Chemical synthesis of the pentasaccharide related to the repeating unit of the O-antigen of Enterobacter cloacae G2277

Article abstract of DOI:10.1016/j.tet.2015.06.095

Abstract A practical and highly efficient total synthesis of the pentasaccharide related to the O-antigen of Enterobacter cloacae G2277, the causative agent of nosocomial infection, has been accomplished in the form of its 4-methoxyphenyl glycoside. The u

Full text of DOI:10.1016/j.tet.2015.06.095

Tetrahedron 71 (2015) 6155e6163
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Chemical synthesis of the pentasaccharide related to the repeating
unit of the O-antigen of Enterobacter cloacae G2277
*
Darshita Budhadev, Balaram Mukhopadhyay
Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, Nadia 741246, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 4 May 2015
Received in revised form 25 June 2015
Accepted 26 June 2015
Available online 2 July 2015
A practical and highly efficient total synthesis of the pentasaccharide related to the O-antigen of En-
terobacter cloacae G2277, the causative agent of nosocomial infection, has been accomplished in the form
of its 4-methoxyphenyl glycoside. The unique pentasaccharide, /2)-
-Rhap-(1/4)- -GalpA-(1/3)-
-GlcpNAc-(1/, was assembled by a [3þ2] convergent approach
as well as a sequential assembly of five rationally protected monosaccharide building blocks. In the
convergent approach, -Galp-(1/3)- -GlcpNAc disaccharide was synthesized with a potential site
for the uronic acid and the -Rhap-(1/2)- -Rhap-(1/2)- -Rhap trisaccharide trichloroacetimidate
a-L-Rhap-(1/2)-a-L-Rhap-(1/2)-
a
-L
a-
D
a-D
a-
D
a-D
Keywords:
a
-L
a-
L
a-L
Oligosaccharide
Glycosylation
Supported catalyst
TEMPO-oxidation
O-antigens
was glycosylated to form the protected pentasaccharide in good yield. A TEMPO-mediated late stage
oxidation of 6-OH of the galactose moiety resulted the characteristic uronic acid. Finally, global de-
protection gave the target pentasaccharide. Both strategies were found to be equally efficient in respect
to the yield of the target pentasaccharide derivative.
Ó 2015 Elsevier Ltd. All rights reserved.
1. Introduction
a disaccharide,
-Rhap-(1/2)-
further disconnected to two monosaccharides that can be derived
from commercially available -GlcNH2 and -Gal. On the otherhand,
a
a
-
D
-Galp-(1/3)-
a
-
D
-GlcpNAc and a trisaccharide,
a-
L
-
L-Rhap-(1/2)-
a-L-Rhap. The disaccharide was
Enterobacter cloacae are the causative agent for various noso-
comial infections.1 It is further complicated by the emergence of
multidrug resistant strains.2 Although the serotyping scheme for E.
cloacae based on O-antigens has been established in 1983, only
a few O-polysaccharide structures have been reported so far.3 Re-
cently, Perepelov et al.4 reported the structure of the O-poly-
saccharide from E. cloacae G2277. Herein, we report the total
chemical synthesis of that pentasaccharide repeating unit of the O-
polysaccharide from E. cloacae in the form of its 4-methoxyphenyl
glycoside (1, Fig. 1). Establishment of the chemical pathway for the
synthesis of the target pentasaccharide will pave the path for
making pure material in quantity and help further biological
studies. Moreover, the selective removal of the 4-methoxyphenyl
group will allow the formation of suitable glycoconjugate with
aglycons using trichloroacetimidate chemistry.
D
D
2. Results and discussion
Critical evaluation of the retrosynthetic analysis revealed that
a convergent [3þ2] approach will suit best for the synthesis of the
linear pentasaccharide. Therefore, it was first disconnected to
* Corresponding author. Tel.: þ91 9748261742; fax: þ91 33 2587 3020; e-mail
address: sugarnet73@hotmail.com (B. Mukhopadhyay).
Fig. 1. Structure of the target pentasaccharide 1.
http://dx.doi.org/10.1016/j.tet.2015.06.095
0040-4020/Ó 2015 Elsevier Ltd. All rights reserved.

6156
D. Budhadev, B. Mukhopadhyay / Tetrahedron 71 (2015) 6155e6163
the trisaccharide can be prepared from three suitably protected
rhamnose derivatives through sequential glycosylations. These
rhamnose derivatives may be obtained from commercially avail-
able
(Fig. 2).
The known galactose derivative 25 was treated with p-ani-
L-rhamnose through rational protecting group manipulations
saldehydedimethylacetal in the presence of 10-camphorsulfonic
acid (CSA)6 to afford the 4,6-O-(4-methoxy benzylidene) de-
rivative 3 in 89% yield. The remaining hydroxyl groups were further
benzylated using BnBr in the presence of NaH7 to give the fully
protected derivative 4 in 94% yield. Regioselective opening of the 4-
methoxybenzylidene acetal using NaCNBH3 and TFA6 followed by
acetylation using Ac2O in pyridine8 furnished the desired donor 6 in
96% yield. Next, the donor 6 was coupled to the known acceptor 79
through activation of the thioglycoside using NIS in the presence of
H2SO4-silica10 at ꢀ50 ꢁC to form the disaccharide 8 in 85% isolated
yield. Only the desired 1,2-cis disaccharide was formed as evident
Scheme 1. Synthesis of the disaccharide acceptor 9.
by the 1H signal at
d
5.69 (d, 1H, J1 ,2 4.0 Hz) and the 13C signal at
0 0
d
97.4 assigned to the newly formed linkage. The 4-O-acetate group
of the galactose donor 6 is the key for the exclusive formation of the
1,2-cis linkage.11 Finally, Zemplen de-O-acetylation12 of the
disaccharide 8 gave the disaccharide acceptor 9 in 95% yield
(Scheme 1).
Further, the known thiotolyl
L
-rhamnose derivative 1114 was cou-
pled with the disaccharide acceptor 10 using NIS and H2SO4-silica
to afford the protected trisaccharide 12 in 91% yield. The newly
formed 1,2-transglycosidic linkage was confirmed by the 1H signal
00 00
In a separate experiment, the disaccharide acceptor 10 was
prepared from suitably protected
L-rhamnose derivatives derived
at
d d 99.0. CAN-me-
4.99 (d, 1H, J1 ,2 1.5 Hz) and the 13C signal at
from commercially available
L
-rhamnose following the reported
diated15 oxidative cleavage of the 4-methoxyphenyl group resulted
the corresponding hemiacetal 13 in 81% yield, which was sub-
sequently treated with trichloroacetonitrile in the presence of
DBU16 to furnish the trisaccharide trichloroacetimidate 14 in 90%
yield (Scheme 2). Considering the reactivity of the tri-
chloroacetimidate derivative, it was directly used for glycosylation
without further characterization.
literature procedure.13 The structure of the disaccharide acceptor
was satisfactorily characterized by NMR and mass spectrometry
and matched satisfactorily with the data available in the literature.
Scheme 2. Synthesis of the trisaccharide trichloroacetimidate donor 14.
The disaccharide acceptor 9 was coupled with the trisaccharide
donor 14 through the activation of the trichloroacetimidate by
H2SO4-silica17 to furnish the protected pentasaccharide 15 in 82%
isolated yield. Once the protected pentasaccharide was obtained,
the 4-methoxybenzyl group was selectively deprotected through
DDQ18 mediated oxidative cleavage. The primary OH group thus
obtained, was oxidized to the corresponding uronic acid 17 using
TEMPO in the presence of iodosobenzene diacetate.19 It is worth
Fig. 2. Retrosynthetic analysis for the synthesis of the target pentasaccharide 1.

D. Budhadev, B. Mukhopadhyay / Tetrahedron 71 (2015) 6155e6163
6157
noting that the 4-methoxyphenyl group at the reducing end of the
protected pentasaccharide remained unaffected by the TEMPO-
mediated oxidation. Next, the benzylidene group was hydrolysed
by 80% AcOH at 80 ꢁC20 to afford the pentasaccharidediol 18 in 87%
yield. At this point the azido functionality was converted to the
required acetamido moiety by the treatment of thioacetic acid.21
Subsequently, Zemplen de-O-acetylation using NaOMe in MeOH
gave the pentasaccharide derivative 19 in 81% yield. Finally,
hydrogenolysis using 10% PdeC cartridge in a continuous flow
hydrogenation assembly furnished the target pentasaccharide 1 in
85% yield (Schemes 3 and 4).
in MeOH gave the trisaccharide acceptor 22 in 95% yield. Further
glycosylation of the same donor 20 with the acceptor 22 resulted
the tetrasaccharide 23 in 90% yield. Zemplen de-O-acetylation us-
ing NaOMe in MeOH afforded the tetrasaccharide acceptor 24 in
96% yield. Final glycosylation of the tetrasaccharide acceptor 24
with the known donor 11 through activation of the thioglycoside
using NIS in the presence of H2SO4-silica furnished the protected
pentasaccharide 15 in 93% yield. The protected pentasaccharide 15
was converted to the target pentasaccharide 1 by the strategy
depicted in Scheme 3.
3. Conclusions
In conclusion, we have accomplished the total synthesis of the
pentasaccharide repeating unit of Enterobacter cloacae G2277 in the
form of its 4-methoxyphenyl glycoside starting from commercially
available sugars. The total synthesis has been achieved through
a convergent [3þ2] strategy as well as the sequential approach.
Both strategies found to be almost equally efficient in terms of the
overall yield. H2SO4-silica alone or in conjunction with NIS was
proved to be a better alternative to classical acids such as TfOH or
TMSOTf for the activation of trichloroacetimidate and thioglyco-
sides, respectively. The 4-methoxyphenyl group at the reducing
end may be deprotected selectively from the per-O-acetyl de-
rivative of the target pentasaccharide and further coupled to suit-
able aglycon using trichloroacetimidate chemistry.
4. Experimental
4.1. General
All solvents and reagents were dried prior to use according to
standardized methods.23 The commercially purchased reagents
were used without any further purification unless mentioned oth-
erwise. Dichloromethane was dried and distilled over P2O5 to make
it anhydrous and moisture-free. All reactions were monitored by
Thin Layer Chromatography (TLC) on Silica-Gel 60-F254 with de-
tection by fluorescence followed by charring after immersion in 10%
ethanolic solution of H2SO4. Flash chromatography was performed
with Silica Gel 230e400 mesh. Optical rotations were measured on
sodium-line at ambient temperature.1H and 13C NMR wererecorded
on Bruker 500 MHz spectrometer.1H NMR values were denoted as H
for the reducing end glucosamine unit, H0 for the galacturonic acid
unit, H00 for the rhamnose unit connected to the 4-O-position of the
galacturonic acid unit, H000 for the fourth rhamnose unit from the
reducing end and H0000 for the non-reducing end rhamnose unit.
Scheme 3. Synthesis of the target pentasaccharide 1.
4.2. Preparation of H2SO4-silica:24
To a slurry of silica gel (10 g, 200e400 mesh) in dry diethyl ether
(50 mL) was added commercially available concentrated H2SO4
(1 mL), and the slurry was shaken for 5 min. The solvent was
evaporated under reduced pressure, resulting in free flowing
H2SO4-silica, which was dried at 110 ꢁC for 3 h and used for the
reactions.
4.3. 4-Tolyl 4,6-O-(4-methoxybenzylidene)-1-thio-b-D-gal-
actopyranoside (3)
Scheme 4. Synthesis of the protected pentasaccharide 15 through sequential
glycosylations.
