Efficient one-pot per-: O -acetylation-thioglycosidation of native sugars, 4,6- O -arylidenation and one-pot 4,6- O -benzylidenation-acetylation of S -/ O -glycosides catalyzed by Mg(OTf)2

Article abstract of DOI:10.1039/c6ra23198e

A sequential one-pot per-O-acetylation-S-/O-glycosidation of native mono and disaccharides under solvent free conditions using 0.5 mole% of Mg(OTf)₂ as a non-hygroscopic, recyclable catalyst is reported. Regioselective 4,6-O-arylidenation of glycosides and thioglycosides with benzaldehyde or p-methoxybenzaldehyde dimethyl acetal is catalyzed by 10 mole% of Mg(OTf)₂ to produce the corresponding 4,6-O-arylidenated product in high yields. Mg(OTf)₂ can also mediate sequential one-pot benzylidenation-acetylation of mono and disaccharide based glycosides and thioglycosides in high yield.

Full text of DOI:10.1039/c6ra23198e

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ARTICLE
Efficient one-pot per-O-acetylation–thioglycosidation of native
sugars, 4,6-O-arylidenation and one-pot 4,6-O-benzylidenation–
acetylation of S-/O-glycosides catalyzed by Mg(OTf)2
Received 00th January 20xx,
Accepted 00th January 20xx
Mana Mohan Mukherjee, Nabamita Basu,† Aritra Chaudhury and Rina Ghosh*
DOI: 10.1039/x0xx00000x
www.rsc.org/
A sequential one-pot per-O-acetylation– S-/O-glycosidation of native mono and disaccharides under solvent free condition
using 0.5 mole% of Mg(OTf)2 as non hygroscopic, recyclable catalyst is reported. Regioselective 4,6-O-arylidenation of
glycosides and thioglycosides with benzaldehyde or p-methoxybenzaldehyde dimethyl acetal is catalyzed by 10 mole% of
Mg(OTf)2 to produce the corresponding 4,6-O-arylidenated product in high yields. Mg(OTf)2 can also mediate sequential
one-pot benzylidenation–acetylation of mono and disaccharides based glycosides and thioglycosides in high yield.
8g
sieves,8e Al2O3,8f sulphonic acid functionalised γ-Al2O3 and
sulfamic acid.8h Beside these few other catalysts like I2,9a,b N-
Introduction
bromosuccinimide,9c Cu(ClO4)2.6H2O9d and even ionic liquids9e
The central principle of the atom economy and green
chemistry is the design of synthetic strategies that minimise
waste by using stoichiometric reagent and catalytic
promoters.1a-d Advancement of synthetic carbohydrate
chemistry demands extensive functional group transformation
by means of suitable protection and deprotection of hydroxy
groups.1e In this context, per-O-acetylation of native sugars is
the most commonly utilised functional group transformation
as these readily made per-O-acetylated sugars can be easily
activated by Lewis acid and transformed towards other
glycosyl donors like glycosyl halides or thioglycosides.2 The
classical method for carrying out per-O-acetylation is via
excess reagent like acetic anhydride or acetyl chloride in large
excess of pyridine as base as well as solvent in spite of its well
documented toxicity.3 The poor nucleophilicity of hydroxy
groups in carbohydrates sometimes necessitates addition of
pyridine derivatives like 4-dimethylaminopyridine (DMAP) or
4-pyrrolidino pyridine as co catalyst to activate the acetylating
agents or accelerate the reaction.4 So far many reports have
been made in this direction utilising acid or bases which
include (i) bases like NaOAc,5a NaOH/TBAB,5b imidazole5c and
DABCO;5d (ii) Lewis Acids such as ZnCl2,6a FeCl3,6b BF3.Et2O,6c
Cu(OTf)2,6d Sc(OTf)3,6e In(OTf)3,6f Ce(OTf)3,6g SnCl4,6h LiClO46i and
Fe2(SO4)3;6j (iii) protic acids such as H2SO4,7a H3BO3/H2SO47b and
p-TSA;7c (iv) heterogeneous catalysts like montmorillonite K-
10,8a H-β-Zeolite,8b H2SO4-SiO2,8c HClO4-SiO2,8d molecular
and microwave condition9f were also used. A few among the
above catalysts such as Cu(OTf)2,6d SnCl4,6h p-TSA,7c I2,9a,b and
