Concise synthesis of a tetra- and a trisaccharide related to the repeating unit of the O-antigen from Providencia rustigianii O34 in the form of their p-methoxyphenyl glycosides

Article abstract of DOI:10.1039/c2ra22407k

Concise synthesis of a tetra- and a trisaccharide related to the repeating unit of the O-antigen from Providencia rustigianii O34 is reported. Synthesis of the target oligosaccharides was achieved by rational protecting group manipulations on the commercially available monosaccharides followed by stereoselective glycosylations, using H₂SO₄-silica for trichloroacetimidate activation and in conjunction with N-iodosuccinimide for thioglycoside activation. The Royal Society of Chemistry.

Full text of DOI:10.1039/c2ra22407k

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Concise synthesis of a tetra- and a trisaccharide related
to the repeating unit of the O-antigen from Providencia
rustigianii O34 in the form of their p-methoxyphenyl
glycosides3
Cite this: RSC Advances, 2013, 3, 201
Prashant Ranjan Verma and Balaram Mukhopadhyay*
Concise synthesis of a tetra- and a trisaccharide related to the repeating unit of the O-antigen from
Providencia rustigianii O34 is reported. Synthesis of the target oligosaccharides was achieved by rational
protecting group manipulations on the commercially available monosaccharides followed by stereo-
selective glycosylations, using H2SO4-silica for trichloroacetimidate activation and in conjunction with
N-iodosuccinimide for thioglycoside activation.
Received 5th October 2012,
Accepted 26th October 2012
DOI: 10.1039/c2ra22407k
www.rsc.org/advances
of the target oligosaccharides and further glyco-conjugates can
be prepared with suitable aglycons, as required for the vaccine
candidates, by using well-established trichloroacetimidate
chemistry. The advantage of using a p-methoxyphenyl glyco-
side is the fact that it remains stable during routine protecting
group manipulations.
Introduction
Bacterial O-antigens are important for bacterial pathogenesis
as they are exposed at the outer surface of the bacterial cell
surface and are thus responsible for binding with the receptors
of the host cells. Consequently, they become the target for host
antibodies. Therefore, the repeating units of the bacterial
O-antigens are good targets for designing synthetic carbohy-
drate vaccines against bacterial attack.1 Since carbohydrates
are more stable than proteins, they are used in various
commonly used vaccines.2 Synthetic oligosaccharide vaccines
are also promising against diseases like influenza,3 malaria4
and cancer.5
Providencia, the genera belonging to the Proteeae tribe of
the gram-negative bacterial family Enterobacteriaceae causes
several types of enteric diseases, wound and urinary tract
infections. Providencia rustigianii is one among the six species
of the genus Providencia.6 Recently Knirel et al. reported the
detailed structure of a heptasaccharide repeating unit of the
O-antigen from P. rustigianii O34 from its lipopolysaccharide.7
Herein, we report the chemical synthesis of a tetra- and a
trisaccharide related to the heptasaccharide repeating unit of
the O-antigen from P. rustigianii O34 (Fig. 1). Syntheses of the
tetra- and trisaccharides are planned to find the immunogenic
part of the entire heptasaccharide repeating unit from P.
rustigianni O34. The oligosaccharides were synthesized in the
form of their p-methoxyphenyl glycosides. This type of glyco-
side may be cleaved selectively from the per-O-acetylated form
Results and discussion
The synthesis of the tetrasaccharide 1 commenced with the
glycosylation between known glucosamine acceptor 38 and the
trichloroacetimidate donor 49 in the presence of H2SO4-
silica.10 Reaction in CH2Cl2 at 0–5 uC afforded the desired
´
in 91% yield. Zemplen de-
b-linked disaccharide
5
O-acetylation11 of the disaccharide 5 gave the disaccharide
acceptor 6 in 96% yield. Synthesis of the L-fucose donor started
with known p-tolyl 1-thio-b-L-fucopyranoside 7.12 Reaction of 7
with 2,2-dimethoxy propane (DMP) in the presence of 10-
camphorsulfonic acid (CSA)13 resulted in the corresponding
3,4-O-isopropylidene derivative 8 in 90% yield. The 2-OH group
Indian Institute of Science Education and Research-Kolkata (IISER-K), Mohanpur
Campus, P. O. BCKV Campus Main Office, Mohanpur, Nadia 741252, India.
E-mail: sugarnet73@hotmail.com; Tel: +91 9748261742
Electronic supplementary information (ESI) available: 1H and 13C NMR spectra
3
Fig. 1 Structures of the target tetrasaccharide (1) and the trisaccharide (2).
of all new compounds. See DOI: 10.1039/c2ra22407k
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was later protected by a 4-methoxybenzyl group by using
4-methoxybenzyl chloride in the presence of NaH in DMF14 to
afford the suitably protected fucosyl donor 9 in 83% yield.
Glycosylation of donor 9 with the disaccharide acceptor 6 was
achieved by N-iodosuccinimide (NIS) in the presence of H2SO4-
silica in CH2Cl2 at 240 uC. The desired 1,2-cis linked
trisaccharide 10 was obtained in 83% yield. No trace of the
1,2-trans isomer was evident after chromatographic purifica-
tion. Further, oxidative cleavage of the 4-methoxybenzyl group
using DDQ15 gave the trisaccharide acceptor 11 in 81% yield.
Final glycosylation of the trisaccharide acceptor 11 with the
known mannosyl donor 1216 using NIS in the presence of
H2SO4-silica in CH2Cl2 at 5–10 uC afforded the fully protected
tetrasaccharide 13 in 84% yield. The N-phthalimido group was
de-protected using ethylene diamine in n-butanol17 and
sequentially acetylated using Ac2O in pyridine. Hydrolysis of
the acetals by 80% acetic acid at 80 uC18 followed by catalytic
´
hydrogenation and Zemplen de-O-acetylation gave the target
tetrasaccharide 1 in 63% yield over four steps (Scheme 1).
Synthesis of the trisaccharide 2 was started with p-methox-
yphenyl b-L-fucopyranoside 14. Reaction of 14 with DMP in the
presence of CSA in acetone furnished the corresponding 3,4-
O-isopropylidene derivative 15 in 92% yield. The 2-OH group
was benzylated using BnBr and NaH in DMF to afford fully
protected compound 16 in 90% yield. Hydrolysis of the
isopropylidene group using 80% AcOH at 80 uC afforded the
diol 17 in 94% yield. Selective protection of the 3-OH group
with the 4-methoxybenzyl group was achieved using stanny-
lene chemistry19 to give the suitably protected fucosyl acceptor
18 in 83% yield. Glycosylation of the acceptor 18 with known
glucosyl donor 1920 with NIS in the presence of H2SO4-silica
afforded the required 1,2-trans disaccharide 20 in 85% yield.