A mixture of known 4-tolyl-1-thio-b-D-galactopyranoside 2
After successful completion of the total synthesis of the target
pentasaccharide via (2þ3) strategy, we wanted to compare the
efficiency of the sequential glycosylation strategy. Therefore, the
disaccharide acceptor 9 was reacted with the known donor 2022
using NIS in the presence of H2SO4-silica to afford the tri-
saccharide 21 in 92% isolated yield. De-O-acetylation using NaOMe
(3.0 g, 10.5 mmol), 4-anisaldehyde dimethyl acetal (2.7 mL,
15.7 mmol) and CSA (50 mg) in anhydrous CH3CN (20 mL) was
stirred at room temperature for 3 h when TLC (EtOAc) showed
complete conversion of starting material. Et3N was added to neu-
tralize the solution. After evaporating the solvents in vacuo, the
crude product was purified by flash chromatography using n-

6158
D. Budhadev, B. Mukhopadhyay / Tetrahedron 71 (2015) 6155e6163
hexane-EtOAc (1:2) as eluent to furnish pure compound 3 (3.8 g,
SC6H4CH3). 13C NMR (CDCl3, 125 MHz)
d: 159.3, 138.2, 137.7, 137.6,
89%) as amorphous white mass. ½a D25
ꢂ
þ 102 (c 1.0, CHCl3); Rf (n-
132.6(2), 130.1, 129.9, 129.6(2), 129.5(2), 128.5(2), 128.4(2), 128.3(2),
128.0,127.9(2), 127.8, 113.8(2) (ArC), 88.0 (C-1), 82.6, 77.6, 75.7, 73.4,
72.1, 69.1, 66.9, 67.2, 55.3 (CH2C6H4OCH3), 21.1 (SC6H4CH3). HRMS
(ESI): (MþNa)þ, found 609.2286. C35H38O6SNa requires 609.2287.
hexane-EtOAc, 1:2) 0.45; IR (neat): 1742, 1628, 1565, 1539, 1434,
1363, 1181, 1043, 761 cmꢀ1; 1H NMR (500 MHz, CDCl3)
d: 7.56, 7.10
(2d, 4H, J 8.0 Hz, C6H4OCH3), 7.30, 6.85 (2d, 4H, J 8.5 Hz, SC6H4CH3),
5.42 (s, 1H, CHC6H4OCH3), 4.41 (d, 1H, J1,2 9.0 Hz, H-1), 4.31 (dd, 1H,
J5,6a 1.0 Hz, J6a,6b 12.5 Hz, H-6a), 4.11 (d,1H, J3,4 1.5 Hz, H-4), 3.95 (dd,
1H, J5,6b 1.0 Hz, J6a,6b 12.5 Hz, H-6b), 3.8 (s, 3H, CHC6H4OCH3), 3.61
(m, 2H, H-2, H-3), 3.45 (d, 1H, H-5), 2.35 (s, 3H, SC6H4CH3). 13C NMR
4.6. 4-Tolyl 4-O-acetyl-2,3-di-O-benzyl-6-O-(4-
methoxybenzyl)-1-thio-b-D-galactopyranoside (6)
(CDCl3, 125 MHz) d: 160.2, 138.3, 134.2(2), 130.2, 129.6(2), 127.9(2),
Compound 5 (4.0 g, 6.8 mmol) was treated with Ac2O (15 mL)
and pyridine (15 mL). The reaction was stirred at room temperature
for 2 h when TLC (n-hexane-EtOAc; 2:1) showed complete con-
version of the starting material to a faster moving spot. Solvents
were evaporated in vacuo and co-evaporated with toluene. The
crude product was purified by flash chromatography (n-hexane-
EtOAc, 2:1) to give the pure donor 6 (4.1 g, 96%) as white foam.
126.9, 113.4(2) (ArC), 101.1 (CHC6H4OCH3), 87.0 (C-1), 75.3, 73.6,
69.8, 69.2, 68.6, 55.2 (CHC6H4OCH3), 21.2 (SC6H4CH3). HRMS (ESI):
(MþNa)þ, found 427.1189. C21H24O6SNa requires 427.1191.
4.4. 4-Tolyl 2,3-di-O-benzyl-4,6-O-(4-methoxybenzylidene)-1-
thio-b-D-galactopyranoside (4)
½
a 2D5
1604, 1580, 1521, 1445, 1358, 1232, 1170, 1030, 833, 754, 682 cmꢀ1
1H NMR (500 MHz, CDCl3)
: 7.47, 7.06 (2d, 4H, J 8.0 Hz, SC6H4CH3),
ꢂ
þ 98 (c 1.1); Rf (n-hexane-EtOAc, 2:1) 0.54; IR (neat): 1742,
To the solution of compound 3 (3.8 g, 9.4 mmol) in DMF (30 mL),
sodium hydride (0.9 g, 37.6 mmol, 60% in mineral oil) followed by
benzyl bromide (3.4 mL, 28.2 mmol) were added. The reaction was
completed after 2 h as judged by TLC (n-hexane-EtOAc; 2:1). MeOH
(5 mL) was added to quench the reaction. The solvents were
evaporated and the residue was dissolved in CH2Cl2 (30 mL) and
washed with brine solution (2ꢃ50 mL). The organic layer was
separated, dried over Na2SO4, evaporated in vacuo and finally pu-
rified by flash chromatography using n-hexane-EtOAc (3:1) to af-
;
d
7.41e7.24 (m, 12H, ArH), 6.89 (m, 2H, C6H4OCH3), 5.62 (s, 1H, H-4),
4.76 (d, 2H, J 11.0 Hz, CH2Ph), 4.72 (d, 1H, J 10.0 Hz, CH2Ph), 4.62 (d,
1H, J1,2 9.5 Hz, H-1), 4.48 (d, 2H, J 12.0 Hz, CH2Ph), 4.38 (d, 1H, J
11.5 Hz, CH2Ph), 3.81 (s, 3H, CH2C6H4OCH3), 3.71 (t, 1H, J5,6a, J5,6b
6.5 Hz, H-5), 3.62 (m, 2H, H-3, H-6a), 3.59 (dd, 1H, J1,2 9.5 Hz, J2,3
6.0 Hz, H-2), 3.49 (dd,1H, J5,6a 6.5 Hz, J6a,6b 9.5 Hz, H-6b), 2.31 (s, 3H,
COCH3), 2.09 (s, 3H, SC6H4CH3). 13C NMR (CDCl3, 125 MHz)
d: 170.3
ford the pure product 4 (5.1 g, 94%) as colourless syrup. ½a D25
þ 112
ꢂ
(COCH3), 159.4, 138.3, 137.6, 129.9, 129.8, 129.7(2), 129.6(2),
128.4(2), 128.3(2), 128.2(2), 128.2(2), 127.8(2), 127.7, 113.8(2) (ArC),
88.1 (C-1), 81.3, 76.8, 75.9, 75.7, 73.3, 71.9, 67.9, 66.9, 55.3
(CH2C6H4OCH3), 21.1 (SC6H4CH3), 20.9 (COCH3). HRMS (ESI):
(MþNa)þ, found 651.2391. C37H40O7SNa requires 651.2392.
(c 1.1, CHCl3). Rf (n-hexane-EtOAc, 3:1) 0.42; IR (neat): 1753, 1621,
1587, 1533, 1428, 1353, 1178, 1039, 753 cmꢀ1
;
1H NMR (500 MHz,
CDCl3) : 7.62, 7.04 (2d, 4H, J 8.0 Hz, SC6H4CH3), 7.47e7.28 (m, 12H,
d
ArH), 6.93 (m, 2H, C6H4OCH3), 5.45 (s, 1H, CHC6H4OCH3), 4.74, 4.72
(2s, 4H, CH2Ph), 4.58 (d,1H, J1,2 9.5 Hz, H-1), 4.36 (dd,1H, J5,6a 1.5 Hz,
J6a,6b 12.5 Hz, H-6a), 4.13 (d, 1H, J3,4 3.0 Hz, H-4), 3.97 (dd, 1H, J5,6b
1.5 Hz, J6a,6b 12.5 Hz, H-6b), 3.85 (m, 4H, H-2, CHC6H4OCH3), 3.62
(dd, 1H, J2,3 9.0 Hz, J3,4 3.0 Hz, H-3), 3.39 (d, 1H, J4,5 0.5 Hz, H-5), 2.33
4.7. 4-Methoxyphenyl 4-O-acetyl-2,3-di-O-benzyl-6-O-(4-
methoxybenzyl)-
a
-D-galactopyranosyl-(1/3)-2-azido-4,6-O-
(s, 3H, SC6H4CH3). 13C NMR (CDCl3, 125 MHz)
d
: 160.1, 138.6, 138.1,
benzylidene-2-deoxy-a-D-glucopyranoside (8)
137.6, 133.4(2), 130.6, 129.6(2), 128.7, 128.4(2), 128.3(2), 128.2(2),
128.0(2), 127.8(2), 127.7, 127.6, 113.4(2) (ArC), 101.2 (CHC6H4OCH3),
86.6 (C-1), 81.4, 75.4, 75.3, 73.6, 71.7, 69.7, 69.4, 55.3 (CHC6H4OCH3),
21.1 (SC6H4CH3). HRMS (ESI): (MþNa)þ, found 607.2127.
A mixture of donor 6 (4.1 g, 6.5 mmol), known acceptor 7 (2.0 g,
5 mmol) and MS 4 A (2.0 g) in dry CH2Cl2 (30 mL) was stirred under
ꢀ
nitrogen for 1 h. NIS (1.9 g, 8.5 mmol) was added to it and the
mixture was cooled to ꢀ50 ꢁC followed by addition of H2SO4-silica
(150 mg). The mixture was allowed to stir at the same temperature
for 30 min when TLC (n-hexane-EtOAc; 2:1) revealed that entire
acceptor 4 was consumed. Et3N was added to neutralize the re-
action. The reaction mixture was immediately filtered through
a pad of Celite. The filtrate was successively washed with Na2S2O3
(2ꢃ50 mL), NaHCO3 (2ꢃ50 mL) and brine (50 mL). The organic layer
was collected, dried (Na2SO4) and evaporated in vacuo. The crude
product thus obtained, was purified by flash chromatography using
n-hexane-EtOAc (4:1) to give the pure disaccharide 8 (3.8 g, 85%) as
C
35H36O6SNa requires 607.2130.
