Concise synthesis of the trisaccharide repeating unit of the O-polysaccharide from Aeromonas hydrophila A19 (O:14)

Article abstract of DOI:10.1016/j.carres.2013.06.009

Chemical synthesis of the trisaccharide repeating unit of the O-polysaccharide from Aeromonas hydrophila A19 (O:14) is reported in the form of its p-methoxyphenyl glycosides. Suitably protected monosaccharide synthons were prepared either by literature pr

Full text of DOI:10.1016/j.carres.2013.06.009

Carbohydrate Research 379 (2013) 26–29
Contents lists available at SciVerse ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
Note
Concise synthesis of the trisaccharide repeating unit of the
O-polysaccharide from Aeromonas hydrophila A19 (O:14)
⇑
Kumar Bhaskar Pal, Balaram Mukhopadhyay
Department of Chemical Sciences, Indian Institute of Science Education and Research-Kolkata, 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:
Received 1 May 2013
Received in revised form 11 June 2013
Accepted 12 June 2013
Available online 22 June 2013
Chemical synthesis of the trisaccharide repeating unit of the O-polysaccharide from Aeromonas hydrophila
A19 (O:14) is reported in the form of its p-methoxyphenyl glycosides. Suitably protected monosaccharide
synthons were prepared either by literature procedure or by strategies developed in house. Stereoselec-
tive glycosylations were accomplished by the activation of thioglycosides using N-iodosuccinimide in
conjunction with H2SO4–silica in good to excellent yields.
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
Bacterial oligosaccharides
Glycosylation
H2SO4–silica
Bacterial O-polysaccharide (O-antigen) is important for various
host–pathogen interaction mechanisms such as adhesion to the
epithelial cells, resistance to the antimicrobial compounds and
immunostimulatory activities. Thus, the repeating unit of the O-
polysaccharide is of particular interest to elucidate the exact bio-
logical activities they are involved in. Aeromonas hydrophila is a
Gram-negative mesophilic motile bacterium of the family Aeromo-
nadaceae.1 Initial understanding indicated that they are important
pathogens for fish and other cold-blooded species.2 However, in re-
cent times it has been established that the genus Aeromonas is also
responsible for various human infections in both immuno-compe-
tent like gastroenteritis and wound infection and immuno-com-
promised patients. It can lead to grave diseases like septicemia.3–
is suitable for the a
-glycosylation due to remote participation.14
The use of H2SO4–silica as an alternative to the traditional Lewis
acid promoters like TfOH15 or TMSOTf16 was found to be beneficial.
The similar glycosylation reactions promoted by TfOH and TMSOTf
afforded the desired disaccharide in 75% and 81% yields respec-
tively. The solid promoter is easy to handle and can be weighed di-
rectly as required. It is devoid of toxic fumes associated with TfOH
or TMSOTf and very stable at room temperature. The desiccant
property of silica gel is also advantageous to maintain the dry con-
dition in a glycosylation reaction. Further, regioselective opening of
the benzylidene acetal of the disaccharide 5 using Et3SiH in the
presence of BF3ꢁEt2O17 at 0 °C furnished the disaccharide acceptor
6 in 83% yield. Then, the disaccharide acceptor 6 was glycosylated
5
Out of the 24 species belonging to the genus Aeromonadaceae,
with the known p-tolyl 2,3,4-tri-O-acetyl-1-thio-a-L-rhamnopyr-
only three (A. hydrophila, A. caviae and A. veronii bv. Sobria) are
found in 85% of human infections and clinical isolates.6 Recently,
Corsaro et al.7 reported the structure of the O-polysaccharide iso-
lated from A. hydrophila A19 (O:14) that has a trisaccharide repeat-
anoside (7)18 using NIS in the presence of H2SO4–silica afforded
the trisaccharide 8 in 84% yield. Hydrogenolysis of the benzyl
groups using H2 in the presence of Pd–C as catalyst using the flow
hydrogenation assembly (H-CubeÒ, ThalesNano, Hungary) afforded
the trisaccharide triol 9 in 81% yield. Finally, Zemplén de-O-acety-
lation using NaOMe in MeOH furnished the target trisaccharide, p-
ing unit containing two
a-D-glucose and one a-L-rhamnose
moieties. In this communication we report the chemical synthesis
of the trisaccharide repeating unit in the form of its p-methoxy-
phenyl glycoside (1, Fig. 1).
