequence of reactions involving deacetylation and selective TEM-
PO-mediated oxidation22 of the primary hydroxyl group to the
carboxylic group in biphasic reaction conditions without affecting
the secondary hydroxyl groups present in the molecule. Conver-
sion of the N-phthalimido group to acetamido group23 followed
by hydrogenolysis over Pearlmann’s catalyst24 of compound 14
furnished the target pentasaccharide 1 as its 4-methoxyphenyl
glycoside in 71% overall yield. The presence of signals at d 5.47
(d, J = 7.9 Hz, H-1A), 5.08 (d, J = 8.3 Hz, H-1D), 4.76 (br s, H-1B),
4.47 (br s, H-1C), 4.26 (br s, H-1E) in the 1H NMR and at d 100.4
(C-1E), 100.2 (C-1D), 99.7 (C-1C), 97.6 (C-1B), 97.1 (C-1A) in the
13C NMR spectra confirmed the successful formation of pentasac-
charide 1 (Scheme 2).
4.1.1. Ethyl 2,3-di-O-acetyl-4-O-allyl-1-thio-a-L-
rhamnopyranoside 3
To a solution of compound 7 (5 g, 20.13 mmol) in anhydrous
THF (25 mL) were added powdered sodium hydroxide (2.5 mg,
62.5 mmol), allyl bromide (5 mL, 57.78 mmol) and tetrabutylam-
monium bromide (200 mg) and the reaction mixture was allowed
to stir at room temperature for 6 h. The reaction mixture was
poured into water and extracted with CH2Cl2 (150 mL). The organic
layer was washed with water, dried (Na2SO4) and concentrated un-
der reduced pressure. A solution of the crude product in 80% aq
AcOH (80 mL) was allowed to stir at 80 °C for 1.5 h and evaporated
to dryness under reduced pressure. A solution of the crude product
in acetic anhydride–pyridine (50 mL; 1:1 v/v) was stirred at room
temperature for 2 h. The solvents were removed under reduced
pressure and the crude product was purified over SiO2 using hex-
ane–EtOAc (5:1) as eluant to give pure 3 (6 g, 90%) as white solid;
Rf (20% EtOAc–hexane) 0.3; mp 62–64 °C; [
max: (KBr) 3020, 2361, 1745, 1603, 1369, 1216, 1097, 834,
762 cmꢀ1 1H NMR (300 MHz, CDCl3):
5.92–5.79 (m, 1H,
a
]
D ꢀ190 (c 1.0, CHCl3);
3. Conclusion
m
;
d
In conclusion, the first total synthesis of a pentasaccharide
repeating unit of the O-antigen of E. coli O48: H21 strain, as its
4-methoxyphenyl glycoside, has been achieved in a concise man-
ner using a block synthetic strategy. Most of the intermediates
are solid and all glycosylation steps are highly stereoselective
and reproducible for scale-up. A one-pot reaction condition has
been applied for the stereoselective glycosylation followed by re-
moval of 4-methoxybenzyl group protection. Selective TEMPO-
mediated oxidation of a primary hydroxyl group in a pentasaccha-
ride derivative was achieved using a two-step, one-pot phase
transfer oxidation protocol without affecting other secondary hy-
droxyl groups present in the molecules. 4-Methoxybenzyl group
has been chosen as the temporary protecting group at the reducing
end.
CH@CH2), 5.30–5.13 (m, 5H, H-1, H-2, H-3, CH@CH2), 4.19–4.07
(m, H-5, O–CH2–CH@CH2), 3.38 (t, J = 9.6 Hz, 1H, H-4), 2.69–2.55
(m, 2H, SCH2CH3), 2.14, 2.05 (2 s, 6H, 2COCH3), 1.33 (t, J = 7.4 Hz,
3H, SCH2CH3), 1.28 (d, J = 6.1 Hz, 3H, CCH3); 13C NMR (75 MHz,
CDCl3): d 169.7, 169.4 (2COCH3), 134.6 (CH@CH2), 116.7 (CH@CH2),
81.8 (C-1), 78.7 (C-4), 73.7 (PhCH2), 72.1 (C-3), 71.8 (C-2), 68.2
(C-5), 25.3 (SCH2CH3), 20.9, 20.8 (2COCH3), 17.8 (CCH3), 14.9
(SCH2CH3); ESI-MS: 355.1 [M+Na]+, Anal. Calcd for C15H24O6S
(332.13): C, 54.20; H, 7.28. Found: C, 54.04; H, 7.42.