4.5. 4-Tolyl 2,3-di-O-benzyl-6-O-(4-methoxybenzyl)-1-thio-
b-
D-galactopyranoside (5)
A solution of the acetal 4 (5.1 g, 8.7 mmol) in anhydrous DMF
(50 mL) was cooled to 0 ꢁC followed by addition of solid NaCNBH3
(2.7 g, 43.6 mmol). The mixture was stirred under nitrogen for
30 min. A solution of TFA (6.7 mL, 87.3 mmol) in dry DMF (50 mL)
was added dropwise to the reaction mixture. The resulting sus-
pension was stirred for 2 h at 0 ꢁC and then 10 h at room temper-
ature. Solid NaHCO3 was added to neutralize the mixture. DMF was
evaporated and the residue was diluted with EtOAc (50 mL). The
solution was filtered over Celite pad and washed successively with
NaHCO3 (2ꢃ50 mL) and brine (50 mL). The organic phase was
collected, dried (Na2SO4) and evaporated. The residue was purified
by flash chromatography using n-hexane-EtOAc (2:1) to afford pure
a white foam. ½a 2D5
þ 98 (c 1.0, CHCl3); Rf (n-hexane-EtOAc, 4:1)
ꢂ
0.34; IR (KBr): 2110, 1746, 1719, 1634, 1613, 1368, 1215, 1040 cmꢀ1
;
1H NMR (500 MHz, CDCl3)
d
0: 7.38e6.85 (m, 23H, ArH), 5.74 (dd, 1H,
0
0
0
0
0
0
0
J3 ,4 3.5 Hz, J4 ,5 1.0 Hz, H-4 ), 5.69 (d, 1H, J1 ,2 4.0 Hz, H-1 ), 5.53 (d,
1H, J1,2 4.0 Hz, H-1), 5.45 (s, 1H, CHPh), 4.78 (d, 1H, J 10.5 Hz, CH2Ph),
4.58 (m, 3H, H-50, CH2Ph), 4.50 (m, 2H, CH2Ph), 4.46 (t, 1H, J2,3, J3,4
6.5 Hz, H-3), 4.41 (d, 1H, J 11.0 Hz, CH2Ph), 4.23 (dd. 1H, J5,6a 5.0 Hz,
compound 5 (4.7 g, 91%) as colourless syrup. ½a D25
ꢂ
þ 134 (c 1.0,
J6a,6b 10.0 Hz, H-6a), 4.12 (m,1H, H-5), 4.02 (dd,1H, J2 ,3 10.0 Hz, J3 ,4
0
0
0
0
CHCl3); Rf (n-hexane-EtOAc, 2:1) 0.41; IR (neat): 1738, 1614, 1591,
3.5 Hz, H-30), 3.88 (t, 1H, J3,4, J4,5 9.5 Hz, H-4), 3.79 (s, 3H,
1527,1431,1363,1228,1175,1037, 857, 748 cmꢀ1;1H NMR (500 MHz,
C6H4OCH3), 3.77 (m, 4H, H-20, CH2C6H4OCH3), 3.74 (t, 1H, J5,6b, J6a,6b
CDCl3)
d: 7.47e7.24 (m, 14H, ArH), 7.05 (d, 2H, J 8.0 Hz, SC6H4CH3),
9.5 Hz, H-6b), 3.63 (dd, 1H, J5,6a 5.0 Hz, J6a ,6b 9.5 Hz, H-6a0), 3.49
0 0 0
6.87 (m, 2H, C6H4OCH3), 4.83, 4.74 (2d, 2H, J 10.5 Hz, CH2Ph), 4.72,
4.67 (2d, 2H, J 11.5 Hz, CH2Ph), 4.57 (d,1H, J1,2 9.5 Hz, H-1), 4.51, 4.48
(2d, 2H, J 11.5 Hz, CH2C6H4OCH3), 4.09 (s, 1H, H-4), 3.81 (s, 3H,
CH2C6H4OCH3), 3.75 (m, 2H, H-5, H-6a), 3.70 (t, 1H, J1,2, J2,3 9.5 Hz,
H-2), 3.55 (m, 2H, H-3, H-6b), 2.51 (d, 1H, J 1.5 Hz, OH), 2.3 (s, 3H,
(m, 2H, H-2, H-6b0), 2.0 (s, 3H, COCH3). 13C NMR (CDCl3, 125 MHz)
d:
170.1 (COCH3), 159.2,155.6,150.1,138.3,138.2,129.9,129.6(2),129.4,
128.4(2), 128.2(2), 128.1(2), 128.0(2), 127.4, 127.3, 127.2(2), 126.2(2),
118.2(2), 114.7(2), 113.8(2) (ArC), 102.1 (CHPh), 98.3 (C-1), 97.4 (C-
10), 82.8, 75.6, 74.6, 73.1, 72.2, 72.0, 71.6, 68.8, 68.0, 67.9, 67.8, 62.8,

D. Budhadev, B. Mukhopadhyay / Tetrahedron 71 (2015) 6155e6163
6159
61.8, 55.6 (C6H4OCH3), 55.2 (CH2C6H4OCH3), 20.9 (COCH3). HRMS
(ESI) (MþNa)þ, found 926.3472. C50H53N3O13Na requires 926.3476.
was separated, dried (Na2SO4) and evaporated in vacuo. The crude
product thus obtained, was purified by flash chromatography using
n hexane-EtOAc (3:1) as eluent to afford pure trisaccharide 12
4.8. 4-Methoxyphenyl 2,3-di-O-benzyl-6-O-(4-
(2.4 g, 91%) as white foam. ½a D25
þ 74 (c 0.9, CHCl3); Rf (n-hexane-
ꢂ
methoxybenzyl)-
benzylidene-2-deoxy-
a
-
D
-galactopyranosyl-(1/3)-2-azido-4,6-O-
-glucopyranoside (9)
EtOAc, 3:1) 0.35; IR (Neat): 2108, 1772, 1723, 1626, 1607, 1372, 1218,
a
-D
1015 cmꢀ1; 1H NMR (500 MHz, CDCl3)
d
: 7.39e7.28 (m, 20H, ArH),
00 00
6.93, 6.82 (2d, 4H, J 9.0 Hz, C6H4OCH3), 5.49 (dd, 1H, J1 ,2 010 .5 Hz,
00
00 00
00 00
00 00
Compound 8 (3.8 g, 4.2 mmol) was dissolved in MeOH (20 mL)
and NaOMe in MeOH (0.5M, 2 mL) was added to it. The solution was
stirred at room temperature for 12 h. The solution was neutralized
with DOWEX 50W Hþ resin, filtered and the solvents were evap-
orated under reduced pressure. The residue was purified by flash
chromatography using n-hexane-EtOAc (2:1) to afford the desired
J2 ,3 3.5 Hz H-2 ), 5.38 (dd, 1H, J2 ,3 3.5 Hz, J3 ,4 010 Hz, H-3 ), 5.34
0
0
00 00
,
(d,1H, J1,2 1.5 Hz, H-1), 5.16 (d,1H, J1 ,2 1.5 Hz, H-10)0 , 5.05 (t,1H, J3 ,4
00
00 00
00 00
J4 ,5 10.0 Hz, H-4 ), 4.99 (d, 1H, J1 ,2 1.5 Hz, H-1 ), 4.91 (ABq, 2H, J
11.0 Hz, CH2Ph), 4.71 (m, 6H, CH2Ph), 4.16 (t, 1H, J1,2, J2,3 2.0 Hz, H-2),
4.12 (t, 1H, J1 ,2 , J2 ,3 2.5 Hz, H-20), 4.05 (dd, 1H, J2 ,3 3.0 Hz, J3 ,4
0
0
0
0
0
0
0
0
9.5 Hz, H-30), 3.92 (m, 2H, H-3, H-500), 3.81 (m, 2H, H-5, H-50), 3.78
disaccharide acceptor 9 (3.5 g, 95%) as white foam. ½a D25
ꢂ
þ 84 (c 0.8,
(s, 3H, C6H4OCH3), 3.6 (t, 1H, J3,4, J4,5 9.5 Hz, H-4), 3.44 (t, 1H, J3 ,4
,
0
0
0
0
0
CHCl3); Rf (n-hexane-EtOAc, 2:1) 0.31; IR (KBr): 2075, 1782, 1730,
J4 ,5 9.5 Hz, H-4 ), 2.13, 2.05, 2.02 (3s, 9H, 3ꢃ COCH3)1.34 (d, 3H, J5,6
1650, 1621, 1378, 1225, 970 cmꢀ1
;
1H NMR (500 MHz, CDCl3)
d:
6.0 Hz, CeCH3), 1.27 (d, 3H, J5 ,6 6.0 Hz, CeCH3). 1.09 (d, 3H, J5 ,6
0
0
00 00
7.38e6.87 (m, 23H, ArH), 5.76 (d, 1H, J1 ,2 3.5 Hz, H-10), 5.55 (d, 1H,
J1,2 3.5 Hz, H-1), 5.47 (s, 1H, CHPh), 4.8, 4.73 (2d, 2H, J 11.5 Hz,
CH2Ph), 4.66 (t, 1H, J2,3, J3,4 9.5 Hz, H-3), 4.58 (m, 3H, CH2Ph), 4.48
6.0 Hz, CeCH3). 13C NMR (CDCl3, 125 MHz)
d
: 170, 169.9, 169.7 (3ꢃ
0
0
COCH3), 154.8, 150.1, 138.4(2), 138.3, 138.2, 128.5(2), 128.4(4),
128.3(3), 128.2(2), 127.9(2), 127.8(3), 127.7, 127.6, 127.5(2), 117.4(2),
114.6(2) (ArC), 100.3 (C-10), 99 (C-100), 97.7 (C-1), 80.3, 80.2, 79.5,
79.1, 75.7, 75.5, 75.3, 74.2, 72.5 (2), 71.1, 69.7, 69.1, 68.8, 68.6, 66.8,
55.6 (C6H4OCH3), 20.9, 20.8, 20.7 (3ꢃ COCH3), 18, 17.9, 17.3
(3ꢃCeCH3). HRMS (ESI) (MþNa)þ, found 1071.4351. C59H68O17Na
requires 1071.4354.
(d, 1H, J 12.0 Hz, CH2Ph), 4.31 (t, 1H, J5 ,6a , J5 ,6b 5.0 Hz, H-50), 4.24
(m, 2H, H-40, H-6a), 4.14 (m, 1H, H-5), 3.91 (m, 4H, H-20, H-30, H-4,
H-6a0), 3.82 (m, 1H, H-6b0), 3.80 (s, 3H, C6H4OCH3), 3.78 (s, 3H,
CH2C6H4OCH3), 3.73 (t, 1H, J5,6b, J6a,6b 9.5 Hz, H-6b), 3.51 (dd, 1H, J1,2
0
0
0
0
3.5 Hz, J2,3 10.0 Hz, H-2). 13C NMR (CDCl3, 125 MHz)
d: 159.1, 155.5,
150.0, 138.2, 138.1, 136.7, 130, 129.4(2), 129.3, 128.3(2), 128.2(2),
128.1(2), 127.7(2), 127.6, 127.3, 127.1(2), 126.2(2), 118.1(2), 114.7(2),
113.7(2) (ArC), 102.0 (CHPh), 98.2 (C-1), 97.1 (C-10), 82.8, 76.9, 74.6,
73.2, 72.5, 71.8, 71.3, 69.1, 68.7, 68.6, 67.8, 62.8, 61.8, 55.6
(C6H4OCH3), 55.1 (CH2C6H4OCH3). HRMS (ESI) (MþNa)þ, found
884.3366. C48H51N3O12Na requires 884.3370.
4.11. 2,3,4-Tri-O-acetyl-
benzyl- -rhamnopyranosyl-(1/2)-3,4-di-O-benzyl-
rhamnopyranosyl trichloroacetimidate (14)
a-L-rhamnopyranosyl-(1/2)-3,4-di-O-
a
-L
a-L-
The trisaccharide 12 (2.4 g, 2.3 mmol) was treated with CAN
(3.7 g, 6.9 mmol) in CH3CNeH2O (30 mL, 9:1). The reaction was
continued for 30 min till TLC (n-hexane-EtOAc 2:1) showed com-
plete conversion of the starting material to a slower running spot.