The known p-tolyl 2,3-di-O-benzyl-1-thio-b-d-glucopyranoside
(3)8 was acetylated using Ac2O in pyridine to afford the corre-
sponding diacetate compound 4 in 93% yield. It was then glycosyl-
ated with the known acceptor 2 using NIS in the presence of
H2SO4–silica9–13 at ꢀ40 °C to furnish the 1,2-cis disaccharide 5 in
89% isolated yield. The particular donor having 6-O-acetyl group
methoxyphenyl 4-O-(
(1?2)-b- -glucopyranoside (1) in 78% yield over two steps
(Scheme 1).
In conclusion, we have developed a concise strategy for the syn-
a-L-rhamnopyranosyl)-a-D-glucopyranosyl-
D
thesis of the trisaccharide repeating unit of the O-polysaccharide
isolated from Aeromonas hydrophila A19 (O:14) in the form of its
p-methoxyphenyl glycoside. Required glycosylations were accom-
plished by the activation of thioglycosides using N-iodosuccini-
mide in conjunction with H2SO4–silica in good to excellent yields
with absolute stereoselectivity. The strategy developed is capable
to achieve the target oligosaccharide in good quantity that leaves
⇑
Corresponding author. Mobile: +91 9748261742; fax: +91 33 23347425.
E-mail address: sugarnet73@hotmail.com (B. Mukhopadhyay).
0008-6215/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.carres.2013.06.009

K. B. Pal, B. Mukhopadhyay / Carbohydrate Research 379 (2013) 26–29
27
under reduced pressure resulting in free flowing H2SO4–silica that
was dried at 110 °C for 3 h and used for the reactions.
3)-α-L-Rhap-(1
4)-α-D-Glcp-(1
2
OH
O
1.3. p-Tolyl 4,6-di-O-acetyl-2,3-di-O-benzyl-1-thio-b-D-
glucopyranoside (4)
1
α-D-Glcp
OMP
OH
O
HO
O
Me
HO
O
To a solution of p-tolyl 2,3-di-O-benzyl-1-thio-b-D-glucopyran-
OH
OH
1
HO
oside (3) (3.0 g, 6.4 mmol) in dry pyridine (20 mL), Ac2O (15 mL)
was added and the solution was stirred at room temperature for
2 h when TLC (n-hexane–EtOAc; 2:1) showed complete conversion
of the starting material to a faster moving compound. Then the sol-
vents were evaporated in vacuo and co-evaporated with toluene.
The residue was purified by flash chromatography using n-hex-
ane–EtOAc (2:1) as eluent to afford pure compound 4 (3.3 g, 93%)
OH
O
HO
Figure 1. Structure of the repeating unit and the target trisaccharide 1.
the scope for further utilization of the molecule in vaccine
designing.
as amorphous white mass. ½a D25
ꢂ
+128 (c 1.0, CHCl3). 1H NMR (CDCl3,
500 MHz) d: 7.33–7.12 (m, 14H, ArH), 5.04 (t, 1H, J3,4, J4,5 10.0 Hz,
H-4), 4.92, 4.83, 4.72, 4.65 (4d, 4H, AB system, J 11.0 Hz, CH2Ph),
4.61 (d, 1H, J1,2 9.5 Hz, H-1), 4.23 (dd, 1H, J5,6a 5.5 Hz, J6a,6b
12.0 Hz, H-6a), 4.13 (dd, 1H, J5,6b 2.0 Hz, J6a,6b 12.0 Hz, H-6b), 3.68
(t, 1H, J2,3, J3,4 9.5 Hz, H-3), 3.58 (m, 1H, H-5), 3.54 (t, 1H, J2,3, J3,4
9.5 Hz, H-2), 2.36 (s, 3H, SC6H4CH3), 2.09, 1.93 (2s, 6H, 2 ꢃ COCH3).
13C NMR (CDCl3, 125 MHz) d: 170.6, 169.5 (2 ꢃ COCH3), 138.0,
137.9, 137.8, 132.9(3), 129.6(2), 129.2, 128.4(3), 128.2(2), 127.9,
127.7(3) (ArC), 87.7 (C-1), 83.8, 80.5, 75.8, 75.4, 75.3, 69.7, 62.6
(C-6), 21.04, 20.7 (2 ꢃ COCH3), 20.7 (SC6H4CH3). HRMS calcd for
1. Experimental
1.1. General methods
All solvents and reagents were dried prior to use according to
literature methods.19 The commercially purchased reagents were
used without any further purification unless mentioned otherwise.
