H2SO4-silica: An efficient promoter for selective removal of benzylidene and isopropylidene groups in the presence of p-methoxybenzyl group

Article abstract of DOI:10.1080/07328303.2015.1069829

Selective removal of the benzylidene and isopropylidene protections in the presence of acid-labile p-methoxybenzyl group using H₂SO₄-silica in methanol is reported. The deprotection reactions were found to be clean and result in the

Full text of DOI:10.1080/07328303.2015.1069829

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H SO -Silica: An Efficient Promoter for
2
4
Selective Removal of Benzylidene and
Isopropylidene Groups in the Presence of
p-Methoxybenzyl Group
a
a
Prashant Rajan Verma & Balaram Mukhopadhyay
a
Department of Chemical Sciences, Indian Institute of Science
Education and Research Kolkata, Mohanpur 741246, India
Published online: 29 Jul 2015.
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To cite this article: Prashant Rajan Verma & Balaram Mukhopadhyay (2015) H SO -Silica: An
2
4
Efficient Promoter for Selective Removal of Benzylidene and Isopropylidene Groups in the
Presence of p-Methoxybenzyl Group, Journal of Carbohydrate Chemistry, 34:6, 319-337, DOI:
10.1080/07328303.2015.1069829
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Journal of Carbohydrate Chemistry, 34:319–337, 2015
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 0732-8303 print / 1532-2327 online
DOI: 10.1080/07328303.2015.1069829
H SO -Silica: An Efficient
2
4
Promoter for Selective
Removal of Benzylidene and
Isopropylidene Groups in the
Presence of p-Methoxybenzyl
Group
Prashant Rajan Verma and Balaram Mukhopadhyay
Department of Chemical Sciences, Indian Institute of Science Education and Research
Kolkata, Mohanpur 741246, India
GRAPHICAL ABSTRACT
Selective removal of the benzylidene and isopropylidene protections in the presence
of acid-labile p-methoxybenzyl group using H SO -silica in methanol is reported. The
2 4
deprotection reactions were found to be clean and result in the desired products in good
to excellent yields.
Keywords
2 4
H SO -silica; Deprotection; Benzylidene; Isopropylidene; p-Methoxy-
benzyl group
INTRODUCTION
Protecting group manipulation is the key to successful oligosaccharide synthe-
sis.[ To meet the requirement of definite stereo- and regioselectivity, various
1]
Received May 4, 2015; accepted July 2, 2015.
Address correspondence to Balaram Mukhopadhyay, Department of Chemical Sciences,
Indian Institute of Science Education and Research Kolkata, Mohanpur 741246, India.
E-mail: sugarnet73@hotmail.com
3
19

20 P. R. Verma and B. Mukhopadhyay
3
protecting groups have been introduced. Considering the stepwise synthesis
of complex oligosaccharides, use of orthogonal protecting groups becomes in-
evitable. Benzylidene and isopropylidene groups are the most often used pro-
[
2–6]
tecting groups for cis-diols in synthetic carbohydrate chemistry,
whereas
[
7]
the p-methoxybenzyl group has found its utility as a useful ether protec-
tion that can be cleaved selectively in the presence of frequently used ben-
zyl ethers. Selective removal of the p-methoxybenzyl group in the presence
of benzylidene or isopropylidene protection is possible through the oxidative
[
8]
[9]
cleavage using DDQ or by using polymer-supported sulphonamides. How-
ever, removal of benzylidene and isopropylidene protections in the presence
of the p-methoxybenzyl group is rare in the literature.[
10,11]
This is primarily
due to the acid-labile nature of the p-methoxybenzyl group that results in re-
moval of the group along with the benzylidene and isopropylidene protections.
With our experience using H2SO4-silica[
12–21]
as a mild acid source for vari-
ous carbohydrate transformations, we envisaged that it might provide the ad-
equate acidity for the hydrolysis of the benzylidene and isopropylidene protec-
tions without affecting the p-methoxyphenyl group. In fact, we have observed
that the isopropylidene protection may be cleaved selectively in the presence of
[
22]
the p-methoxybenzyl group using H2SO4-silica as an acid source.
Although
H2SO4-silica was successfully utilized for the hydrolysis of benzylidenes,[
its selective removal in the presence of the p-methoxybenzyl group was never
explored. Herein, we report the selective removal of benzylidene and isopropy-
lidene protections in the presence of the p-methoxyphenyl group using H2SO4-
silica with a diverse set of sugar derivatives.
23]
Results and Discussion
To begin with, H2SO4-silica (50 mg) was added to a solution of p-tolyl 3-O-
acetyl-4,6-O-benzylidene-2-O-(4-methoxybenzyl)-1-thio-α-D-mannopyranoside
(
1) (1 mmol) in methanol (5 mL) and the mixture was allowed to stir at
room temperature. After 90 min, TLC showed complete conversion of the
starting material to a slower-moving spot. After the reaction mixture was
filtered, solvent was evaporated, and the crude material was purified by
column chromatography to afford p-tolyl 3-O-acetyl-2-O-(4-methoxybenzyl)-
1
-thio-α-D-mannopyranoside (2) as evident from the NMR and mass spectra
(
Sch. 1).
Scheme 1: Removal of benzylidene protection in the presence of p-methoxybenzyl group.

Selective Hydrolysis of Benzylidene
3
21
Table 1: Optimization of the reaction conditiona
Entry
Solvent
Product
Yield (%)
Time (hr)
1
2
3
4
MeOH
EtOH
2
90
90
95
—
1.5
2.5
1
2
CH
2
Cl
2
3
toluene
No reaction
48
a
Starting material 1 (1 mmol) was dissolved in solvent (5 mL) and then treated with H SO -silica
2
4
(
50 mg).
The control experiment with only silica gel did not produce any such de-
protection product, and direct addition of concentrated H2SO4 gave a complex
mixture of compounds. Therefore, it is evident that H2SO4-silica is the key in
such selective deprotection.
Optimization of the reaction condition was tried with different solvents
(Table 1). In ethanol, the desired product was formed in the same yield as in
methanol, but the transformation took a longer time. In dichloromethane, si-
multaneous cleavage of the p-methoxybenzyl group along with benzylidene re-
sulted in the exclusive formation of the corresponding triols. A similar reaction
with toluene failed.
Once the optimized reaction condition was established, the generality of
the method was tested with a series of different sugar derivatives having the
p-methoxybenzyl group along with either benzylidene or isopropylidene protec-
tion. These derivatives were subjected to H2SO4-silica under a similar reaction
condition using MeOH as the reaction solvent. To our satisfaction, all deriva-
tives resulted in the desired diols in good to excellent yields. In the case of ben-
zylidene derivatives of hexoses, compounds having an acyl/aryl group adjacent
to the benzylidene acetal took a longer time for completion than those having
alkyl groups. Isopropylidene removal was faster than benzylidene as expected
and deoxy sugars reacted faster. The pure products obtained after flash chro-
1
13
matography gave satisfactory H and C NMR and mass spectra. The results
of these reactions are summarized in Figure 1. It is worth mentioning that
the catalyst was removed from the reaction mixture by simple filtration and
reused for the next batch of reactions. No significant change in reactivity was
observed even over five such cycles.
CONCLUSION
In conclusion, H2SO4-silica has been used efficiently for the selective removal
of benzylidene or isopropylidene protection in the presence of the acid-labile

22 P. R. Verma and B. Mukhopadhyay
3
Figure 1: Removal of benzylidene and isopropylidene protections in the presence of
p-methoxybenzyl group using H SO -silica in MeOH. Starting material (1 mmol) was dissolved
2
4
in MeOH (5 mL) and then treated with H SO -silica (50 mg). Yields are those after flash
2
4
chromatography and exhaustive drying of pure compounds isolated.
p-methoxybenzyl group. The reactions were performed in MeOH, and the cata-
lyst used was recovered by simple filtration and reused multiple times without
compromising the outcome. Therefore, the strategy can be regarded as green
in nature. It is possible to scale up the reaction with similar efficiency. A reac-
tion of compound 1 (20 mmol) yielded the desired diol 2 in 88% isolated yield.
We believe that this cheap, environmentally friendly, safe, and easy-to-handle
reagent system will find its application in synthesis of rationally protected
sugar derivatives.
EXPERIMENTAL
General
All solvents and reagents were dried prior to use according to standardized
[
24]
methods.
The commercially purchased reagents were used without any fur-
ther purification unless mentioned otherwise. Dichloromethane wad dried and
distilled over P2O5 to make it anhydrous and moisture-free. All reactions were