The solvents were evaporated and the crude material was subjected
to flash chromatography using n-hexane-EtOAc (2:1) to afford the
desired trisaccharide hemiacetal 13 (1.7 g, 81%). Rf (n-hexane-
EtOAc, 2:1) 0.26. Compound 13 (1.7 g, 1.8 mmol) was dissolved in
dry CH2Cl2, DBU (0.3 mL, 2.3 mmol) was added followed by tri-
chloroacetonitrile (1.8 mL, 18 mmol) and the solution was stirred
under nitrogen for 20 min when TLC (n-hexane-EtOAc: 3:2) in-
dicated complete conversion of the starting material to a faster
running spot. The solvents were evaporated in vacuo and the crude
product, thus obtained, was subjected to flash chromatography
using n-hexane-EtOAc (3:1) to afford the desired tri-
chloroacetamidate donor 14 (1.8 g, 90%). Rf (n-hexane-EtOAc, 3:1)
0.39. The material was used for the next reaction without any fur-
ther characterization.
4.9. 4-Methoxyphenyl 3,4-di-O-benzyl-
a-L-rhamnopyranosyl-
(1/2)-3,4-di-O-benzyl- -rhamnopyranoside (10)
a-L
The compound was prepared by following the reported litera-
ture procedure.13 The NMR data of the disaccharide matched sat-
isfactorily with the reported data. 1H NMR (500 MHz, CDCl3)
d:
7.41e7.29 (m, 20H, ArH), 6.95, 6.84 (2d, 4H, J 9.0 Hz, C6H4OCH3),
5.38 (d,1H, J1,2 1.5 Hz, H-1), 5.14 (s, 1H, H-10), 4.91 (ABq, 2H, J 11.0 Hz,
CH2Ph), 4.76 (m, 4H, CH2Ph), 4.68 (d, 1H, J 11.0 Hz, CH2Ph), 4.65 (d,
1H, J 10.5 Hz, CH2Ph), 4.19 (m, 2H, H-2, H-20), 4.08 (dd, 1H, J2,3 3 Hz,
0
0
0
0
0
J3,4 9.5 Hz, H-3), 3.93 (dd, 1H, J2 ,3 3.0 Hz, J3 ,4 9.5 Hz, H-3 ), 3.89 (m,
1H, H-5), 3.83 (m, 1H, H-50), 3.78 (s, 3H, C6H4OCH3), 3.54 (t, 1H, J3,4
,
J4,5 9.5 Hz, H-4), 3.48 (t, 1H, J3 ,4 , J4 ,5 9.5 Hz, H-40), 1.32 (d, 3H, J5,6
0
0
0
0
6 Hz, CeCH3), 1.29 (d, 3H, J5 ,6 6 Hz, CeCH3). 13C NMR (CDCl3,
0
0
125 MHz) : 154.8, 150.2, 138.4, 138.3, 138.2, 138, 128.6, 128.5 (2),
d
128.4(4), 128.3(3), 128(2), 127.9(4), 127.8, 127.7(2), 127.6, 117.4(2),
114.6(2) (ArC), 100.8 (C-10), 97.7 (C-1), 80.2, 79.9, 79.5 (2), 75.4, 75.3,
74.5, 72.4, 72.2, 68.7, 68.5, 68, 55.6 (C6H4OCH3), 18, 17.9 (2ꢃ CeCH3).
HRMS (ESI) calcd for C47H52O10Na (MþNa)þ: 799.3458, found:
799.3455.
4.12. 4-Methoxyphenyl 2,3,4-tri-O-acetyl-
anosyl-(1/2)-3,4-di-O-benzyl- -rhamnopyranosyl-(1/2)-
3,4-di-O-benzyl- -rhamnopyranosyl-(1/4)-2,3-di-O-ben-
zyl-6-O-(4-methoxybenzyl)- -galactopyranosyl-(1/3)-2-
azido-4,6-O-benzylidene-2-deoxy- -glucopyranoside (15)
a-L-rhamnopyr-
a-L
a-L
a-D
4.10. 4-Methoxyphenyl 2,3,4-tri-O-acetyl-
anosyl-(1/2)-3,4-di-O-benzyl- -rhamnopyranosyl-(1/2)-
3,4-di-O-benzyl- -rhamnopyranoside (12)
a
-L
-rhamnopyr-
a-D
a-L
a-
L
A mixture of disaccharide acceptor 9 (1.0 g, 1.2 mmol), tri-
chloroacetamidate donor 14 (1.8 g, 1.6 mmol) and freshly activated
ꢀ
A mixture of disaccharide acceptor 10 (2.0 g, 2.6 mmol), known
MS 4 A (1.0 g) in dry CH2Cl2 (20 mL) was stirred under nitrogen for
donor 11 (1.3 g, 3.3 mmol) and MS 4 A (2.0 g) in dry CH2Cl2 (30 mL)
1 h at room temperature. After cooling the reaction mixture to 0 ꢁC,
H2SO4-silica (50 mg) was added and the mixture was allowed to stir
at the same temperature for 10 min when TLC (n-hexane-EtOAc;
3:2) showed complete consumption of acceptor 9. The reaction
mixture was neutralized with Et3N and filtered through a pad of
Celite. The filtrate was diluted with CH2Cl2 and was successively
washed with NaHCO3 (2ꢃ50 mL) and brine (50 mL). The organic
layer was separated, dried (Na2SO4) and evaporated in vacuo. The
crude product thus obtained was purified by flash chromatography
ꢀ
was stirred under nitrogen atmosphere for 1 h. NIS (980 mg,
4.4 mmol) was added to the reaction mixture and it was cooled to
0 ꢁC. H2SO4-silica (50 mg) was added to the reaction mixture and it
was stirred for 10 min till TLC (n-hexane-EtOAc; 3:1) indicated
complete consumption of acceptor 10. The reaction mixture was
diluted with CH2Cl2 (30 mL) and filtered through a pad of Celite.
The filtrate was successively washed with aq Na2S2O3 (2ꢃ50 mL),
satd aq NaHCO3 (2ꢃ50 mL) and brine (50 mL). The organic layer

6160
D. Budhadev, B. Mukhopadhyay / Tetrahedron 71 (2015) 6155e6163
using n-hexane-EtOAc (1.5:1) to give the pure pentasaccharide 15
138.4(3), 138.3, 138.2(2), 136.9, 129.5, 128.5(2), 128.4(4), 128.3(4),
128.2(2),128.1(2),128(2), 127.9(2), 127.8(2), 127.6(3), 127.5(3), 127.3,
127.0(2), 126.4(2), 118.2(3), 114.8(3) (ArC), 100.3 (CHPh), 102.1 (C-
100),100.2 (C-1000), 99.1 (C-10000), 98.4 (C-1), 97.1 (C-10), 82.9, 80.3, 79.8,
79.3(2), 77.6, 76.3, 75.6, 75.5, 75.3, 75.2, 74.4, 73, 72.5, 72.1, 71.5(2),
71.2, 70.4, 69.7 (2), 69.2, 68.9, 68.8, 66.8, 62.9, 62.0, 61.5, 55.7
(C6H4OCH3), 20.9(2), 20.8 (3ꢃ COCH3), 18.1, 18.0, 17.2 (3ꢃCeCH3).
HRMS (ESI) (MþNa)þ, found 1688.6727. C92H103N3O26Na requires
1688.6728.
(1.7 g, 82%). ½a 2D5
þ 78 (c 0.8, CHCl3); Rf (n-hexane-EtOAc, 1.5:1)
ꢂ
0.44; IR (Neat): 2107, 1758, 1731, 1645, 1613, 1375, 1219, 1033 cmꢀ1
;
1H NMR (500 MHz, CDCl3)
d
: 7.37e6.85 (m, 43H, ArH), 5.59 (d, 1H,
J1 ,2 3.0 Hz, H-10), 5.52 (d, 1H, J1,2 3.5 Hz, H-1), 5.45 (m, 2H, H-20000
,
0
0
8.0 Hz, H-30000), 5.24 (d, 1H,
0000,40000
0000,30000
CHPh), 5.36 (dd, 1H, J2
3.0 Hz, J3
J1 ,2 1.5 Hz, H-100), 4.99 (m, 3H, H-1000, H-10000, H-40000), 4.87 (d, 1H, J
11.0 Hz, CH2Ph), 4.85 (d, 1H, J 11.5 Hz, CH2Ph), 4.79 (d, 1H, J 11.5 Hz,
CH2Ph), 4.74 (d, 1H, J 12.0 Hz, CH2Ph), 4.68 (d, 1H, J 11.5 Hz, CH2Ph),
4.64 (d, 1H, J 11.0 Hz, CH2Ph), 4.63 (d, 1H, J 11.0 Hz, CH2Ph), 4.59 (m,
3H, H-3, CH2Ph), 4.39 (m, 5H, CH2Ph), 4.23 (m, 3H, H-30, H-50, H-6a),
00 00
4.14. 4-Methoxyphenyl 2,3,4-tri-O-acetyl-
anosyl-(1/2)-3,4-di-O-benzyl- -rhamnopyranosyl-(1/2)-
3,4-di-O-benzyl- -rhamnopyranosyl-(1/4)-2,3-di-O-ben-
zyl- -galactopyranosyluronic acid-(1/3)-2-azido-4,6-O-
benzylidene-2-deoxy- -glucopyranoside (17)
a-L-rhamnopyr-
4.12 (m, 1H, H-50000), 4.09 (m, 2H, H-200, H-5), 3.94 (t, 1H, J3 ,4 , J4 ,5
0
a-L
0
0
0
3.5 Hz, H-40), 3.86 (m, 3H, H-2000, H-4, H-500), 3.82e3.73 (m, 11.0H, H-
a-L
20, H-300, H-5000, H-6b, H-6a0, C6H4OCH3, CH2C6H4OCH3), 3.61 (m, 2H,
a-D
H-3000, H-6b0), 3.53 (t, 1H, J3 ,4 , J4 ,5 9.5 Hz, H-400), 3.44 (dd, 1H, J1,2
a-D
00 00
00 00
9.5 Hz, H-4000), 2.10,
6.5 Hz, 6.5 Hz,
000,4000
000,5000
0000,60000
3.5 Hz, J2,3 10.0 Hz, H-2), 3.35 (t, 1H, J3
, J4
2.04, 2.00 (3s, 9H, 3ꢃ COCH3), 1.22 (d, 3H, J5
To a solution of the pentasaccharide derivative 16 (1.3 g,
0.8 mmol) in CH2Cl2eH2O (2:1, 20 mL), TEMPO (20 mg, 0.12 mmol)
was added followed by [bis-(acetoxy)-iodo]benzene (BAIB)
(480 mg, 1.5 mmol) and the mixture was vigorously stirred at room
temperature for 2 h till TLC (EtOAc) indicated complete conversion
of the starting material to a lower running spot. Na2S2O3 solution
(10% in H2O, 10 mL) was added to quench the reaction. The mixture
was then extracted with CH2Cl2 (2ꢃ30 mL). The combined organic
layer was dried over Na2SO4, filtered and evaporated in vacuo. The
crude product was purified by flash chromatography using n-hex-
ane-EtOAc (1:1) as eluent to furnish the uronic acid derivative 17
00 00
000,6000
CeCH3), 1.15 (d, 3H, J5
6.5 Hz, CeCH3), 1.01 (d, 3H, J5 ,6 6 Hz,
CeCH3). 13C NMR (CDCl3, 125 MHz)
d: 170 (2), 169.8 (3ꢃ COCH3),
159.2, 155.6(2), 150.0(2), 139.0, 138.6, 138.5(2), 138.4(2), 138.3(3),
138.2(3), 136.9, 129.5, 129.4, 128.4(3), 128.3(3), 128.2(3), 128.1(2),
128.0(2), 127.9(2), 127.8(2), 127.6, 127.5(3), 127.3, 127.0(2), 126.3(2),
118.2(2), 118.1(2), 114.7(3), 113.7, 110.7 (ArC), 102.2 (CHPh), 100.2 (C-
1000), 100.1 (C-100), 98.9 (C-10000), 98.4 (C-1), 97.3 (C-10), 82.9, 80.4,
80.2, 79.5, 79.3, 77.6, 75.6, 75.4, 75.2, 75.1, 73.1, 73, 72.8, 72.4, 72,
71.9, 71.8, 71.4, 71.2, 71.1, 66.7, 62.9, 61.8, 60.4, 56.3, 55.6
(C6H4OCH3), 55.2 (CH2C6H4OCH3), 69.7, 69.4, 68.8, 68.6, 20.9, 20.8,
20.7 (3ꢃ COCH3), 18.2, 17.8, 17.2 (3ꢃCeCH3). HRMS (ESI) (MþNa)þ,
found 1808.7302. C100H111N3O27Na requires 1808.7303.