Dichloromethane wad 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 detec-
tion by fluorescence followed by charring after immersion in 10%
ethanolic solution of H2SO4. Flash chromatography was performed
with Silica Gel 230–400 mesh. Optical rotations were measured on
sodium D-line at ambient temperature. 1H and 13C NMR spectra
were recorded on Bruker AVANCE 500 MHz spectrometer.
C
31H34O7SNa (M+Na)+: 573.1923, found: 573.1919.
1.4. p-Methoxyphenyl-4,6-di-O-acetyl-2,3-di-O-benzyl-b-D-
glucopyranosyl-(1?2)-4,6-O-benzylidene-3-O-benzoyl-b-D-
glucopyranoside (5)
A mixture of acceptor 2 (1.0 g, 2.1 mmol), donor 4 (1.5 g,
2.7 mmol) and MS 4 Å (2.0 g) in dry CH2Cl2 (20 mL) was stirred un-
der nitrogen atmosphere for 30 min at ꢀ40 °C. Then NIS (790 mg,
3.5 mmol) was added followed by H2SO4–silica (100 mg) and the
mixture was stirred at ꢀ40 °C for another 30 min when TLC (n-hex-
ane–EtOAc; 2:1) showed complete consumption of the acceptor.
1.2. Preparation of H2SO4–silica
To slurry of silica gel (10 g, 200–400 mesh) in dry diethyl ether
(50 mL) was added commercially available concentrated H2SO4
(1 mL) and the slurry shaken for 5 min. The solvent was evaporated
O
Ph
O
O
O
OR
OMP
OBn
BzO
O
Ph
O
NIS
O
RO
O
+
STol
OMP
BnO
BzO
H2SO4-silica
89%
OBn
OAc
OBn
OH
2
O
3 R = H
Ac2O, Py
93%
4 R = Ac
AcO
5
STol
OBn
O
Me
AcO
BnO
O
O
HO
OMP
OBn
O
OMP
OBn
BzO
BzO
AcO
H2, Pd-C
81%
OAc
OAc
7
O
Me
O
O
Et3SiH
AcO
NIS
OBn
BF3.Et2O
83%
AcO
OBn
OAc
OAc
H2SO4-silica
OAc
O
O
84%
6
8
AcO
OH
OH
O
O
OMP
OH
O
OMP
OH
BzO
O
HO
O
Me
O
O
Me
HO
NaOMe
O
AcO
OH
OAc
MeOH
96%
AcO
OH
OH
HO
OAc
O
OH
O
9
AcO
1
HO
Scheme 1. Synthesis of the trisaccharide 1.

28
K. B. Pal, B. Mukhopadhyay / Carbohydrate Research 379 (2013) 26–29
The mixture was filtered through a pad of CeliteÒ and the filtrate
was washed successively with aq Na2S2O3 (2 ꢃ 30 mL), saturated
NaHCO3 (2 ꢃ 30 mL) and H2O (30 mL). The organic layer was col-
lected, dried (Na2SO4) and filtered. The solvent was evaporated in
vacuo and the residue was purified by flash chromatography using
n-hexane–EtOAc (2.5:1) as eluent to afford pure disaccharide 5
washed successively with aq Na2S2O3 (2 ꢃ 30 mL), saturated
NaHCO3 (2 ꢃ 30 mL) and H2O (30 mL). The organic layer was col-
lected, dried (Na2SO4) and filtered. The solvent was evaporated in
vacuo and the crude residue thus obtained was purified by flash
chromatography using n-hexane–EtOAc (2:1) as eluent to afford
pure trisaccharide 7 (1.1 g, 84%) as white foam. ½a D25
ꢂ
+97 (c 0.9,
(1.7 g, 89%) as white amorphous mass. ½a D25
ꢂ
+103 (c 0.9, CHCl3).