4.1.2. Ethyl 2-O-benzyl-4,6-O-benzylidene-3-O-(4-
methoxybenzy)-1-thio-b-D-galactopyranoside 4
To a solution of compound 8 (5 g, 16 mmol) in dry CH3OH
(120 mL) was added dibutyltin oxide (4.8 g, 19.28 mmol) and the

R. Panchadhayee, A. K. Misra / Tetrahedron: Asymmetry 20 (2009) 1550–1555
1553
reaction mixture was allowed to stir at 80 °C for 3 h and concen-
4.1.4. 4-Methoxyphenyl (2,3-di-O-acetyl-
rhamnopyranosyl)-(1?3)-4,6-O-benzylidene-2-deoxy-2-N-
phthalimido-b- -glucopyranoside 10
a-L-
trated under reduced pressure. To a solution of the stannylidene
acetal in anhydrous DMF (30 mL) was added 4-methoxybenzyl
chloride (3.2 mL, 23.6 mmol) and the reaction mixture was al-
lowed to stir at 80 °C for 10 h and the solvents were evaporated un-
der reduced pressure. To a solution of the crude product in dry THF
(50 mL) were added powdered NaOH (2 g, 50 mmol), benzyl bro-
mide (3.8 mL, 31.95 mmol) and tetrabutylammonium bromide
(100 mg) and the reaction mixture was allowed to stir at room
temperature for 4 h. The reaction was quenched with CH3OH
(5 mL) and the solvents were removed under reduced pressure.
The crude product was dissolved in CH2Cl2 (150 mL) and the or-
ganic layer was washed with water, dried (Na2SO4) and concen-
trated under reduced pressure. The crude product was purified
over SiO2 using hexane–EtOAc (8:1) as eluant to give pure 4
(7.4 g, 88%) as a white solid; Rf (30% EtOAc–hexane) 0.5; mp 140–
D
To a solution of compound 9 (6 g, 7.75 mmol) in AcOH-H2O
(90 mL; 20:1 v/v) were added NaOAcꢁ3H2O (4.3 g, 31.62 mmol)
and PdCl2 (1 g, 5.64 mmol) and the reaction mixture was al-
lowed to stir at room temperature for 12 h. The solvents were
removed under reduced pressure and the crude product was
purified over SiO2 using hexane–EtOAc (4:1) as eluant to give
pure 10 (4.5 g, 79%) as a white solid; Rf (30% EtOAc–hexane)
0.3; mp 100–102 °C; ½a D25
ꢂ
¼ ꢀ136:8 (c 1.0, CHCl3);
mmax: (KBr)
3471, 2921, 2363, 1747, 1716, 1386, 1225, 1099, 767 cmꢀ1
;
1H
NMR (300 MHz, CDCl3): d 7.88–7.28 (m, 9H, Ar-H), 6.82 (d,
J = 9.0 Hz, 2H, Ar-H), 6.72 (d, J = 9.0 Hz, 2H, Ar-H), 5.74 (d,
J = 8.4 Hz, 1H, H-1A), 5.60 (s, 1H, PhCH), 5.07 dd, J = 6.5 Hz, 1H,
H-3B), 4.72–4.65 (m, 2H, H-2B, H-3A), 4.57–4.51 (m, 2H, H-1B,
H-2A), 4.44–4.42 (m, 1H, H-5A), 3.96–3.75 (m, 4H, H-4A, H-5B,
H-6abA), 3.72 (s, 3H, OCH3), 3.52 (m, 1H, H-4B), 1.99, 1.79 (2 s,
6H, 2COCH3), 0.76 (d, J = 6.1 Hz, 3H, CCH3); 13C NMR (75 MHz,
CDCl3): d 171.1, 169.0 (2COCH3), 168.5, 168.4 (Phth), 155.7–
114.5 (Ar-C), 102.1 (PhCH), 98.2 (C-1A), 97.6 (C-1B), 80.2 (C-
4A), 74.8 (C-3A), 71.5 (C-3B), 71.4 (C-4B), 70.6 (C-2B), 69.0 (C-
5A), 68.6 (C-6A), 66.6 (C-5B), 56.3 (C-2A), 55.4 (OCH3), 20.8,
20.5 (2COCH3), 16.7 (CCH3); ESI-MS: 756.2 [M+Na]+. Anal. Calcd
for C38H39NO14 (733.24): C, 62.20; H, 5.36. Found: C, 62.03; H,
5.50.
