Synthesis of two trisaccharides related to the triterpenoid saponin eryloside isolated from the sponge Erylus nobilis

Article abstract of DOI:10.1016/j.tetasy.2011.06.025

The chemical synthesis of two trisaccharides related to the triterpenoid saponin eryloside from commercially available d-galactose, l-arabinose and d-glucosamine hydrochloride via rational protecting group manipulations is reported. The required glycosyla

Full text of DOI:10.1016/j.tetasy.2011.06.025

Tetrahedron: Asymmetry 22 (2011) 1108–1113
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Tetrahedron: Asymmetry
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Synthesis of two trisaccharides related to the triterpenoid saponin
eryloside isolated from the sponge Erylus nobilis
⇑
Santanu Mandal, Rituparna Das, Balaram Mukhopadhyay
Indian Institute of Science Education and Research-Kolkata (IISER-K), Mohanpur Campus, P.O. BCKV Campus Main Office, Mohanpur, Nadia 741252, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The chemical synthesis of two trisaccharides related to the triterpenoid saponin eryloside from commer-
cially available D-galactose, L-arabinose and D-glucosamine hydrochloride via rational protecting group
manipulations is reported. The required glycosylations were carried out by the extensive use of thiogly-
coside chemistry where the activations were achieved by using NIS in the presence of La(OTf)3.
Ó 2011 Elsevier Ltd. All rights reserved.
Received 5 May 2011
Accepted 27 June 2011
Available online 27 July 2011
Dedicated to Professor Rabindranath
Mukherjee, Department of Chemistry,
Indian Institute of Technology Kanpur.
1. Introduction
2. Results and discussion
The abundance of steroidal and triterpenoid saponins in starfish
and sea cucumbers provides representative groups of echinoderm
metabolites.1 This group of biomolecules are of great medicinal
interest as they exhibit diverse bioactivities, such as antiviral, anti-
fungal, cytotoxic and haemolytic activities. These metabolites are
rare in other marine organisms that include the most studied mar-
ine organisms, sponges. In sponges, the saponins are generally
regarded as a minor structural group of metabolites. However, a
growing number of saponins have recently been isolated from
these animals.2 Recently, Shin et al.3 have reported the isolation
of saponins, erylosides from the sponge Erylus nobilis Thiele
collected from the Jaeju Island, Korea. Erylosides have shown mod-
The selection of the p-methoxyphenyl glycoside as the final
reducing end glycoside was triggered by the fact that it can be
selectively cleaved to open up the scope for further glycoconjugate
formation through trichloroacetimidate chemistry. Further study
of the retrosynthetic scheme revealed that a 3,4,6-protected p-
methoxyphenyl galactopyronoside or a 3,4-protected p-methoxy-
phenyl arabinopyranoside could be used as the reducing end
acceptor. For the N-acetyl glucosamine moiety, the corresponding
N-phthalimido thioglycoside would be the best choice, as it would
confirm the exclusive formation of the b-linkage as required. After
the formation of the disaccharide, the 3,4-protection of either gal-
actose or arabinose moieties can be cleaved; further protection of
the 4-position will furnish the desired disaccharide acceptor. Final-
ly, the non-reducing end of the arabinopyranosyl moiety can be
glycosylated by using thioglycoside chemistry. The hydrazine med-
iated cleavage of the N-phthalimido group followed by acetylation
and global de-O-acylation will provide the target trisaccharides
(Scheme 1).
erate cytotoxicity (LC50 317
cell line K562. Structural elucidation revealed that erylosides
posses lanostane-based carbon framework as an aglycone
with a branched oligosaccharide having N-acetyl -glucosamine,
-galactose and -arabinose residues or, two -arabinose residues
lg/mL) against the human leukaemia
a
D
D
L
L
with an N-acetyl glucosamine moiety. As the formation of the
oligosaccharide framework is an integral part of the saponin bio-
synthesis and the role of the oligosaccharide towards the bioactiv-
ity of the saponin is not clearly understood, a systematic chemical
approach for the synthesis of the sugar part is highly relevant.
Herein, we report the chemical synthesis of two trisaccharides
related to the saponins erylosides from commercially available
At first, the 6-O-position of the known p-methoxyphenyl
3,4-isopropylidene-b-D
-galactopyranoside 34 was benzoylated by
using a molar equivalent of benzoyl cyanide (BzCN)5 in the pres-
ence of catalytic Et3N to afford the acceptor, p-methoxyphenyl
6-O-benzoyl-3,4-isopropylidene-b-D-galactopyranoside 4 in 87%
yield. Acceptor 4 was glycosylated with the known p-tolyl 3,4,6-
D
-glucosamine hydrochloride,
D
-galactose and
L
-arabinose through
tri-O-acetyl-2-deoxy-2-phthalimido-1-thio-b-D-glucopyranoside
56 using N-iodosuccinimide (NIS) in the presence of La(OTf)3 to
afford the disaccharide, p-methoxyphenyl 3,4,6-tri-O-acetyl-2-
7
rational protecting group manipulation strategies and stereoselec-
tive glycosylations (Fig. 1).
deoxy-2-phthalimido-b-
3,4-O-isopropylidene-b- -galactopyranoside 6 in 82% yield. The
use of TMSOTf instead of La(OTf)3 resulted in only 68% yield of
D-glucopyranosyl-(1?2)-6-O-benzoyl-
D
⇑
Corresponding author. Tel.: +91 9748 261742; fax: +91 33 2587 3031.
E-mail address: sugarnet73@hotmail.com (B. Mukhopadhyay).
0957-4166/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2011.06.025

S. Mandal et al. / Tetrahedron: Asymmetry 22 (2011) 1108–1113
1109
HO
O
R
HO
HO
O
O
OMP
O
OH OH
HO
O
R
O
COOH
HO
HO
O
HO
HO
O
O
NHAc
O
OH OH
1 R = CH2OH
2 R = H
O
HO
HO
NHAc
MP = p-Methoxyphenyl
Figure 1. Structure of the triterpenoid saponin and the synthetic targets.