Further, oxidative cleavage of the 4-methoxybenzyl group using
DDQ gave the disaccharide acceptor 21 in 81% yield. Final
glycosylation with the trichloroacetimidate donor 22 in the
presence of H2SO4-silica afforded the fully protected trisac-
charide 23 in 80% yield. Only the 1,2-cis glycoside was evident
after chromatographic purification. The azido functionality
was converted to the desired acetamido group by treating the
trisaccharide 23 with thiolacetic acid for 48 h at room
temperature.21 Hydrolysis of the benzylidene acetal using
80% AcOH at 80 uC followed by catalytic hydrogenation and
de-O-acetylation afforded the target trisaccharide 2 in 67%
yield over four steps (Scheme 2).
Scheme 1 Synthesis of the tetrasaccharide 1.
Experimental section
General methods
Conclusion
All reagents and solvents were dried prior to use according to
standard methods.22 Commercial reagents were used without
further purification unless otherwise stated. Analytical TLC
was performed on silica gel 60-F254 (Merck) with detection by
fluorescence and/or by charring following immersion in a 10%
ethanolic solution of sulfuric acid. Flash chromatography was
performed with silica gel 230–400 mesh (Qualigens, India).
Optical rotations were measured at the sodium D-line at
ambient temperature, with a Perkin Elmer 141 polarimeter. 1H
In conclusion, we have reported the synthesis of a tetra- and a
trisaccharide related to the repeating unit of the O-antigen
from Providencia rustigianii O34. The synthesized oligosacchar-
ides are in the form of their p-methoxyphenyl glycosides. After
global de-protection and per-O-acetylation, the p-methoxyphe-
nyl group can be removed selectively and further glyco-
conjugate formation can be achieved through trichloroaceti-
midate chemistry.
202 | RSC Adv., 2013, 3, 201–207
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127.5(2), 126.2, 118.5(2), 114.5(2) (ArC), 101.5 (CHPh), 99.9 (C-
19), 97.9 (C-1), 82.9, 80.8, 77.6, 75.0, 74.9, 74.6, 74.5, 73.3, 73.2,
68.6, 68.1, 66.6, 55.6 (C6H4OCH3), 55.3 (C-2), 20.1 (COCH3).
HRMS calcd. for C57H55O14NNa (M+Na)+: 1000.3520; found:
1000.3518.
P-METHOXYPHENYL 3,4,6-TRI-O-BENZYL-B-D-GLUCOPYRANOSYL-(1 A 3)-4,
6-O-BENZYLIDENE-2-DEOXY-2-PHTHALIMIDO-B-D-GLUCOPYRANOSIDE (6). To
a solution of the disaccharide 5 (1.7 g, 1.7 mmol) in dry MeOH
(30 mL), NaOMe (3 mL, 0.5M in MeOH) was added and the
solution was stirred at room temperature for 2 h. After
neutralizing the solution with DOWEX 50W H+ resin, the
mixture was filtered and the filtrate was evaporated in vacuo.
The syrupy residue thus obtained was purified by flash
chromatography using n-hexane–EtOAc, 1 : 1 as the eluent to
afford pure disaccharide 5 (1.55 g, 96%) as a colourless glass.
1
[a]2D5 +153 (c 1.0, CHCl3). H NMR (CDCl3, 500 MHz) d: 7.66–
6.71 (m, 28H, ArH), 5.86 (d, 1H, J1,2 = 8.5 Hz, H-1), 5.61 (s, 1H,
CHPh), 4.85 (t, 1H, J2,3, J3,4 = 8.5 Hz, H-3), 4.66, 4.64 (2d, 2H, J =
11.0 Hz, CH2Ph), 4.54 (t, 1H, J1,2, J2,3 = 8.5 Hz, H-2), 4.51 (d, 1H,
J = 11.0 Hz, CH2Ph), 4.42 (dd, 1H, J5,6a = 5.5 Hz, J6a,6b = 10.5 Hz,
H-6a), 4.35 (d, 1H, J = 11.0 Hz, CH2Ph), 4.28 (d, 1H, J19,29 = 8.0
Hz, H-19), 4.16, 4.04 (2d, 2H, J = 11.0 Hz, CH2Ph),3.87 (m, 2H,
H-4, H-6b), 3.78 (m, 1H, H-5), 3.71 (s, 3H, C6H4OCH3), 3.49 (m,
2H, H-29, H-49), 3.31 (t, 1H, J29,39, J39,49 = 8.5 Hz, H-39), 3.21 (dd,
1H, J59,6a9 = 4.0 Hz, J6a9,6b9 = 10.5 Hz, H-6a9), 3.16 (m, 1H, H-59),
2.96 (dd, 1H, J59,6b9 = 1.5 Hz, J6a9,6b9 = 10.5 Hz, H-6b9), 2.94 (bs,
1H, OH). 13C NMR (CDCl3, 125 MHz) d: 155.6, 150.5, 138.6,
138.1(2), 136.4, 133.8, 131.8, 129.6, 128.4(2), 128.3(3), 128.2(2),
128.0, 127.5(2), 127.4(2), 126.4(2), 123.5, 118.6(2), 114.5(2)
(ArC), 102.3 (C-19), 102.1 (CHPh), 98.1 (C-1), 84.1, 80.7, 77.1,
76.9, 75.1, 74.8, 74.7, 72.8, 72.6(2), 68.7, 68.5, 66.2, 55.9 (C-2),
55.6 (C6H4OCH3). HRMS calcd. for C55H53O13NNa (M+Na)+:
958.3415; found: 958.3418.
Scheme 2 Synthesis of the trisaccharide 2.
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.
P-TOLYL 3,4-O-ISOPROPYLIDENE-1-THIO-B-L-FUCOPYRANOSIDE (8). To a
mixture of compound 7 (3.0 g, 11.1 mmol) in acetone (30 mL),
was added 2,2-DMP (2.7 mL, 22.2 mmol), followed by CSA (50
mg), and the mixture was stirred at room temperature for 3 h,
after which TLC (n-hexane–EtOAc, 2 : 1) showed complete
conversion of the starting material to a faster-moving spot. The
solution was neutralized with Et3N and evaporated in vacuo.
The residue was purified by flash chromatography using
n-hexane–EtOAc, 2 : 1, to afford pure compound 8 (3.1 g, 90%)
as a light yellow glass. [a]2D5 +155 (c 1.1, CHCl3). 1H NMR
(CDCl3, 500 MHz) d: 7.44, 7.12 (2d, 4H, J = 6.5 Hz, ArH), 4.35 (d,
1H, J1,2 = 9.5 Hz, H-1), 4.02 (m, 2H, H-3, H-4), 3.84 (m, 1H,
H-5), 3.51 (dd, 1H, J1,2 = 9.5 Hz, J2,3 = 8.0 Hz, H-2), 2.53 (bs, 1H,
OH), 2.32 (s, 3H, S-C6H4CH3), 1.42, 1.33 (2s, 6H, 2 6
isopropylidene-CH3), 1.41 (d, 3H, J5,6 = 6.5 Hz, H-6). 13C
NMR (CDCl3, 125 MHz) d: 138.2, 133.1(2), 129.7(2), 128.2,
109.8 (isopropylidene-C), 88.1 (C-1), 79.0, 76.3, 72.7, 71.3, 28.1,
26.3 (2 6 isopropylidene-CH3), 21.1 (SC6H4CH3), 16.9 (C-6).