(1.1 g, 87%) as white amorphous mass. ½a D25
þ 108 (c 0.8, CHCl3); Rf
ꢂ
(n-hexane-EtOAc, 1:1) 0.24; IR (KBr): 2350, 2095, 1683, 1194,
782 cmꢀ1 1H NMR (500 MHz, CDCl3)
; d: 7.38e7.00 (m, 35H, ArH),
0
0
0
4.13. 4-Methoxyphenyl 2,3,4-tri-O-acetyl-
anosyl (1/2)-3,4-di-O-benzyl- -rhamnopyranosyl-(1/2)-
3,4-di-O-benzyl- -rhamnopyranosyl-(1/4)-2,3-di-O-ben-
zyl- -galactopyranosyl-(1/3)-2-azido-4,6-O-benzylidene-
2-deoxy- -glucopyranoside (16)
a
-L-rhamnopyr-
7.05, 6.85 (2d, 4H, J 9.0 Hz, C6H4OCH3), 5.66 (d,1H, J1 ,2 3.5 Hz, H-1 ),
a-L
5.5 (d, 1H, J1,2 3.5 Hz, H-1), 5.45 (m, 2H, CHPh, H-20000), 5.36 (dd, 1H,
a
-L
J2
3.0 Hz, J3
10.0 Hz, H-30000), 5.12 (s, 1H, H-100), 5.06 (s, 1H,
0000,40000
0000,30000
H-1000), 5.01 (t, 1H, J3
J4
10.0 Hz, H-40000), 4.95 (s, 1H, H-10000),
0000,40000 0000,50000
a
-D
a-
D
4.86 (d, 1H, J 11.0 Hz, CH2Ph), 4.79 (d, 1H, J 11.5 Hz, CH2Ph), 4.72 (m,
3H, CH2Ph), 4.62 (m, 2H, H-3, CH2Ph), 4.56 (m, 2H, CH2Ph), 4.49 (d,
1H, J 11.5 Hz, CH2Ph), 4.44 (d, 1H, J 10.5 Hz, CH2Ph), 4.39 (d, 2H, J
11.5 Hz, CH2Ph), 4.24 (dd, 1H, J5,6a 5.0 Hz, J6a,6b 20.0 Hz, H-6a), 4.14
(m, 1H, H-5), 4.04 (s, 1H, H-2000), 3.95 (s, 1H, H-200), 3.86 (m, 5H, H-30,
H-4, H-40, H-50, H-50000), 3.78 (m, 4H, H-20, C6H4OCH3), 3.72 (m, 3H,
To a solution of the pentasaccharide 15 (1.7 g, 0.9 mmol) in
CH2Cl2eH2O (4:1; 25 mL), DDQ (432 mg, 1.9 mmol) was added and
the reaction mixture was stirred at room temperature for 2 h. The
reaction mixture was then washed with H2O (2ꢃ50 mL). The or-
ganic layer was collected, dried over Na2SO4, filtered and evapo-
rated in vacuo. The product thus obtained, was purified using flash
chromatography using n-hexane-EtOAc (2:1) as eluent to furnish
H-3000, H-5000, H-6b), 3.62 (dd, 1H, J2 ,3 2.5 Hz, J3 ,4 9.5 Hz, H-300),
00 00
00 00
9.5 Hz, H-4000), 3.45 (m, 1H, H-500), 3.34 (m,
000,4000
3.52 (t, 1H, J3
000,5000
, J4
2H, H-2, H-400), 2.09, 2.04, 2.00 (3s, 9H, 3ꢃ COCH3), 1.25 (d, 3H, J5 ,6
00 00
the pentasaccharide derivative 16 (1.3 g, 84%) as white foam. ½a D25
ꢂ
þ
6.5 Hz, CeCH3), 1.20 (d, 3H, J5
000,6000 0000,60000
6.5 Hz, CeCH3), 1.01 (d, 3H, J5
112 (c 0.9, CHCl3); Rf (n-hexane-EtOAc, 2:1) 0.28; IR (Neat): 2101,
6.0 Hz, CeCH3). 13C NMR (CDCl3, 125 MHz)
d: 172.6 (COOH), 170 (2),
1762, 1719, 1638, 1603, 1368, 1213, 1035 cmꢀ1
;
1H NMR (500 MHz,
169.7 (3ꢃ COCH3),155.6,150.1, 138.6,138.4(2),138.2(2),138.0,137.9,
136.8, 129.5, 128.5(2), 128.3(5), 128.2(2), 128.1(2), 128.0(2), 127.9(4),
127.7(4), 127.6, 127.5, 127.4(3), 127.3, 127.0(2), 126.4(2), 118.1(2),
114.8(2), 114.1 (ArC), 102.4 (CHPh), 100.1 (C-100), 100 (C-1000), 99 (C-
10000), 98.4 (C-1), 97.6 (C-10), 82.5, 80.3, 79.9, 79.2, 76.4, 75.7, 75.6,
75.5, 75.3, 75.1, 74.5, 74.4, 74, 72.9, 72.4, 72.2 (2), 72, 71.7, 71.1, 69.7,
69.2, 68.8, 68.7, 66.7, 62.9, 61.5, 55.6 (C6H4OCH3), 20.9, 20.8, 20.7
(3ꢃ COCH3), 17.9, 17.6, 17.2 (3ꢃCeCH3). HRMS (ESI) (MþNa)þ, found
1702.6521. C92H101N3O27Na requires 1702.6520.
CDCl3) : 7.38e7.01 (m, 35H, ArH), 7.04, 6.85 (2d, 4H, J 9.0 Hz,
d
C6H4OCH3), 5.58 (d, 1H, J1 ,2 3.5 Hz, H-10), 5.50 (d, 1H, J1,2 3.5 Hz, H-
0
0
1), 5.45 (dd, 1H, J1
1.5 Hz, J2
0000,30000
3.5 Hz, H-20000), 5.42 (s, 1H,
0000,40000
3.5 Hz, J3
10.0 Hz, H-30000), 5.06 (d,
0000,20000
0000,30000
CHPh), 5.36 (dd, 1H, J2
1H, J1 ,2 1.5 Hz, H-100), 5.02 (t, 1H, J3
J4
10.0 Hz, H-40000),
1.5 Hz, H-10000),
0000,40000 0000,50000
00 00
1.5 Hz, H-1000), 4.95 (d, 1H, J1
000,2000
0000,20000
4.98 (d, 1H, J1
4.87, 4.81 (2d, 2H, J 11.0 Hz, CH2Ph), 4.74 (m, 3H, CH2Ph), 4.64 (d,1H,
J 10.5 Hz, CH2Ph), 4.62 (d, 1H, J 11.5 Hz, CH2Ph), 4.56 (d, 1H, J 11.0 Hz,
CH2Ph), 4.53 (m, 2H, H-3, CH2Ph), 4.43 (d, 1H, J 11.5 Hz, CH2Ph), 4.38
(d, 1H, J 13.0 Hz, CH2Ph), 4.34 (d, 1H, J 12.0 Hz, CH2Ph), 4.22 (dd, 1H,
4.15. 4-Methoxyphenyl 2,3,4-tri-O-acetyl-
anosyl-(1/2)-3,4-di-O-benzyl- -rhamnopyranosyl-(1/2)-
3,4-di-O-benzyl- -rhamnopyranosyl-(1/4)-2,3-di-O-ben-
zyl- -galactopyranosyluronicacid-(1/3)-2-azido-2-deoxy-
-glucopyranoside (18)
a-L-rhamnopyr-
0
0
0
0
0
0
0
J5 ,6a 5.0 Hz, J6a ,6b 10.5 Hz, H-6a ), 4.12 (m, 3H, H-5,H-3 , H-5 ), 4.09
a-L
00
00 00
00 00
000,2000
000,3000
, J2
(t,1H, J1 ,2 , J2 ,3 2.5 Hz, H-2 ), 4.04 (t,1H, J1
2.5 Hz, H-2000),
a-L
3.92 (dd, 1H, J5,6a 3.0 Hz, J6a,6b 10.5 Hz, H-6a), 3.84 (m, 5H, H-20, H-4,
a-D
H-40, H-5000, H-50000), 3.78 (s, 3H, H-500, C6H4OCH3), 3.76 (m, 1H, H-500),
a-D
3.71 (m, 3H, H-300, H-3000, H-6b), 3.63 (t, 1H, J5 ,6a , J6a ,6b 9.5 Hz, H-
0
0
0
0
6a0), 3.54 (t, 1H, J3 ,4 J4 ,5 9.5 Hz, H-400), 3.45 (dd, 1H, J1,2 3.5 Hz, J2,3
The acid derivative 17 (1.1 g, 0.65 mmol) was treated with 80%
00 00 00 00
000,4000
10.5 Hz, H-2), 3.34 (t, 1H, J3
, J4
9.5 Hz, H-4000), 2.09, 2.04, 2 (3s,
000,5000
AcOH (10 mL) at 80 ꢁC for 2 h resulting in the hydrolysis of the
benzylidene ring. The solvents were evaporated and co-evaporated
with toluene. The crude product was purified by flash chromatog-
raphy using n-hexane-EtOAc (1:2) as eluent to furnish pure
00 00
000,6000
9H, 3ꢃ COCH3), 1.28 (d, 3H, J5 ,6 5.5 Hz, CeCH3), 1.24 (d, 3H, J5
6.0 Hz, CeCH3). 13C NMR (CDCl3,
0000,60000
6.5 Hz, CeCH3), 0.99 (d, 3H, J5
125 MHz)
d
: 170.0(2), 169.8 (3ꢃ COCH3), 155.6, 150.2, 138.5,

D. Budhadev, B. Mukhopadhyay / Tetrahedron 71 (2015) 6155e6163
6161
derivative 18 (906 mg, 87%). ½a D25
ꢂ
þ 132 (c 0.8, CHCl3); Rf (n-hex-
80, 79.3, 79.2, 78.2, 76, 75.3, 75.2, 74.7, 74.6, 74.5, 74.4, 73.5, 72.5,
72.4, 72.2 (2), 71.8, 71.7, 71.6, 70.8, 69.3, 68.6, 68.4, 62.6, 62.2, 55.6
(C6H4OCH3), 22.7 (NHCOCH3), 18.2, 18.1, 17.5 (3ꢃ CeCH3). HRMS
(ESI) (MþNa)þ, found 1504.6091. C81H95NO25Na requires
1504.6091.