Cu(ClO4)2.6H2O9d have been employed previously in
conjugation with BF3.Et2O for the one-pot sequential per-O-
acetylation – thioglycosidation reaction. In spite of their
effectiveness on many instances these catalysts even suffer
from many flaws like use of large excess of acetic anhydride,
environmentally hazardous volatile organic solvents (VOSs),
expensive catalysts, moisture intolerance, requirement of
catalyst preparation or incompatibility with carbohydrate
derivatives carrying acid sensitive protecting group. In some
instances, isomerized product mixture of furanose and
pyranose are obtained during acetylation of native sugars.6j, 8i
Therefore, there is strong need to search an effective catalyst
that is mild, non-toxic, and economically viable yet allows just
stoichiometric amount of the reagent and avoids use of toxic
VOSs. Moreover that can be employed for undertaking more
than one steps in one-pot in order to develop more efficient
and expeditious transformations.
After smooth preparation of S- and/or O-glycosides, 4,6-O-
benzylidene protection is of immense importance in the
synthesis of complex carbohydrates2g,h as these can be
selectively transformed to the corresponding 6-deoxy sugars
under oxidative condition.10a-e These benzylidene acetals can
either be selectively transformed under reductive
conditions11a-c to their corresponding 4-O-benzylated or 6-O-
benzylated analogue leaving the alternate hydroxy group free
to be used further as glycosyl acceptor during oligosaccharide
synthesis or to produce the corresponding 4,6-diol.11d-11f In
earlier days when benzaldehyde was employed as electrophile
a. Department of Chemistry, Jadavpur University, Jadavpur, Kolkata,
West Bengal, India, 700032.
E mail ghoshrina@yahoo.com; ghosh_rina@hotmail.com
† At present: Department of Organic Chemistry, IACS, Jadavpur, Kolkata 700032,
India.
for
4,6-O-benzylidene
protection,
most
of
such
or
12b
transformations were catalysed by ZnCl2,12a H2SO4
Electronic
Supplementary
Information
(ESI)
available:
See
DOI: 10.1039/x0xx00000x
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Journal Name
TsOH12c and later when benzaldehyde dimethylacetal was thiophenol and 1.2 equivalent of BF3.Et2O at
0
oC for
proved to be a better reagent, transacetalations were carried thiophenylation step. An exothermic reaction started
out with Lewis acids [VO(OTf)2]13a or Brønsted acids like immediately and a clear reaction mixture was obtained within
HBF4,13b CSA13c,d and TfOH13e including silica supported few minutes resulting in a complete consumption of the
14b
reagents (NaHSO4-SiO2,14a H2SO4-SiO2 and HClO4-SiO2,14c) or starting material (checked by TLC). Proceeding through a
15a-c
other reagents like I2
or 2,4,6 trichloro-1,3,5-triazine.15d number of such experiments 1.0 equivalent acetic anhydride
However some of these catalysts suffer from limitations too per hydroxy group with 0.5 mol% (0.005 equivalent) of the
like those having short shelf life, or often being corrosive and catalyst at room temperature was found to be most effective
expensive or tough to handle due to moisture sensitivity.
for the per O-acetylation reaction in terms of time of per O-
In continuation of our research on complex oligosaccharide acetylation step (Table 1); then to this reaction mixture
synthesis16 we needed to prepare a number of S- and O- thiophenol followed by lowering of the temperature to 0 oC,
glycosides and 4,6-O-benzylidenated carbohydrate derivatives BF3. Et2O was added and the reaction mixture was kept for 8
and we sought to modify even our own developed method hours at room temperature to produce phenyl 2,3,4,6-tetra-O-
16h
based on FeCl3 with a more efficient, non-hygroscopic and acetyl-1-thio-β-D-glucopyanoside
1b.