HO
O
O
OH
O
O
OBz
O
R
HO
HO
BzCN
O
O
OMP
OMP
OMP
O
O
O
Et3N, rt
OH
OH
4
OH OH
3
O
HO
HO
OAc
O
OBz
O
NHAc
O
AcO
AcO
STol
NPhTh
OMP
1
R = CH2OH
O
2 R = H
80% AcOH
O
5
O
AcO
AcO
80 °C
MP = p-methoxyphenyl
NPhTh
NIS, La(OTf)3
AcO
6
PO
R
HO
HO
OBz
O
AcO
HO
OBz
O
O
PO
PO
i. Trimethyl
OMP
HO
OP
OMP
orthoacetate, CSA
O
OMP
STol
+
O
O
O
ii. 80% AcOH
O
O
OP
O
AcO
AcO
AcO
AcO
AcO
AcO
PO
PO
NHAc
NPhTh
NPhTh
1
R = CH2OP
R = H
7
8
2
commercially
available L-arabinose
AcO
O
OBz
O
AcO
AcO
AcO
AcO
PO
R
O
O
OP
O
OMP
STol
O
PO
PO
OMP
STol
NPhTh
PhTh = Phthalimido
+
PO
OAc
OAc
O
i. NH2-NH2
ii. Ac2O, Py
O
9
OH
AcO
AcO
1 R = CH2OP
NIS, La(OTf)3
NPhTh
2 R = H
AcO
10
HO
AcO
OH
O
OBz
O
AcO
AcO
commercially
HO
HO
commercially
available D-glucosamine
O
O
OMP
OMP
NaOMe
MeOH
available D-galactose
or L-arabinose
O
O
O
OAc
AcO
AcO
O
OH OH
O
Scheme 1. Retrosynthetic analysis for the target oligosaccharides.
O
NHAc
HO
HO
AcO
NHAc
the disaccharide. Therefore, La(OTf)3 was proved to be the better
choice as a promoter for the NIS-mediated activation of thioglyco-
sides in this particular case. Hydrolysis of the isopropylidene using
80% aq AcOH at 80 °C8 afforded diol 7 in 85% yield. The reaction of
compound 7 with trimethyl orthoacetate in the presence of CSA9
followed by the rearrangement of the orthoester using 80% aq
AcOH at rt furnished the disaccharide acceptor 8 in 81% yield.
Further glycosylation of the disaccharide acceptor 8 with the
11
1
Scheme 2. Synthesis of the target trisaccharide 1.
pyranosyl-(1?2)-3-O-(b-
oside 1 in 78% yield (Scheme 2).
L-arabinopyranosyl)-b-D-galactopyran-
The synthesis of the target trisaccharide 2 was started with the
glycosylation between the known acceptor, p-methoxyphenyl 3,4-
known p-tolyl 2,3,4-tri-O-acetyl-1-thio-b-L
-arabinopyranoside 910
was accomplished by using NIS in the presence of La(OTf)3 to
O-isopropylidene-b-L
-arabinopyranoside 1213 and donor 5 using
furnish the trisaccharide, p-methoxyphenyl 3,4,6-tri-O-acetyl-2-
NIS in the presence of La(OTf)3. The reaction resulted in the forma-
tion of disaccharide 13 in 88% yield. The 3,4-O-isopropylidene moi-
ety was then hydrolysed by 80% aq AcOH at 80 °C to afford diol 14
in 91% yield. The reaction of diol 14 with trimethyl orthoacetate
in the presence of catalytic CSA followed by a rearrangement
induced by 80% aq AcOH at rt furnished the disaccharide accep-
tor, p-methoxyphenyl 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-
deoxy-2-phthalimido-b-
benzoyl-3-O-(2,3,4-tri-O-acetyl-b-
D
-glucopyranosyl-(1?2)-4-O-acetyl-6-O-
-arabinopyranosyl)-b- -galac-
L
D
topyranoside 10 in 84% yield. The hydrazine mediated cleavage of
the phthalimido group11 followed by acetylation using Ac2O and
pyridine afforded the trisaccharide 11 in 82% yield. Finally, Zem-
plen de-O-acylation12 using NaOMe in MeOH afforded the target
trisaccharide, p-methoxyphenyl 2-acetamido-2-deoxy-b-
D
-gluco-
b-D-glucopyranosyl-(1?2)-4-O-acetyl-b-L-arabinopyranoside 15

1110
S. Mandal et al. / Tetrahedron: Asymmetry 22 (2011) 1108–1113
O
O
O
O
OAc
OMP
NIS, La(OTf)3
O
O
O
AcO
AcO
+
OMP
STol
NPhTh
O
O
AcO
AcO
OH
NPhTh
12
5
AcO
13
AcO
HO
HO
HO
O
O
i. Trimethyl
O
O
OMP
OMP
orthoacetate, CSA
80% AcOH
80 °C
O
O
ii. 80% AcOH
AcO
AcO
AcO
AcO
AcO
NPhTh
15
NPhTh
AcO
14
AcO
AcO
AcO
AcO
AcO
O
STol
O
O
OMP
O
OAc
i. NH2-NH2
ii. Ac2O, Py
9
OAc
AcO
AcO
O
O
NIS, La(OTf)3
NPhTh
AcO
16
HO
AcO
HO
HO
AcO
AcO
O
O
OMP
O
O
O
O
OMP
O
NaOMe
MeOH
O
OH OH
OAc
O
AcO
O
AcO
AcO
NHAc
HO
HO
NHAc
17
2
Scheme 3. Synthesis of the target trisaccharide 2.
in 86% yield. Glycosylation between the disaccharide acceptor 15
and donor 9 using NIS in the presence of La(OTf)3 resulted in the
formation of trisaccharide 16 in 81% yield. Hydrazine mediated
cleavage of the N-phthalimido group and subsequent acetylation
of the free amine using Ac2O in pyridine afforded the correspond-
ing acetamido trisaccharide 17 in 85% yield. Global deprotection of
the acetate groups using NaOMe in MeOH furnished the target tri-
by fluorescence and/or by charring following immersion in a 10%
ethanolic solution of sulfuric acid. An orcinol dip, prepared by
the careful addition of concentrated sulfuric acid (20 cm3) to an
ice-cold solution of 3,5-dihydroxytoluene (360 mg) in EtOH
(150 cm3) and water (10 cm3), was used to detect deprotected
compounds by charring. Flash chromatography was performed
with silica gel 230–400 mesh (Merck, India). Optical rotations were
measured at the sodium D-line at ambient temperature, with a
Perkin Elmer 141 polarimeter. 1H NMR and 13C NMR spectra were
recorded on a Bruker Avance spectrometer at 500 and 125 MHz,
respectively, using Me4Si or CH3OH as internal standards, as
appropriate.
saccharide, p-methoxyphenyl 2-acetamido-2-deoxy-b-
D-glucopyr-
anosyl-(1?2)-3-O-(b- -arabinopyranosyl)-b- -arabinopyranoside
L
L
2 in 80% yield (Scheme 3).
3. Conclusion
In conclusion, the chemical synthesis of two trisaccharides re-
lated to the triterpenoid saponin eryloside isolated from the
sponge, Erylus nobilis has been accomplished. The derived trisac-
charides in the form of their p-methoxyphenyl glycoside open up
the scope for further glycoconjugates formations by selective
cleavage of the OMP followed by trichloroacetimidate chemistry
with a suitable aglycon. Furthermore La(OTf)3 has been success-
fully used for the NIS-mediated activation of thioglycosides. The
Lewis acid catalyst was found to be a better alternative than the
traditional TfOH or TMSOTf.