HRMS calcd. for C16H22O4SNa (M+Na)+: 333.1136; found:
333.1139.
P-METHOXYPHENYL 2-O-ACETYL-3,4,6-TRI-O-BENZYL-B-D-GLUCOPYRANO
SYL-(1
A 3)-4,6-O-BENZYLIDENE-2-DEOXY-2-PHTHALIMIDO-B-D-GLUCOPY
RANOSIDE (5). A mixture of the acceptor 3 (1.0 g, 2.0 mmol),
donor 4 (2.5 g, 4.0 mmol) and MS 4 Å (2.0 g) in dry CH2Cl2 (25
mL) was stirred under a nitrogen atmosphere for 30 min. The
mixture was cooled to 5–10 uC in a ice-water bath and H2SO4-
silica (50 mg) was added. After stirring for 45 min, TLC
(n-hexane–EtOAc, 2 : 1) showed complete consumption of the
donor. The mixture was neutralized with Et3N and filtered. The
filtrate was evaporated in vacuo and the residue was purified by
flash chromatography using n-hexane–EtOAc, 2 : 1 as eluent to
afford pure disaccharide 5 (1.75 g, 91%) as a light yellow foam.
1
[a]2D5 +101 (c 1.1, CHCl3). H NMR (CDCl3, 500 MHz) d: 7.76–
6.72 (m, 28H, ArH), 5.65 (d, 1H, J1,2 = 8.5 Hz, H-1), 5.37 (s, 1H,
CHPh), 4.80 (dd, 1H, J19,29 = 8.0 Hz, J29,39 9.5 Hz, H-29), 4.77 (dd,
1H, J2,3 = 8.5 Hz, J3,4 = 10.0 Hz, H-3), 4.65, 4.63 (2d, 2H, J = 11.0
Hz, CH2Ph), 4.57 (dd, 1H, J1,2 = 8.5 Hz, J2,3 = 9.5 Hz, H-2), 4.46
(m, 5H, H-19, 2 6 CH2Ph), 4.32 (dd, 1H, J5,6a = 5.5 Hz, J6a,6b
=
11.0 Hz, H-6a), 3.91 (t, 1H, J29,39, J39,49 = 9.5 Hz, H-39), 3.80 (t,
1H, J5,6b, J6a,6b = 11.0 Hz, H-6b), 3.71 (s, 3H, C6H4OCH3), 3.68
(m, 1H, H-5), 3.59 (t, 1H, J39,49, J49,59 = 9.5 Hz, H-49), 3.41 (m, 2H,
H-6a9, H-6b9), 3.38 (t, 1H, J3,4, J4,5 = 9.5 Hz, H-4), 3.05 (m, 1H,
H-59), 1.35 (s, 3H, COCH3). 13C NMR (CDCl3, 125 MHz) d: 168.8
(COCH3), 155.5, 150.6, 138.2, 138.1, 137.8, 137.1, 134.2, 131.7,
129.2, 128.4(2), 128.3(2), 128.2(3), 128.0(2), 127.8(2), 127.7,
P-TOLYL 3,4-O-ISOPROPYLIDENE-2-O-(4-METHOXYBENZYL)-1-THIO-B-L-
FUCOPYRANOSIDE (9). To a solution of compound 8 (3.0 g, 9.7
mmol) in dry DMF (20 mL) was added NaH (930 mg, 50% in
mineral wax) followed by 4-methoxybenzyl chloride (1.7 mL,
12.6 mmol) and the mixture was stirred at room temperature
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for 4 h. Excess NaH was neutralized by careful addition of
MeOH (2 mL) and the mixture was evaporated in vacuo. The
residue was dissolved in diethyl ether (30 mL) and washed
successively with H2O (30 mL) and brine (30 mL). The organic
layer was collected, dried (Na2SO4), filtered and evaporated.
The residue was purified by flash chromatography using
n-hexane–EtOAc, 4 : 1 to afford pure compound 9 (3.45 g, 83%)
as a light yellow syrup. [a]2D5 +141 (c 1.0, CHCl3). 1H NMR
(CDCl3, 500 MHz) d: 7.45–6.85 (m, 8H, ArH), 4.75, 4.60 (2d, 2H,
J = 11.0 Hz, CH2C6H4OCH3), 4.50 (d, 1H, J1,2 = 9.5 Hz, H-1), 4.19
(C-6). HRMS calcd. for C72H75O18NNa (M+Na)+: 1264.4882;
found: 1264.4885.
P-METHOXYPHENYL 3,4-O-ISOPROPYLIDENE-A-L-FUCOPYRANOSYL-(1A2)-
3,4,6-TRI-O-BENZYL-B-D-GLUCOPYRANOSYL-(1
A 3)-4,6-O-BENZYLIDENE-2-
DEOXY-2-PHTHALIMIDO-B-D-GLUCOPYRANOSIDE (11). To a solution of
compound 10 (1.3 g, 1.0 mmol) in CH2Cl2–H2O (4 : 1, 20 mL),
DDQ (450 mg, 2.0 mmol) was added and the mixture was
allowed to stir at room temperature for 3 h, after which TLC
(n-hexane–EtOAc, 1 : 1) showed complete conversion of the
starting material to a slower moving spot. The mixture was
diluted with CH2Cl2 (15 mL) and washed successively with H2O
(3630 mL). The organic layer was collected, dried (Na2SO4),
filtered and evaporated in vacuo. The residue was purified by
flash chromatography using n-hexane–EtOAc, 2 : 1, as the
eluent to afford the pure trisaccharide acceptor 11 (950 mg,
(t, 1H, J2,3, J3,4 = 6.0 Hz, H-3), 4.01 (dd, 1H, J3,4 = 6.0 Hz, J4,5
=
2.0 Hz, H-4), 3.79 (s, 3H, C6H4OCH3), 3.76 (dd, 1H, J4,5 = 2.0 Hz,
J5,6 = 6.5 Hz, H-5), 3.46 (dd, 1H, J1,2 = 9.5 Hz, J2,3 = 6.0 Hz, H-2),
2.32 (s, 3H, S-C6H4CH3), 1.39, 1.35 (2s, 6H, 2 6 isopropylidene-
CH3), 1.37 (d, 3H, J5,6 = 6.5 Hz, H-6). 13C NMR (CDCl3, 125
MHz) d: 159.2, 137.4, 132.6(2), 130.1, 129.9(2), 129.8, 129.4(2),
113.6(2) (ArC), 109.6 (isopropylidene-C), 86.4 (C-1), 79.8, 77.8,
76.4, 73.1, 72.3, 55.2 (C6H4OCH3), 27.9, 26.3 (2 6 isopropyli-
dene-CH3), 21.1 (SC6H4CH3), 16.8 (C-6). HRMS calcd. for
C24H30O5SNa (M+Na)+: 453.1712; found: 453.1716.