The
resulting
recyclable one. Recently Mg(OTf)2 has been used as highly thioglycoside was obtained as a single β anomer, due to
stable, non-hygroscopic and recyclable catalyst17a for many neighbouring group participation by C-2 acetate.
organic
transformations
like
silylation
of
α- In order to extend the scope of this reaction a series of native
hydroxyphosphonates,17b tetrahydroquinolene synthesis,17c mono and disaccharides were subjected to per-O-acetylation
and 1,3-dipolar cycloaddition reaction.17d For time and cost followed by one pot S-/O-glycosidation, and the results are
effectiveness and also due to environmental reasons summarised in Table 2. Per O-acetylation of glucose 1a under
minimisation of overall isolated steps during a total target this condition was completed at room temperature within 3
synthesis is advisable. Sometimes this is managed by minutes (checked by TLC) and then sequential one-pot
undertaking two or more reactions sequentially in one-pot. In thioglycosidation separately with thiophenol, ethanethiol and
this context we report herein Mg(OTf)2 as an inexpensive, thiocresol produced the corresponding thioglycosides 1b, 1c
recyclable, eco-friendly and multi-functional potent catalyst and 1d in 95%, 89% and 87% respective yields (entries 1, 2 and
for the extensive functional group manipulations of 3, Table 2). Scale up reaction using 5 g 1a produced 91% of
carbohydrate derivatives: For one-pot per-O-acetylation–S-/- phenyl 2,3,4,6-tetra-O-acetyl-1-thio-β-D-glucopyanoside 1b
;
O-glycosidation of native sugars, for 4,6-O-arylidenation and the yield is comparable with that of the pilot reaction (entry 1,
also for one-pot 4,6-O-benzylidenation – acetylation of mono Table 2). Similar sequential one-pot O-glycosidation using 4-
and disaccharide derivatives.
methoxyphenol afforded the corresponding O-glycoside 1e in
85% yield (entry 4, Table 2).
Reaction sequence akin to the previous one with D-galactose
2a produced the corresponding S- and O-glycosides 2b, 2c and
2d in 94%, 84% and 86% yield, respectively (entries 5, 6 and 7,
Table 2). The preparative scale reaction with 5 g of 2a
Result and discussion
For optimisation of reaction condition for one-pot acetylation
– S-/O-glycosidation, D-glucose 1a was initially allowed to react
with a varied quantity of acetic anhydride (1.5 to 1.0
equivalent per hydroxy group) in the presence of catalytic
amount of Mg(OTf)2 (0.1 to 0.001 equivalent) at room
temperature under neat condition for acetylation step; and
this was followed by in situ addition of 1.1 equivalent of
produced
phenyl
2,3,4,6-tetra-O-acetyl-1-thio-β-D-
galactopyanoside 2b in 89% yield (entry 5, Table 2). Per O-
acetylation of D-mannose 3a underwent smoothly at room
temperature within 3 minutes (checked by TLC) and then its
sequential one-pot thioglycosidation separately using
thiophenol and ethanethiol generated the corresponding α-
thioglycosides in 93% and 91% yields, respectively (entries 8
and 9, Table 2). Phenyl 2,3,4,6-tetra-O-acetyl-1-thio-α-D-
mannopyanoside 3b was prepared in 87% yield starting from 5
g of D-mannose (entry 8, Table 2).