4.1.1. p-Methoxyphenyl 6-O-benzyl-3,4-O-isopropylidene-b-D-
galactopyranoside 4
To a solution of 3 (3.1 g, 9.5 mmol) in CH2Cl2 (30 mL), BzCN
(1.2 mL, 9.7 mmol) was added followed by Et3N (200 L) and the
l
mixture was stirred at 0–5 °C for 10 min until the starting material
had completely disappeared (TLC). The excess BzCN was neutral-
ized with MeOH and the solvents were evaporated to give the
crude product as a syrup. It was purified by flash chromatography
using n-hexane–EtOAc (1.5:1) to afford pure 4 (3.6 g, 87%) as a col-
ourless glass. ½a D25
ꢀ
¼ þ79 (c 1.0, CHCl3). 1H NMR (500 MHz, CDCl3)
d: 8.08–6.67 (m, 9H, ArH), 4.72 (dd, 1H, J6a,6b 11.5 Hz, J5,6a 3.0 Hz,
H-6a), 4.67 (d, 1H, J1,2 8.5 Hz, H-1), 4.62 (m, 1H, H-6b), 4.24 (m,
2H, H-3, H-4), 3.89 (t, 1H, J1,2, J2,3 8.5 Hz, H-2), 3.73 (s, 3H, C6H4–
OCH3), 3.72 (m, 1H, H-5), 1.59, 1.43 (2s, 6H, 2 ꢁ isopropylidene-
CH3). 13C NMR (125 MHz, CDCl3) d: 166.2 (COPh), 155.4, 151.0,
133.1, 129.8, 129.7(2), 128.4(2), 118.6(2), 114.4(2) (ArC), 110.8
[C(CH3)2], 101.6 (C-1), 78.9, 73.3, 73.2, 71.4, 63.6, 55.5 (C6H4–
OCH3), 26.3, 22.6 (2 ꢁ isopropylidene CH3). HRMS calcd. for
4. Experimental
4.1. General
All reagents and solvents were dried prior to use according to
standard methods.14 Commercial reagents were used without fur-
ther purification unless otherwise stated. Analytical TLC was per-
formed on Silica Gel 60-F254 (Merck or Whatman) with detection
C
23H26O8Na (M+Na)+: 453.1525, found: 453.1521.

S. Mandal et al. / Tetrahedron: Asymmetry 22 (2011) 1108–1113
1111
4.1.2. p-Methoxyphenyl 3,4,6-tri-O-acetyl-2-deoxy-2-phtha-
limido-b- -glucopyranosyl-(1?2)-6-O-benzoyl-3,4-O-isopro-
pylidene-b- -galactopyranoside 6
perature for 1 h. After neutralizing with Et3N, the solvents were
evaporated in vacuo and the crude product was suspended in
80% aq AcOH (20 mL) and stirred at room temperature for
45 min. After removing the solvents in vacuo, the crude product
was purified by flash chromatography using n-hexane–EtOAc
(2:1) as eluent to afford the pure compound 8 (1.7 g, 81%) as a col-
D
D
A mixture of compound 4 (2.0 g, 4.6 mmol), compound 5 (3.3 g,
6.0 mmol) and MS 4 Å (2.0 g) in dry CH2Cl2 (30 mL) was stirred un-
der nitrogen for 30 min. Next, NIS (1.75 g, 7.8 mmol) was added
and the mixture was cooled to 10 °C using ice-water bath. After
stirring for 15 min, La(OTf)3 (25 mg) was added and the mixture
was allowed to stir at 10 °C until complete consumption of accep-
tor 4 was evident by TLC (45 min). The mixture was immediately
filtered through a pad of Celite and the filtrate was washed succes-
sively with Na2S2O3 (2 ꢁ 30 mL), NaHCO3 (2 ꢁ 30 mL) and brine
(30 mL). The organic phase was collected, dried (Na2SO4) and evap-
orated to a syrup. The crude product thus obtained was purified by
flash chromatography using n-hexane–EtOAc (1:1) to afford pure
ourless gel. ½a 2D5
ꢀ
¼ þ98 (c 1.0, CHCl3). 1H NMR (500 MHz, CDCl3) d:
0
0
0
0
7.97–6.62 (m, 13H, ArH), 5.83 (dd, 1H, J2 ,3 9.0 Hz, J3 ,4 10.5 Hz, H-
30), 5.73 (d, 1H, J1 ,2 8.5 Hz, H-10), 5.25 (d, 1H, J3,4 3.0 Hz, H-4), 5.19
0
0
(dd, 1H, J3 ,4 10.5 Hz, J4 ,5 10.5 Hz, H-40), 4.84 (d, 1H, J1,2 7.5 Hz, H-
1), 4.36 (m, 2H, H-20, H-6a0), 4.29 (m, 2H, H-6a, H-6b0), 3.98 (dd, 1H,
J5,6b 2.0 Hz, J6a,6b 12.0 Hz, H-6b), 3.91 (m, 2H, H-5, H-50), 3.81 (dd,
1H, J1,2 7.5 Hz, J2,3 10.5 Hz, H-2), 3.75 (dd, 1H, J2,3 10.5 Hz, J3,4
2.0 Hz, H-3), 3.72 (s, 3H, C6H4OCH3), 2.91, 2.79 (2br s, 2H,
2 ꢁ OH), 2.03, 2.02, 2.01, 1.85 (4s, 12H, 4 ꢁ COCH3). 13C NMR
(125 MHz, CDCl3) d: 171.0, 170.7, 170.1, 169.5 (4 ꢁ COCH3), 165.9
(COPh), 155.3, 150.9, 134.2, 133.3, 131.4, 129.8, 129.7(2), 129.5,
128.4(2), 123.7, 123.6, 123.4, 118.5(2), 114.3(2) (ArC), 100.4 (C-
1), 98.5 (C-10), 79.9, 72.0, 71.2, 70.9, 70.6, 69.3, 68.7, 62.1, 61.7,
55.6 (C6H4OCH3), 54.8, 20.8, 20.7, 20.6, 20.4 (4 ꢁ COCH3). HRMS
calcd for C42H43O18NNa (M+Na)+: 872.2378, found: 872.2381.
0
0
0
0
compound 6 (3.2 g, 82%) as a white foam. ½a D25
¼ þ91 (c 1.1, CHCl3).