1
81%) as a light yellow syrup. [a]2D5 +81 (c 1.1, CHCl3). H NMR
(CDCl3, 500 MHz) d: 7.83–6.71 (m, 28H, ArH), 5.81 (d, 1H, J19,29
= 8.5 Hz, H-19), 5.38 (s, 1H, CHPh), 4.60 (d, 1H, J1,2 = 9.0 Hz,
H-1), 4.47 (d, 1H, J199,299 = 2.5 Hz, H-199), 3.70 (s, 3H,
C6H4OCH3), 1.21 (d, 3H, J599,699 = 6.0 Hz, H-699). 13C NMR
(CDCl3, 125 MHz) d: 155.5, 150.6, 139.2, 138.0, 137.7, 137.6,
137.2, 134.0, 131.7, 129.1, 128.5(3), 128.4(2), 128.3(2), 128.2(2),
128.1(2), 127.9(2), 127.8(2), 127.8, 127.7, 127.5(2), 126.1(2),
123.5, 118.6(2), 114.5(2) (ArC), 108.7 (isopropylidene-C), 101.3
(CHPh), 100.1 (C-19), 98.7 (C-1), 97.9 (C-199), 83.7, 80.3, 79.8,
78.3, 77.6, 76.6, 75.6, 74.9, 74.7, 74.4, 74.3, 73.5, 70.4, 68.6,
66.5, 64.0, 56.0 (C-2), 55.6 (C6H4OCH3), 28.0, 26.1 (2 6
P-METHOXYPHENYL 3,4-O-ISOPROPYLIDENE-2-O-(4-METHOXYBENZYL)-A-
L-FUCOPYRANOSYL-(1 A 2)-3,4,6-TRI-O-BENZYL-B-D-GLUCOPYRANOSYL-(1 A 3)-
4,6-O-BENZYLIDENE-2-DEOXY-2-PHTHALIMIDO-B-D-GLUCOPYRANOSIDE (10). A
mixture of the disaccharide acceptor 6 (1.2 g, 1.3 mmol), donor
9 (730 mg, 1.7 mmol) and MS 4 Å (1.5 g) in dry CH2Cl2 (20 mL)
was stirred under nitrogen for 30 min. The mixture was cooled
to 240 uC after adding NIS (500 mg, 2.2 mmol). H2SO4-silica
(50 mg) was added and the mixture was stirred for 90 min. The
mixture was filtered and washed with CH2Cl2 (10 mL). The
filtrate was washed successively with aq. Na2S2O3 (2 630 mL),
aq. NaHCO3 (2 630 mL) and brine (30 mL). The organic layer
was separated, dried (Na2SO4), filtered and evaporated. The
residue was purified by flash chromatography using n-hexane–
EtOAc, 2 : 1, as the eluent to afford pure trisaccharide 10 (1.7
isopropylidene-CH3), 16.1
(C-6). HRMS calcd.
for
C64H67O17NNa (M+Na)+: 1144.4307; found: 1144.4311.
P-METHOXYPHENYL 2-O-ACETYL-3,4, 6-TRI-O-BENZYL- A-D -
MANNOPYRANOSYL-(1 2)-3,4-O-ISOPROPYLIDENE-A-L-FUCOPYRANOSYL-(1
A
A 2)-3,4,6-TRI-O-BENZYL-B-D-GLUCOPYRANOSYL-(1 A 3)-4,6-O-BENZYLIDENE-
2-DEOXY-2-PHTHALIMIDO-B-D-GLUCOPYRANOSIDE (13). A mixture of the
trisaccharide acceptor 11 (900 mg, 0.8 mmol), donor 12 (600
mg, 1.0 mmol) and MS 4 Å (1.0 g) in dry CH2Cl2 (15 mL) was
stirred under nitrogen for 30 min. The mixture was cooled to
5–10 uC in an ice-water bath after adding NIS (290 mg, 1.3
mmol). H2SO4-silica (30 mg) was added and the mixture was
stirred for 45 min. The mixture was filtered and washed with
CH2Cl2 (20 mL). The combined filtrate was washed succes-
sively with aq. Na2S2O3 (2 6 30 mL), aq. NaHCO3 (2630 mL)
and brine (30 mL). The organic layer was separated, dried
(Na2SO4), filtered and evaporated. The residue thus obtained
was purified by flash chromatography using n-hexane–EtOAc,
2 : 1, as the eluent to afford pure tetrasaccharide 13 (1.1 g,
84%) as a colourless foam. [a]2D5 +91 (c 1.0, CHCl3). 1H NMR
1
g, 83%) as a colourless foam. [a]2D5 +76 (c 1.1, CHCl3). H NMR
(CDCl3, 500 MHz) d: 7.38–6.72 (m, 32H, ArH), 5.82 (d, 1H, J1,2
=
8.5 Hz, H-1), 5.42 (s, 1H, CHPh), 4.93 (d, 1H, J = 11.0 Hz,
CH2Ph), 4.86 (d, 1H, J199,299 = 3.0 Hz, H-199), 4.85 (t, 1H, J2,3, J3,4
= 8.5 Hz, H-3), 4.65 (t, 1H, J1,2, J2,3 = 8.5 Hz, H-2), 4.63, 4.59 (2d,
2H, J = 11.0 Hz, CH2Ph), 4.49 (d, 1H, J19,29 = 8.0 Hz, H-19), 4.47,
4.45, 4.41 (3d, 3H, J = 11.0 Hz, CH2Ph), 4.36, 4.32 (2d, 2H, J =
11.0 Hz, CH2Ph), 4.30 (m, 1H, H-599), 4.08 (dd, 1H, J299,399 = 8.5
Hz, J399,499 = 5.5 Hz, H-399), 3.98 (t, 1H, J39,49, J49,59 = 8.5 Hz, H-49),
3.91 (dd, 1H, J399,499 = 5.5 Hz, J499,599 = 3.0 Hz, H-499), 3.79 (s, 3H,
CH2C6H4OCH3), 3.75 (m, 1H, H-29), 3.71 (s, 3H, OC6H4OCH3),