CHCl3). 1H NMR (CDCl3, 500 MHz) d: 8.07–6.78 (m, 24H, ArH),
1H NMR (CDCl3, 500 MHz) d: 8.04–6.80 (m, 24H, ArH), 5.84 (t,
5.76 (d, 1H, J1 ,2 3.5 Hz, H-10), 5.74 (t, 1H, J2,3, J3,4 10.5 Hz, H-3),
0
0
1H, J2,3, J3,4 9.5 Hz, H-3), 5.72 (d, 1H, J1 ,2 3.5 Hz, H-10), 5.54 (s,
5.20 (d, 1H, J1,2 7.5 Hz, H-1), 5.18 (dd, 1H, J1 ,2 1.5 Hz, J2 ,3
0
0
00 00
00 00
1H, CHPh), 5.38 (d, 1H, J1,2 7.5 Hz, H-1), 4.85 (t, 1H, J3 ,4 , J4 ,5
3.0 Hz, H-200), 5.14 (dd, 1H, J2 ,3 3.0 Hz, J3 ,4 10.0 z, H-300), 4.92
0
0
0
0
00 00
00 00
9.5 Hz, H-40), 4.83, 4.57, 4.54, 4.49 (4d, 4H, J 11.5 Hz, 2 ꢃ CH2Ph),
4.40 (m, 1H, H-5), 4.22 (dd, 1H, J1,2 7.5 Hz, J2,3 9.5 Hz, H-2), 3.88
(t, 1H, J3,4, J4,5 9.5 Hz, H-4), 3.86–3.78 (m, 3H, H-30, H-6a, H-6b),
(d, 1H, J1 ,2 1.5 Hz, H-100), 4.89 (t, 1H, J3 ,4 , J4 ,5 10.0 Hz, H-400),
00 00
00 00
00 00
0
0
0
0
4.80 (d, 1H, J 11.0 Hz, CH2C6H5), 4.79 (t, 1H, J3 ,4 , J4 ,5 9.0 Hz, H-
40), 4.54 (m, 5H, CH2C6H5), 4.21 (t, 1H, J3,4, J4,5 9.5 Hz, H-4), 4.13
3.77 (s, 3H, OC6H4OCH3), 3.72 (m, 1H, H-50), 3.67 (dd, 1H, J5 ,6a
(t, 1H, J1,2, J2,3 7.5 Hz, H-2), 3.87 (dd, 1H, J5 ,6a 3.5 Hz, J6a ,6b
0
0
0
0
0
0
2.0 Hz, J6a ,6b 12.5 Hz, H-60a), 3.58 (dd, 1H, J5 ,6b 3.5 Hz, J6a ,6b
11.5 Hz, H-60a), 3.81 (dd, 1H, J5 ,6b 1.0 Hz, J6a ,6b 11.5 Hz, H-60b),
3.77 (s, 3H, C6H4OCH3), 3.77–3.68 (m, 3H, H-30, H-5, H-50), 3.61
(m, 2H, H-500, H-6a), 3.56 (dd, 1H, J5,6b 4.5 Hz, J6a,6b 13.0 Hz, H-6b),
0
0
0
0
0
0
0
0
0
0
12.5 Hz, H-60b), 3.54 (dd, 1H, J1 ,2 3.5 Hz, J3 ,4 9.5 Hz, H-20), 2.02,
1.52 (s, 6H, 2 ꢃ COCH3). 13C NMR (CDCl3) d: 170.6, 169.3
(2 ꢃ COCH3), 165.1 (COPh), 155.6, 149.9, 138.4, 137.5, 136.7,
133.5, 129.8(2), 128.6(2), 128.5(2), 128.4(3), 128.3(2), 128.2(3),
128.1(3), 126.1(3), 117.5(2), 114.8(2) (ArC), 101.7 (C-1), 101.4
(CHPh), 95.5 (C-10), 79.0, 78.6, 78.1, 75.2, 74.6, 73.0, 72.3, 68.8,
68.5, 67.7, 66.3, 61.4, 55.6 (C6H4OCH3), 20.7, 20.4 (2 ꢃ COCH3).
HRMS calcd for C51H52O15Na (M+Na)+: 927.3204, found: 927.3207.