ꢀ
1H NMR (500 MHz, CDCl3) d: 8.00–6.63 (m, 13H, ArH), 5.91 (dd, 1H,
J2 ,3 10.5 Hz, J3 ,4 9.0 Hz, H-30), 5.57 (d, 1H, J1 ,2 8.5 Hz, H-10), 5.16
0
0
0
0
0
0
(dd, 1H, J3 ,4 9.0 Hz, J4 ,5 10.5 Hz, H-40), 4.67 (d, 1H, J1,2 8.0 Hz, H-
1), 4.56 (dd, 1H, J5,6a 5.5 Hz, J6a,6b 13.0 Hz, H-6a), 4.47 (dd, 1H,
0
0
0
0
0
0
0
0
J5,6b 8.0 Hz, J6a,6b 13.0 Hz, H-6b), 4.36 (dd, 1H, J1 ,2 8.5 Hz, J2 ,3
10.5 Hz, H-20), 4.28 (dd, 1H, J6a ,6b 10.5 Hz, J6a ,5 3.0 Hz, H-6a0),
4.00 (m, 3H, H-4, H-5, H-50), 3.92 (m, 2H, H-3, H-6b0), 3.70 (s, 3H,
C6H4–OCH3), 3.69 (dd, 1H, J1,2 8.0 Hz, J2,3 9.5 Hz, H-2), 2.06, 2.02,
1.86 (3s, 9H, 3 ꢁ COCH3), 1.14, 0.81 (2s, 6H, 2 ꢁ isopropylidene-
CH3). 13C NMR (125 MHz, CDCl3) d: 170.7, 170.0, 169.5
(3 ꢁ COCH3), 167.6, 167.5 (2 ꢁ phthalimido C@O), 166.1 (COPh),
155.4, 151.2, 133.9, 133.1, 131.9, 131.8, 131.7, 131.6, 129.7,
129.6(2), 128.3(2), 123.3, 118.8(2), 114.3(2) (ArC), 110.4
[C(CH3)2], 100.7 (C-1), 100.4 (C-10), 83.5, 78.3, 73.0, 71.9, 70.9,
70.5, 68.8, 63.5, 62.0, 55.5 (C6H4OCH3), 55.2, 27.2, 25.6 (2 ꢁ isopro-
pylidene-CH3), 20.6, 20.5, 20.4 (3 ꢁ COCH3). HRMS calcd for
0
0
0
0
4.1.5. p-Methoxyphenyl 3,4,6-tri-O-acetyl-2-deoxy-2-phtha-
limido-b-D-glucopyranosyl-(1?2)-4-O-acetyl-6-O-benzoyl-3-O-
(2,3,4-tri-O-acetyl-b-L-arabinopyranosyl)-b-D-galactopyrano-
side 10
A mixture of compound 8 (01.5 g, 1.8 mmol), compound 9
(765 mg g, 2.0 mmol) and MS 4 ÅA (2.0 g) in dry CH2Cl2 (25 mL)
was stirred under nitrogen for 45 min. Next, NIS (527 mg,
2.3 mmol) was added and the mixture was cooled to 15 °C fol-
lowed by the addition of La(OTf)3 (20 mg) and the mixture was
allowed to stir at the same temperature for 1 h when all acceptor
disaccharide 8 was consumed (Rf 0.4, n-hexane–EtOAc; 1:1). The
mixture was immediately filtered through a pad of Celite and the
filtrate was washed successively with Na2S2O3 (2 ꢁ 30 mL), NaH-
CO3 (2 ꢁ 30 mL) and brine (30 mL). The organic layer was sepa-
rated, dried (Na2SO4) and concentrated in vacuo. The crude
product thus obtained was purified by flash chromatography using
n-hexane–EtOAc (1:1.5) to give the pure trisaccharide 10 (1.6 g,
C
43H45O17NNa (M+Na)+: 870.2585, found: 870.2582.
4.1.3. p-Methoxyphenyl 3,4,6-tri-O-acetyl-2-deoxy-2-phtha-
limido-b- -glucopyranosyl-(1?2)-6-O-benzoyl-b- -galactopy-
ranoside 7
D
D
Compound 6 (3.0 g, 3.5 mmol) was dissolved in AcOH–H2O (9:1,
30 mL) and the solution was stirred at 80 °C for 2 h until the start-
ing material was completely converted to a slower running spot
(TLC). After evaporating the solvents and co-evaporating with tol-
uene, the crude product was purified by flash chromatography
using n-hexane–EtOAc (1:2) to afford pure disaccharide 7 (2.4 g,
85%) as a white foam. 1H NMR (500 MHz, CDCl3) d: 7.98–6.59 (m,
84%) as a white foam. ½a D25
ꢀ
¼ þ101 (c 1.1, CHCl3). 1H NMR
00 00
(500 MHz, CDCl3) d: 7.97–6.73 (m, 13H, ArH), 5.95 (d, 1H, J1 ,2
8.5 Hz, H-100), 5.77 (dd, 1H, J2 ,3 9.0 Hz, J3 ,4 10.5 Hz, H-30), 5.38
0
0
0
0
(d, 1H, J3,4 3.0 Hz, H-4), 5.16 (t, 1H, J3 ,4 , J4 ,5 10.0 Hz, H-40), 5.07
0
0
0
0
(dd, 1H, J2 ,3 7.5 Hz, J3 ,4 3.5 Hz, H-300), 5.02 (d, 1H, J1 ,2 8.5 Hz,
00 00
00 00
0
0
13H, ArH), 5.82 (dd, 1H, J2 ,3 9.0 Hz, J3 ,4 9.5 Hz, H-30), 5.74 (d, 1H,
H-10), 4.98 (d, 1H, J1,2 7.5 Hz, H-1), 4.94 (m, 1H, H-400), 4.38 (dd,
0
0
0
0
J1 ,2 8.5 Hz, H-10), 5.18 (dd, 1H, J3 ,4 9.5 Hz, J4 ,5 10.0 Hz, H-40),
1H, J5 ,6a 7.5 Hz, J6a ,6b 11.5 Hz, H-6a0), 4.34–4.23 (m, 4H, H-20, H-
200, H-6a, H-6b0), 4.17–4.10 (m, 2H, H-5, H-6b), 4.06 (dd, 1H, J1,2
7.5 Hz, J2,3 10.5 Hz, H-2), 3.94 (m, 2H, H-3, H-5a00), 3.78 (m, 1H,
H-50), 3.74 (s, 3H, C6H4OCH3), 3.70 (m, 1H, H-5b00), 2.21, 2.11,
2.06, 2.01, 1.99, 1.84, 1.83 (7s, 21H, 7 ꢁ COCH3). 13C NMR
(125 MHz, CDCl3) d: 170.6(2), 170.4, 170.1, 170.0, 169.5, 169.4
(7 ꢁ COCH3), 167.3, 167.2 (2 ꢁ phthalimido CO), 165.9 (COPh),
155.5, 150.7, 134.3, 134.0, 133.3, 131.3, 129.7(2), 129.6, 129.5,
128.4(2), 128.3, 123.7, 118.0(2), 114.5(2) (ArC), 102.8 (C-10),
100.8 (C-1), 97.0 (C-100), 80.8, 78.6, 76.1, 75.3, 74.2, 72.1, 70.8,
70.7, 68.5, 64.9, 62.2, 62.1, 61.3, 55.6 (C6H4OCH3), 55.4, 20.9,
20.8(2), 20.7(2), 20.6(2) (7 ꢁ COCH3). HRMS calcd for C53H57O25N-
Na (M+Na)+: 1130.3117, found: 1130.3112.