Table 1 Optimisation of reaction condition of one-pot acetylation – thioglycosidation
After successful per-O-acetylation followed by in situ
stereoselective S- aryl/alkyl or O-aryl glycoside preparation of
native hexoses we turned our attention to similar reactions of
commonly used pentose sugars. Reaction of D-xylose 4a with 3
equivalent of Ac2O, 0.5 mole% Mg(OTf)2 followed by in situ
addition of thiophenol and BF3.Et2O produced the
corresponding
phenyl
2,3,4-tri-O-acetyl-1-thio-β-D-
xylopyranoside 4b in 86% yield (entry 10, Table 2). L-Rhamnose
5a after robust per-O-acetylation, in reaction separately with
thiophenol and 4-methoxyphenol produced the corresponding
S- and O-glycosides 5b and 5c in 84% and 87% respective yields
(entries 11 and 12, Table 2). The efficiency of this protocol was
2 | J. Name., 2012, 00, 1-3
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ARTICLE
Scheme 1 Per-O-acetylation and their one-pot conversion to S-aryl/alkyl or O-aryl glycoside of native sugars
Table 2 Sequential one-pot acetylation-S-or-O-glycosidation of native sugars
supported by preparative scale reaction with 5 g of 5a which acetylation for these native disaccharides were performed at
o
produced
phenyl
2,3,4-tri-O-acetyl-1-thio-α-L- 80 C for 5 minutes and after full consumption of free sugar
rhamnopyanoside 5b in 80% yield, comparable with the pilot (checked by TLC); sequential one-pot thioglycosidation then
reaction (entry 11, Table 2). p-Tolyl 2,3,4-tri-O-acetyl-1-thio-β- produced the corresponding phenyl 2,3,4,6-tetra-O-acetyl-β-D-
→4)
L-fucopyranoside 6b was prepared from L-fucose 6a via glucopyranosyl-(1
-2,3,6-tri-O-acetyl-1-thio-β-D-
sequenꢀal one-pot per-O-acetylaꢀon thioglycosidaꢀon in 86% glucopyranoside 8b in 77% yield (entry 16, Table 2). Similarly
̶
overall yield (entry 13, Table 2). The reaction with 2-deoxy-2- lactose produced the corresponding phenyl 2,3,4,6-tetra-O-
phthalimidoglucopyranoside 7a was carried out at 80 oC for 15 acetyl-β-D-glucopyranosyl-(1
-2,3,6-tri-O-acetyl-1-thio-β-D-
→4)
minutes, and then sequential in situ thioglycosidation galactopyranoside 9b in 85% overall yield, and its preparative
separately with thiophenol and thiocresol produced the scale reaction based on 2 g of 9a produced 9b in 83% overall
corresponding β-D-thioglycosides 7b and 7c in 78% and 73% yield (entry 17, Table 2). In case of maltose the corresponding
respective yields (entries 14 and 15, Table 2).
S-/ O-glycosides 10b and 10c were obtained in 91% and 83%
This per O-acetylation followed by in situ S- or O-glycoside overall yields, respectively (entries 18 and 19, Table 2).
preparation was also successful for the disaccharides like Preparative scale reaction with 2 g of native maltose produced
→4)
The per-O- phenyl 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl-(1 -2,3,6-
cellobiose 8a
,
lactose 9a and maltose 10a
.
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Journal Name
HO
O
Ar
PhOH(OMe)2 Or PMPCH(OMe)2
Mg(OTf)2 (10 mole%),
96
95
94
93
92
91
90
89
88
87
O
Y
O
HO
O
RO
RO
X
X
Dry MeCN, rt
Y
a
b; Ar = Ph
c;
Ar = PMP
HO
HO
O
OHOH
O
RO
X
Y
Glucose (2b)
X
RO
11a; X=  SPh, Y= OH, R= H.
12a; X=  STol, Y= OH, R= H.
13a; X=  SEt, Y= OH, R= H.
14a; X= OMP, Y= OH, R= H.
15a; X= O-p-BrPh, Y= OH, R= H.
Y
Galactose (3b)
23a; X= SPh, Y= OH, R= H.
24a; X= STol, Y= OH, R= H.
25a; X= SPh, Y= OH, R= Bn.
X= OMP, Y= OH, R= H.
27a; X= O-o-Allyl phenol, Y= OH, R= H.


26a;
16a;
X=  Napthyl, Y= OH, R= H.
17a; X=  OMe, Y= OBn, R= H.
18a; X=  OMe, Y= OH, R= Bn.
19a; X=  OAll, Y= NPhth, R= H.