142 °C; ½a 2D5
ꢂ
¼ þ2:2 (c 1.0, CHCl3);
mmax: (KBr) 3441, 2863, 2361,
1616, 1515, 1456, 1400, 1352, 1254, 1172, 1096, 1058, 1028,
1005, 817, 735 cmꢀ1 1H NMR (300 MHz, CDCl3): d 7.57–7.28 (m,
;
12H, Ar-H), 6.85 (d, J = 8.5 Hz, 2H, Ar-H), 5.47 (s, 1H, PhCH), 4.93–
4.82 (Abq, J = 10.2 Hz, 2H, PhCH2), 4.70 (br s, 2H, CH3OPhCH2),
4.44 (d, J = 9.6 Hz, 1H, H-1), 4.30 (d, J = 12.3 Hz, 1H, H-6A), 4.12 (d,
J = 3.2 Hz, 1H, H-4), 3.96 (d, J = 12.3 Hz, 1H, H-6b), 3.88 (t,
J = 9.5 Hz, 1H, H-2), 3.57 (dd, J = 9.2, 3.4 Hz, 1H, H-3), 3.34 (br s,
1H, H-5), 2.88–2.73 (m, 2H, SCH2CH3), 1.36 (t, J = 7.4 Hz, 3H,
SCH2CH3); 13C NMR (75 MHz, CDCl3): d 159.3, 138.5–113.8 (Ar-C),
101.4 (PhCH), 84.4 (C-1), 80.6 (C-5), 76.8 (C-3), 75.6 (PhCH2), 74.0
(CH3OPhCH2), 71.4 (C-4), 69.8 (C-2), 69.4 (C-6), 55.1 (OCH3), 23.7
(SCH2CH3), 15.1 (SCH2CH3); ESI-MS: 545.2 [M+Na]+. Anal. Calcd
for C30H34O6S (522.21): C, 68.94; H, 6.56. Found: C, 68.78; H, 6.75.
4.1.5. 4-Methoxyphenyl (2-O-benzyl-4,6-O-benzylidene-
galactopyranosyl)-(1?4)-(2,3-di-O-acetyl-
rhamnopyranosyl)-(1?3)-4,6-O-benzylidene-2-deoxy-2-N-
phthalimido-b- -glucopyranoside 11
a-D-
a-L-
D
To a solution of compound 10 (3 g, 4.08 mmol) and compound
4 (2.6 g, 4.97 mmol) in anhydrous CH2Cl2 (60 mL) was added MS
4 Å (5 g) and the reaction mixture was allowed to stir at room
temperature for 1 h under argon. The reaction mixture was cooled
4.1.3. 4-Methoxyphenyl (2,3-di-O-acetyl-4-O-allyl-
rhamnopyranosyl)-(1?3)-4,6-O-benzylidene-2-deoxy-2-N-
phthalimido-b- -glucopyranoside 9
a-L-
D
To a solution of compound 2 (5 g, 9.93 mmol) and compound 3
(4 g, 12 mmol) in anhydrous CH2Cl2 (60 mL) was added MS 4 Å
(5 g) and the reaction mixture was allowed to stir at room tem-
perature for 1 h under argon. The reaction mixture was cooled
to ꢀ20 °C and N-iodosuccinimide (NIS; 3.8 g, 16.88 mmol) fol-
lowed by trimethylsilyltrifluoromethane sulfonate (TMSOTf;
to ꢀ50 °C and NIS (1.3 g, 5.77 mmol) followed by TMSOTf (25
lL)
was added to it and the reaction mixture was allowed to stir at
the same temperature for 45 min. After consumption of the start-
ing materials (TLC; 20% EtOAc–hexane) the reaction mixture was
warmed up to 0 °C and allowed to stir at 0 °C for 30 min. The reac-
tion mixture was filtered through a CeliteÒ bed and washed with
CH2Cl2 (100 mL). The organic layer was washed with 5% aq
Na2S2O3, satd aq NaHCO3 and water, dried (Na2SO4) and concen-
trated to dryness. The crude product was purified over SiO2 using
hexane–EtOAc (5:1) as eluant to give pure 11 (3.4 g, 77%) as a
white solid; Rf (30% EtOAc–hexane) 0.3; mp 121–123 °C;
30 lL) was added and the reaction mixture was allowed to stir