Selective Hydrolysis of Benzylidene
3
23
monitored by thin layer chromatography (TLC) on silica gel 60-F254 with detec-
tion by fluorescence followed by charring after immersion in 10% ethanolic so-
lution of H2SO4. Flash chromatography was performed with silica gel 230–400
1
13
1
1
mesh. H, C, H- H COSY, and HSQC NMR were recorded on a Bruker 500-
MHz spectrometer. All proton signals were assigned based on the 2D spectra.
Anomeric carbons and carbons associated with the functional groups were as-
signed with the help of 13C and HSQC spectra.
Preparation of H SO -silica
2
4
To a slurry of silica gel (10 g, 200–400 mesh) in dry diethyl ether (50 mL)
was added commercially available concentrated H2SO4 (3 mL) with shaking
for 5 min. The solvent was evaporated under reduced pressure resulting in
◦
free-flow H2SO4-silica that was then dried at 110 C for 3 h at atmospheric
pressure.
Synthesis of the Starting Materials
p-Tolyl 3-O-acetyl-4,6-O-benzylidene-2-O-(4-methoxybenzyl)-1-thio-α-D-
mannopyranoside (1)
To a solution of known p-tolyl 4,6-O-benzylidene-2-O-(4-methoxybenzyl)-
[
25]
1-thio-α-D-mannopyranoside
(500 mg, 1 mmol) in pyridine (3 mL), Ac2O
(2 mL) was added and the solution was allowed to stir at rt for 2 h. The solvents
were evaporated in vacuo and the residue was purified by flash chromatogra-
phy using n-hexane-EtOAc (3:1) to afford pure compound 1 as colorless gel
1
(
520 mg, 96%). H NMR (CDCl3, 500 MHz) δ: 7.49–6.87 (m, 13H, ArH), 5.58 (s,
1
H, CHPh), 5.42 (d, 1H, J1,2 = 1.0 Hz, H-1), 5.31 (dd, 1H, J2,3 = 3.5 Hz, J3,4 =
1
0.5 Hz, H-3), 4.62, 4.49 (ABq, 2H, JAB = 12.0 Hz, CH2C6H4OMe), 4.40 (m, 1H,
H-5), 4.25–4.21 (m, 3H, H-2, H-6a, H-6b), 3.89 (t, 1H, J3,4, J4,5 = 10.5 Hz, H-4),
3
.81 (s, 3H, CH2C6H4OCH3), 2.36 (s, 3H, SC6H4CH3), 2.05 (s, 3H, OCOCH3).
C NMR (CDCl3, 125 MHz) δ: 170.1 (COCH3), 159.5, 141.0, 138.0, 137.2,
32.4(2), 129.9(2), 129.7(2), 129.3, 129.0, 128.5(2), 126.2(2), 113.9(2) (ArC),
01.8 (CHPh), 86.8 (C-1), 76.2, 72.6, 70.4, 68.5, 65.2, 55.2 21.1 (SC6H4CH3),
1
3
1
1
2
5
+
0.9 (COCH3). HRMS Calcd. for C30H32O7SNa (M+Na) : 559.1766; found
59.1760.
p-Tolyl 3-O-benzoyl-4,6-O-benzylidene-2-O-(4-methoxybenzyl)-1-thio-α-D-
mannopyranoside (4)
To a solution of known p-tolyl 4,6-O-benzylidene-2-O-(4-methoxybenzyl)-
[
25]
1-thio-α-D-mannopyranoside
(500 mg, 1 mmol) in pyridine (3 mL), BzCl

24 P. R. Verma and B. Mukhopadhyay
3
(1.5 mL) was added and the solution was allowed to stir at rt for 2 h. The
solvents were evaporated in vacuo and the residue was dissolved in CH2Cl2
15 mL) and washed successively with water (20 mL) and brine (20 mL).
(
The organic layer was separated, dried (Na2SO4), filtered, and evaporated in
vacuo. The residue thus obtained was purified by flash chromatography us-
ing n-hexane-EtOAc (3:1) to afford pure compound 4 as colorless gel (570 mg,
1
9
4%). H NMR (CDCl3, 500MHz) δ: 8.08–6.66 (m, 18H, ArH), 5.65 (s, 1H,
CHPh), 5.54 (dd, 1H, J2,3 = 3.0 Hz, J3,4 = 9.0 Hz, H-3), 5.47 (s, 1H, H-1),
4
5
1
.60 (ABq, 1H, J = 12.0 Hz, CH2C6H4OMe), 4.49 (m, 2H, CH2C6H4OMe, H-
AB
) 4.44 (t, 1H, J3,4 J4,5 = 9.5 Hz, H-4), 4.36 (d,1H, J1,2 = 1.0 Hz, H-2), 4.29 (dd,
H, J5,6a = 4.5 Hz, J
= 10.5 Hz, H-6a), 3.95 (t, 1H, J
= 9.5 Hz, J
6
a,6b
5,6b
6a,6b
=
10.0 Hz, H-6b), 3.72 (s, 3H, CH2C6H4OCH3), 2.36 (s, 3H, SC6H4CH3). 13C
NMR (CDCl3, 125MHz) δ: 165.7 (COPh), 159.4, 138.0, 137.2, 133.1, 132.5(2),
1
1
7
30.15, 129.9, 129.84, 129.8, 129.7, 129.2, 129, 128.9, 128.45, 128.3, 128.2,
26.1, 101.7 (CHPh), 87.0 (C-1), 77.1 (C-2), 76.3 (C-4), 72.7 (CH2C6H4OCH3),
1.1 (C-3), 68.52 (C-5), 55.1 (CH2C6H4OCH3), 21.1 (SC6H4CH3). HRMS Calcd.
+
for C35H34O7SNa (M+Na) : 621.1923; found 621.1918.
p-Tolyl 3-O-allyl-4,6-O-benzylidene-2-O-(4-methoxybenzyl)-1-thio-α-D-
mannopyranoside (6)
To a solution of known p-tolyl 4,6-O-benzylidene-2-O-(4-methoxybenzyl)-
[
25]
1
-thio-α-D-mannopyranoside
(500 mg, 1 mmol) in dry DMF (5 mL), NaH
(100 mg, 50% in mineral oil) was added followed by AllBr (1.5 mmol) and the
mixture was allowed to stir at rt for 3 h. Then MeOH (1 mL) was added to
quench excess NaH and the solvents were evaporated. The residue was dis-
solved in CH2Cl2 (20 mL) and washed successively with water (20 mL) and
brine (20 mL). The organic layer was separated, dried (Na2SO4), filtered, and
evaporated. The residue was purified by flash chromatography to afford com-
1
pound 6 as light yellow syrup (490 mg, 91%). H NMR (CDCl3, 500 MHz) δ:
6
5
4
.84–7.38 (m, 18H, ArH), 5.96 (m, 1H, CH2-CH = CH2), 5.51 (s, 1H, CHPh),
.43 (d, 1H, J1,2 = 1.5 Hz, H-1), 5.29, 5.22 (2dd, 1H, CH2-CH = CH2), 4.64,
.54 (ABq, 2H, J = 12.0 Hz, CH2C6H4OMe), 4.19 (m, 1H, H-5), 4.11 (m, 3H,
AB
H-2, H-4, CH2-CH = CH2), 3.92 (m, 2H, H-6a, CH2-CH = CH2), 3.84 (m, 1H,
H-6b), 3.78 (s, 3H, CH2C6H4OCH3), 3.64 (dd, 1H, J3,2 = 3.0 Hz, J3,4 = 9.5 Hz,
H-3), 2.35 (s, 3H, SC6H4OCH3). 13C NMR (CDCl3, 125MHz) δ: 159.4, 138.0,
1
34.2 (CH2-CH = CH2), 132.4 (2), 131.3, 130.1, 129.8(2), 129.7(2), 129.6(2),
1
28.7(2), 128.5(2), 117.8 (CH2-CH = CH2), 113.7 (2) (ArC), 100.2 (CHPh), 86.4
(C-1), 79.1 (C-3), 74.5, 73.3 (C-5), 71.4 (CH2C6H4OMe), 70.4 (CH2-CH = CH2),
67.2, 62.9 (C-6), 55.5 (CH2C6H4OCH3), 21.1 (SC6H4CH3). HRMS Calcd. for
+
C31H34O6SNa (M+Na) : 557.1974; found 557.1972.