0
0
0
0
3.52 (dd, 1H, J1 ,2 3.5 Hz, J2 ,3 9.5 Hz, H-20), 2.03, 2.01, 1.96, 1.93,
1.47 (5s, 15H, 5 ꢃ COCH3). 13C NMR (CDCl3) d: 171.0, 170.1,
170.0, 169.8, 169.2 (5 ꢃ COCH3), 165.1 (COPh), 155.4, 150.2,
138.5, 137.9, 137.6, 133.5, 129.9(2), 129.8, 128.4(2), 128.3(3),
128.2(3), 128.0(3), 127.5(2), 127.4(4), 117.6(2), 114.7(2) (ArC),
101.3 (C-1), 99.2 (C-100), 95.1 (C-10), 79.0, 78.0, 77.2, 75.1, 74.5,
74.3, 73.9, 73.1, 72.8, 70.5, 69.8, 68.8, 68.6, 68.1, 67.7, 67.4, 61.3,
55.6 (C6H4OCH3), 20.8, 20.7, 20.6(2), 20.4 (5 ꢃ COCH3), 16.9 (C-
CH3). HRMS calcd for C63H70O22Na (M+Na)+: 1201.4256, found:
1201.4253.
0
0
0
0
1.5. p-Methoxyphenyl-4,6-di-O-acetyl-2,3-di-O-benzyl-b-D-
glucopyranosyl-(1?2)-6-O-benzyl-3-O-benzoyl-b-D-
glucopyranoside (6)
To a stirred solution of compound 5 (1.5 g, 1.65 mmol) and Et3-
SiH (3.2 mL, 19.8 mmol) in dry CH2Cl2 (20 mL), BF3.Et2O (420 L,
1.7. p-Methoxyphenyl-4,6-di-O-acetyl-b-
(1?2)-3-O-benzoyl-4-O-(2,3,4-tri-O-acetyl-
rhamnopyranosyl)-b- -glucopyranoside (9)
D-glucopyranosyl-
l
a-L-
3.3 mmol) was added at 0 °C and the mixture was allowed to stir
for 2 min when TLC (n-hexane–EtOAc; 2:1) showed complete con-
version of the starting material to a slower moving spot. The mix-
ture was washed successively with H2O (2 ꢃ 30 mL), saturated
NaHCO3 (2 ꢃ 30 mL) and brine (30 mL). The organic layer was col-
lected, dried (Na2SO4) and filtered. The solvent was evaporated in
vacuo and the residue was purified by flash chromatography using
n-hexane–EtOAc (2:1) as eluent to afford pure disaccharide accep-
D
A
dilute solution of the protected trisaccharide 8 (1.0 g,
0.8 mmol) in MeOH (100 mL) containing AcOH (0.5 mL) was
passed through the 10% Pd–C cartridge of a flow hydrogenation
assembly (H-cubeÒ, Thales Nano, Hungary) and the process was re-
peated three times for complete removal of the benzyl ethers. The
solvents were evaporated in vacuo and the residue was purified by
flash chromatography using CH2Cl2–MeOH (8:1) as eluent to afford
tor 6 (1.25 g, 83%) as colourless foam. ½a D25
ꢂ
+117 (c 1.0, CHCl3). 1H
NMR (CDCl3, 500 MHz) d: 8.07–6.77 (m, 24H, ArH), 5.77 (d, 1H,
pure compound 9 (620 mg, 81%) as white foam. ½a D25
ꢂ
+123 (c 0.8,
J1 ,2 3.5 Hz, H-10), 5.59 (t, 1H, J2,3, J3,4 9.5, H-3), 5.26 (d, 1H, J1,2
CHCl3). 1H NMR (CDCl3, 500 MHz) d: 8.10–6.82 (m, 9H, ArH), 5.60
0
0
8.0 Hz, H-1), 5.85 (t, 1H, J3 ,4 , J4 ,5 10.0 Hz, H-40), 4.80 (d, 1H, J
11.5 Hz, CH2Ph), 5.54 (m, 5H, CH2Ph), 4.16 (dd, 1H, J1,2 8.0 Hz, J2,3
9.5 Hz, H-2), 3.99 (t, 1H, J3,4, J4,5 9 Hz, H-4), 3.95–3.70 (m, 6H, H-
30, H-5, H-50, H-6a, H-6a0 , H-6b0 ), 3.76 (s, 3H, OC6H4OCH3), 3.63 (dd,
(t, 1H, J2,3, J3,4 9.5 Hz, H-3), 5.51 (d, 1H, J1 ,2 3.5 Hz, H-10), 5.13
0
0
0
0
0
0