at the same temperature for 45 min. The reaction mixture was
quenched with Et3N (0.1 mL), filtered through a CeliteÒ bed and
washed with CH2Cl2 (150 mL). The organic layer was washed with
5% aq Na2S2O3, satd aq NaHCO3 and water, dried (Na2SO4) and
concentrated to dryness. The crude product was purified over
SiO2 using hexane–EtOAc (5:1) as eluant to give pure 9 (7 g,
91%) as a white solid; Rf (30% EtOAc–hexane) 0.4; mp 166–
½
a 2D5
ꢂ
¼ ꢀ4 (c 1.0, CHCl3);
m
max: (KBr) 3471, 2929, 2361, 1747,
1717, 1386, 1223, 1097, 1044, 767 cmꢀ1
;
1H NMR (300 MHz,
CDCl3): d 7.88–7.29 (m, 19H, Ar-H), 6.82 (d, J = 9.0 Hz, 2H, Ar-H),
6.73 (d, J = 9.0 Hz, 2H, Ar-H), 5.76 (d, J = 8.4 Hz, 1H, H-1A), 5.60
(s, 1H, PhCH), 5.52 (s, 1H, PhCH), 5.21 (m, 1H, H-3B), 4.91 (d,
J = 3.1 Hz, 1H, H-1C), 4.74 (d, J = 11.7 Hz, 1H, PhCH2a), 4.69–4.52
(m, 5H, H-1B, H-2A, H-3A, H-2B, PhCH2b), 4.43 (dd, J = 4.3 Hz, 1H,
H-5A), 4.18 (d, J = 2.7 Hz, 1H, H-4C), 4.13 (d, J = 12.8 Hz, 1H,
H-6aC), 4.01–3.93 (m, 2H, H-3C, H-6bC), 3.91–3.76 (m, 5H, H-2C,
H-4A, H-5B, H-6abA), 3.72 (s, 3H, OCH3), 3.68 (br s, 1H, H-5C),
3.28 (t, J = 9.1 Hz, 1H, H-4B), 1.98, 1.83 (2 s, 6H, 2COCH3), 0.94
(d, J = 6.1 Hz, 3H, CCH3); 13C NMR (75 MHz, CDCl3): d 169.6,
169.0 (2COCH3), 168.5, 168.4 (Phth), 155.6–114.4 (Ar-C), 101.9
(PhCH), 100.8 (PhCH), 99.8 (C-1C), 98.1 (C-1A), 97.1 (C-1B), 80.3
(C-4B), 80.2 (C-4A), 77.7 (C-3C), 76.1 (C-5B), 74.3 (C-3A), 73.3
(C-4C), 70.5 (PhCH2), 69.8 (C-2B), 69.1 (C-3B), 68.6 (C-6C), 68.4
(C-6A), 67.3 (C-5A), 66.5 (C-2C), 63.3 (C-5C), 56.1 (C-2A), 55.3
(OCH3), 21.1, 20.4 (2COCH3), 17.4 (CCH3); ESI-MS: 1096.3
[M+Na]+. Anal. Calcd for C58H59NO19 (1073.37): C, 64.86; H,
5.54. Found: C, 64.68; H, 5.75.
168 °C; ½a 2D5
ꢂ
¼ þ9:3 (c 1.0, CHCl3);
m
max: (KBr) 3020, 2362, 1754,
1721, 1601, 1368, 1216, 929, 760 cmꢀ1
;
1H NMR (300 MHz,
CDCl3): d 7.81–7.28 (m, 9H, Ar-H), 6.81 (d, J = 9.1 Hz, 2H, Ar-H),
6.72 (d, J = 9.0 Hz, 2H, Ar-H), 5.81 (m, 1H, -CH@CH2), 5.73 (d,
J = 8.4 Hz, 1H, H-1A), 5.60 (s, 1H, PhCH), 5.24–5.10 (m, 3H, H-3B,
–CH@CH2), 4.73–4.65 (m, 2H, H-2B, H-3A), 4.59–4.52 (m, 2H, H-
1B, H-2A), 4.44–4.13 (m, 1H, H-5A), 3.98–3.83 (m, 6H, H-4A, H-
5B, H-6abA, CH2–CH@CH2O), 3.71 (s, 3H, OCH3), 3.15 (t, J = 9.7 Hz,
1H, H-4B), 1.99, 1.79 (2 s, 6H, 2COCH3), 0.74 (d, J = 6.1 Hz, 3H,
CCH3); 13C NMR (75 MHz, CDCl3):
d 169.2, 169.1 (2COCH3),
168.5, 168.4 (Phth), 155.6–134.6 (Ar-C), 134.0 (–CH@CH2),
131.6–118.7 (Ar-C), 116.3 (–CH@CH2), 102.0 (PhCH), 98.2 (C-1A),
97.5 (C-1B), 80.2 (C-4A), 78.5 (C-4B), 74.5 (C-3A), 73.1 (O-CH2–),
70.9 (C-3B), 70.3 (C-2B), 68.6 (C-6A), 67.8 (C-5A), 66.6 (C-5B), 56.2
(C-2A), 55.4 (OCH3), 20.9, 20.5 (2COCH3), 17.0 (CCH3); ESI-MS:
796.3 [M+Na]+. Anal. Calcd for C41H43NO14 (773.27): C, 63.64; H,
5.60. Found: C, 63.48; H, 5.73.

1554
R. Panchadhayee, A. K. Misra / Tetrahedron: Asymmetry 20 (2009) 1550–1555
4.1.6. Ethyl (6-O-acetyl-2,3,4-tri-O-benzyl-
galactopyranosyl)-(1?3)-4,6-O-benzylidene-2-deoxy-2-N-
phthalimido-1-thio-b- -galactopyranoside 12
To a solution of compound 5 (2 g, 4.37 mmol) and compound 6
(4.2 g, 6.60 mmol) in anhydrous CH2Cl2 (40 mL) was added MS 4 Å
(4 g) and the reaction mixture was allowed to stir at room temper-
ature for 20 min. under argon. The reaction mixture was cooled to
a
-
D
-
3H, CCH3); 13C NMR (75 MHz, CDCl3): d 169.7, 169.1, 169.0
(3COCH3), 168.8–167.2 (Phth), 155.6–114.5 (Ar-C), 101.5 (PhCH),
100.9 (PhCH), 100.3 (PhCH), 100.1 (C-1C), 99.1 (C-1A), 98.2 (C-1D),
98.1 (C-1E), 97.6 (C-1B), 80.2 (C-2E), 79.7 (C-5B), 78.6 (C-4C), 78.5
(C-2B), 77.2 (C-2C), 76.0 (C-4A), 75.6 (C-3A), 75.3 (C-5A), 74.3 (2C,
2PhCH2), 74.1 (C-4E), 73.4 (C-4D), 73.2 (PhCH2), 72.8 (PhCH2),
70.5 (C-3D), 69.7 (C-3B), 69.5 (C-6C), 69.2 (C-6A), 69.1 (C-3C), 68.6
(C-6E), 67.6 (C-4B), 66.6 (C-5D), 66.5 (C-5E), 63.5 (C-3E), 62.6 (C-
5C), 61.9 (C-6D), 56.1 (C-2A), 55.4 (OCH3), 52.9 (C-2D), 20.7 (2C),
20.4 (3COCH3), 17.6 (CCH3); ESI-MS: 1949.7 [M+Na]+. Anal. Calcd
for C108H106N2O31 (1926.68): C, 67.28; H, 5.54. Found: C, 67.10;
H, 5.70.
D
ꢀ20 °C and TfOH (50
lL) was added after which it is allowed to stir
at the same temperature for 2 h. The reaction mixture was
quenched with Et3N (0.1 mL), filtered through a CeliteÒ bed and
washed with CH2Cl2 (100 mL). The organic layer was washed with
satd aq NaHCO3 and water, dried (Na2SO4) and concentrated to
dryness. The crude product was purified over SiO2 using hexane–
EtOAc (6:1) as eluant to give pure 12 (3.4 g, 85%) as a white solid;
4.1.8. 4-Methoxyphenyl (sodium 2,3,4-tri-O-benzyl-
galactopyranosyl uronate)-(1?3)-(4,6-O-benzylidene-2-
acetamido-2-deoxy-b- -galactopyranosyl)-(1?3)-(2-O-benzyl-
4,6-O-benzylidene- -galactopyranosyl)-(1?4)-(
rhamnopyranosyl)-(1?3)-4,6-O-benzylidene-2-acetamido-2-
deoxy-b- -glucopyranoside 14
a-D-
Rf (30% EtOAc–hexane): 0.4; mp 142–144 °C; ½a D25
¼ þ81 (c 1.0,
ꢂ
CHCl3); mmax
:
(KBr) 33427, 3020, 2361, 1360, 1216, 726,
D
670 cmꢀ1
;
1H NMR (300 MHz, CDCl3): d 7.79–7.67 (m, 4H, Ar-H),
a
-D
a-L-
7.48–7.15 (m, 20H, Ar-H), 5.24 (s, 1H, PhCH), 5.21 (d, J = 10 Hz,
1H, H-1D), 4.97 (d, J = 3.1 Hz, 1H, H-1E), 4.82 (d, J = 11.5 Hz, 1H,
PhCH2a), 4.78 (t, J = 10.9 Hz, 1H, H-2D), 4.71–4.67 (m, 2H, PhCH2),
4.60–4.51 (m, 3H, H-3D, PhCH2), 4.43 (d, J = 11.5 Hz, 1H, PhCH2a),
4.31–4.27 (m, 2H, H-4D, H-4E), 3.94–3.91 (m, 1H, H-2E), 3.83 (d,
J = 11.9 Hz, 1H, H-6aE), 3.77–3.71 (m, 2H, H-3E, H-6aD), 3.60–3.54
(m, 2H, H-5D, H-6bE), 3.46 (s, 1H, H-5E), 3.27–3.24 (m, 1H, H-6bD),
2.85–2.68 (m, 2H, SCH2CH3), 1.23 (t, J = 7.5 Hz, 3H, SCH2CH3); 13C
NMR (75 MHz, CDCl3): d 169.8 (COCH3), 168.6, 168.4 (Phth),
138.6–123.3 (Ar-C), 100.9 (PhCH), 98.3 (C-1E), 80.3 (C-1D), 78.6
(C-3E), 76.2 (C-3D), 75.6 (C-2E), 74.4 (PhCH2), 74.2 (C-5D), 73.4 (C-
4D), 73.3 (PhCH2), 73.1 (PhCH2), 70.2 (C-5E), 69.6 (C-4E), 69.5 (C-
6D), 22.7 (SCH2CH3), 20.8 (COCH3), 14.9 (SCH2CH3); ESI-MS: 938.4
[M+Na]+. Anal. Calcd for C52H53NO12S (915.33): C, 68.18; H, 5.83.