Selective Hydrolysis of Benzylidene
3
25
p-Tolyl 3-O-benzyl-4,6-O-benzylidene-2-O-(4-methoxybenzyl)-1-thio-α-D-
mannopyranoside (8)
To a solution of known p-tolyl 4,6-O-benzylidene-2-O-(4-methoxybenzyl)-
[
25]
1-thio-α-D-mannopyranoside
(500 mg, 1 mmol) in dry DMF (5 mL), NaH
(100 mg, 50% in mineral oil) was added followed by BnBr (1.5 mmol) and the
mixture was allowed to stir at rt for 3 h. Then MeOH (1 mL) was added to
quench excess NaH and the solvents were evaporated. The residue was dis-
solved in CH2Cl2 (20 mL) and washed successively with water (20 mL) and
brine (20 mL). The organic layer was separated, dried (Na2SO4), filtered, and
evaporated. The residue was purified by flash chromatography to afford com-
1
pound 8 as light yellow syrup (550 mg, 93%). H NMR (CDCl3, 500 MHz) δ:
7
.54–6.84 (m, 18H, ArH), 5.65 (s, 1H, CHPh), 5.39 (d, 1H, J1,2 = 1.5 Hz, H-
1
), 4.82 (ABq, 1H, J = 11.5 Hz,
= 12.0 Hz, CH2Ph), 4.65 (ABq, 3H, J
AB
AB
CH2Ph, CH2C6H4OMe), 4.30 (m, 2H, H-3, H-4), 4.23 (dd, 1H, J5,6a = 3.5 Hz,
= 9.5 Hz, H-6a), 4.03 (q, 1H, J1,2 = 1.5 Hz, J2,3 = 3.0 Hz, H-2), 3.97
J
6
a,6b
(dd, 1H, J
= 3.0 Hz, J
= 9.5 Hz, H-6b), 3.90 (m, 1H, H-5), 3.81 (s,
13
5
,6b
6a,6b
3
1
1
7
H, CH2C6H4OCH3), 2.34 (s, 3H, SC6H4OCH3). C NMR (CDCl3, 125MHz) δ:
59.4, 138.4, 137.9, 137.6, 132.3(2), 129.9, 129.9(2), 129.8(2), 128.8, 128.3(2),
28.2(2), 127.6(2), 126.1(2), 113.8(2), 101.5 (CHPh), 87.5 (C-1), 79.1 (C-4),
7.4 (C-2), 76.1, 72.9 (CH2Ph), 72.6 (CH2C6H4OMe), 68.5 (C-6), 65.3, 55.2
+
(
6
CH2C6H4OCH3), 21.1 (SC6H4CH3). HRMS Calcd. for C35H36O6SNa (M+Na) :
07.2130; found 607.2125.
Ethyl 3-O-benzyl-4,6-O-benzylidene-2-O-(4-methoxybenzyl)-1-thio-α-D-
mannopyranoside (10)
To a solution of known ethyl 4,6-O-benzylidene-2-O-(4-methoxybenzyl)-
[
26]
1-thio-α-D-mannopyranoside
(450 mg, 1 mmol) in dry DMF (5 mL), NaH
(100 mg, 50% in mineral oil) was added followed by BnBr (1.5 mmol) and the
mixture was allowed to stir at rt for 3 h. Then MeOH (1 mL) was added to
quench excess NaH and the solvents were evaporated. The residue was dis-
solved in CH2Cl2 (20 mL) and washed successively with water (20 mL) and
brine (20 mL). The organic layer was separated, dried (Na2SO4), filtered, and
evaporated. The residue was purified by flash chromatography to afford com-
1
pound 10 as colorless foam (510 mg, 94%). H NMR (CDCl3, 500 MHz) δ:
6
.86–7.52 (m, 14H, ArH), 5.64 (s, 1H, CHPh),5.28, (d, 1H, J1,2 = 1.0 Hz, H-
1), 4.80 (d, 1H, CH2Ph), 4.68, 4.62 (ABq, 2H, CH2C6H4OMe), 4.29 (t, 1H, J4,3
=
9.5 Hz, J4,5 = 9.5 Hz, H-4), 4.23 (m, 2H, H-5, H-6a), 3.92 (m, 3H, H-2, H-
3
, H-6b), 3.81 (s, 3H, CH2C6H4OCH3), 2.63 (m, 2H, SCH2CH3), 1.26 (t, 3H,
1
3
SCH2CH3). C NMR (CDCl3, 125MHz) δ: 159.3, 138.5, 137.7, 129.9, 129.7,
1
8
6
28.8, 128.3(2), 128.1(2), 127.6(2), 127.5, 126.1, 113.8(2) (ArC), 101.4 (CHPh),
3.6(C-1), 79.2 (C-4),77.6, 76.4, 72.9 (CH2Ph), 72.7 (CH2C6H4OMe), 68.6 (C-6),
4.6, 55.3 (C6H4OCH3), 25.3 (SCH2CH3), 14.9 (SCH2CH3). HRMS Calcd. for
+
C30H34O6SNa (M+Na) : 545.1974; found 545.1970.

26 P. R. Verma and B. Mukhopadhyay
3
Ethyl 4,6-O-benzylidene-2,3-di-O-(4-methoxybenzyl)-1-thio-α-D-
mannopyranoside (12)
To a solution of known ethyl 4,6-O-benzylidene-2-O-(4-methoxybenzyl)-1-
[
26]
thio-α-D-mannopyranoside
(450 mg, 1 mmol) in dry DMF (5 mL), NaH
(100 mg, 50% in mineral oil) was added followed by PMBCl (1.5 mmol) and
the mixture was allowed to stir at rt for 4 h. Then MeOH (1 mL) was added
to quench excess NaH and the solvents were evaporated. The residue was dis-
solved in CH2Cl2 (20 mL) and washed successively with water (20 mL) and
brine (20 mL). The organic layer was separated, dried (Na2SO4), filtered, and
evaporated. The residue was purified by flash chromatography to afford com-
1
pound 12 as colorless foam (520 mg, 91%). H NMR (CDCl3, 500 MHz) δ:
6
4
4
.86–7.54 (m, 13H, ArH), 5.65 (s, 1H, CHPh), 5.28 (d, 1H, J1,2 = 1.0 Hz, H-1),
.73 (m, 3H, CH2C6H4OMe), 4.75 (ABq, 1H, J
= 12.0 Hz, CH2C6H4OMe),
AB
.28 (m, 3H, H-4, H-5, H-6a), 3.93 (m, 2H, H-3, H-6b), 3.87 (dd, 1H, J1,2
=
1.0 Hz, J2,3 = 3.0 Hz, H-2), 3.83, 3.82 (2s, 6H, CH2C6H4OCH3), 2.64 (m,
13
2
1
1
6
1
5
H, SCH2CH3), 1.29 (t, 3H, SCH2CH3). C NMR (CDCl3, 125 MHz) δ: 159.3,
59.1, 137.7, 130.5, 129.9, 129.7(2), 129.2(2), 128.8, 128.1(2), 126.1(2), 113.8(2),
13.7(2) (ArC), 101.4, 83.6 (C-1), 79.2, 77.6, 76.0, 72.7 (CH2Ph), 72.6 (CH2Ph),
8.6 (C-6), 64.6, 55.23 (CH2C6H4OMe), 55.2 (CH2C6H4OMe), 25.3 (SCH2CH3),
+
4.9 (SCH2CH3). HRMS Calcd. for C31H36O7SNa (M+Na) : 575.2079; found
75.2075.
p-Tolyl 2-O-benzoyl-4,6-O-benzylidene-3-O-(4-methoxybenzyl)-1-thio-β-D-
glucopyranoside (14)
The compound was prepared by following the literature procedure.[27]
p-Tolyl 4,6-O-benzylidene-2,3-di-O-(4-methoxybenzyl)-1-thio-β-D-
glucopyranoside (16)
The compound was prepared by following the literature procedure.[28]
p-Tolyl 2-azido-4,6-O-benzylidene-2-deoxy-3-O-(4-methoxybenzyl)-1-thio-β-D-
galactopyranoside (18)
To a solution of known p-tolyl 2-azido-4,6-O-benzylidene-2-deoxy-1-thio-β-
[
29]
D-galactopyranoside
(400 mg, 1 mmol) in dry DMF (5 mL), NaH (100 mg,
50% in mineral oil) was added followed by PMBCl (1.5 mmol) and the mixture
was allowed to stir at rt for 4 h. Then MeOH (1 mL) was added to quench
excess NaH and the solvents were evaporated. The residue was dissolved
in CH2Cl2 (20 mL) and washed successively with water (20 mL) and brine
(20 mL). The organic layer was separated, dried (Na2SO4), filtered, and evap-
orated. The residue was purified by flash chromatography to afford compound
1
1
8 as colorless gel (480 mg, 92%). H NMR (CDCl3, 500 MHz) δ: 7.62–6.85 (m,