0
0
0
0
0
0
0
0
0
0
0
0
0
0
4.80 (d, 1H, J1,2 7.5 Hz, H-1), 4.57 (dd, 1H, J5 ,6a 5.5 Hz, J6a ,6b
12.0 Hz, H-6a0), 4.44 (dd, 1H, J5 ,6b 8.0 Hz, J6a ,6b 12.0 Hz, H-6b0),
0
0
0
0
4.38 (dd, 1H, J1 ,2 8.5 Hz, J2 ,3 9.0 Hz, H-20), 4.24 (dd, 1H, J5,6a
4.5 Hz, J6a,6b 12.5 Hz, H-6a), 3.97 (dd, 1H, J5,6b 2.0 Hz, J6a,6b
12.5 Hz, H-6b), 3.89 (m, 1H, H-5), 3.84 (m, 2H, H-4, H-50), 3.79 (t,
1H, J1,2, J2,3 7.5 Hz, H-2), 3.71 (s, 3H, C6H4OCH3), 3.57 (dd, 1H, J2,3
7.5 Hz, J3,4 1.5 Hz, H-3), 2.91, 2.79 (2br s, 2H, 2 ꢁ OH), 2.04, 2.02,
1.85 (3s, 9H, 3 ꢁ COCH3). 13C NMR (125 MHz, CDCl3) d: 170.7,
170.1, 169.5 (3 ꢁ COCH3), 166.4 (COPh), 155.2, 150.8, 134.1,
133.3, 131.4, 129.7(2), 129.5, 128.9, 128.4(2), 123.5(2), 118.1(2),
114.3(2), 114.0 (ArC), 100.1 (C-1), 98.4 (C-10), 80.2, 72.2, 72.1,
72.0, 70.7, 68.7, 68.4, 62.9, 61.6, 55.6 (C6H4OCH3), 54.6, 20.6,
20.5, 20.4 (3 ꢁ COCH3).
0
0
0
0
4.1.6. p-Methoxyphenyl 3,4,6-tri-O-acetyl-2-acetamido-2-deoxy-
4.1.4. p-Methoxyphenyl 3,4,6-tri-O-acetyl-2-deoxy-2-phtha-
b-D-glucopyranosyl-(1?2)-4-O-acetyl-6-O-benzoyl-3-O-(2,3,4-tri-
limido-b-
benzoyl-b-
To a solution of compound 7 (2.0 g, 2.5 mmol) in dry CH3CN
(20 mL) was added trimethylorthoacetate (480 L, 3.8 mmol)
followed by CSA (25 mg) and the solution was stirred at room tem-
D
-glucopyranosyl-(1?2)-4-O-acetyl-6-O-
O-acetyl-b-
L
-arabinopyranosyl)-b- -galactopyranoside 11
D
D- galactopyranoside 8
To a solution of compound 10 (1.5 g, 1.35 mmol) in EtOH
(50 mL) was added hydrazine monohydrate (1 mL) and the
reaction mixture was allowed to stir at 80 °C for 12 h. The solvents
were removed under reduced pressure and the residue was
l

1112
S. Mandal et al. / Tetrahedron: Asymmetry 22 (2011) 1108–1113
dissolved in pyridine (10 mL) followed by Ac2O (7 mL) and the
solution was stirred at room temperature for 12 h. The solvents
were evaporated in vacuo and the crude product thus obtained
was purified by flash chromatography using n-hexane–EtOAc
(1:6) to give the pure trisaccharide 11 (1.1 g, 82%) as a white foam.
124.1, 123.1, 118.2(2), 114.2(2) (ArC), 110.3 [C(CH3)2], 99.6 (C-10),
98.6 (C-1), 80.0, 76.8, 72.8, 72.0, 70.6, 69.1, 62.9, 62.4, 55.6
(C6H4OCH3), 54.7, 27.8, 25.9 (2 ꢁ isopropylidene-CH3), 20.8, 20.6,
20.4 (3 ꢁ COCH3). C35H39O15NNa (M+Na)+: 736.2217, found:
736.2213.
1H NMR (500 MHz, CDCl3) d: 6.98, 6.80 (2d, 2H,
J 9.0 Hz,
0
0
C6H4OCH3), 6.31 (d, 1H, J 8.5 Hz, NHAc), 5.50 (dd, 1H, J2 ,3 8.5 Hz,
4.1.9. p-Methoxyphenyl 3,4,6-tri-O-acetyl-2-deoxy-2-phtha-
limido-b-D-glucopyranosyl-(1?2)-b-D-arabinopyranoside 14
J3 ,4 10.5 Hz, H-30), 5.48 (m, 1H, H-400), 5.22 (d, 1H, J1 ,2 8.0 Hz, H-
0
0
0
0
10), 5.20 (d, 1H, J1 ,2 8.0 Hz, H-100), 5.10 (m, 2H, H-300, H-4), 5.07
A solution of compound 13 (3.0 g, 4.2 mmol) in 80% aq AcOH
(30 mL) was stirred at 80 °C for 3 h. Then the solvents were evap-
orated and co-evaporated with toluene to remove residual AcOH.
The residue was purified by flash chromatography using n-hex-
ane–EtOAc (1:4) as the eluent to give pure disaccharide diol 14
(2.6 g, 91%) as a white foam. 1H NMR (500 MHz, CDCl3) d: 7.47
00 00
(t, 1H, J3 ,4 , J4 ,5 10.5 Hz, H-40), 4.90 (d, 1H, J1,2 7.0 Hz, H-1), 4.43
(m, 2H, H-5a00, H-200), 4.28–4.23 (m, 2H, H-5b00, H-6a0), 4.15–4.09
(m, 3H, H-3, H-6a, H-6b), 3.97 (m, 1H, H-2), 3.87–3.83 (m, 2H, H-
5, H-6b0), 3.74 (m, 1H, H-50), 3.77 (s, 3H, C6H4OCH3), 3.63 (m, 1H,
H-20), 2.17, 2.14, 2.13, 2.12, 2.05, 2.00, 1.99, 1.98 (8s, 24H,
8 ꢁ COCH3), 1.94 (s, 3H, NHCOCH3). 13C NMR (125 MHz, CDCl3) d:
170.6 (NHAc), 170.6, 170.5, 170.4, 170.3, 170.0, 169.9, 169.7,
169.5 (8 ꢁ COCH3), 155.6, 151.2, 118.4(2), 114.5(2) (ArC), 106.2
(C-100), 101.2 (C-1), 100.2 (C-10), 81.8, 81.2, 72.4, 71.9, 70.7, 68.6,
66.3, 63.0, 61.7, 61.6, 56.1, 55.7, 22.7 (NHCOCH3), 20.7(8)
(8 ꢁ COCH3). HRMS calcd for C47H57O24NNa (M+Na)+: 1042.3168,
found: 1042.3163.