3.69 (m, 1H, H-299), 3.55 (t, 1H, J3,4, J4,5 = 8.5 Hz, H-4), 3.53-3.43
(m, 4H, H-6”, H-6b, H-6a9, H-6b9), 3.16 (m, 1H, H-5), 1.29, 1.23
(2s, 6H, 2 6 isopropylidene-CH3), 1.27 (d, 3H, J = 6.5 Hz,
C-CH3). 13C NMR (CDCl3, 125 MHz) d: 158.9, 155.5, 150.7,
138.8, 138.2, 138.1, 137.3, 133.9, 131.8, 130.5, 129.7, 129.0,
128.9(2), 128.4(2), 128.3(2), 128.2(3), 128.1(2), 128.0(2),
127.9(2), 127.7(2), 127.6, 127.5(2), 127.1, 126.1(2), 123.4,
118.5(2), 114.5(2), 113.6(2) (ArC), 108.3 (isopropylidene-C),
101.2 (CHPh), 100.3 (C-19), 98.0 (C-1), 97.2 (C-199), 84.5, 81.4,
80.1, 77.5, 76.6, 76.1, 75.9, 74.7(2), 74.6, 74.1, 73.4, 71.2, 68.9,
68.6, 66.5, 63.6, 56.0 (C-2), 55.6 (C6H4OCH3), 55.3
(CH2C6H4OCH3), 28.4, 26.4 (2 6 isopropylidene-CH3), 16.2
(CDCl3, 500 MHz) d: 7.72–6.79 (m, 43H, ArH), 5.92 (d, 1H, J1,2
8.5 Hz, H-1), 5.42 (s, 1H, CHPh), 4.92 (d, 1H, J199,299 = 2.0 Hz,
H-199), 4.89 (d, 1H, J1999,2999 = 1.5 Hz, H-1999), 4.54 (d, 1H, J19,29
=
=
8.5 Hz, H-19), 3.77 (s, 3H, C6H4OCH3), 2.20 (s, 3H, COCH3),
1.35, 1.33 (2s, 6H, 2 6 isopropylidene-CH3), 1.29 (d, 3H, J599,699
= 6.5 Hz, H-699). 13C NMR (CDCl3, 125 MHz) d: 170.3 (COCH3),
167.9, 167.8 (2 6 phthalimido CO), 155.5, 150.7, 138.9,138.6,
138.4, 138.2, 138.1, 137.9, 137.3, 133.9, 131.8(2), 129.0,
128.5(2), 128.2(9), 128.1(6), 128.0(4), 127.9(4), 127.8(3),
127.6(2), 127.5, 127.4(2), 127.3, 127.2(2), 126.1(2), 118.6(2),
114.4(2) (ArC), 108.6 (isopropylidene-C), 101.2 (CHPh), 100.3
(C-19), 98.9 (C-1999), 97.9 (C-1), 97.6 (C-199), 84.3, 81.3, 80.3,
204 | RSC Adv., 2013, 3, 201–207
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78.0, 77.3, 77.2, 76.0, 75.3, 74.9, 74.8, 74.6, 74.0, 73.8, 73.4,
73.3, 72.0, 71.4, 69.0, 68.9, 68.6, 68.4, 66.4, 63.6, 55.8,
55.6(C6H4OCH3), 28.5, 26.4 (2 6 isopropylidene-CH3), 21.2
(COCH3), 16.1 (C-6). HRMS calcd. for C93H97O23NNa (M+Na)+:
1618.6349; found: 1618.6352.
P-METHOXYPHENYL 2-O-BENZYL-3,4-O-ISOPROPYLIDENE-B-L-
FUCOPYRANOSIDE (16). To a solution of compound 15 (3.0 g, 9.7
mmol) in dry DMF (30 mL) was added NaH (930 mg, 19.4
mmol, 50% in mineral wax) followed by BnBr (1.7 mL, 14.6
mmol) and the mixture was stirred at room temperature for 3
h. Excess NaH was neutralized by careful addition of MeOH
(2.0 mL) and H2O (50 mL) was added and stirred for 45 min.
Then the solution was extracted by Et2O (3 6 40 mL) and the
combined organic layer was dried (Na2SO4), filtered and
evaporated. The crude material thus obtained was purified
by flash chromatography using n-hexane–EtOAc (4 : 1) to give
pure compound 16 (3.5 g, 90%) as a light yellow syrup. [a]D25
+148 (c 1.0, CHCl3). 1H NMR (CDCl3, 500 MHz) d: 7.44–6.83 (m,
9H, ArH), 4.93, 4.88 (2d, 2H, J = 11.5 Hz, CH2Ph), 4.78 (d, 1H,
J1,2 = 8.0 Hz, H-1), 4.21 (dd, 1H, J2,3 = 7.0 Hz, J3,4 = 5.5 Hz, H-3),
4.03 (dd, 1H, J3,4 = 5.5 Hz, J4,5 = 2.5 Hz, H-4), 3.91 (m, 1H, H-5),
3.78 (s, 3H, C6H4OCH3), 3.63 (dd, 1H, J1,2 = 8.0 Hz, J2,3 = 7.0 Hz,
H-2), 1.43, 1.37 (2s, 6H, 2 6 isopropylidene-CH3), 1.42 (d, 3H,
J5,6 = 6.0 Hz, H-6). 13C NMR (CDCl3, 125 MHz) d: 155.2, 151.5,
138.2, 128.2(3), 127.6, 118.6(2), 114.4(3) (ArC), 109.7 (isopro-
pylidene-C), 102.1 (C-1), 79.2, 79.1, 76.2, 73.7, 68.8, 55.6
(C6H4OCH3), 27.8, 26.3 (2 6 isopropylidene-CH3), 16.6 (C-6).
HRMS calcd. for C23H28O6Na (M+Na)+: 423.1784; found:
423.1788.
P-METHOXYPHENYL 2-O-BENZYL-3-O-(4-METHOXYBENZYL)-B-L-
FUCOPYRANOSIDE (18). A solution of compound 16 (3.2 g, 8.0
mmol) in 80% aq. AcOH (30 mL) was stirred at 80 uC for 2 h.