Selective Hydrolysis of Benzylidene
3
27
13H, ArH), 5.43 (s, 1H, CHPh), 4.63 (s, 2H, CH2C6H4OMe), 4.63 (m, 2H, H-
6a, H-1), 4.05 (d, 1H, J3,4 = 3.0 Hz, H-4), 3.98 (dd, 1H, J = 1.5 Hz, H-6b),
3.80 (s, 3H, CH2C6H4OCH3), 3.73 (t, 1H, J1,2 = 10.0 Hz, J2,3 = 9.5 Hz, H-2),
3.43 (dd, 1H, J2,3 = 9.5 Hz, J3,4 = 3.5 Hz, H-3), 3.37 (bd, 1H, H-5), 2.33 (s,
3
H, SC6H4OCH3). 13C NMR (CDCl3, 125MHz) δ: 159.4, 138.6, 137.7, 134.9(2),
129.7, 0129.5(2), 129.1, 128.1(2), 126.6, 126.1(2), 126.1(2), 113.8 (ArC), 101.2
(
CHPh), 85.1 (C-1), 79.1 (C-3), 72.1 (C-4), 71.2, 69.8 (C-5), 69.4 (C-6), 59.6 (C-2),
5
5.2 (CH2C6H4OCH3), 21.2 (S-C6H4-CH3). HRMS Calcd. for C28H29N3O5SNa
+
(
M+Na) : 542.1726; found 542.1722.
p-Methoxyphenyl 3,4-O-isopropylidene-2,6-di-O-(4-methoxybenzyl)-β-D-
galactopyranoside (20)
To a solution of known p-methoxyphenyl 3,4-O-isopropylidene-β-D-
[
30]
galactopyranoside
(350 mg, 1 mmol) in dry DMF (5 mL), NaH (100 mg, 50%
in mineral oil) was added followed by PMBCl (3.0 mmol) and the mixture was
allowed to stir at rt for 6 h. Then MeOH (1 mL) was added to quench excess
NaH and the solvents were evaporated. The residue was dissolved in CH2Cl2
(20 mL) and washed successively with water (20 mL) and brine (20 mL).
The organic layer was separated, dried (Na2SO4), filtered, and evaporated.
The residue was purified by flash chromatography to afford compound 20 as
1
light yellow syrup (550 mg, 90%). H NMR (CDCl3, 500 MHz) δ: 7.35–6.79 (m,
12H, ArH), 4.86–4.78 (m, 3H, CH2C6H4OMe, H-1), 4.56, 4.49 (ABq, 2H, JAB
=
12.0 Hz, CH2C6H4OMe), 4.23 (t, 1H, J4,3 = 6.5 Hz, J4,5 = 5.5 Hz, H-4),
4
.19 (dd, 1H, J2,3 = 2.0 Hz, J3,4 = 5.5 Hz, H-3), 3.99 (m, 1H, H-5), 3.82 (m,
1H, 2×CH2C6H4OCH3, C6H4-OCH3, H-6a, H-6b), 3.66 (dd, 1H, J1,2 = 6.5 Hz,
1
1
3
J2,3 = 8.0 Hz, H-2), 1.42, 1.35 (2s, 6H, isopropylidene-CH3). C NMR (CDCl3,
1
1
25 MHz) δ: 159.2, 159.18, 151.4, 130.3, 130.25, 129.8(2), 129.2(2), 118.4(2),
14.5(2), 113.7(2), 113.6(2) (ArC), 110.1 (isopropylidene-C), 102.1 (C-1), 79.1
(
C-4), 78.9 (C-2), 73.6 (C-3), 73.3 (CH2Ph), 73.29 (CH2Ph), 72.6 (C-5), 69.3 (C-6),
5
5.6 (C6H4-OCH3), 55.3 (CH2-C6H4-OCH3), 55.2 (CH2-C6H4-OCH3), 27.8, 26.3
+
(
2×isopropylidene-CH3). HRMS Calcd. for C32H38O9Na (M+Na) : 589.2414;
found 589.2410.
p-Methoxyphenyl 6-O-tert-butyldiphenylsilyl-3,4-O-isopropylidene-2-O-
(4-methoxybenzyl)-β-D-galactopyranoside (22)
To a solution of known p-methoxyphenyl 6-O-tert-butyldiphenylsilyl-3,4-
[
31]
O-isopropylidene-β-D-galactopyranoside
(560 mg, 1 mmol) in dry DMF
(5 mL), NaH (100 mg, 50% in mineral oil) was added followed by PMBCl
(1.5 mmol) and the mixture was allowed to stir at rt for 2 h. Then MeOH
(1 mL) was added to quench excess NaH and the solvents were evaporated.
The residue was dissolved in CH2Cl2 (20 mL) and washed successively with
water (20 mL) and brine (20 mL). The organic layer was separated, dried

28 P. R. Verma and B. Mukhopadhyay
3
(
Na2SO4), filtered, and evaporated. The residue was purified by flash chro-
1
matography to afford compound 22 as colorless gel (580 mg, 85%). H NMR
(
CDCl3, 500 MHz) δ: 6.78–7.72 (m, 18H, ArH), 4.88 (ABq, 2H, JAB = 11.5 Hz,
CH2C6H4OMe), 4.79 (d, 1H, J1,2 = 8.0 Hz, H-1), 4.23 (m, 2H, H-3, H-4), 3.97 (m,
3
3
H, H-5, H-6a, H-6b), 3.80 (s, 3H, CH2C6H4OCH3), 3.76 (s, 3H, C6H4OCH3),
.66 (q, 1H, J = 6.0 Hz, 7.5 Hz, H-2), 1.41, 1.34 (2s, 6H, isopropylidene-
1
3
CH3), 1.08 (s, 9H, SiC(CH3)3). C NMR (CDCl3, 125 MHz) δ: 159.2, 155.2,
151.5, 135.6(2), 135.59(2), 133.3, 130.3, 129.8(2), 129.7, 129.7, 129.6, 127.7(2),
127.6(2), 118.4(2), 114.5(2), 113.7(2) (ArC), 110.0 (isopropylidene-C), 102.2
(C-1), 79.1, 79.0 (C-2), 73.6, 73.4, 73.3, 62.9 (C-6), 55.6 (C6H4OCH3), 55.3
(
1
7
C6H4-OCH3), 27.8, 26.3 (2×isopropylidene-CH3), 26.7, 27.0(3) (SiC(CH3)3),
+
9.2 (SiC(CH3)3). HRMS Calcd. for C40H48O8SiNa (M+Na) : 707.3016; found
07.3010.
p-Methoxyphenyl 2,3-O-isopropylidene-4-O-(4-methoxybenzyl)-α-L-
rhamnopyranoside (24)
To a solution of known p-methoxyphenyl 2,3-O-isopropylidene-α-L-
[
32]
rhamnopyranoside
(310 mg, 1 mmol) in dry DMF (5 mL), NaH (100 mg,
50% in mineral oil) was added followed by PMBCl (1.5 mmol) and the mix-
ture was allowed to stir at rt for 1 h. Then MeOH (1 mL) was added to
quench excess NaH and the solvents were evaporated. The residue was dis-
solved in CH2Cl2 (20 mL) and washed successively with water (20 mL)
and brine (20 mL). The organic layer was separated, dried (Na2SO4), fil-
tered, and evaporated. The residue was purified by flash chromatography
1
to afford compound 24 as colorless gel (400 mg, 93%). H NMR (CDCl3,
5
00 MHz) δ: 7.31–6.82 (ArH), 5.59 (s, 1H, H-1), 4.87 (ABq, 1H, J = 11.5 Hz,
CH2C6H4OMe), 4.60 (ABq, 1H, CH2C6H4OMe), 4.42 (t, 1H, J = 6.5 Hz, H-
), 4.36 (dd, 1H, J1,2 <1.0 Hz, J2,3 = 5.5 Hz, H-2), 3.85 (m, 1H, H-5), 3.80
s, 3H, CH2C6H4OCH3), 3.77 (s, 3H, C6H4OCH3), 3.28 (q, 1H, J3,4 = 7.0 Hz,
J4,5 = 7.0 Hz, H-4), 1.61, 156 (2s, 6H, isopropylidene-CH3), 1.22 (d, 3H, J
6.5 Hz, C-CH3). 13C NMR (CDCl3, 125MHz) δ: 159.2, 154.9, 150.1, 130.4,
3
(
=
1
29.6(2), 117.7(2), 114.6(2), 113.8(2), 113.7(2) (ArC), 109.4 (isopropylidene-C),
6.1 (C-1), 80.7 (C-4), 78.7 (C-3), 76.0 (C-2), 72.7 (CH2Ph), 65.4 (C-5), 55.6
9
(
CH2C6H4OCH3), 28.0, 26.4 (2×isopropylidene-CH3), 17.8 (C-CH3). HRMS
+
Calcd. for C24H30O7Na (M+Na) : 453.1889; found 453.1885.
p-Tolyl 3,4-O-isopropylidene-2-O-(4-methoxybenzyl)-1-thio-β-L-fucopyranoside
(
26)
The compound was prepared by the reported method in the literature.[33]