ane-EtOAc, 1:2) 0.21; IR (Neat): 2362, 2105, 1690, 1187, 764 cmꢀ1
;
1H NMR (500 MHz, CDCl3)
d: 7.42e7.27 (m, 30H, ArH), 7.05, 6.84
0000,20000
0000,30000
(2d, 4H, C6H4OCH3), 5.47 (dd, 1H, J1
2.0 Hz, J2
3.5 Hz, H-
0000,40000
3.5 Hz, J3
20000), 5.45 (d, 1H, J1,2 3 Hz, H-1), 5.38 (dd, 1H, J2
0000,30000
10.0 Hz, H-30000), 5.19 (d, 1H, J1 ,2 1.5 Hz, H-100), 5.1 (d, 1H, J1
00 00
000,2000
1.0 Hz, H-1000), 5.06 (m, 2H, H-10, H-40000), 4.98 (d, 1H, J1
1.5 Hz, H-
4.17. 4-Methoxyphenyl
a
-L
-rhamnopyranosyl-(1/2)-
a-L-
0000,20000
10000), 4.9 (d, 1H, J 11.0 Hz, CH2Ph), 4.89 (d, 1H, J 11.5 Hz, CH2Ph), 4.83
(d, 1H, J 11.0 Hz, CH2Ph), 4.82 (d, 1H, J 11.5 Hz, CH2Ph), 4.73 (m, 2H,
CH2Ph), 4.67 (m, 3H, CH2Ph), 4.63, 4.62 (2d, 2H, J 11.5 Hz, CH2Ph),
4.58 (d, 1H, J 10.5 Hz, CH2Ph), 4.16 (m, 2H, H-200, H-30), 4.09 (m, 1H,
H-2000), 4.01 (m, 3H, H-3, H-50, H-6a), 3.89 (m, 3H, H-40, H-5, H-50000),
3.81 (m, 3H, H-20, H-500, H-5000), 3.78 (m, 5H, H-300, H-3000, C6H4OCH3),
00 00
rhamnopyranosyl-(1/2)-
galactopyranosyluronicacid-(1/3)-2-acetamido-2-deoxy-a-D-
glucopyranoside (1)
a
-
L
-rhamnopyranosyl-(1/4)-a-D-
The solution of the compound 19 (680 mg, 0.45 mmol) in MeOH
(10 mL) and AcOH (1 mL) was passed through flow hydrogenation
assembly fitted with a PdeC cartridge at 50 ꢁC at normal atmo-
spheric pressure of hydrogen. The reaction was found to be com-
plete after three cycles as judged by TLC (CH2Cl2eMeOH; 5:1). The
solvents were evaporated in vacuo and the residue was purified by
HPLC using C18 column; CH3CNeH2O mixture was used as eluent
to furnish the desired pentasaccharide 1 (370 mg, 85%) as white
3.74 (m,1H, H-6b), 3.67 (t,1H, J3,4, J4,5 10.0 Hz, H-4), 3.58 (t,1H, J3 ,4
,
J4 ,5 9.5 Hz, H-400), 3.39 (t, 1H, J3
, J4
9.5 Hz, H-4000), 3.05 (dd,
00 00
000,4000
000,5000
1H, J1,2 3.5 Hz, J2,3 9.5 Hz, H-2), 2.11, 2.05, 2.02 (3s, 9H, 3ꢃ COCH3),
1.31 (m, 6H, 2ꢃ CeCH3), 1.04 (d, 3H, J5
6.5 Hz, CeCH3). 13C NMR
: 172.2 (COOH), 170.0, 169.9, 169.8 (3ꢃ COCH3),
0000,60000
(CDCl3, 125 MHz)
d
155.6, 150.3, 139.2, 138.4, 138.3, 138.2, 138.1, 137.7, 136.9, 128.7(2),
128.6(2), 128.5(2), 128.4(4), 128.3(5), 128.1(2), 127.9(3), 127.8(2),
127.7, 127.6(3), 127.5(2), 118.2(2), 114.7(2), 114.0 (ArC), 101.9 (C-100),
101.0 (C-1000), 100.1 (C-10), 99.0 (C-10000), 98.9 (C-1), 82.2, 80.3, 79.9,
79.2, 78.4, 75.9, 75.5(2), 75.1, 74.8, 74.4, 74.3, 72.4, 72.3, 72.2, 71.6,
71.5(2), 71.1, 69.7, 69.5, 69.2, 68.8, 66.8, 62.3, 61.6, 61.3, 55.6
(C6H4OCH3), 20.9, 20.8, 20.7 (3ꢃ COCH3), 18.1, 18, 17.2 (3ꢃCeCH3).
HRMS (ESI) (MþNa)þ, found 1614.6206. C85H97N3O27Na requires
1614.6207.
amorphous mass. ½a D25
ꢂ
þ 48 (c 0.7, MeOH); IR (KBr): 2375, 1760,
1618, 1386, 1232, 1057, 744 cmꢀ1; 1H NMR (500 MHz, CDCl3)
d: 7.06,
6.84 (2d, 4H, J 9.0 Hz, C6H4OCH3), 5.32 (m, 2H, H-1, H-100), 5.29 (s,
1H, H-1000), 5.13 (s, 1H, H-10000), 4.92 (s, 1H, H-10), 4.17 (m, 1H, H-2),
4.03 (m, 8H, H-20, H-200, H-20000, H-3, H-30, H-300, H-3000, H-30000), 3.86
(m, 3H, H-2000, H-4, H-40), 3.77e3.6 (m, 13H, H-400, H-4000, H-40000, H-5,
H-50, H-500, H-5000, H-50000, H-6, C6H4OCH3),2.06 (s, 3H, NHCOCH3),
1.26 (bd, 9H, J 6.0 Hz, (3ꢃCeCH3). 13C NMR (CDCl3, 125 MHz)
d:
175.2 (COOH), 171.1 (NHCOCH3), 156.9, 152.4, 119.6(2), 115.6(2)
(ArC), 103.4 (C-10), 102.4 (C-1000), 102.2 (C-10000), 102.1 (C-100), 99.2 (C-
1), 81.6, 79.9, 79.3, 78.2, 74.5, 74.4, 74.3, 74.1, 74, 73.4, 72.3, 72.2, 72,
71.9, 71.8, 71.1, 70.6, 70.3, 63.2, 62.2, 56.1 (C6H4OCH3), 53.9, 22.8
(NHCOCH3), 18.1, 18, 17.9 (3ꢃCeCH3). HRMS (ESI) (MþNa)þ, found
964.3273. C39H59NO25Na requires 964.3274.
4.16. 4-Methoxyphenyl
O-benzyl- -rhamnopyranosyl-(1/2)-3,4-di-O-benzyl-
rhamnopyranosyl-(1/4)-2,3-di-O-benzyl- -galactopyr-
-glucopyr-
a-L-rhamnopyranosyl-(1/2)-3,4-di-
a
-L
a-L-
a-D
anosyluronicacid-(1/3)-2-acetamido-2-deoxy-a-D
anoside (19)
Compound 18 (906 mg, 0.6 mmol) was dissolved in thioacetic
acid (10 mL) and the mixture was stirred at room temperature in
dark for 3 days, until TLC (CH2Cl2eMeOH 6:1) confirmed complete
conversion of the starting material. The solvents were evaporated
and co-evaporated with toluene. The crude residue was dissolved
in MeOH (10 mL). NaOMe in MeOH (2 mL, 0.5 M) was added to the
solution and stirred for 12 h. DOWEX 50W Hþ resin was added to
neutralize the solution. It was then filtered through a cotton plug
and the filtrate was evaporated in vacuo and the residue was pu-
rified by a short flash column using CH2Cl2eMeOH (6:1) to afford
the pentasaccharide 19 (680 mg, 81%) as white compound.
4.18. 4-Methoxyphenyl 2-O-acetyl-3,4-di-O-benzyl-
nopyranosyl-(1/4)-2,3-di-O-benzyl-6-O-(4-methoxybenzyl)-
-galactopyranosyl (1/3)-2-azido-4,6-O-benzylidene-2-
deoxy- -glucopyranoside (21)
a-L-rham-
a-D
a-D
To a mixture of disaccharide acceptor 9 (1.5 g, 1.7 mmol) and
known donor 4-tolyl 2-O-acetyl-3,4-di-O-benzyl-1-thio- -rham-
a-L
ꢀ
nopyranoside 20 (1.1 g, 2.3 mmol) in dry CH2Cl2 (20 mL), 4 A
powdered molecular sieves (1.0 g) was added and the mixture was
stirred under nitrogen atmosphere for 1 h. NIS (662 mg, 2.9 mmol)
was added to the mixture and it was cooled to 0 ꢁC. H2SO4-silica
(50 mg) was added to the reaction mixture and it was stirred for
10 min when TLC (hexane-EtOAc; 3:1) showed complete con-
sumption of acceptor 9. Et3N was added to neutralize the reaction.