Found: C, 68.0; H, 6.0.
D
A solution of compound 13 (1.5 g, 0.78 mmol) in 0.05 M CH3ONa
in CH3OH (100 mL) was allowed to stir at room temperature for
45 min. and neutralized with Dowex-50W X8 (H+) resin. The reaction
mixture was filtered and concentrated under reduced pressure. To a
solution of the crude product in CH2Cl2 (20 mL) and H2O (3.5 mL)
were added aq solution of NaBr (1 mL; 1 M), aq solution of TBAB
(2 mL; 1 M), TEMPO (80 mg, 0.5 mmol), satd aq solution of NaHCO3
(8 mL) and 4% aq NaOCl (10 mL) in succession and the reaction mix-
ture was allowed to stir at 0–5 °C for 3 h. The reaction mixture was
neutralized by the addition of 1 M aq HCl solution. To the reaction
mixture were added tert-butanol (25 mL), 2-methyl-but-2-ene
(30 mL; 2 M solution in THF), aq. solution of NaClO2 (1 g in 5 mL)
and aq solution of NaH2PO4 (1 g in 5 mL) and the reaction mixture
was allowed to stir at room temperature for 3 h. The reaction mixture
was diluted with satd aq NaH2PO4 and extracted with CH2Cl2
(100 mL). The organic layer was washed with water, dried (Na2SO4)
and concentrated to dryness. The crude product was purified over
SiO2 using toluene–EtOAc (1:1) as eluant to give pure 14 (1.1 g,
4.1.7. 4-Methoxyphenyl (6-O-acetyl-2,3,4-tri-O-benzyl-
a-D-
galactopyranosyl)-(1?3)-(4,6-O-benzylidene-2-deoxy-2-N-
phthalimido-b-
D
-galactopyranosyl)-(1?3)-(2-O-benzyl-4,6-O-
-galactopyranosyl)-(1?4)-(2,3-di-O-acetyl-a-L-
benzylidene-
a
-D
rhamnopyranosyl)-(1?3)-4,6-O-benzylidene-2-deoxy-2-N-
78%) as a yellow oil; Rf (50% EtOAc–toluene) 0.2; ½a D25
¼ þ47 (c 1.0,
ꢂ
phthalimido-b- -glucopyranoside 13
D
CHCl3);
mmax: (neat) 3430, 3020, 2361, 1596, 1350, 1216, 960, 761,
;
To a solution of compound 11 (1.5 g, 1.38 mmol) and compound
12 (1.5 g, 1.64 mmol) in anhydrous CH2Cl2 (20 mL) was added MS
4 Å (2 g) and the reaction mixture was allowed to stir at room tem-
perature for 1 h under argon. The reaction mixture was cooled to
670 cmꢀ1 1H NMR (300 MHz, CDCl3): d 7.74–6.78 (m, 43H, Ar-H),
6.73 (d, J = 9.0 Hz, 2H, Ar-H), 6.64 (d, J = 9.0 Hz, 2H, Ar-H), 5.66 (d,
J = 8.5 Hz, 1H, H-1D), 5.50 (d, J = 8.5 Hz, 1H, H-1A), 5.46 (br s, 2H,
2PhCH), 5.31 (s, 1H, PhCH), 4.79–4.64 (m, 4H, 2PhCH2), 4.61–4.48
(m, 3H, H-1B, H-1C, H-1E), 4.46–4.26 (m, 10H, H-2A, H-2D, H-3A, H-
3C, H-3D, H-4C, 2PhCH2), 4.16 (d, J = 11.6 Hz, 1H, H-6aD), 4.12–4.04
(m, 3H, H-4D, H-4E, H-5A), 4.02–3.87 (m, 4H, H-2E, H-3E, H-4A, H-
6bD), 3.86–3.69 (m, 5H, H-2C, H-6abA, H-6abC), 3.68–3.62 (m, 1H, H-
3B), 3.61 (s, 3H, OCH3), 3.58–3.50 (m, 3H, H-2B, H-5B, H-5C), 3.45–
3.43 (m, 1H, H-5E), 3.34–3.29 (m, 2H, H-4B, H-5D), 0.70 (d,