Selective Hydrolysis of Benzylidene
3
29
p-Methoxyphenyl 3,4-O-isopropylidene-2-O-(4-methoxybenzyl)-β-D-
fucopyranoside (28)
.82–7.35 (m, 8H, ArH), 4.86 (ABq, 2H, JAB = 11.0 Hz, CH2C6H4OMe),
.77 (d, 1H, J1,2 = 8.0 Hz, H-1), 4.20 (t, 1H, J3,2 = 7.0 Hz, H-3), 4.03 (dd, 1H,
6
4
J4,3 = 2.0 Hz, J4,5 = 2.0 Hz, H-4), 3.91 (m, 1H, H-5), 3.79 (s, 3H, C6H4OCH3),
3
.78 (s, 3H, C6H4OCH3), 3.63 (t, 1H, J2,1 = 8.0 Hz, J2,3 = 7.0 Hz, H-2), 1.43,
13
1.26 (2s, 6H, 2×isopropylidene-CH3), 1.43 (d, 3H, J6,5 = 6.5 Hz, H-6). C NMR
(CDCl3, 125 MHz) δ: 159.2, 155.2, 151.5, 130.4, 129.8(2), 118.6(2), 114.4(2),
113.6(2) (ArC), 109.7 (isopropylidene-C), 102.1 (C-1), 79.1 (C-3), 78.8 (C-2), 76.2
(
(
4
C-4), 73.3 (CH2C6H4OMe), 68.8 (C-5), 55.6, 55.2 (2×C6H4OCH3), 27.8, 26.4
+
2×isopropylidene-CH3), 16.6 (C-6). HRMS Calcd. for C24H30O7Na (M+Na) :
53.1889; found 453.1885.
p-Methoxyphenyl 2-O-(4-methoxybenzyl)-3,4-isopropylidene-β-L-
arabinopyranoside (30)
To
a
solution of known p-methoxyphenyl 3,4-isopropylidene-β-L-
[
34]
arabinopyranoside (300 mg, 1 mmol) in dry DMF (5 mL), NaH (100 mg, 50%
in mineral oil) was added followed by PMBCl (1.5 mmol) and the mixture was
allowed to stir at rt for 1 h. Then MeOH (1 mL) was added to quench excess
NaH and the solvents were evaporated. The residue was dissolved in CH2Cl2
(20 mL) and washed successively with water (20 mL) and brine (20 mL).
The organic layer was separated, dried (Na2SO4), filtered, and evaporated.
The residue was purified by flash chromatography to afford compound 30 as
1
colorless gel (400 mg, 95%). H NMR (CDCl3, 500 MHz) δ: 6.82–7.35 (m, 8H,
ArH), 4.95 (d, J1,2 = 6.5 Hz, H-1), 4.80 (s, 2H, CH2Ph), 4.34 (q, 1H, J = 4.5 Hz,
1
0.Hz, H-4), 4.24 (t, 1H, J3,2 = 7.0 Hz, H-3), 4.07 (dd, 1H, J = 5.0 Hz, 13.0 Hz,
H-5a), 3.86 (dd, 1H, J = 4.5 Hz, 13.0 Hz, H-5b) 3.80 (s, 3H, CH2C6H4OCH3),
3.78 (s, 3H, C6H4OCH3), 3.74 (t, 1H, J2,1 = 7.0 Hz, J2,3 = 7.0 Hz, H-2), 1.46,
1
.37 (2s, 6H, isopropylidene-CH3). 13C NMR (CDCl3, 125 MHz) δ: 159.3, 155.2,
151.0, 130.2, 129.8(2), 118.5(2), 114.5(2), 113.7(2) (ArC), 110.1 (isopropylidene-
C), 101.4 (C-1), 78.9 (C-2), 77.7 (C-3), 73.2 (CH2C6H4OMe), 72.4 (C-4), 62.5
(
C-5), 55.6 (C6H4OCH3), 55.3 (C6H4OCH3), 27.6, 25.8 (2×isopropylidene-CH3).
+
HRMS Calcd. for C23H28O7Na (M+Na) : 439.1733; found 439.1730.
p-Methoxyphenyl 2,3-O-isopropylidene-4-O-(4-methoxybenzyl)-α-L-
rhamnopyranosyl-(1→2)-3,4-O-isopropylidene-β-D-fucopyranoside (32)
To a solution of known p-methoxyphenyl 2,3-O-isopropylidene-α-L-
[
35]
rhamnopyranosyl-(1→2)-3,4-O-isopropylidene-β-D-fucopyranoside
mmol) in dry DMF (5 mL), NaH (100 mg, 50% in mineral oil) was added
followed by PMBCl (1.5 mmol) and the mixture was allowed to stir at rt for
h. Then MeOH (1 mL) was added to quench excess NaH and the solvents
were evaporated. The residue was dissolved in CH2Cl2 (20 mL) and washed
(500 mg,
1
1

30 P. R. Verma and B. Mukhopadhyay
3
successively with water (20 mL) and brine (20 mL). The organic layer was
separated, dried (Na2SO4), filtered, and evaporated. The residue was puri-
fied by flash chromatography to afford compound 34 as colorless gel (550 mg,
1
8
9%). H NMR (CDCl3, 500 MHz) δ: 6.78–7.28 (m, 8H, ArH), 5.53 (s, 1H, H-
’), 4.82, (ABq, 1H, JAB = 11.5 Hz, CH2C6H4OMe), 4.71 (d, 1H, J1,2 = 8.0 Hz,
1
H-1’), 4.58 (ABq, 1H, JAB = 11.0 Hz, CH2C6H4OMe), 4.25 (m, 2H, H-3, H-3’),
4.20 (d, 1H, J1,2 <1.0 Hz, J2,3 = 6.0 Hz, H-2’), 4.07 (m, 3H, H-2, H-4, H-5’),
3.94 (m, 1H, H-5), 3.94 (s, 3H, CH2C6H4OCH3), 3.75 (s, 3H, C6H4OCH3), 3.24
(
m, 1H, H-4’), 1.57, 1.51, 1.37, 1.35 (4×isopropylidene-CH3), 1.44 (d, 1H, J =
13
6
1
1
7
5
.5 Hz, H-6), 1.28 (d, 1H, J = 6.5 Hz, H-6’). C NMR (CDCl3, 125 MHz) δ:
59.0, 155.1, 151.5, 130.7, 129.5(2), 118.2(2), 114.5(2), 113.6(2) (ArC), 110.2,
09.01 (2×isopropylidene–CH3), 100.1 (C-1), 95.9 (C-1’), 80.7, 80.0, 76.7, 76.3,
6.2 (C-2’), 74.6, 72.5 (CH2C6H4OMe), 68.9 (C-5), 64.8, 55.6 (C6H4OCH3),
5.2 (CH2C6H4OCH3), 28.0, 27.97, 26.4, 26.36 (4×isopropylidene-CH3), 17.62
+
(
6
C-6’), 16.62(C-6). HRMS Calcd. for C33H44O11Na (M+Na) : 639.2781; found
39.2785.
General Procedure for Removal of the Benzylidene and
Isopropylidene Groups
To a solution of the starting material (1 mmol) in commercial-grade MeOH
(
5 mL), H2SO4-silica (50 mg) was added and the mixture was stirred at rt for
the required time (Table 1). After completion of reaction, the reaction mixture
was filtered through a pad of Celite, solvents were evaporated in vacuo, and
the crude product thus obtained was purified by flash chromatography using
n-hexane-EtOAc mixture as eluent to afford the pure diol product.
p-Tolyl 3-O-acetyl-2-O-(4-methoxybenzyl)-1-thio-α-D-mannopyranoside (2)
1H NMR (CDCl3, 500 MHz) δ: 7.11–7.33 (m, 8H, ArH), 5.39 (d, 1H, J1,2
=
1.5 Hz, H-1), 5.05 (dd, 1H, J3,2 = 3.0 Hz, J3,4 = 9.5 Hz, H-3), 4.58, 4.46
(ABq, 2H, J
= 12.0 Hz, CH2C6H4OMe), 4.15 (m, 2H, H-4, H-5), 4.08 (q,
AB
1H, J2,1 = 1.5 Hz, J2,3 = 3.0Hz, H-2) 3.86 (bs, 2H, H-6a, H-6b), 3.80 (s,
13
3H, CH2C6H4OCH3), 2.34 (s, 3H, SC6H4CH3), 2.05 (s, 3H, OCOCH3).
C
NMR (CDCl3, 125 MHz) δ: 171.1 (COCH3), 159.4, 138.1, 132.5(2), 129.97(2),
129.9, 129.6(2), 129.4, 113.8(2) (ArC), 86.1 (C-1), 76.5 (C-2), 74.3 (C-3), 73.3,
7
2.3 (CH2Ph), 66.4, 62.4 (C-6), 55.3 (CH2C6H4CH3), 21.1 (SC6H4CH3), 21.0
+
(
COCH3). HRMS Calcd. for C23H28O7SNa (M+Na) : 471.1453; found 471.1448.
p-Tolyl 3-O-benzoyl-2-O-(4-methoxybenzyl)-1-thio-α-D-mannopyranoside (5)
1H NMR (CDCl3, 500 MHz) δ: 8.05–667 (m, 13H, ArH), 5.45 (d, 1H, 1.5 Hz,
H-1), 5.32 (dd, 1H, J2,3 = 3.0 Hz, J3,4 = 9.5 Hz, H-3), 4.59, 4.47 (ABq, 2H,
J
= 12.0 Hz, CH2C6H4OMe), 4.34 (t, 1H, J3,4 = 10.0 Hz, J4,5 = 9.5 Hz, H-
AB
4), 4.25 (m, 1H, H-5), 4.22 (q, 1H, J1,2 = 1.5 Hz, J2,3 = 3.0 Hz, H-2), 3.91