(dd, 1H, J1 ,2 2.0 Hz, J2 ,3 3.5 Hz, H-200), 5.10 (dd, 1H, J2 ,3 3.5 Hz,
00 00
00 00
00 00
00 00
J3 ,4 10.0 Hz, H-300), 5.07 (d, 1H, J1,2 8.0 Hz, H-1), 4.95 (d, 1H, J1 ,2
00 00
1.5 Hz, H-100), 4.88 (t, 1H, J3 ,4 , J4 ,5 10.0 Hz, H-400), 4.73 (t, 1H,
00 00
00 00
1H, J5,6b 4.0 Hz, J6a,6b 12.5 Hz, H-6b), 3.54 (dd, 1H, J1 ,2 3.5 Hz, J2 ,3
J3 ,4 , J4 ,5 9.5 Hz, H-40), 4.16 (t, 1H, J3,4, J4,5 9.5 Hz, H-4), 4.01 (t,
0
0
0
0
0
0
0
0
10.0 Hz, H-20), 2.98 (br s, 1H, OH), 2.04 (s, 3H, COCH3), 1.48 (s,
3H, COCH3). 13C NMR (CDCl3) d: 170.6, 169.2 (2 ꢃ COCH3), 166.1
(COPh), 155.3, 150.1, 138.3, 137.4, 133.3, 129.8(2), 129.4,
128.4(3), 128.3(2), 128.1(2), 127.9(3), 127.8, 127.7(3), 127.5(3),
127.4, 117.5(2), 114.7(2) (ArC), 101.2 (C-1), 95.3 (C-10), 79.0,
78.11, 76.1, 75.2, 74.2, 73.7, 73.4, 72.8, 71.0, 69.8, 68.8, 67.6,
61.5, 55.6 (OCH3), 20.6, 20.3 (2 ꢃ COCH3). HRMS calcd for C51H54-
O15Na (M+Na)+: 929.3360, found: 929.3356.
1H, J1,2, J2,3 9.5 Hz, H-2), 4.00 (m, 1H, H-60a), 3.89 (dd, 1H, J5 ,6b
0
0
3.0 Hz, J6a ,6b 12.0 Hz, H-6b0 ), 3.77 (s, 3H, C6H4OCH3), 3.69 (dd, 1H,
0
0
J5,6a 3.5 Hz, J6a,6b 12.5 Hz, H-6a), 3.62 (m, 5H, H-30, H-5, H-50, H-
500, H-6b), 3.49 (dd, 1H, J1 ,2 3.5 Hz, J2 ,3 9.5 Hz, H-20), 2.09, 1.99,
1.96, 1.90, 1.81 (s, 15H, 5 ꢃ COCH3), 0.61 (d, 3H, J 6.5 Hz, –CH3).
13C NMR (CDCl3) d: 170.6, 170.5, 170.1(2), 169.7 (5 ꢃ COCH3),
165.7 (COPh), 155.9, 150.3, 133.7, 129.9(2), 129.5, 128.6(2),
118.7(2), 114.8(2) (ArC), 101.9 (C-1), 98.7 (C-100), 98.2 (C-10), 76.4,
75.7, 75.3, 75.3, 72.5, 72.1, 70.4, 70.0, 69.4, 68.6, 68.1, 67.4, 61.2,
60.8, 55.6 (C6H4OCH3), 20.9, 20.7(3), 20.6 (5 ꢃ COCH3), 16.8 (CH3).
HRMS calcd for C42H52O22Na (M+Na)+: 931.2848, found: 931.2844.
0
0
0
0
1.6. p-Methoxyphenyl-4,6-di-O-acetyl-2,3-di-O-benzyl-b-
glucopyranosyl-(1?2)-6-O-benzyl-3-O-benzoyl-4-O-(2,3,4-tri-
O-acetyl- -rhamnopyranosyl)-b- -glucopyranoside (8)
D-
a
-L
D
1.8. p-Methoxyphenyl b-D-glucopyranosyl-(1?2)-4-O-(a-L-
A mixture of acceptor 6 (1.0 g, 1.1 mmol), donor 7 (570 mg,
1.4 mmol) and MS 4 Å (1.5 g) in dry CH2Cl2 (15 mL) was stirred un-
der nitrogen atmosphere for 30 min at 0 °C. Then, NIS (410 mg,
1.8 mmol) was added followed by H2SO4–silica (75 mg) and the
mixture was stirred for another 30 min when TLC (n-hexane–
EtOAc; 3:1) showed complete consumption of the acceptor. The
mixture was filtered through a pad of CeliteÒ and the filtrate was
rhamnopyranosyl)-b- -glucopyranoside (1)
D
To a solution of compound 9 (600 mg, 0.66 mmol) in MeOH
(10 mL), NaOMe (1 mL, 0.5 M in MeOH) was added and the solu-
tion was stirred at room temperature for 12 h. The solution was
neutralized by DOWEX 50 W H+ resin, filtered through a cotton
plug and the solvents were evaporated in vacuo to afford pure tar-