The reaction mixture was diluted and filtered through a pad of
Celite. The filtrate was then successively washed with aq Na2S2O3
(2ꢃ50 mL), satd aq NaHCO3 (2ꢃ50 mL) and brine (50 mL). The
organic layer was separated, dried (Na2SO4) and evaporated in
vacuo. The crude trisaccharide thus obtained, was purified by flash
chromatography using n-hexane-EtOAc (3:1) as eluent to afford
½
a 2D5
2365, 2090, 1688, 1178, 784 cmꢀ1
ꢂ
þ 82 (c 0.7, CHCl3); Rf (CH2Cl2eMeOH, 6:1) 0.31; IR (Neat):
;
1H NMR (500 MHz, CDCl3)
d:
7.39e7.25 (m, 30H, ArH), 6.96, 6.83 (2d, 4H, J 9.0 Hz, C6H4OCH3),
5.92 (d, 1H, JNH,2 9.0 Hz, NHCOCH3), 5.41 (d, 1H, J1,2 4 Hz, H-1), 5.19
00
1.5 Hz, H-1000), 5.02 (d,1H,
00 00
000,2000
(d, 1H, J1 ,2 1.5 Hz, H-1 ), 5.11 (d,1H, J1
J1,2 1.5 Hz, H-10000), 4.86 (m, 2H, H-10, CH2Ph), 4.81 (d, 1H, J 12 Hz,
CH2Ph), 4.78 (d, 1H, J 11.5 Hz, CH2Ph), 4.67 (m, 3H, CH2Ph), 4.62 (d,
1H, J 11.5 Hz, CH2Ph), 4.59 (m, 3H, CH2Ph), 4.52 (d, 1H, J 11.5 Hz,
00 00
00 00
CH2Ph), 4.26 (m, 1H, H-2), 4.12 (dd, 1H, J1 ,2 2.0 Hz, J2 ,3 5.0 Hz, H-
200), 4.08 (s, 1H, H-2000), 4.04 (d, 1H, J1
1.5 Hz, H-20000), 3.96 (dd,
pure trisaccharide 21 (1.9 g, 92%). ½
aꢂ2D5 þ 132 (c 1.0, CHCl3); Rf (n-
0000,20000
1H, J2 ,3 2.5 Hz, J3 ,4 10.0 Hz, H-30), 3.89 (m, 2H, H-300, H-3000), 3.81
(m, 5H, H-20, H-4, H-5, H-50000, H-6a), 3.77 (s, 3H, C6H4OCH3), 3.68
(m, 6H, H-3, H-30000, H-40, H-50, H-500, H-5000), 3.58 (dd, 1H, J5,6b 5.5 Hz,
hexane-EtOAc, 3:1) 0.34; IR (neat): 2367, 1751, 1594, 1382, 1227,
0
0
0
0
1050 cmꢀ1; 1H NMR (500 MHz, CDCl3)
d: 7.43e6.82 (m, 33H, ArH),
5.61 (d, 1H, J1 ,2 4.0 Hz, H-10), 5.54 (d, 1H, J1, 2 2.5 Hz, H-1), 5.51 (s,
0
0
J6a,6b 11.5 Hz, H-6b), 3.42 (m, 2H, H-400, H-4000), 3.38 (t, 1H, J3
,
1H, CHPh), 5.48 (d, 1H, J2 ,3 2.0 Hz, H-200), 5.2 (s, 1H, H-100), 4.89 (d,
0000,40000
00 00
J3
9.5 Hz, H-40000), 2.02 (s, 3H, NHCOCH3), 1.29 (d, 3H, J5 ,6
1H, J 10.5 Hz, CH2Ph), 4.81 (d, 1H, J 11.5 Hz, CH2Ph), 4.74 (d, 1H, J
00 00
0000,40000
6.5 Hz, CeCH3), 1.21 (d, 3H, J5
6.5 Hz, CeCH3), 1.18 (d, 3H, J5
11.0 Hz, CH2Ph), 4.56 (m, 4H, H-3, H-30, CH2Ph), 4.45 (m, 3H, CH2Ph),
000,6000
0000,60000
6.0 Hz, CeCH3). 13C NMR (CDCl3, 125 MHz)
d
: 171.1 (NHCOCH3),
4.33 (t, 1H, J5 ,6 , J6a ,6b 6.5 Hz, H-6a0), 4.29 (s, 2H, CH2Ph), 4.24 (m,
0 0 0 0
170.7 (COOH), 155.5, 150, 139.3, 138.4, 138.3, 138.2(2), 137.6, 137.0,
128.7(2), 128.6(3), 128.5(4), 128.4(5), 128.3(2), 128.1(3), 127.9(2),
127.8(5), 127.7(2), 127.6, 123.5, 118.2(2), 114.8(2), 114.0 (ArC), 101.8
(C-10), 100.8 (C-10000), 100.7 (C-100), 100.3 (C-1000), 97.5 (C-1), 84.1, 80.5,
1H, H-6a), 4.14 (m, 1H, H-5), 3.98 (d, 1H, J3 ,4 9.5 Hz, H-40), 3.94 (d,
0 0
1H, J1 ,2 4.0 Hz, H-20), 3.88 (m, 2H, H-300, H-500), 3.80 (s, 3H,
C6H4OCH3), 3.76 (m, 4H, CH2C6H4OCH3, H-4), 3.71 (m, 2H, H-50, H-
0
0
0
0
0
6b), 3.67 (d, 1H, J5 ,6 6 Hz, H-6 ), 3.49 (dd, 1H, J1,2 3.0 Hz, J2,3 10.0 Hz,

6162
D. Budhadev, B. Mukhopadhyay / Tetrahedron 71 (2015) 6155e6163
00
00 00
00 00
H-2), 3.38 (t, 1H, J3 ,4 , J4 ,5 9 Hz, H-4 ), 2.06 (s, 3H, COCH3), 1.27 (d,
n-hexane-EtOAc (2.5:1) to give the pure tetrasaccharide 23 (2.0 g,
3H, J5 ,6 6.5 Hz, CeCH3). 13C NMR (CDCl3, 125 MHz)
d
: 169.7
90%). ½a 2D5
þ 76 (c 0.9, CHCl3); Rf (n-hexane-EtOAc, 2.5:1) 0.31; IR
ꢂ
00 00
(COCH3), 159.2, 155.6, 150.2, 138.7, 138.4, 138.1, 138, 136.9, 130.3,
129.5, 129.4 (2), 128.5 (3), 128.2 (4), 128, 127.9(3), 127.7, 127.5(3),
127.4, 127.3, 127.2(2), 127.1, 127, 126.4, 126.3(3), 118.2(2), 114.8(2),
113.7(2) (ArC), 102.3 (CHPh), 99.1 (C-100), 98.4 (C-1), 97.3 (C-10), 82.9,
79.8, 78, 77.9, 75.2, 74.4, 73.6, 73.1, 73, 71.7, 71.5 (2), 69.4, 68.8, 68.7,
68.6, 68.4, 62.9, 61.9, 55.6 (C6H4OCH3), 55.2 (CH2C6H4OCH3), 21.1
(COCH3), 18.1 (CeCH3). HRMS (ESI) (MþNa)þ, found 1252.4993.
(neat): 2380, 1764, 1603, 1372, 1237, 1035 cmꢀ1; 1H NMR (500 MHz,
0
0 0
CDCl3) d: 7.4e6.86 (m, 43H, ArH), 5.62 (d, 1H, J1 ,2 3.5 Hz, H-1 ), 5.53
(d, 1H, J1,2 3.5 Hz, H-1), 5.51 (s, 1H, H-2000), 5.47 (s, 1H, CHPh), 5.3 (d,
1H, J1 ,2 3.5 Hz, H-100), 4.9 (d, 2H, J 11.0 Hz, CH2Ph), 4.84 (s, 1H, H-
00 00
1000), 4.75 (2d, 2H, J 11.0 Hz, CH2Ph), 4.7 (d, 1H, J 11.5 Hz, CH2Ph), 4.64
(d, 1H, J 11.0 Hz, CH2Ph), 4.58 (m, 5H, H-3, 2ꢃ CH2Ph), 4.45 (m, 4H,
2ꢃ CH2Ph), 4.25 (m, 3H, H-30, H-5, H-6), 4.15 (t, 1H, J5 ,6a , J6a ,6b
0
0
0
0
C
70H75N3O17Na requires 1252.4994.
7.0 Hz, H-6a0), 4.08 (s, 1H, H-200), 3.96 (m, 2H, H-300, H-40), 3.9 (t, 1H,
J3,4, J4,5 9.0 Hz, H-4), 3.8 (br s, 6H, C6H4OCH3, CH2C6H4OCH3),3.76
(m, 3H, H-20, H-300, H-5000), 3.71 (m,1H, H-60), 3.65 (m, 2H, H-50, H-6),
4.19. 4-Methoxyphenyl 3,4-di-O-benzyl-
anosyl-(1/4)-2,3-di-O-benzyl-6-O-(4-methoxybenzyl)-
galactopyranosyl-(1/3)-2-azido-4,6-O-benzylidene-2-deoxy-
-glucopyranoside (22)
a-L-rhamnopyr-
00 00 00 00
a
-D-
3.47 (dd, 1H, J1,2 3.5 Hz, J2,3 10.5 Hz, H-2), 3.42 (t, 1H, J3 ,4 , J4 ,5
9.5 Hz, H-400), 3.41 (t, 1H, J3
, J4
9.5 Hz, H-4000), 2.14 (s, 3H,
000,5000
000,4000
00 00
000,6000
6.0 Hz, CeCH3), 1.15 (d, 3H, J5 ,6 5.5 Hz,
a
-D
COCH3), 1.26 (d, 3H, J5
CeCH3). 13C NMR (CDCl3, 125 MHz)
d: 169.9 (COCH3), 159.1, 157.6,
To the methanolic solution of trisaccharide 21 (1.9 g, 1.5 mmol)
155.6, 150.1, 139.0(2), 138.7, 138.6(3), 138.4(2), 138.3(2), 138.2(2),
138.1(2), 136.9(2), 129.5, 129.4, 128.4(2), 128.3(3), 128.2(3), 128.1(3),
128.1, 127.9(2), 127.8, 127.7, 127.6(2), 127.5, 127.4(2), 127.3, 127.1(2),
126.3(2), 118.2(2), 114.8(2), 113.7, 110.7 (ArC), 102.2 (CHPh), 100 (C-
100), 99.3 (C-1000), 98.4 (C-1), 97.3 (C-10), 82.9, 80.1, 77.8, 75.3, 75.2, 73,
72.9, 72.8, 72, 71.9, 71.7, 71.6, 71.4, 69, 68.8(2), 68.5, 68.2, 69,
68.8(2), 68.5, 68.2, 62.9, 61.8, 56.3 (C6H4OCH3), 55.2
(CH2C6H4OCH3), 21.1 (COCH3), 18.2, 18.1 (2ꢃ CeCH3). HRMS (ESI)
(MþNa)þ, found 1578.6512. C90H97N3O21Na requires 1578.6512.
in MeOH (20 mL), NaOMe (10 mL, 0.5M) was added. The reaction
was stirred for 12 h, as monitored by TLC (n-hexane-EtOAc 2:1).
DOWEX 50W Hþ resin was added to neutralize the reaction. The
solution was filtered and the solvents were evaporated under re-
duced pressure and the residue was purified by a flash column
using n-hexane-EtOAc (2:1) to afford the desired trisaccharide ac-
ceptor 22 (1.74 g, 95%). ½a D25
þ 64 (c 0.8, CHCl3); Rf (n-hexane-
ꢂ
EtOAc, 2:1) 0.32; IR (neat): 2373, 1762, 1579, 1373, 1241, 1057,
710 cmꢀ1 1H NMR (500 MHz, CDCl3)
; d: 7.43e6.82 (m, 33H, ArH),
5.64 (d, 1H, J1 , 2 2.5 Hz, H-10), 5.54 (d, 1H, J1, 2 3.5 Hz, H-1), 5.51 (s,
1H, CHPh), 5.28 (s, 1H, H-100), 4.86, 4.78, 4.74 (3d, 3H, J 11.0 Hz,
CH2Ph), 4.61 (d, 2H, J 11.0 Hz, CH2Ph), 4.58 (d, 1H, J2,3 3.5 Hz, H-3),
4.52 (m, 2H, CH2Ph), 4.46 (d, 2H, J 11.0 Hz, CH2Ph)0, 4.42 (d, 1H, J
4.21. 4-Methoxyphenyl 3,4-di-O-benzyl-
anosyl-(1/2)-3,4-di-O-benzyl- -rhamnopyranosyl-(1/4)-
2,3-di-O-benzyl-6-O-(4-methoxybenzyl)- -galactopyr-
anosyl-(1/3)-2-azido-4,6-O-benzylidene-2-deoxy-a-D-gluco-
pyranoside (24)
a-L-rhamnopyr-
0
0
a-L
a-D
0
0
0
0
12.5 Hz, CH2Ph), 4.33 (t,1H, J5 ,56a , J6a ,6b 6.0 Hz, H-6a ), 4.3 (s,1H, H-
30), 4.24 (dd, 1H, J5,6a 4.5 Hz, J6a, 6b 10.0 Hz, H-6a), 4.15 (m, 1H, H-5),
0
4.09 (s, 1H, H-200), 3.98 (d, 1H, J2 ,3 10.5 Hz, H-4 ), 3.91 (m, 2H, H-4,
H-500), 3.8 (m, 4H, H-20, C6H4OCH3), 3.76 (s, 3H, CH2C6H4OCH3), 3.72
(m, 2H, H-300, H-6b), 3.69 (m, 2H, H-50, H-6b0),3.49 (dd, 1H, J1,2
To a solution of the tetrasaccharide derivative 23 (2.0 g,
1.3 mmol) in MeOH (20 mL), NaOMe (2 mL, 1M) was added and the
solution was stirred at room temperature for 12 h. After neutrali-
zation with DOWEX 50W Hþ resin, the solution was filtered and the
solvents were evaporated under reduced pressure. The residue thus
obtained was purified by flash chromatography using n-hexane-
EtOAc (2:1) as eluent to afford the desired tetrasaccharide acceptor
0
0
3.5 Hz, J2,3 10 Hz, H-2), 3.45 (t, 1H, J3 ,4 , J4 ,5 9.0 Hz, H-400), 1.27 (d,
00 00
00 00
3H, J5 ,6 6.5 Hz, CeCH3). 13C NMR (CDCl3, 125 MHz)