Selective Hydrolysis of Benzylidene
3
31
(
bd, 2H, H-6a, H-6b), 3.72 (s, 3H, CH2C6H4OCH3), 2.34 (s, 3H, SC6H4OCH3).
C NMR (CDCl3, 125MHz) δ: 166.5 (COPh), 159.3, 138.0, 133.3, 132.6(2),
1
3
129.9, 129.8(2), 129.8, 129.6, 129.5, 129.3, 128.4(2), 113.8(2), 86.2 (C-1), 76.6
(
(
5
C-2), 74.9 (C-3), 73.5 (C-5), 72.3 (CH2C6H4OMe), 66.54 (C-4), 62.4 (C-6), 55.1
+
CH2C6H4OCH3), 21.1 (SC6H4CH3). HRMS Calcd. for C28H30O7SNa (M+Na) :
33.1610; found 533.1605.
p-Tolyl 3-O-allyl-2-O-(4-methoxybenzyl)-1-thio-α-D-mannopyranoside (7)
1H NMR (CDCl3, 500 MHz) δ: 6.86–7.33 (m, 13H, ArH), 5.93 (m, 1H, CH2-
CH = CH2), 5.40 (d, 1H, J1,2 = 1.5 Hz, H-1), 5.31, 5.24 (2dd, 1H, CH2-CH =
CH2), 4.64, 4.55 (ABq, 2H, J = 12.0 Hz, CH2C6H4OMe), 4.15 (m, 1H, H-5),
AB
4
3
.05 (m, 3H, H-2, H-4, CH2-CH = CH2), 3.94 (m, 2H, H-6a, CH2-CH = CH2),
.87 (m, 1H, H-6b), 3.80 (s, 3H, CH2C6H4OCH3), 3.61 (dd, 1H, J3,2 = 3.0 Hz,
J3,4 = 9.5 Hz, H-3), 2.57 (bs, 1H, -OH), 2.34 (s, 3H, SC6H4OCH3), 2.03 (bs,
1
3
1
1
H, -OH). C NMR (CDCl3, 125 MHz) δ: 159.4, 138.0, 134.2 (CH2-CH = CH2),
32.5(2), 130.1, 129.9(2), 129.7, 129.6(2), 117.9 (CH2-CH = CH2), 113.8(2)
(
ArC), 86.5 (C-1), 79.2 (C-3), 74.6, 73.1 (C-5), 71.7 (CH2C6H4OMe), 70.4 (CH2-
CH = CH2), 67.3, 62.8 (C-6), 55.3 (CH2C6H4OCH3), 21.1 (SC6H4CH3). HRMS
+
Calcd. for C24H30O6SNa (M+Na) : 469.1661; found 469.1659.
p-Tolyl 3-O-benzyl-2-O-(4-methoxybenzyl)-1-thio-α-D-mannopyranoside (9)
1H NMR (CDCl3, 500 MHz) δ: 7.39–6.82 (m, 13H, ArH), 5.44 (d, 1H, 1.0 Hz,
H-1), 4.60–4.44 (m, 4H, CH2Ph, CH2C6H4OMe), 4.14 (m, 1H, H-5), 4.08 (t, 1H,
J3,4 = 9.0Hz, J4,5 = 9.5 Hz, H-4), 4.02 (q, 1H, J1,2 = 1.5 Hz, J2,3 = 3 Hz, H-2),
3
3
3
1
.89 (dd, 1H, J5,6a = 3.5 Hz, J
= 11.5 Hz, H-6a), 3.82 (t, 1H, H-6b), 3.79 (s,
6
a,6b
H, CH2C6H4OCH3), 3.69 (dd, 1H, J2,3 = 3.0 Hz, J3,4 = 9.5 Hz, H-3), 2.34 (s,
H, SC6H4OCH3). 13C NMR (CDCl3, 125MHz) δ: 159.4, 138.1, 137.7, 132.5(2),
30.0, 129.9(2), 129.7, 129.6(2), 128.6(2), 128.0(2), 127.9(2), 113.9(2) (ArC), 86.4
(C-1), 79.5 (C-3), 74.8 (C-2), 73.1 (C-5), 71.8 (CH2Ph), 71.6 (CH2C6H4OMe),
6
7.4 (C-4), 62.8 (C-6), 55.3 (CH2C6H4OCH3), 21.1 (SC6H4CH3). HRMS Calcd.
+
for C28H32O6SNa (M+Na) : 519.1817; found 519.1822.
Ethyl 3-O-benzyl 2-O-(4-methoxybenzyl)-1-thio-α-D-mannopyranoside (11)
1
1
H NMR (CDCl3, 500 MHz) δ: H NMR (CDCl3, 500 MHz) δ: 6.83–7.36 (m,
1
5H, ArH), 5.33 (d, 1H, J1,2 = 0.5 Hz, H-1), 4.62 (ABq, 1H, CH2Ph), 4.54 (ABq,
2
H, CH2C6H4OMe), 4.43 (ABq, 1H, CH2Ph), 4.06 (t, 1H, J4,3 = 9.5 Hz, J4,5
=
9.5 Hz, H-4), 3.99 (m, 1H, H-5), 3.87 (m, 3H, H-2, H-6a, H-6b), 3.38 (s, 3H,
CH2C6H4OCH3), 3.65 (q, 1H, J3,2 = 3.0 Hz, J3,4 = 9.5 Hz, H-3), 2.64 (m, 2H,
SCH2CH3), 1.27 (t, 3H, SCH2CH3). 13C NMR (CDCl3, 125 MHz) δ: 159.4, 137.7,
1
3
29.8, 129.6(2), 128.5(2), 127.9, 127.87(2), 113.8(2) (ArC), 82.2 (C-1), 79.8 (C-
), 75.1 (C-2), 72.4 (C-5), 71.9 (CH2Ph), 71.6 (CH2C6H4OMe), 67.5 (C-4), 62.8