After evaporating the solvents the residue was purified by flash
chromatography using n-hexane–EtOAc (2 : 1) to afford the
diol 17 (2.7 g, 94%) as a white amorphous solid. The slurry of
compound 17 (2.5 g, 6.9 mmol) and Bu2SnO (1.9 g, 7.6 mmol)
in dry MeOH (30 mL) was refluxed for 2 h. After evaporating
the solvents, the residue was re-dissolved in dry DMF (25 mL),
followed by the addition of 4-methoxybenzyl chloride (1.2 mL,
9.0 mmol) and Bu4NI (2.5 g, 6.9 mmol). The solution was
stirred at 60 uC for 12 h. After removal of the solvents, the
residue was dissolved in CH2Cl2 and washed successively with
Na2S2O3 (30 mL), NaHCO3 (30 mL) and brine (30 mL). The
organic layer was collected, dried (Na2SO4), filtered and
evaporated. The residue was purified by flash chromatography
using n-hexane–EtOAc (4 : 1) to afford pure compound 18 (2.8
g, 83%) as a light yellow syrup. [a]2D5 +143 (c 1.0, CHCl3). 1H
NMR (CDCl3, 500 MHz) d: 7.39–6.82 (m, 13H, ArH), 4.99, 4.81
(2d, 2H, J = 11.0 Hz, CH2Ph), 4.80 (d, 1H, J1,2 = 8.0 Hz, H-1),
4.68 (s, 2H, CH2C6H4OCH3), 3.82 (m, 1H, H-2), 3.81 (s, 3H,
CH2C6H4OCH3), 3.78 (s, 3H, OC6H4OCH3), 3.73 (m, 1H, H-3),
3.61 (m, 1H, H-5), 3.55 (m, 1H, H-4), 2.47 (bs, 1H, OH), 1.38 (d,
3H, J5,6 = 6.5 Hz, H-6). 13C NMR (CDCl3, 125 MHz) d: 159.4,
155.2, 151.6, 138.5, 129.9, 129.5(2), 128.3(2), 128.1(2), 127.6,
118.6(2), 114.5(2), 113.9(2) (ArC), 102.9 (C-1), 80.5, 78.5, 75.3,
72.1, 70.2, 69.3, 55.6 (OC6H4OCH3), 55.3 (CH2C6H4OCH3), 16.4
(C-6). HRMS calcd. for C28H32O7Na (M+Na)+: 503.2046; found:
503.2049.
P-METHOXYPHENYL A-D-MANNOPYRANOSYL-(1 A 2)-A-L-FUCOPYRANOSYL-
(1
A 2)-B-D-GLUCOPYRANOSYL-(1 A 3)-2-ACETAMIDO-2-DEOXY-B-D-
GLUCOPYRANOSIDE (1). To a solution of the compound 13 (1.0 g,
0.6 mmol) in n-butanol (15 mL) was added ethylene diamine
(80 mL, 1.2 mmol) and the solution was stirred at 110 uC for 24
h. After evaporating the solvents in vacuo, the residue was
dissolved in pyridine (10 mL) followed by Ac2O (10 mL) and the
solution was stirred at room temperature for 2 h. The solvents
were evaporated in vacuo and the residue was dissolved in 80%
aq. AcOH (20 mL) and the solution was then stirred at 80 uC for
2 h, after which TLC (n-hexane–EtOAc, 1 : 1) showed complete
conversion of the starting material to a slower moving spot.
After evaporating the solvents the residue was dissolved in
MeOH (100 mL) and the solution was passed through a H-cube
flow hydrogenation assembly using a 10% Pd-C cartridge with
a flow rate of 1 mL min21. Complete removal of the benzyl
groups was achieved after two cycles, as determined by the
mass spectra. The solvents were evaporated and the residue
was re-dissolved in MeOH (10 mL). NaOMe (1 mL, 0.5M in
MeOH) was added and the solution was stirred at room
temperature for 2 h. Excess NaOMe was neutralized by
DOWEX 50W H+ resin, filtered and evaporated. The residue
was passed through a short flash column using CH2Cl2-MeOH
(3 : 1) to get pure target tetrasaccharide 1 (315 mg, 63% over
four steps). [a]2D5 +62 (c 0.8, MeOH). 1H NMR (CD3OD, 500
MHz) d: 6.94, 6.81 (2d, 4H, J 7.5 Hz, C6H4OCH3), 5.37 (d, 1H,
J199,299 = 3.5 Hz, H-199), 5.16 (bs, 1H, H-1999), 4.75 (d, 1H, J1,2
=
8.5 Hz, H-1), 4.59 (d, 1H, J19,29 = 8.5 Hz, H-19), 3.73 (s, 3H,
C6H4OCH3), 2.03 (s, 3H, NHCOCH3), 1.20 (d, 3H, J = 6.5 Hz, C–
CH3). 13C NMR (CD3OD, 125 MHz) d: 173.6 (NHCOCH3), 156.8,
153.3, 119.1(2), 115.6(2) (ArC), 102.9 (C-1), 102.8 (C-1999), 102.2
(C-19), 99.8 (C-199), 80.8, 79.1, 78.2, 78.0(2), 74.9, 74.4, 74.1,
72.4, 72.0(2), 70.9, 70.1, 68.8, 67.4, 62.9, 62.5, 56.1
(C6H4OCH3),22.7 (NHCOCH3), 16.4 (C–CH3). HRMS calcd. for
C33H51O21NNa (M+Na)+: 820.2851; found: 820.2854.
P-METHOXYPHENYL 3,4-O-ISOPROPYLIDENE-B-L-FUCOPYRANOSIDE (15).
To a mixture of compound 14 (3.0 g, 11.1 mmol) and 2,2-DMP
(2.7 mL, 22.2 mmol) in dry acetone (20 mL) was added CSA (50
mg), and the mixture was stirred at room temperature for 2 h.
The solution was neutralized with Et3N and the solvents were
evaporated. The residue was purified by flash chromatography
using n-hexane–EtOAc (3 : 1) to afford pure compound 15 (3.2
1
g, 92%) as a colourless gel. [a]2D5 +170 (c 1.1, CHCl3). H NMR
(CDCl3, 500 MHz) d: 6.99, 6.82 (2d, 4H, J = 9.0 Hz, ArH), 4.63 (d,
1H, J1,2 = 8.0 Hz, H-1), 4.12 (dd, 1H, J2,3 = 8.0 Hz, J3,4 = 6.0 Hz,
H-3), 4.04 (dd, 1H, J3,4 = 6.0 Hz, J4,5 = 1.6 Hz, H-4), 3.94 (m, 1H,
H-5), 3.78 (t, 1H, J1,2, J2,3 = 8.0 Hz, H-2), 3.76 (s, 3H,
C6H4OCH3), 1.56, 1.37 (2s, 6H, 2 6 isopropylidene-CH3), 1.43
(d, 3H, J5,6 = 6.5 Hz, H-6). 13C NMR (CDCl3, 125 MHz) d: 155.5,
151.2, 118.7(2), 114.5(3) (ArC), 109.9 (isopropylidene-C), 101.7
(C-1), 78.7, 76.2, 73.3, 69.3, 55.6 (C6H4OCH3), 28.2, 26.3 (2 6
isopropylidene-CH3), 16.6 (C-6). HRMS calcd. for C16H22O6Na
(M+Na)+: 333.1314; found: 333.1318.