0
0
0
0
0
0
0
0
(m, 4H), 6.42 (m, 4H) (ArH), 5.85 (dd, 1H, J2 ,3 10.5 Hz, J3 ,4
9.0 Hz, H-30), 5.55 (d, 1H, J1 ,2 9.0 Hz, H-10), 5.13 (dd, 1H, J3 ,4
0
0
0
0
9.0 Hz, J4 ,5 10.0 Hz, H-40), 4.60 (d, 1H, J1,2 7.5 Hz, H-1), 4.37–4.30
0
0
(m, 2H, H-20, H-6a0), 4.21 (dd, 1H, J6a ,6b 12.0 Hz, J6a ,5 5.5 Hz, H-
6b0), 4.01 (m, 1H, H-50), 3.94 (m, 2H, H-4, H-5a), 3.78 (dd, 1H, J1,2
7.5 Hz, J2,3 8.5 Hz, H-2), 3.67 (m, 1H, H-3), 3.66 (s, 3H, C6H4–
OCH3), 3.37 (dd, 1H, J4,5b 1.5 Hz, J5a,5b 13.0 Hz, H-5b), 2.12, 2.03,
1.83 (3s, 9H, 3 ꢁ COCH3). 13C NMR (125 MHz, CDCl3) d: 170.6,
169.9, 169.4 (3 ꢁ COCH3), 167.9, 167.7 (2 ꢁ phthalimido C@O),
154.9, 149.9, 134.8, 133.9, 133.7, 132.6, 124.3, 124.1, 118.4(2),
114.1(2) (ArC), 100.1 (C-10), 99.4 (C-1), 82.5, 72.0, 71.8, 70.2, 68.8,
67.8, 65.7, 61.8, 55.5 (C6H4OCH3), 54.3, 20.6, 20.5, 20.3
(3 ꢁ COCH3). C32H35O15NNa (M+Na)+: 696.1904, found: 696.1901.
0
0
0
0
4.1.7. p-Methoxyphenyl 2-acetamido-2-deoxy-b-
D
-glucopyr-
anosyl-(1?2)-3-O-(b-L-arabinopyranosyl)-b-D-galactopyran-
oside 1
Compound 11 (500 mg, 0.5 mmol) was dissolved in dry MeOH
(10 mL) and then NaOMe (1 mL, 0.5 M in MeOH) was added and
the solution was stirred at room temperature for 5 h. After neutral-
izing with DOWEX 50W H+ resin and filtration, the solvents were
evaporated in vacuo to afford pure compound 1 (238 mg, 78%) as
4.1.10. p-Methoxyphenyl 3,4,6-tri-O-acetyl-2-deoxy-2-phtha-
limido-b-
anoside 15
To a solution of 14 (2.5 g, 3.7 mmol) in dry CH3CN (20 mL), tri-
methyl orthoacetate (715 L, 5.6 mmol) was added followed by
D-glucopyranosyl-(1?2)-4-O-acetyl-b-D-arabinopyr-
white amorphous powder. ½a D25
ꢀ
¼ þ72 (c 0.9, MeOH). 1H NMR
(500 MHz, D2O) d: 6.97, 6.84 (2d, 4H, J 9.0 Hz, C6H4OCH3), 5.38
(d, 1H, J1 ,2 7.5 Hz, H-100), 5.01 (d, 1H, J1 ,2 8.5 Hz, H-10), 4.73 (d,
1H, J1,2 9.5 Hz, H-1), 3.77 (s, 3H, C6H4OCH3), 1.51 (s, 3H, NHCOCH3).
13C NMR (125 MHz, D2O) d: 173.6 (NHCOCH3), 154.6, 150.5,
117.1(2), 115.7(2) (ArC), 107.9 (C-100), 102.3 (C-1), 100.2 (C-10),
84.2, 81.5, 77.7, 77.3, 76.2, 75.4, 73.6, 69.7, 68.3, 66.2, 62.1, 61.6,
61.1, 56.3, 55.7, 21.7 (NHCOCH3). C26H39O16NNa (M+Na)+:
644.2167, found: 644.2162.
l
00 00
0
0
CSA (20 mg). The mixture was stirred at room temperature until
complete conversion of the starting material to a faster moving
spot on TLC (ꢂ45 min). The solvents were evaporated in vacuo
and the residue was dissolved in AcOH–H2O (9:1, 25 mL) and stir-
red at room temperature for 1 h. Next, the solvents were evapo-
rated in vacuo and the residue was purified by flash
chromatography using n-hexane–EtOAc (1:2) as the eluent to give
4.1.8. p-Methoxyphenyl 3,4,6-tri-O-acetyl-2-deoxy-2-phthalim-
pure compound 15 (2.3 g, 86%) as a colourless gel. ½a D25
¼ þ93 (c
ꢀ
ido-b-
D
-glucopyranosyl-(1?2)-3,4-O-isopropylidene-b-
D
-arabi-
1.1, CHCl3). 1H NMR (500 MHz, CDCl3) d: 7.48 (m, 4H), 6.43 (m,
4H) (ArH), 5.85 (dd, 1H, J2 ,3 10.5 Hz, J3 ,4 9.0 Hz, H-30), 5.60 (d,
0
0
0
0
nopyranoside 13
1H, J1 ,2 8.5 Hz, H-10), 5.16 (m, 1H, H-4), 5.14 (dd, 1H, J3 ,4 9.0 Hz,
0
0
0
0
A mixture of donor 5 (3.6 g, 6.6 mmol), acceptor 12 (1.5 g,
5.1 mmol) and MS 4 Å (2.0 g) in dry CH2Cl2 (30 mL) was stirred un-
der nitrogen for 30 min. Next, NIS (1.9 g, 8.6 mmol) was added fol-
lowed by La(OTf)3 (50 mg) and the mixture was allowed to stir for
45 min at 5–10 °C when TLC (n-hexane–EtOAc, 4:1) showed com-
plete conversion of the acceptor. The mixture was filtered through
a pad of CeliteÒ and the filtrate was washed successively with aq
Na2S2O7 (2 ꢁ 30 mL), aq NaHCO3 (2 ꢁ 30 mL) and brine (30 mL).