J = 6.0 Hz, 3H, CCH3); 13C NMR (75 MHz, CDCl3): d 168.4–167.8
(Phth), 155.5–114.3 (Ar-C), 101.5 (PhCH), 100.5 (PhCH), 100.2 (PhCH),
99.6 (3C, C-1B, C-1C, C-1E), 99.2 (C-1A), 97.9 (C-1D), 80.3 (2C, C-2E, C-
5B), 77.7 (C-2B), 77.1 (C-4C), 76.3 (C-2C), 75.3 (C-4A), 75.3 (C-5A),
75.0 (2C, C-3A, C-4D), 74.5 (C-4E), 74.2 (C-3D), 73.3 (PhCH2), 72.3
(PhCH2), 71.5 (3C, C-3C, 2PhCH2), 70.3 (C-3B), 69.3 (2C, C-6A, C-6C),
68.9 (C-4B), 68.4 (C-6D), 66.4 (2C, C-5D, C-5E), 66.3 (C-3E), 63.6 (C-
5C), 56.2 (C-2A), 55.4 (OCH3), 53.3 (C-2D), 17.0 (CCH3); ESI-MS:
1837.0 [M+1]+. Anal. Calcd for C102H97N2NaO29 (1836.61): C, 66.66;
H, 5.32. Found: C, 66.47; H, 5.50.
ꢀ20 °C and NIS (450 mg, 2.0 mmol) followed by TMSOTf (5
lL)
was added to it and the reaction mixture was allowed to stir at
the same temperature for 1 h. The reaction mixture was quenched
with Et3N (0.1 mL), filtered through a CeliteÒ bed and washed with
CH2Cl2 (100 mL). The organic layer was washed with 5% aq
Na2S2O3, satd aq NaHCO3 and water, dried (Na2SO4) and concen-
trated to dryness. The crude product was purified over SiO2 using
hexane–EtOAc (3:1) as eluant to give pure 13 (2 g, 75%) as a white
solid; Rf (30% EtOAc–hexane) 0.3; mp 127–129 °C; ½a D25
¼ þ66 (c
ꢂ
1.0, CHCl3);
mmax: (KBr) 3469, 2926, 2860, 2361, 1717, 1457,
1387, 1225, 1099, 1046, 725 cmꢀ1 1H NMR (300 MHz, CDCl3): d
;
7.90–6.92 (m, 43H, Ar-H), 6.81 (d, J = 9.0 Hz, 2H, Ar-H), 6.74 (d,
J = 9.0 Hz, 2H, Ar-H), 5.74 (d, J = 8.3 Hz, 1H, H-1D), 5.59 (d,
J = 8.5 Hz, 1H, H-1A), 5.56 (s, 1H, PhCH), 5.51 (s, 1H, PhCH), 5.28
(s, 1H, PhCH), 5.25–5.22 (m, 1H, H-2B), 5.18–5.09 (m, 1H, H-3B),
5.07–4.96 (m, 2H, H-1E, PhCH2a), 4.88–4.82 (m, 2H, H-4C, PhCH2b),
4.78–4.66 (m, 3H, H-1C, H-2A, H-3D), 4.64–4.54 (m, 7H, H-1B, H-2D,
H-3A, 2PhCH2), 4.51–4.42 (m, 3H, H-3C, PhCH2), 4.34–4.17 (m, 3H,
H-4D, H-4E, H-6aE), 4.12–4.04 (m, 2H, H-5A, H-6bE), 3.97–3.92 (m,
4H, H-2E, H-4A, H-6abA), 3.89–3.84 (m, 2H, H-2C, H-6aC), 3.82–3.75
(m, 2H, H-3E, H-6bC), 3.73 (s, 3H, OCH3), 3.67–3.54 (m, 3H, H-5B,
H-5C, H-6aD), 3.52–3.34 (m, 2H, H-5D, H-5E), 3.32–3.23 (m, 2H, H-
4B, H-6bD), 1.90, 1.89, 1.84 (3 s, 9H, 3COCH3), 0.90 (d, J = 6.0 Hz,
4.1.9. 4-Methoxyphenyl (sodium
uronate)-(1?3)-(2-acetamido-2-deoxy-b-
(1?3)-( -galactopyranosyl)-(1?4)-( -rhamnopyranosyl)-
(1?3)-2-acetamido-2-deoxy-b- -glucopyranoside 1
a-D
-galactopyranosyl
D
-galactopyranosyl)-
a
-D
a-L
D
To a solution of compound 15 (1 g, 0.54 mmol) in n-butanol
(25 mL) was added ethylene diamine (0.2 mL, 3.0 mmol) and the

R. Panchadhayee, A. K. Misra / Tetrahedron: Asymmetry 20 (2009) 1550–1555
2. Ørskov, I.; Ørskov, F.; Jann, B.; Jann, K. Bacteriol. Rev. 1977, 41, 667–710.