20a; X=  SPh, Y= NPhth, R= H.
21a; X=  OMP, Y= NPhth, R= H.
Cycle Cycle Cycle Cycle Cycle
1
2
3
4
5
HO
HO
OH
O
22a; X= Carboxybenzylpropyl,

HO
Y= NPhth, R= H,
Figure 1 Recyclability of catalyst
SPh
28a
tri-O-acetyl-1-thio-α-D-glucopyranoside 10b in 87% overall
yield (entry 18, Table 2). All these products were characterized
by melting point (mp) and spectral analysis; the data
corresponded well with the literature values.
After completion of sequential one-pot per-O-acetylation –
thioglycosidation the reaction mixture was poured into water.
The aqueous phase was evaporated under reduced pressure
and the Mg(II) salt was recovered as a white solid and reused
after drying overnight over P2O5. This recycle protocol was
repeated five times, and the percentage of the catalyst
recovery was always more than 90% while the yields of the
phenyl 2,3,4,6-tetra-O-acetyl-1-thio-β-D-glucopyranoside 2b
Scheme 2 4,6-O-arylidenation of monosaccharides
CH3CN at ambient temperature, which produced the
corresponding 4,6-O-benzylidene acetal 11b in 87% yield. The
reaction retains its productivity even after scale up based on 2
g of substrate. (entry 1, Table 3).
Under similar reaction condition, other phenyl thioglycosides
of 2-NPhth-β-D-Glc, β-D-Gal and α-D-Man furnished the
corresponding 4,6-O-benzylidene derivatives (20b, 23b, 25b
and 28b) in 82%, 88% (for scale up 82%), 84% (for scale up
82%) and 68% respective yields (entries 11, 14, 16 and 19
respectively, Table 3). Efficient 4,6-O-benzylidenation was also
possible for p-tolyl 1-thio-β-D-glycopyranosides 12a and 24a
which produced 12b and 24b (entries 2 and 15, Table 3) and
for ethyl 1-thio-β-D-glucopyranoside 13a that afforded 13b
(entry 3, Table 3), in high yields. The efficacy of the present
process was further established under scale-up condition for
the preparation of 12b, 13b and 24b using 2 g starting material
(77%, 79% and 80% yields, respectively; entries 2, 3 and 15,
Table 3).
Among other substrates while methyl α-D-glucopyranoside
derivatives 17a and 18a generated the corresponding 4,6-O-
benzylidene glucopyranosides (17b and 18b) in 83% and 85%
respective yields (entries 8 and 9, Table 3), p-methoxyphenyl,
p-bromophenyl and 2-napthyl β-D-glucopyranosides furnished
and
phenyl
2,3,4,6-tetra-O-acetyl-1-thio-β-D-
galactopyranoside 3b were always more than 93% and 90%,
respectively (Figure 1).