32 P. R. Verma and B. Mukhopadhyay
3
(
C-6), 55.2 (C6H4OCH3), 25.4 (SCH2CH3), 14.8 (SCH2CH3) HRMS Calcd. for
+
C23H30O6SNa (M+Na) : 457.1661; found 457.1656.
Ethyl 2,3-di-O-(4-methoxybenzyl)-1-thio-α-D-mannopyranoside (13)
1H NMR (CDCl3, 500 MHz) δ: 6.85–7.28 (m, 8H, ArH), 5.32 (s, 1H, CHPh),
4.62, 4.55, 4.47, 4.34 (ABq, 4H, CH2C6H4OMe), 4.02 (m, 2H, H-4, H-5), 3.87
(m, 3H, H-2, H-6a, H-6b), 3.80, 3.79 (2s, 6H, CH2C6H4OCH3), 3.63 (dd, 1H,
J3,2 = 3.0 Hz, J3,4 = 6.0 Hz, H-3), 2.64 (m, 2H, SCH2CH3), 1.27 (t, 3H,
SCH2CH3). 13C NMR (CDCl3, 125 MHz) δ: 159.4, 159.3, 129.9, 129.8, 129.6(2),
1
2
4
13.9(2), 113.8(2) (ArC), 87.2 (C-1), 79.3, 75.1, 72.3, 71.8, 71.2, 67.4, 62.9, 55.3,
+
5.3 (SCH2CH3), 14.8 (SCH2CH3). HRMS Calcd. for C24H32O7SNa (M+Na) :
87.1766; found 487.1761.
p-Tolyl 2-O-benzoyl-3-O-(4-methoxybenzyl)-1-thio-β-D-glucopyranoside (15)
1H NMR (CDCl3, 500 MHz) δ: 6.71–8.08 (m, 13H, ArH), 5.22 (dd, 1H, J1,2
=
10.0 Hz, J2,3 = 9.5 Hz, H-2), 4.78 (d, 1H, J1,2 = 10.0 Hz, H-1), 4.66, 4.53
(ABq, J
= 11.0 Hz, CH2C6H4OMe), 3.94 (dd, 1H, J6a,5 = 3.0 Hz, J
=
AB
6a,6b
1
2.0 Hz, H-6a), 3.82 (dd, 1H, J6 = 5.0 Hz, J
= 12.0 Hz, H-6b), 3.72
b,5
6b,6a
(
s, 3H, CH2C6H4OMe), 3.69 (m, 2H, H-3, H-4), 3.46 (m, 1H, H-5), 2.31 (s,
3
1
H, SC6H4CH3). 13C NMR (CDCl3, 125 MHz) δ: 165.2, 159.4, 138.4, 133.3,
33.1(2), 129.9, 129.8, 129.75, 129.68(2), 129.67(2), 128.6, 128.5(2), 113.9(2)
(
ArC), 86.6 (C-1), 83.5, 79.4 (C-5), 74.4 (CH2Ph), 72.4 (C-4), 70.3, 62.6 (C-
6
), 55.6 (CH2C6H4OCH3), 21.1 (SC6H4CH3). HRMS Calcd. for C28H30O7SNa
+
(
M+Na) : 533.1610; found 533.1605.
p-Tolyl 2,3-di-O-(4-methoxybenzyl)-1-thio-β-D-glucopyranoside (17)
.43–6.87 (m, 8H, ArH), 4.91 (ABq, 2H, CH2C6H4OMe), 4.70 (ABq, 1H,
7
JAB = 10.0 Hz, CH2C6H4OMe), 4.64 (m, 2H, H-1, CH2C6H4OMe), 3.87 (dd,
1
3
1
H, J6a,5 = 3.0 Hz, J
= 11.5 Hz, H-6a), 3.81 (s, 3H, CH2C6H4OCH3),
6
a,6b
.80 (s, 3H, CH2C6H4OCH3), 3.74 (dd, 1H, J
= 5.5 Hz, J
=
6b,5
6a,6b
1.5 Hz), 3.51 (m, 3H, H-2, H-3, H-4), 3.32 (m, 1H, H-5), 2.34 (s, 3H,
1
3
SC6H4CH3). C NMR (CDCl3, 125 MHz) δ: 159.5, 138.0, 132.5(2), 130.4, 130.1,
1
7
5
29.9(2), 129.8(2), 129.6(2), 114.1(2), 113.9(2) (ArC), 88.1(C-1), 85.7, 80.6,
9.1 (C-5), 75.0 (2×CH2C6H4OMe), 70.4, 62.8 (C-6), 55.3 (CH2C6H4OCH3),
5.2 (CH2C6H4OCH3), 21.1 (S-C6H4-CH3). HRMS Calcd. for C29H34O7SNa
+
(
M+Na) : 549.1923; found 549.1921.
p-Tolyl 2-azido-2-deoxy-3-O-(4-methoxybenzyl)-1-thio-β-D-galactopyranoside
19)
(
1H NMR (CDCl3, 500 MHz) δ: 7.48–6.87 (m, 8H, ArH), 4.61 (s, 2H,
CH2C6H4OMe), 4.33 (d, 1H, J1,2 = 10.5 Hz, H-1), 3.98 (bs, 1H, H-4), 3.9 (m,
1
1
H, H-6a), 3.80 (s, 3H, CH2C6H4OCH3), 3.78 (m, 1H, H-6b), 3.58 (t, 1H, J1,2 =
0.0 Hz, J2,3 = 9.5 Hz, H-2), 3.45 (m, 1H, H-5), 3.41 (dd, 1H, J3,2 = 6.5 Hz,

Selective Hydrolysis of Benzylidene
3
33
J3,4 = 3.0 Hz), 2.52 (s, 1H, -OH), 2.33 (s, 3H, SC6H4CH3), 2.28 (bs,
1
3
1
1
H, -OH). C NMR (CDCl3, 125 MHz) δ: 159.7, 138.6, 133.8(2), 129.8(2),
29.7(2), 128.9, 127.3, 114.0(2) (ArC), 86.2 (C-1), 80.6 (C-3), 78.1 (C-5), 71.8
(
(
4
CH2C6H4OMe), 66.1 (C-4), 62.7 (C-6), 60.8 (C-2), 55.3 (CH2C6H4OCH3), 21.1
+
S-C6H4-CH3). HRMS Calcd. for C21H25N3O5SNa (M+Na) : 454.1413; found
54.1409.
p-Methoxyphenyl 2,6-di-O-(4-methoxybenzyl)-β-D-galactopyranoside (21)
1H NMR (CDCl3, 500 MHz) δ: 7.31–7.27 (m, 12H, ArH), 4.99 (ABq, 1H,
JAB = 12.0 Hz, CH2C6H4OMe), 4.85 (d, 1H, J = 8.0 Hz, H-1), 4.72 (ABq,
1
H, J = 12.0 Hz, CH2C6H4OMe), 4.50 (s, 2H, CH2C6H4OMe), 4.01 (m, 1H,
AB
H-5), 3.79 (s, 6H, CH2C6H4OCH3), 3.78 (m, 4H, C6H4OCH3, H-6a), 3.75 (m,
2
H, H-6b, H-2), 3.69 (t, 1H, J4,3 = 6.0 Hz, J4,5 = 5.5 Hz, H-4), 3.56 (dd, 1H,
13
J3,2 = 6.0 Hz, J3,4 = 3.5 Hz, H-3), 2.73 (bs, 1H, -OH), 2.59 (bs, 1H, -OH).
C
NMR (CDCl3, 125MHz) δ: 159.43, 159.27, 155.28, 151.3, 130.3, 129.9, 129.8(2),
1
7
6
29.4(2), 118.4(2), 114.5(2), 113.9(2), 113.8(2) (ArC), 102.8 (C-1), 78.49 (C-2),
4.4 (CH2C6H4OMe), 73.6 (C-4), 73.4 (CH2C6H4OMe), 73.1 (C-3), 69.0 (C-
), 68.8 (C-5), 55.6 (C6H4OCH3), 55.2 (2×CH2C6H4OCH3). HRMS Calcd. for
+
C29H34O9Na (M+Na) : 549.2101; found 549.2098.
p-Methoxyphenyl 6-O-tert-butyldiphenylsilyl-2-O-(4-methoxybenzyl)-β-D-
galactopyranoside (23)
1H NMR (CDCl3, 500 MHz) δ: 6.79–7.70 (m, 18H, ArH), 5.00 (ABq, 1H,
JAB = 11.0 Hz, CH2C6H4OMe), 4.85 (d, 1H, J1,2 = 8.0 Hz, H-1), 4.73 (ABq,
1
H, J
= 11.0 Hz, CH2C6H4OMe), 4.08 (m, 1H, H-5), 3.95 (d, 2H, H-6a,
AB
H-6b), 3.80 (s, 3H, CH2C6H4OCH3), 3.78 (m, 4H, H-2, C6H4OCH3), 3.65 (m,
1
3
2H, H-3, H-4), 2.67, 2.56 (2d, 2H, -OH), 1.07 (s, 9H, SiC(CH3)3). C NMR
(CDCl3, 125 MHz) δ: 159.4, 155.2, 151.4, 135.6(2), 135.5(2), 133.0, 132.8, 130.3,
129.9(2), 129.8, 129.77, 128.6, 127.7(3), 114.5(2), 113.98(2), 113.9(2) (ArC),
102.8 (C-1), 78.5 (C-2), 74.7, 74.4, 73.3, 68.6 (C-5), 65.0, 63.2 (C-6), 55.6
(
C6H4OCH3), 55.2 (C6H4OCH3), 26.8 (SiC(CH3)3), 19.1 (SiC(CH3)3). HRMS
+
Calcd. for C37H44O8SiNa (M+Na) : 667.2703; found 667.2697.
p-Methoxyphenyl 4-O-(4-methoxybenzyl)-α-L-rhamnopyranoside (25)
1
H NMR (CDCl3, 500 MHz) δ: 7.30–6.81 (ArH), 5.38 (d, 1H, J1,2 = 1.5 Hz,
H-1), 4.72 (ABq, 2H, J = 11.0 Hz, CH2C6H4OMe), 4.11 (bd, 1H, H-2), 4.09
AB
(
m, 1H, H-3), 3.88 (m, 1H, H-5), 3.80 (s, 3H, CH2C6H4OCH3), 3.77 (s, 3H,
CH2C6H4OCH3), 3.42 (t, 1H, J4,3 = 9.0 Hz, J4,5 = 9.5 Hz, H-4), 2.64 (bs, 1H,
1
3
-
OH), 2.45 (bs, 1H, -OH), 1.32 (d, 3H, J = 6.0 Hz, C-CH3). C NMR (CDCl3,
1
9
5
25 MHz) δ: 159.5, 154.9, 150.2, 130.3, 129.6(2), 117.5(2), 114.6(2), 114.1(2)
8.1 (C-1), 81.2 (C-4), 74.7 (CH2C6H4OMe), 71.2 (C-3), 71.0 (C-2), 67.9 (C-5),
5.6, 55.3, 18.0 (C-CH3). HRMS Calcd. for C21H26O7Na (M+Na) : 413.1576;
+
found 413.1572.