P-METHOXYPHENYL 2,3-DI-O-BENZOYL-4,6-O-BENZYLIDENE-B-D-
GLUCOPYRANOSYL-(1
A 4)-2-O-BENZYL-3-O-(4-METHOXYBENZYL)-B-L-
FUCOPYRANOSIDE (20). A mixture of the acceptor 18 (1.5 g, 3.1
mmol), donor 19 (2.4 g, 4.1 mmol) and MS 4 Å (2.0 g) in dry
CH2Cl2 (25 mL) was stirred under nitrogen for 30 min. The
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mixture was cooled to 5–10 uC in an ice-water bath after adding
NIS (1.2 g, 5.3 mmol). H2SO4-silica (50 mg) was added and the
mixture was stirred for 90 min. The mixture was filtered and
washed with CH2Cl2 (10 mL). The filtrate was washed
successively with aq. Na2S2O3 (2 6 30 mL), aq. NaHCO3 (2
6 30 mL) and brine (30 mL). The organic layer was separated,
dried (Na2SO4), filtered and evaporated. The residue was
purified by flash chromatography using n-hexane–EtOAc, 2 : 1,
as the eluent to afford pure disaccharide 20 (2.1 g, 85%) as a
colourless foam. [a]D25 +109 (c 1.1, CHCl3). 1H NMR (CDCl3, 500
MHz) d: 8.02–6.78 (m, 28H, ArH), 5.75 (t, 1H, J29,39, J39,49 = 9.0
Hz, H-39), 5.63 (dd, 1H, J19,29 = 8.0 Hz, J29,39 = 9.0 Hz, H-29), 5.48
(s, 1H, CHPh), 5.07 (d, 1H, J19,29 = 8.0 Hz, H-19), 4.96, 4.86 (2d,
2H, J = 11.0 Hz, CH2Ph), 4.76 (d, 1H, J1,2 = 7.5 Hz, H-1), 4.71 (s,
2H, CH2C6H4OCH3), 4.30 (dd, 1H, J59,6a9 = 5.0 Hz, J6a9,6b9 = 10.5
Hz, H-6a9), 4.12 (t, 1H, J39,49 = 9.0 Hz, J49,59 = 9.0 Hz, H-49), 4.03
(dd, 1H, J1,2 = 7.5 Hz, J2,3 = 8.5 Hz, H-2), 3.86 (m, 2H, H-4,
H-6b9), 3.78 (s, 3H, CH2C6H4OCH3), 3.76 (s, 3H, OC6H4OCH3),
3.64 (m, 1H, H-59), 3.50 (dd, 1H, J2,3 = 8.5 Hz, J3,4 = 3.0 Hz, H-3),
3.48 (m, 1H, H-5), 1.15 (d, 1H, J5,6 = 6.5 Hz, H-6). 13C NMR
(CDCl3, 125 MHz) d: 165.7, 164.9 (2 6 COPh), 159.3, 155.1,
151.5, 138.7, 136.9, 133.0, 132.9, 130.4, 129.8(2), 129.7(2),
129.5, 129.4, 129.3(2), 128.9, 128.3(3), 128.2(3), 128.1(4), 127.6,
126.1(2), 118.9(2), 114.3(2), 113.8(2) (ArC), 103.1 (C-1), 101.7 (C-
19), 101.3 (CHPh), 80.4, 78.4, 78.3, 75.2, 73.1, 72.5, 72.4, 70.1,
68.6, 66.5 (C-69), 55.6 (CH2C6H4OCH3), 55.2 (OC6H4OCH3),
16.6 (C-6). HRMS calcd. for C55H54O14Na (M+Na)+: 961.3411;
found: 961.3417.
DEOXY-A-D-GALACTOPYRANOSYL)-B-L-FUCOPYRANOSIDE (23). A mixture of
the disaccharide acceptor 21 (1.0 g, 1.2 mmol), donor 22 (1.1 g,
2.4 mmol) and MS 4 Å (1.5 g) in dry CH2Cl2 (20 mL) was stirred
under a nitrogen atmosphere for 30 min. The mixture was
cooled to 240 uC and H2SO4-silica (30 mg) was added. After
stirring for 2 h, TLC (n-hexane–EtOAc, 2 : 1) showed complete
consumption of the donor, the mixture was neutralized with
Et3N and filtered. The filtrate was evaporated in vacuo and the
residue was purified by flash chromatography using n-hexane–
EtOAc, 2 : 1, as the eluent to afford pure trisaccharide 23 (1.1
g, 80%) as a light yellow foam. [a]2D5 +103 (c 0.9, CHCl3). 1H
NMR (CDCl3, 500 MHz) d: 8.00–6.72 (m, 24H, ArH), 5.83 (t, 1H,
J299,399, J399,499 = 9.5 Hz, H-399), 5.71 (s, 1H, CHPh), 5.61 (dd, 1H,
J199,299 = 8.0 Hz, J299,399 = 9.5 Hz, H-299), 5.54 (m, 2H, H-19, H-39),
5.46 (bs, 1H, H-49), 5.08, 4.84 (2d, 2H, J = 10.5 Hz, CH2Ph), 4.97
(d, 1H, J199,299 = 8.0 Hz, H-199), 4.67 (d, 1H, J1,2 = 7.5 Hz, H-1),
4.52 (m, 1H, H-6a99), 4.31 (m, 2H, H-6a9, H-6b9), 4.14 (t, 1H,
J39,49 = 9.5 Hz, J49,59 = 9.5 Hz, H-499), 4.06 (m, 2H, H-2, H-3), 3.99
(m, 1H, H-6b99), 3.86 (d, 1H, J4,5 = 3.0 Hz, H-4), 3.74 (s, 3H,
OC6H4OCH3), 3.72 (m, 1H, H-59), 3.63 (m, 1H, H-599), 3.61 (dd,
1H, J19,29 = 3.0 Hz, J29,39 = 9.5 Hz, H-29), 3.52 (m, 1H, H-5), 2.16,
2.13, 2.05 (3s, 9H, 3 6 COCH3), 1.23 (d, 1H, J5,6 = 6.5 Hz, H-6).
13C NMR (CDCl3, 125 MHz) d: 170.3, 170.1, 169.8 (3 6 COCH3),
165.8, 165.2 (2 6 COPh), 155.2, 151.3, 138.6, 137.0, 133.0,
132.6, 129.9(2), 129.8(2), 129.5, 128.9, 128.3(2), 128.2(2),
128.1(7), 127.6, 126.2(2), 119.0(2), 114.3(2) (ArC), 103.0 (C-1),
101.9 (C-199), 101.1 (CHPh), 99.1 (C-19), 78.1, 77.3, 76.5, 76.0,
74.9, 72.9, 72.2, 70.1, 68.2, 67.7, 67.6, 67.2, 66.2, 61.5, 57.4 (C-
29), 55.6 (OC6H4OCH3), 20.7, 20.6, 20.5 (36COCH3), 16.6 (C-6).
HRMS calcd. for C59H61O20N3Na (M+Na)+: 1154.3746; found:
1154.3750.
P-METHOXYPHENYL 2,3-DI-O-BENZOYL-4,6-O-BENZYLIDENE-B-D-
GLUCOPYRANOSYL-(1
A 4)-2-O-BENZYL-B-L-FUCOPYRANOSIDE (21). To a
solution of compound 20 (2.0 g, 2.1 mmol) in CH2Cl2–H2O
(4 : 1, 20 mL), DDQ (950 mg, 4.2 mmol) 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 slower running spot. The solution was
diluted with CH2Cl2 (mL) and washed with H2O (2 6 40 mL).