The organic layer was separated, dried (Na2SO4), filtered, and evap-
orated in vacuo. The residue was purified by flash chromatography
using n-hexane–EtOAc (1:1) as the eluent to give pure disaccharide
J4 ,5 10.0 Hz, H-40), 4.65 (d, 1H, J1,2 7.5 Hz, H-1), 4.37 (dd, 1H, J1 ,2
0
0
0
0
8.5 Hz, J2 ,3 10.5 Hz, H-20), 4.30 (dd, 1H, J5 ,6a 2.5 Hz, J6a ,6b
0
0
0
0
0
0
12.5 Hz, H-6a0), 4.23 (dd, 1H, J6a ,6b 12.0 Hz, J6a ,5 6.0 Hz, H-6b0),
4.05 (m, 1H, H-50), 3.92 (dd, 1H, J4,5a 2.0 Hz, J5a,5b 13.5 Hz, H-5a),
3.79 (m, 2H, H-2, H-3), 3.68 (s, 3H, C6H4–OCH3), 3.42 (dd, 1H,
J4,5b 0.5 Hz, J5a,5b 13.5 Hz, H-5b), 2.14, 2.12, 2.05, 1.84 (4s, 12H,
4 ꢁ COCH3). 13C NMR (125 MHz, CDCl3) d: 170.7, 170.5, 169.9,
169.5 (4 ꢁ COCH3), 167.8, 167.6 (2 ꢁ phthalimido C@O), 155.0,
149.8, 134.7, 133.8, 133.5, 132.4, 124.5, 124.3, 118.2(2), 114.2(2)
(ArC), 100.2 (C-10), 99.4 (C-1), 82.9, 72.0, 70.5, 70.3, 69.5, 68.9,
64.5, 61.9, 55.5 (C6H4OCH3), 54.4, 21.1, 20.6, 20.5, 20.4
(4 ꢁ COCH3). C34H37O16NNa (M+Na)+: 738.2010, found: 738.2002.
0
0
0
0
13 (3.2 g, 88%) as a white foam. ½a D25
ꢀ
¼ þ108 (c 1.0, CHCl3). 1H NMR
(500 MHz, CDCl3) d: 7.53 (m, 4H), 6.56 (m, 4H) (ArH), 5.89 (dd, 1H,
J2 ,3 10.0 Hz, J3 ,4 9.0 Hz, H-30), 5.66 (d, 1H, J1 ,2 8.5 Hz, H-10), 5.20
0
0
0
0
0
0
(dd, 1H, J3 ,4 9.0 Hz, J4 ,5 10.0 Hz, H-40), 4.62 (d, 1H, J1,2 7.5 Hz, H-
4.1.11. p-Methoxyphenyl 3,4,6-tri-O-acetyl-2-deoxy-2-phtha-
0
0
0
0
1), 4.39 (dd, 1H, J1 ,2 8.5 Hz, J2 ,3 10.0 Hz, H-20), 4.34 (dd, 1H, J6a ,6b
limido-b-
D
-glucopyranosyl-(1?2)-4-O-acetyl-3-O-(2,3,4-tri-O-
0
0
0
0
0
0
12.0 Hz, J6a ,5 5.0 Hz, H-6a0), 4.21 (m, 3H, H-3, H-4, H-6b0), 4.02 (dd,
1H, J4,5a 3.5 Hz, J5a,5b 13.0 Hz, H-5a), 3.95 (m, 1H, H-50), 3.89 (dd,
1H, J1,2 7.5 Hz, J2,3 7.5 Hz, H-2), 3.72 (s, 3H, C6H4–OCH3), 3.68 (dd,
1H, J4,5b 3.5 Hz, J5a,5b 13.0 Hz, H-5b), 2.10, 2.03, 1.84 (3s, 9H,
3 ꢁ COCH3), 1.56, 1.32 (2s, 6H, 2 ꢁ isopropylidene-CH3). 13C NMR
(125 MHz, CDCl3) d: 170.7, 170.1, 169.5 (3 ꢁ COCH3), 167.7, 167.5
(2 ꢁ phthalimido C@O), 155.0, 149.9, 134.0, 133.3, 133.0, 124.3,
acetyl-b-
L
-arabinopyranosyl)-b- -arabinopyranoside 16
D
0
0
A mixture of compound 15 (2.0 g, 2.8 mmol), compound 9
0
(1.4 g, 3.6 mmol) and MS 4 ÅA (2 g) in dry CH2Cl2 (30 mL) was stir-
red under nitrogen for 1 h. NIS (1.1 g, 4.7 mmol) was added and the
mixture was cooled to 10 °C using an ice-water bath. After stirring
for 15 min, La(OTf)3 (25 mg) was added and the mixture was
allowed to stir at 10 °C until complete consumption of acceptor

S. Mandal et al. / Tetrahedron: Asymmetry 22 (2011) 1108–1113
1113
15 was evident by TLC (45 min). The mixture was immediately fil-
tered through a pad of Celite and the filtrate was washed succes-
sively with Na2S2O3 (2 ꢁ 30 mL), NaHCO3 (2 ꢁ 30 mL) and brine
(30 mL). The organic phase was collected, dried (Na2SO4) and evap-
orated to a syrup. The crude product thus obtained was purified by
flash chromatography using n-hexane–EtOAc (1:1.5) to afford pure
55.7, 53.8, 22.6, 22.5, 20.9, 20.8, 20.6(2), 20.5(2) (8 ꢁ COCH3).
39H51O22NNa (M+Na)+: 908.2800, found: 908.2795.
C
4.1.13. p-Methoxyphenyl 2-acetamido-2-deoxy-b-
D-gluco-
pyranosyl-(1?2)-3-O-(b-L-arabinopyranosyl)-b-D-arabinopyr-
anoside 2
compound 16 (2.2 g, 81%) as a white foam. ½a D25
ꢀ
¼ þ91 (c 1.0,
A solution of compound 17 (450 mg, 0.5 mmol) was dissolved in
dry MeOH (10 mL) after which NaOMe (1.0 mL, 0.5 M in MeOH)
was added and the solution was stirred at room temperature for
3 h. After neutralizing the solution with DOWEX 50W H+ and filtra-
tion, the solvents were evaporated in vacuo to afford pure com-
CHCl3). 1H NMR (500 MHz, CDCl3) d: 7.66–7.46 (m, 4H, ArH),
0
0
0
0
6.61–6.56 (2d, 4H, ArH), 5.88 (dd, 1H, J2 ,3 9.0 Hz, J3 ,4 10.5 Hz, H-
30), 5.40 (dd, 1H, J2 ,3 7.5 Hz, J3 ,4 3.5 Hz, H-300), 5.63 (d, 1H, J1 ,2
8.5 Hz, H-10), 5.20 (m, 1H, H-400), 5.17 (m, 1H, H-4), 5.13 (t, 1H,
00 00
00 00
0
0
J3 ,4 , J4 ,5 10.0 Hz, H-40), 4.91 (d, 1H, J1 ,2 7.5 Hz, H-100), 4.59 (d,
pound 2 (240 mg, 80%) as a white amorphous powder.