34 P. R. Verma and B. Mukhopadhyay
3
p-Tolyl 2-O-(4-methoxybenzyl)-1-thio-β-L-fucopyranoside (27)
1H NMR (CDCl3, 500 MHz) δ: 7.49–6.9 (m, 8H, ArH), 4.90, 4.63 (ABq, 2H,
JAB = 11.0 Hz, CH2C6H4OCH3), 4.54 (d, 1H, J1,2 = 10.0 Hz, H-1), 3.80 (s,
3
9
H, C6H4OCH3), 3.72 (bs, 1H, H-4), 3.62 (m, 2H, H-5, H-3), 3.51 (t, 1H, J2,1 =
.0 Hz, J2,3 = 9.0 Hz, H-2), 2.53 (bs, 1H, -OH), 2.34 (s, 3H, SC6H4CH3), 2.22
1
3
(
bs, 1H, -OH), 1.34 (d, 3H, J = 6.5 Hz, C-CH3). C NMR (CDCl3, 125 MHz)
δ: 159.5, 137.7, 132.3(2), 130.2, 130.1, 129.9(2), 129.7(2), 114.0(2) (ArC), 87.7
(
(
C-1), 77.7 (C-2), 75.2 (C-5), 74.8 (C6H4OCH3), 74.4 (C-3), 71.7 (C-4), 21.1
SC6H4CH3), 16.6 (C-6). HRMS Calcd. for C21H26O5SNa (M+Na) : 413.1399;
+
found 413.1395.
p-Methoxyphenyl 2-O-(4-methoxybenzyl)-β-D-fucopyranoside (29)
6
.84–7.31 (m, 8H, ArH), 4.99 (ABq, 1H, JAB = 11.0Hz, CH2C6H4OMe), 4.84
(
3
(
d, 1H, J1,2 = 7.5 Hz, H-1), 3.80 (s, 3H, C6H4OCH3), 3.79 (s, 3H, C6H4OCH3),
1
3
.76–3.65 (m, 4H, H-2, H-3, H-4, H-5), 1.38 (d, 3H, J6,5 = 6.5 Hz, H-6). C NMR
CDCl3, 125 MHz) δ: 159.5, 155.3, 151.4, 130.3, 129.9(2), 118.4(2), 114.5(2),
1
14.0(2) (ArC), 102.7 (C-1), 78.2, 74.3 (CH2Ph), 73.4, 71.1, 70.5, 55.6, 55.3
+
(
2×C6H4OCH3), 16.3 (C-6). HRMS Calcd. for C21H26O7Na (M+Na) : 413.1576;
found 413.1570.
p-Methoxyphenyl 2-O-(4-methoxybenzyl)-β-L-arabinopyranoside (31)
1
H NMR (CDCl3, 500 MHz) δ: 6.83–7.30 (m, 8H, ArH), 4.96 (d, J1,2 =
6
.5 Hz, H-1), 4.87, 4.68 (ABq, 2H, CH2C6H4OMe), 3.98 (bs, 1H, H-4), 3.96
(
dd, J4,5a = 5.0 Hz, J5
= 12.5 Hz, H-5a), 3.80 (s, 3H, CH2C6H4OCH3),
a,5b
3
1
1
1
5
3
.78 (m, 5H, H-2, H-3, C6H4OCH3), 3.62 (dd, 1H, J
= 2.5 Hz, J
=
4
,5b
5a,5b
1
3
2.0 Hz, H-5b), 2.82, 2.57 (2bs, 2H, -OH). C NMR (CDCl3, 125 MHz) δ:
59.5, 155.4, 150.6, 129.9, 129.8(2), 118.4(2), 114.6(2), 114.0(2) (ArC), 101.5 (C-
), 77.3, 73.7 (CH2C6H4OMe), 71.4, 66.7 (C-4), 63.8 (C-5), 55.6 (C6H4OCH3),
+
5.3 (C6H4OCH3). HRMS Calcd. for C20H24O7Na (M+Na) : 399.1420; found
99.1416.
p-Methoxyphenyl 4-O-(4-methoxybenzyl)-α-L-rhamnopyranosyl-(1→2)-β-D-
fucopyranoside (33)
1H NMR (CDCl3, 500 MHz) δ: 7.26–6.72 (m, 8H, ArH), 5.26 (s, 1H, H-
1
’), 5.04 (bs, 1H, OH), 4.92 (bs, 1H, OH), 4.72 (ABq, 1H, JAB = 11.0 Hz,
CH2C6H4OCH3), 4.67 (d, 1H, 8.0 Hz, H-1), 4.54 (ABq, 1H, JAB = 11.0 Hz,
CH2C6H4OCH3), 4.18 (bs, 1H,), 3.74 (s, 3H, CH2C6H4OCH3), 3.72 (s, 3H,
C6H4OCH3), 3.56 (bs, 1H), 2.87 (bs, 2H, 2×OH), 1.29 (d, 1H, 6.0Hz, H-6),
1
1
8
.22 (d, 1H, 6.5 Hz, H-6). 13C NMR (CDCl3, 125 MHz) δ: 159.1, 155.0, 151.3,
30.8, 129.2(2), 117.9(2), 114.5(2), 113.7(2) (ArC), 101.1 (C-1), 100.4 (C-1 ),
1.2, 74.7, 74.1, 72.0, 71.0, 70.4, 67.8, 55.6, 55.2, 18.0, 16.3. HRMS Calcd. for
ꢁ
+
C27H36O11Na (M+Na) : 559.2155; found 559.2151.

Selective Hydrolysis of Benzylidene
3
35
Recovery of the Catalyst
After the reaction was completed, the mixture was filtered through What-
man 1 filter paper and washed with CH2Cl2. The solid catalyst was recovered
◦
and dried for 10 min in the oven at 100 C and reused in further reaction. No
cross-contamination was evident when the catalyst was used for a different
reaction.
Acknowledgments
PRV is thankful to IISER Kolkata for Senior Research Fellowship.
Funding
This work is funded by the Scientific and Engineering Research Board (SERB),
New Delhi, through the grant SB/S1/OC-48/2013 to BM.
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