K. B. Pal, B. Mukhopadhyay / Carbohydrate Research 379 (2013) 26–29
29
get trisaccharide 1 (375 mg, 96%) as white amorphous mass. ½a D25
ꢂ
3. Janda, J. M.; Abbott, S. L. Clin. Microbiol. Rev. 2010, 23, 35–73.
4. Burke, V.; Robinson, J.; Gracey, J.; Petersen, D.; Partridge, K. Appl. Environ.
Microbiol. 1984, 49, 361–366.
5. Thornley, J. P.; Shaw, J. G.; Gryllos, I.; Eley, A. Rev. Med. Microbiol. 1997, 8, 61–
72.
6. Janda, J. M.; Abbott, S. L. Clin. Infect. Dis. 1998, 27, 332–344.
7. Pieretti, G.; Carillo, S.; Lanzetta, R.; Parrilli, M.; Merino, S.; Tomas, J. M.; Corsaro,
M. M. Carbohydr. Res. 2011, 346, 2519–2522.
+78 (c 0.7, MeOH). 1H NMR (CD3OD, 500 MHz) d: 7.05–6.77
(ArH), 5.42 (d, 1H, J1 ,2 3.5 Hz, H-10), 4.95 (d, 1H, J1,2 7.5 Hz, H-1),
4.86 (s, 1H, H-100), 4.08 (m, 1H, H-5), 3.95 (m, 1H, H-500), 3.86–
3.74 (m, 4H, H-200, H-50, H-6a, H-60a), 3.71–3.60 (m, 8H, H-2, H-20,
H-3, H-30, H-300, H-40, H-6b, H-6b0 ), 3.40–3.26 (m, 5H, H-4, H-400, C6-
H4OCH3), 1.23 (d, 3H, J 6.0 Hz, H-600). 13C NMR (CD3OD, 125 MHz) d:
156.8, 152.6, 119.8(2), 115.3(2) (ArC), 103.5 (C-1), 102.8 (C-100),
99.5 (C-10), 79.5, 79.0, 76.7, 75.3, 74.9, 73.7, 73.6, 73.2, 72.3, 72.1,
71.5, 70.5, 62.3 (C-6), 61.6 (C-60), 56.0 (C6H4OCH3), 17.9 (C-600).
0
0
8. Yan, M.-C.; Chen, Y.-N.; Wu, H.-T.; Lin, C.-C.; Chen, C.-T.; Lin, C.-C. J. Org. Chem.
2007, 72, 299–302.
9. Dasgupta, S.; Mukhopadhyay, B. Eur. J. Org. Chem. 2008, 34, 5770–5777.
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11. Roy, B.; Pramanik, K.; Mukhopadhyay, B. Glycoconjugate J. 2008, 25, 157–166.
12. Prashant Ranjan Verma; Mukhopadhyay, Balaram Carbohydr. Res. 2010, 345,
432–436.
Acknowledgement
13. Verma, Priya; Raj, Ritu; Roy, Bimalendu; Mukhopadhyay, Balaram Tetrahedron:
Asymmetry 2010, 21, 2413–2418.
14. Ngoje, G.; Li, Z. Org. Biomol. Chem. 2013, 11, 1879–1886.
15. Veeneman, G. H.; van Leeuwen, S. H.; van Boom, J. H. Tetrahedron Lett. 1990, 31,
1331–1334.
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768.
K.B.P. is thankful to UGC, New Delhi for junior research fellow-
ship. The work is funded by DST, New Delhi, India through SERC
Fast-Track Grant SR/FTP/CS-110/2005.
17. Debenham, S. D.; Toone, E. J. Tetrahedron: Asymmetry 2000, 11, 385–387.
18. Mukhopadhyay, B.; Kartha, K. P. R.; Russell, D. A.; Field, R. A. J. Org. Chem. 2004,
69, 7758–7760.
19. Perrin, D. D.; Amarego, W. L.; Perrin, D. R. Purification of Laboratory Chemicals;
Pergamon: London, 1996.
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