0
0
0
0
00 00
1H, J1,2 7.5 Hz, H-1), 4.47 (dd, 1H, J5 ,6a 7.5 Hz, J6a ,6b 11.5 Hz, H-
6a0), 4.29–4.18 (m, 4H, H-2, H-200, H-5a00, H-6b0), 4.12 (m, 1H, H-
200), 3.93 (m, 1H, H-50), 3.84 (dd, 1H, J4,5b 1.5 Hz, J5a,5b 13.0 Hz, H-
5a), 3.74 (m, 1H, H-3), 3.71 (s, 3H, C6H4OCH3), 3.46 (dd, 1H, J4,5b
0.5 Hz, J5a,5b 13.0 Hz, H-5b), 2.19, 2.10, 2.09, 2.08, 2.07, 1.99, 1.81
(7s, 21H, 7 ꢁ COCH3). 13C NMR (125 MHz, CDCl3) d: 170.6, 170.4,
170.1, 169.9, 169.6, 169.3, 169.2 (7 ꢁ COCH3), 167.4, 167.3
(2 ꢁ phthalimido CO), 155.5, 149.7, 134.3, 134.0, 133.3, 124.8,
124.6, 123.5, 123.3, 118.0(2), 114.3(2) (ArC), 106.9 (C-100), 100.4
(C-10), 98.0 (C-1), 81.5, 80.7, 77.6, 74.3, 71.5, 70.4, 69.8, 69.7,
64.3, 63.3, 62.6, 55.5 (C6H4OCH3), 54.9, 53.4, 22.6, 20.9, 20.8(2),
20.7, 20.6(2) (7 ꢁ COCH3). C46H55O23NNa (M+Na)+: 1012.3063,
found: 1012.3058.
½ ꢀ
a 2D5
¼ þ67 (c 0.9, MeOH). 1H NMR (500 MHz, D2O) d: 6.94, 6.87
0
0
00
0
(2d, 4H, J 9.0 Hz, C6H4OCH3), 5.33 (d, 1H, J1 ,2 7.5 Hz, H-100), 4.93
00 00
(d, 1H, J1 ,2 7.5 Hz, H-10), 4.68 (d, 1H, J1,2 9.0 Hz, H-1), 3.67 (s, 3H,
C6H4OCH3), 1.31 (s, 3H, NHCOCH3). 13C NMR (125 MHz, D2O) d:
174.4 (NHCOCH3), 154.4, 150.4, 116.9(2), 115.3(2) (ArC), 108.8
(C-100), 102.0 (C-10), 99.9 (C-1), 84.3, 81.4, 77.6, 77.2, 76.5, 75.6,
73.4, 69.8, 68.1, 66.1, 61.4, 61.0, 56.0, 55.8, 21.5 (NHCOCH3).
0
0
C
25H37O15NNa (M+Na)+: 614.2061, found: 614.2057.
Acknowledgements
S.M. is thankful to the Council for Scientific and Industrial
Research, New Delhi for Senior Research Fellowship and R.D. is
thankful to the Indian Institute of Science Education and
Research-Kolkata (IISER-K) for the fellowship. The work was
funded by the Department of Science and Technology, New Delhi,
India through Grant SR/S1/OC-67/2009.
4.1.12. p-Methoxyphenyl 3,4,6-tri-O-acetyl-2-acetamido-2-
deoxy-b-
D
-glucopyranosyl-(1?2)-4-O-acetyl-3-O-(2,3,4-tri-O-
acetyl-b-
L
-arabinopyranosyl)-b- -arabinopyranoside 17
D
To a solution of compound 16 (2.0 g, 2.0 mmol) in EtOH (30 mL)
was added hydrazine monohydrate (1 mL) and the reaction mix-
ture was allowed to stir at 80 °C for 12 h. The solvents were re-
moved under reduced pressure after which the residue was
dissolved in pyridine (15 mL) followed by Ac2O (7.5 mL) and the
solution was allowed to stir at room temperature for 12 h. After
removing the solvents in vacuo, the crude product was purified
by flash chromatography using n-hexane–EtOAc (1:6) to give the
References
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D.; Taylor, N. L.; Wright, A. E.; Pomponi, S. A.; Langley, D. Bioorg. Med. Chem.
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pure trisaccharide 17 (1.0 g, 85%) as a white foam. ½a D25
¼ þ98 (c
ꢀ
1.1, CHCl3). 1H NMR (500 MHz, CDCl3) d: 6.95, 6.83 (2d, 2H, J
9.0 Hz, C6H4OCH3), 5.43 (d, 1H, J1 ,2 7.5 Hz, H-100), 5.29–5.22 (m,
00 00
2H, H-4, H-400), 5.14 (m, 1H, H-2000), 5.03 (dd, 1H, J2 ,3 8.5 Hz, J3 ,4
0
0
0
0
10.5 Hz, H-30), 5.01 (m, 1H, H-300), 4.86 (d, 1H, J1,2 7.5 Hz, H-1),
5.07 (m, 1H, H-40), 4.81 (d, 1H, J1 ,2 8.5 Hz, H-10), 4.45 (dd, 1H,
0
0
J5 ,6a 7.5 Hz, J6a ,6b 11.5 Hz, H-6a0), 4.22–4.06 (m, 5H, H-2, H-3, H-
50, H-5a00, H-6b0), 3.98–3.92 (m, 3H, H-20, H-5a, H-5b00), 3.76 (s,
3H, C6H4OCH3), 3.63 (dd, 1H, J4,5b 1.0 Hz, J5a,5b 12.5 Hz, H-5b),
2.13, 2.12, 2.09, 2.08, 2.07, 2.01, 1.95 (7s, 24H, 8 ꢁ COCH3), 1.41
(s, 3H, NHCOCH3). 13C NMR (125 MHz, CDCl3) d: 171.1, 170.6,
170.5, 170.1, 170.0, 169.9, 169.4, 169.2 (8 ꢁ COCH3), 155.4, 150.4,
117.0(2), 115.0(2) (ArC), 106.6 (C-100), 101.4 (C-10), 100.2 (C-1),
81.6, 81.5, 77.7, 77.6, 73.4, 73.1, 71.7, 69.6, 69.0, 64.4, 63.3, 62.8,
0
0
0
0