After efficient sequential one-pot per-O-acetylation-S-/O-
glycosidation of native mono and disaccharides we turned our
attention towards employment of Mg(OTf)2 for preparation of
4,6-O-arylidinated carbohydrate derivatives. At the outset,
phenyl 1-thio-β-D-glucopyranoside 11a was chosen as the
substrate for optimization of reaction condition. 11a was
treated with benzaldehyde dimethylacetal in the presence of
Mg(OTf)2 using CH3CN as solvent (Table 3). After several trial
experiments optimum reaction condition was established as
11a (1.0 equivalent) and benzaldehyde dimethylacetal (1.1
equivalent) in the presence of Mg(OTf)2 (10 mol%) in dry
Table 3 4,6-O-arylidination of monosaccharides
Entry
Product
Time(h)
yield (%)a
Entry
Product
Time(h)
yield (%)a
1
2
3
4
5
6
7
8
9
10
11b
12b
13b
11c
14b
15b
16b
17b
18b
19b
3
3
87, 82b
80, 77b
82, 79b
78
11
12
13
14
15
16
17
18
19
20b
21b
22b
23b
24b
25b
26b
27b
28b
2.5
3
82
85, 81b
3
2
87
3
3
88, 82b
86, 80b
84, 82b
77
3
3
82
2.5
3
81
2.5
3.5
3.5
3
83
3
3
83
85
76
68
2
88
a Isolated yield b Reaction was carried out in 2 g scale
4 | J. Name., 2012, 00, 1-3
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the corresponding desired products (14b, 15b and 16b) in high Lactose, maltose and cellobiose are common disaccharide
yields (82%, 81% and 83%, respectively, entries 5, 6 and 7, units of many biologically important polysaccharides and
Table 3). Similarly preparation of 4,6-O-benzylidene of allyl, p- glycoconjugates in which chain elongation of these units occur
18
ʹ or C ʹ hydroxy
methoxyphenyl and 3-(N-benzoyloxycarbonyl)propyl 2-deoxy- via their C-4 -6
group. With this end in view S-
2-phthalimido glucosides was also found to be very efficient, and O-glycosides of cellobiose, lactose and maltose were next
ʹ,6ʹ
and the desired derivatives 19b, 21b and 22b were obtained in
4
-O-benzylidenated followed by acetylation in one-pot
88%, 85% (81% for scale-up condition) and 87% respective reaction. High combined yields (over two steps) of the final
yields (entries 10, 12 and 13, Table 3). Under similar condition products (31 33 35 37 and 39 in 73%, 84%, 78%, 79%, and
,
,
,
p-methoxyphenyl and o-allylphenyl β-D-galactopyranosides 79% respective yields, entries 2 to 6, Table 4) indicate that the
26a and 27a were converted to their corresponding 4,6-O- yields of the individual steps are quite high.
benzylidene products 26b and 27b in high yields (77% and
76%, respectively, entries 16 and 17, Table 3). The present
arylidenation protocol was further applied for the synthesis of
phenyl 4,6-O-(4-methoxybenzylidene)-1-thio-β-D-
Conclusions
In summary, we have demonstrated Mg(OTf)2 as a mild, non-
hygroscopic, recyclable and inexpensive bench-top catalyst for
robust and convenient one-pot per-O-acetylation – S-/O-
glycosidation of native mono and disaccharides. The catalyst
retains its efficacy even after several cycles of reactions.
Similarly the Mg(OTf)2 catalyzed selective 4,6-O-arylidenation
of monosaccharides and disaccharides was high yielding. These
reactions are equally applicable under scale-up condition also.
Moreover Mg(OTf)2 is also able to mediate one-pot 4,6-O-
benzylidenation-acetylation of various mono and disaccharide
based S- / O-glycosides in high yields. Unlike many of the
reported procedures glycosides or thioglycosides are not
anomerized.
glucopyranoside 11c in 78% yield (entry 4, Table 3) using p-
methoxybenzaldehyde dimethylacetal as the electrophile.
For further elaboration of the efficacy of Mg(OTf)2 towards
synthesis of some glycosyl acceptors and thioglycoside donors
we set out for an one-pot benzylidenation-acetylation of some
S-/O-glycosides based on mono and disaccharides. Using
Mg(OTf)2, preparation of 4,6-O-benzylidene acetal followed by
one-pot acetylation of 2- and 3- hydroxy group of p-tolyl 1-
thio-β-D-glucopyranoside 12a produced p-tolyl 2,3-di-O-acetyl-
4,6-O-benzylidene-1-thio-β-D-glucopyranoside 29 in 77%
overall yield at ambient temperature (entry 1, Table 4). 4,6-O-
Benzylidenation followed by one pot acetylation of β-D-
glucopranoside 40 produced methyl 2,3-di-O-acetyl-4,6-O-
benzylidene-β-D-glucopranoside 41 in 77% overall yield (entry
7, Table 4).