1555
reaction mixture was allowed to stir at 105 °C for 8 h and the sol-
vents were removed under reduced pressure. A solution of the
crude mass in acetic anhydride–pyridine (20 mL, 1:1 v/v) was kept
at room temperature for 6 h and the solvents were removed under
reduced pressure. A solution of the crude mass in 0.1 M sodium
methoxide (30 mL) was allowed to stir at room temperature for
5 h and neutralized with Amberlite IR-120 (H+) resin. The reaction
mixture was filtered and evaporated to dryness. To a solution of
the crude product in CH3OH (30 mL) was added 20% Pd(OH)2–C
(300 mg) and the reaction mixture was allowed to stir at room
temperature under a positive pressure of hydrogen for 24 h. The
reaction mixture was filtered through a CeliteÒ bed and then
washed with CH3OH–H2O (60 mL; 3:1 v/v). The combined filtrate
was evaporated under reduced pressure to furnish compound 1,
which was purified through a Sephadex LH-20 column using
CH3OH–H2O (4:1) as eluant to give pure compound 1 (415 mg,
3. (a) Beutin, L.; Aleksic, S.; Zimmermann, S.; Gleier, K. Med. Microbiol. Immunol.
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Harmsen, D.; Caprioli, A.; Karch, H. J. Med. Microbiol. 1995, 42, 404–410.
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71%) as
a white amorphous powder; Rf (CH2Cl2–CH3OH–
H2O = 10:5:1) 0.3; ½a D25
ꢂ
¼ þ77 (c 1.0, H2O);
mmax: (KBr) 3432,
2943, 1607, 1377, 1145, 1089, 665 cmꢀ1
;
1H NMR (300 MHz,
D2O): d 6.42 (d, J = 8.8 Hz, 2H, Ar-H), 6.21 (d, J = 8.8 Hz, 2H, Ar-H),
5.47 (d, J = 7.9 Hz, 1H, H-1A), 5.08 (d, J = 8.3 Hz, 1H, H-1D), 4.76
(br s, 1H, H-1B), 4.47 (br s, 1H, H-1C), 4.40 (br s, 1H, H-4D), 4.26
(br s, 1H, H-1E), 4.08–3.85 (m, 5H, H-2A, H-2D, H-3A, H-3D, H-4E),
3.76–3.44 (m, 9H, H-3B, H-4C, H-5A, H-5B, H-5C, H-6abA, H-6abC),
3.43–3.22 (m, 9H, H-2B, H-2C, H-2E, H-3C, H-3E, H-4A, H-5E, H-
6abD), 3.16 (s, 3H, OCH3), 3.15–3.10 (m, 1H, H-5D), 2.98–2.91 (m,
1H, H-4B), 1.89 (s, 6H, 2NHCOCH3), 0.72 (d, J = 6.1 Hz, 3H, CCH3);
13C NMR (75 MHz, D2O): d 174.6, 174.2 (2NHCOCH3), 174.0 (COO-
Na), 154.7–114.6 (Ar-C), 100.4 (C-1E), 100.2 (C-1D), 99.7 (C-1C),
97.6 (C-1B), 97.1 (C-1A), 80.7 (C-4B), 79.4 (C-5C), 78.7 (C-3A), 76.4
(C-2C), 74.8 (C-4D), 74.6 (C-5A), 72.0 (C-2B), 70.6 (C-3B), 70.5 (C-
5D), 70.2 (C-5B), 69.2 (2C, C-3C, C-4E), 68.8 (2C, C-4C, C-5E), 68.3
(C-3E), 67.5 (C-4A), 67.0 (C-3D), 65.4 (C-2E), 60.9 (C-6A), 60.6 (2C,
C-6C, C-6D), 55.8 (C-2A), 55.4 (OCH3), 52.3 (C-2D), 23.2, 23.0
(2NHCOCH3), 16.7 (CCH3); ESI-MS: 1037.5 [M+1]+. Anal. Calcd for
C41H61N2NaO27 (1036.64): C, 47.49; H, 5.93. Found: C, 47.27; H,
6.18.
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31, 1331–1334; (b) Konradsson, P.; Udodong, U. E.; Fraser-Reid, B. Tetrahedron
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Acknowledgements
R.P. thanks CSIR, New Delhi for providing a Senior Research Fel-
lowship. This work was supported by Ramanna Fellowship (AKM),
Department of Science and Technology, New Delhi (SR/S1/RFPC-
06/2006).
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