d: 159.2, 155.6,
00 00
150.2, 138.5, 138.3, 138.1, 138.0, 136.9, 130.3, 129.5(2), 129.4,
128.4(2), 128.4(2), 128.3(3), 128.1(2), 127.9(2), 127.8(3), 127.7,
127.7(2), 127.6, 127.5, 127.3, 127.1(2), 126.4(2), 118.2(2), 114.7(2),
113.7(2) (ArC), 102.3 (CHPh), 100.7 (C-100), 98.4 (C-1), 97.2 (C-10),
82.9, 79.9, 79.6, 77.8, 75.1, 74.9, 74, 73.1, 73, 71.7, 71.6, 71.5, 69.5,
68.8, 68.7, 68.5, 68.1, 62.9, 61.9, 55.6 (C6H4OCH3), 55.2
(CH2C6H4OCH3), 18 (CeCH3). HRMS (ESI) (MþNa)þ, found
1210.4888. C68H73N3O16Na requires 1210.4889.
24 (1.86 g, 96%). ½a D25
þ 104 (c 0.8, CHCl3); Rf (n-hexane-EtOAc, 2:1)
ꢂ
0.31; IR (neat): 2356, 1731, 1587, 1378, 1233, 1025 cmꢀ1
;
1H NMR
0
0
(500 MHz, CDCl3)
d
: 7.38e6.85 (m, 43H, ArH), 5.6 (d, 1H, J1 ,2 3.5 Hz,
H-10), 5.52 (d, 1H, J1,2 3.5 Hz, H-1), 5.47 (s, 1H, CHPh), 5.3 (d, 1H, J1 ,2
00 00
2.5 Hz, H-100), 4.96 (d, 1H, J1 3.5 Hz, H-1000), 4.87 (d, 1H, J 10.5 Hz,
000,2000
CH2Ph), 4.86 (d, 1H, J 10.5 Hz, CH2Ph), 4.7 (m, 3H, CH2Ph), 4.59 (m,
5H, H-3, CH2Ph), 4.5 (d, 1H, J 11.0 Hz, CH2Ph), 4.43 (m, 2H, CH2Ph),
4.36 (d, 1H, J 11.0 Hz, CH2Ph), 4.25 (m, H-30, H-5, H-6), 4.09 (br s0,02H,
4.20. 4-Methoxyphenyl 2-O-acetyl-3,4-di-O-benzyl-
nopyranosyl (1/2)-3,4-di-O-benzyl- -rhamnopyranosyl-
(1/4)-2,3-di-O-benzyl-6-O-(4-methoxybenzyl)- -gal-
actopyranosyl-(1/3)-2-azido-4,6-O-benzylidene-2-deoxy-
-glucopyranoside (23)
a-L-rham-
0
H-200, H-2000), 3.95 (t,1H, J3 ,4 , J4 ,5 5.0 Hz, H-4 ), 3.87 (m, 2H, H-3 , H-
4), 3.79, 3.78 (2s, 6H, C6H4OCH3, CH2C6H4OCH3), 3.77 (m, 4H, H-20,
H-50, H-500, H-5000), 3.73 (m, 2H, H-3000, H-60), 3.63 (m, 2H, H-6, H-60),
0
0
0
0
a-L
a-D
a
-
3.44 (m, 2H, H-2, H-400), 3.38 (t, 1H, J3
, J4
9.5 Hz, H-4000), 1.26
000,5000
000,4000
D
00 00
000,6000
000,6000
(d, 3H, J5 ,6 5.5 Hz J5
6.5 Hz, CeCH3), 1.12 (d, 3H, J5
6.0 Hz,
A mixture of acceptor 22 (1.74 g, 1.5 mmol), and another
CeCH3). 13C NMR (CDCl3, 125 MHz)
d: 159.1, 157.6, 155.6, 150.2, 139,
ꢀ
equivalent of known donor 20 (937 mg, 1.9 mmol) and MS 4 A
(1.0 g) in dry CH2Cl2 (20 mL) was stirred under nitrogen for one
hour. To the reaction mixture, NIS (557 mg, 2.5 mmol) was added
and the mixture was cooled to 0 ꢁC followed by addition of H2SO4-
silica (25 mg). The mixture was allowed to stir at the same tem-
perature for 10 min when TLC (n-hexane-EtOAc; 3:2) showed
complete consumption of acceptor 22. Et3N was added to neu-
tralize the reaction. The reaction mixture was immediately filtered
through a pad of Celite. The filtrate was diluted with CH2Cl2 and
was successively washed with Na2S2O3 (2ꢃ50 mL), NaHCO3
(2ꢃ50 mL) and brine (50 mL). The organic layers were together
collected, dried (Na2SO4) and evaporated in vacuo. The crude
product thus obtained, was purified by flash chromatography using
138.7(2), 138.5, 138.4, 138.3 (2), 138.2, 138.1, 136.9, 129.5, 129.4(2),
128.5(2), 128.4(4), 128.3(4), 128.2(2), 128.0(2), 127.9(3), 127.8(3),
127.6(2), 127.5, 127.3, 127.1(2), 126.3(2), 118.2(4), 114.8(2), 113.7(2),
110.7 (ArC), 100.2 (CHPh), 100.7 (C-1000), 100 (C-100), 98.4 (C-1), 97.3
(C-10), 85.7, 82.9, 80.2, 80.1, 79.7, 79.4, 75.3, 75.2, 75.1, 75, 73.2, 73,
72.8, 72.1(2), 72, 71.9, 71.8, 71.4, 69.4, 68.8, 68.5, 67.8, 62.9, 61.9, 56.3
(C6H4OCH3), 55.2 (CH2C6H4OCH3), 18.2 (2ꢃ CeCH3). HRMS (ESI)
(MþNa)þ, found 1536.6406. C88H95N3O20Na requires 1536.6407.
Acknowledgements
D.B. is thankful to UGC, New Delhi for Senior Research Fellow-
ship. This work is funded by the Scientific and Engineering

D. Budhadev, B. Mukhopadhyay / Tetrahedron 71 (2015) 6155e6163
6163
8. (a) Christensen, B. E.; Clarke, R. A. Ind. Eng. Chem. Anal. Ed. 1945, 17, 334e335;
(b) Freed, M.; Wynne, A. M. Ind. Eng. Chem. Anal. Ed. 1936, 8, 278e279.
9. Sau, A.; Panchadhayee, R.; Ghosh, D.; Mishra, A. K. Carbohydr. Res. 2012, 352,
18e22.
Research Board (SERB), New Delhi through the grant SB/S1/OC-48/
2013 to BM.
10. (a) Dasgupta, S.; Roy, B.; Mukhopadhyay, B. Carbohydr. Res. 2006, 341,
2708e2713; (b) Pal, K. B.; Mukhopadhyay, B. Carbohydr. Res. 2013, 379, 26e29;
(c) Verma, P. R.; Mukhopadhyay, B. RSC Adv. 2013, 3, 201e207.
11. Ngoje, G.; Li, Z. Org. Biomol. Chem. 2013, 11, 1879e1886.
Supplementary data
Supplementary data (Copies of the 1H and 13C NMR spectra of
new compounds) associated with this article can be found in the
online version at http://dx.doi.org/10.1016/j.tet.2015.06.095.
ꢁ
12. Zemplen, G. Ber. Dtsch. Chem. Ges. 1926, 59, 1254e1266.
13. Ghosh, T.; Misra, A. K. Carbohydr. Res. 2012, 362, 8e12.
14. Cumpstey, I.; Fairbanks, A. J.; Redgrave, A. J. Tetrahedron 2004, 60, 9061e9074.
15. Classon, B.; Garegg, P. J.; Samuelson, B. Acta Chem. Scand. Ser. B 1984, 38,
419e422.
References and notes
ꢁ
ꢁ
ꢁ
ꢁ
16. Kerekgyarto, J.; Szurmai, Z.; Liptak, A. Carbohydr. Res. 1993, 245, 65e80.
17. Das, R.; Mahanti, M.; Mukhopadhyay, B. Carbohydr. Res. 2014, 399, 15e20.
18. Oikawa, Y.; Yoshioka, T.; Yonemitsu, O. Tetrahedron Lett. 1982, 23, 885e888.
1. (a) Dalben, M.; Varkulja, G.; Basso, M.; Krebs, V. L.; Gibelli, M. A.; van der
Heijden, I.; Rossi, F.; Duboc, G.; Levin, A. S.; Costa, S. F. J. Hosp. Infect. 2008, 70,
ꢁ
19. van den Bos, L. J.; Codee, J. D. C.; van der Toorn, J. C.; Boltje, T. J.; van Boom, J. H.;
ꢁ
ꢁ
~
7e14; (b) Fernandez, A.; Pereira, M. J.; Suarez, J. M.; Poza, M.; Trevino, M.;
Overkleeft, H. S.; van der Marel, G. A. Org. Lett. 2004, 6, 2165e2168.
20. Medgyes, G.; Jerkovich, G.; Kuszmann, J. Carbohydr. Res. 1989, 186, 225e239.
21. Nakahara, Y.; Ogawa, T. Carbohydr. Res. 1996, 292, 71e81.
22. Rajput, V. K.; Mukhopadhyay, B. J. Org. Chem. 2008, 73, 6924e6927.
23. Perrin, D. D.; Amarego, W. L.; Perrin, D. R. Purification of Laboratory Chemicals;
Pergamon: London, 1996.
24. For the use of H2SO4-silica in various carbohydrate reactions, see: (a) Rajput, V.
K.; Roy, B.; Mukhopadhyay, B. Tetrahedron Lett. 2006, 47, 6987e6991; (b) Rajput,
V. K.; Mukhopadhyay, B. Tetrahedron Lett. 2006, 47, 5939e5941; (c) Mukho-
padhyay, B. Tetrahedron Lett. 2006, 47, 4337e4341; (d) Roy, B.; Mukhopadhyay,
B. Tetrahedron Lett. 2007, 48, 3783e3787.
ꢁ
ꢁ
Villalon, P.; Saez-Nieto, J. A.; Regueiro, B. J.; Villanueva, R.; Bou, G. J. Clin. Mi-
crobiol. 2011, 49, 822e828.
2. Bush, K. Curr. Opin. Microbiol. 2010, 13, 558e564.
3. Moule, A. L.; Kuhl, P. M. D.; Galbraith, L.; Wilkinson, S. G. Carbohydr. Res. 1989,
186, 287e293.
4. Perepelov, A. V.; Wang, M.; Filatov, A. V.; Guo, X.; Shashkov, A. S.; Wang, L.;
Knirel, Y. A. Carbohydr. Res. 2014, 387, 10e13.
5. Cao, H.; Huang, S.; Cheng, J.; Li, Y.; Muthana, S.; Son, B.; Chen, X. Carbohydr. Res.
2008, 343, 2863e2869.
6. Huang, L.; Huang, X. Chem.dEur. J. 2007, 13, 529e540.
7. Thollas, B.; Biosset, C. Synlett 2007, 1736e1738.