Experimental
Table 4 Benzylidenation acetylation of carbohydrates
Column chromatography was performed employing silica gel
60-120 (60-120 mesh). Thin-layer chromatography (analytical
and preparative) was performed using Merck silica gel plates
(60-F254) to monitor the reactions and visualized under UV
(254 nm) and/or by charring with 5% ethanolic solution of
sulfuric acid. 1H and 13C NMR spectra were recorded on a
Bruker DPX-300 (300 MHz), a Bruker DPX-400 (400 MHz), a
Bruker DPX-500 (500 MHz). Optical rotations were measured
using Jasco P-1020 digital polarimeter.
General experimental procedure for sequential one-pot per-O-
acetylaꢀon ̶ S/O-glycosidation of native sugars
To a suspension of sugar (500 mg scale) and stoichiometric
acetic anhydride (1.0 equivalent per -OH of sugar) was added
Mg(OTf)2 (0.5 mole % of sugar), and the reaction mixture was
allowed to stir at ambient temperature (for disaccharides the
same was carried out at 80 oC) for appropriate time as
mentioned in Table 1. When the reaction was completed
(checked by TLC), reaction mixture was cooled in ice bath, and
to this thiol/thiophenol/phenol (1.1 equivalent) followed by
BF3.Et2O (1.2 equivalent) were added, and the reaction
mixture was kept on stirring for overnight (8 hours). When TLC
showed complete conversion of starting material, the reaction
mixture was diluted with ethyl acetate, and the mixture was
washed subsequently with cold 5% NaOH solution followed by
brine solution. The organic layer was dried over anhydrous
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0
1
Na2SO4. The solvent was removed under reduced pressure, CHCl3), lit22 mp 106-107 C and [α]25 -8.4(c 1.00, CHCl3).; H-
D
and the crude product was passed through a short pad of silica NMR (300 MHz, CDCl3); δ 2.08 (s, 3H, COCH3), 2.09 (s, 3H,
to give pure S- or O-glycosides.
Compound characterization data
COCH3), 2.12 (s, 3H, COCH3), 2.13 (s, 3H, COCH3), 3.81 (bs, 4H,
OCH3, H5), 4.21 (d, J = 10.4 Hz, 1H, H6), 4.34 (dd, J = 5.0, 12.2
Hz, 1H, H6), 5.00 (d, J = 7.2 Hz, 1H, H1), 5.21-5.33 (m, 3H, H2, H3,
H4), 6.84-6.88 (d, J = 8.9 Hz, 2H, ArH), 6.98-7.01 (d, J = 8.9 Hz,
2H, ArH).; 13C-NMR (75 MHz, CDCl3); δ 20.60(CH3CO), 20.62
(CH3CO), 20.66 (CH3CO), 20.7(CH3CO), 55.6 (OCH3), 61.9, 68.3,
71.2, 71.9, 72.7, 100.3 (C1), 114.5, 118.7, 150.9, 155.8, 169.3
Typical procedure for phenyl 2,3,4,6-tetra-O-acetyl-1-thio-β-D-
glucopyranoside (1b)19
To a suspension of D-glucose 1a (500 mg, 2.8 mmol), and
acetic anhydride (5 equivalent, 14.0 mmol, 143 mg), was
added Mg(OTf)2 (0.005 equivalent, 0.014 mmol, 4.5 mg), and
the reaction mixture was allowed to stir at ambient
temperature for 3 minutes. After the reaction was completed
(checked by TLC), the mixture was cooled in ice bath and to
this thiophenol (1.1 equivalent, 3.08 mmol, 0.4 ml) followed by
BF3.Et2O (1.2 equivalent, 3.36 mmol, 0.44 ml) were added, and
the reaction mixture was kept on stirring for overnight for
completion (8 hours). The reaction mixture was then worked
up as described under the general procedure. The crude
product was passed through a short pad of silica to give pure
product as white solid following elution of the column with
(C=O), 169.4 (C=O), 170.3 (C=O), 170.6 (C=O).