The organic layer was collected, dried (Na2SO4), filtered and
evaporated. The residue was purified by flash chromatography
using n-hexane–EtOAc (3 : 1) to afford pure compound 21 (1.4
g, 81%) as a light yellow syrup. [a]2D5 +123 (c 1.0, CHCl3). 1H
NMR (CDCl3, 500 MHz) d: 7.98–6.79 (m, 24H, ArH), 5.79 (t, 1H,
J29,39, J39,49 = 9.0 Hz, H-39), 5.61 (dd, 1H, J19,29 = 8.0 Hz, J29,39 = 9.0
Hz, H-29), 5.56 (s, 1H, CHPh), 4.97, 4.88 (2d, 2H, J = 11.5 Hz,
CH2Ph), 4.96 (d, 1H, J19,29 = 8.0 Hz, H-19), 4.76 (d, 1H, J1,2 = 7.5
Hz, H-1), 4.42 (dd, 1H, J59,6a9 = 4.5 Hz, J6a9,6b9 = 10.0 Hz, H-6a9),
P-METHOXYPHENYL B-D-GLUCOPYRANOSYL-(1 A 4)-3-O-(2-ACETAMIDO-2-
DEOXY-A-D-GALACTOPYRANOSYL)-B-L-FUCOPYRANOSIDE (2). Compound 23
(1.0 g, 0.9 mmol) was dissolved in thiolacetic acid (10 mL) and
the solution was allowed to stir in the dark for 48 h. After
evaporating the solvents in vacuo and co-evaporating with
toluene, the residue was dissolved in 80% aq. AcOH (15 mL)
and the solution was stirred at 80 uC for 3 h, after which TLC
(n-hexane–EtOAc, 1 : 1) showed complete conversion of the
starting material to a slower moving spot. The solvents were
evaporated and the residue was dissolved in MeOH (80 mL)
and the solution was passed through
a H-cube Flow
Hydrogenation assembly using a 10% Pd–C cartridge with a
flow rate of 1 mL per minute. The hydrogenation was complete
in two cycles, as confirmed by mass spectrometry. The volume
of the methanolic solution was reduced to 10 mL and NaOMe
(1 mL, 0.5M in MeOH) was added. The solution was stirred at
room temperature for 6 h. Excess NaOMe was neutralized by
DOWEX 50W H+ resin, filtered and evaporated. The residue
was purified by passing through a short silica column using
CH2Cl2–MeOH (3 : 1) to get pure target trisaccharide 2 (375
mg, 67% over four steps). [a]2D5 +54 (c 0.8, MeOH). 1H NMR
(D2O, 500 MHz) d: 7.13, 7.00 (2d, 4H, J = 7.5 Hz, C6H4OCH3),
5.23 (d, 1H, J19,29 = 4.0 Hz, H-19), 4.99 (d, 1H, J199,299 = 6.5 Hz,
H-199), 4.65 (d, 1H, J1,2 = 7.5 Hz, H-1), 3.83 (s, 3H, C6H4OCH3),
2.08 (s, 3H, NHCOCH3), 1.38 (d, 3H, J = 6.5 Hz, C–CH3). 13C
NMR (D2O, 125 MHz) d: 174.6 (NHCOCH3), 154.8, 150.9,
118.5(2), 115.1(2) (ArC), 103.9 (C-1), 101.9 (C-199), 99.3 (C-19),
4.03 (t, 1H, J39,49 = 9.0 Hz, J49,59 = 9.0 Hz, H-49), 3.87 (t, 1H, J59,6b9
,
J6a9,6b9 = 10.0 Hz, H-6b9), 3.82 (m, 2H, H-2, H-59), 3.76 (s, 3H,
OC6H4OCH3), 3.72 (m, 2H, H-3, H-4), 3.61 (m, 1H, H-5), 3.37
(bs, 1H, OH), 1.08 (d, 1H, J5,6 6.5 Hz, H-6). 13C NMR (CDCl3,
125 MHz) d: 165.6, 164.9 (2 6 COPh), 155.2, 151.4, 138.6,
136.5, 133.2, 133.1, 129.8(2), 129.7(2), 129.2, 129.1, 129.0,
128.3(6), 128.2(2), 128.0(2), 127.6, 126.0(2), 118.6(2), 114.4(2)
(ArC), 102.8 (2C, C-1, C-19), 101.5 (CHPh), 82.8, 79.1, 78.3, 74.8,
72.8, 72.7, 72.2, 69.9, 68.3, 66.8, 55.6 (OC6H4OCH3), 16.3 (C-6).
HRMS calcd. for C47H46O13Na (M+Na)+: 841.2836; found:
841.2840.
P-METHOXYPHENYL 2,3-DI-O-BENZOYL-4,6-O-BENZYLIDENE-B-D-
GLUCOPYRANOSYL-(1
A 4)-2-O-BENZYL-3-O-(3,4,6-TRI-O-ACETYL-2-AZIDO-2-
206 | RSC Adv., 2013, 3, 201–207
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10 Preparation of H2SO4–silica: To a 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 was shaken for 5 min. The solvent was evaporated
under reduced pressure, resulting in free flowing H2SO4–
silica, which was dried at 110 uC for 3 h and then used for
the reactions. Reference for the use of H2SO4-silica (a)
B. Roy, K. Pramanik and B. Mukhopadhyay, Glycoconjugate
J., 2008, 25, 157–166; (b) S. Dasgupta, K. Pramanik and
B. Mukhopadhyay, Tetrahedron, 2007, 63, 12310–12316; (c)
S. Mandal and B. Mukhopadhyay, Tetrahedron, 2007, 63,
11363–11370; (d) S. Dasgupta and B. Mukhopadhyay, Eur. J.
Org. Chem., 2008, 34, 5770–5777; (e) P. R. Verma and
B. Mukhopadhyay, Carbohydr. Res., 2010, 345, 432–436; (f)
B. Roy, R. A. Field and B. Mukhopadhyay, Carbohydr. Res.,
2009, 344, 2311–2316; (g) P. Verma and B. Mukhopadhyay,
Carbohydr. Res., 2009, 344, 2554–2558.
79.4, 77.0, 76.5, 74.9, 73.4, 71.7, 71.4, 71.3, 70.9, 68.7, 67.5,
61.7, 55.9 (OC6H4OCH3), 22.1 (NHCOCH3), 15.3 (C-6). HRMS
calcd. for C27H41O16NNa (M+Na)+: 658.2323; found: 658.2327.
Acknowledgements
PRV is thankful to IISER-Kolkata for Senior Research
Fellowship. This work is supported by CSIR, New Delhi
through research grant 01(2370)/10/EMR-II to BM.
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