Phenyl 2,3,4,6-tetra-O-acetyl-1-thio-β-D-galactopyranoside (2b)23
Pure product was isolated as white solid following elution of
the column with 30% EA/PE.; Yield 1.14 g, 94% (starting from
2a, 500 mg, 2.8 mmol), scale up yield 10.8 g, 89% (starting with
o
2a, 5 g, 27.8 mmol).; mp (EA/PE) 80-82 C, [α]25D -82.9 (c 1.05,
CHCl3), lit23 mp 81 ˚C and [α]25 -84 (c 1.0, CHCl3).; 1H-NMR
D
(300 MHz, CDCl3); δ 1.97 (s, 3H, COCH3), 2.04 (s, 3H, COCH3),
2.09 (s, 3H, COCH3), 2.12 (s, 3H, COCH3), 3.94 (apparent t, J =
6.3, 6.4 Hz, 1H, H5), 4.08-4.22 (m, 2H, H6, H6’), 4.71 (d, J = 9.9
Hz, 1H, H1), 5.04 (dd, J = 3.2, 9.9 Hz, 1H, H3), 5.24 (t, J = 9.9 Hz,
1H, H2), 5.41 (d, J = 2.5 Hz, 1H, H4), 7.31-7.51 (m, 5H, ArH).; 13C-
NMR (75 MHz, CDCl3); δ 20.5 (CH3CO), 20.60 (CH3CO), 2.63
(CH3CO), 20.8 (CH3CO), 61.6, 67.2, 71.9, 74.4, 76.7, 86.5 (C1),
128.1, 128.9, 132.4, 132.5, 169.4 (C=O), 169.9 (C=O), 170.1
25% EA/PE; Yield 1.16 g, 95% (scale up yield 11.1 g, 91%
starting with 1a, 5 g, 27.8 mmol).; mp (EA/PE) 122 C, [α]25
-
o
D
102.6 (c 1.00, CHCl3), lit19 mp 124 °C and [α]23 -101.5 (c 1.00,
D
CHCl3).; 1H-NMR (300 MHz, CDCl3); δ 1.98 (s, 3H, COCH3), 2.01
(s, 3H, COCH3), 2.07 (s, 3H, COCH3), 2.08 (s, 3H, COCH3), 3.74
(m, 1H, H5), 4.15-4.21 (m, 2H, H6, H6), 4.70 (d, J = 9.9 Hz, 1H,
H1), 4.94-5.07 (m, 2H, H2, H3), 5.22 (apparent t, J = 9.1, 9.2 Hz,
(C=O), 170.3 (C=O).
p-Tolyl 2,3,4,6-tetra-O-acetyl-1-thio-β-D-galactopyranoside (2c)21
1H, H4), 7.32-7.49 (m, 5H, ArH).; 13C-NMR (75 MHz, CDCl3); δ Pure product was isolated as white solid following elution of
20.6 (CH3CO), 20.7 (CH3CO), 62.1, 68.2, 69.9, 73.9, 75.7, 85.6 the column with 30% EA/PE.; Yield 1.05 g, 84% (starting from
(C1), 128.4, 128.9, 131.6, 133.1, 169.2 (C=O), 169.3 (C=O), 2a, 500 mg, 2.8 mmol); mp (EA/PE) 110-112 0C, [α]25D -125.5 (c
170.1 (C=O), 170.5 (C=O).
1.05, CHCl3). Lit21 mp 112 °C and [α]22D -127.0 (c 1.05, CHCl3).;
1H-NMR (300 MHz, CDCl3); δ 1.97 (s, 3H, COCH3), 2.05 (s, 3H,
COCH3), 2.10 (s, 3H, COCH3), 2.12 (s, 3H, COCH3), 2.35 (s, 3H,
CH3), 3.92 (bt, J = 6.5 Hz, 1H, H5), 4.12-4.19 (m, 2H, H6, H6), 4.65
(d, J = 9.9 Hz, 1H, H1), 5.04 (dd, J = 3.2, 9.9 Hz, 1H, H3), 5.22 (t, J
= 9.9 Hz, 1H, H2), 5.41 (d, J = 2.7 Hz, 1H, H4), 7.12-7.14 (d, J =
7.8 Hz, 2H, ArH), 7.40-7.43 (d, J = 8.0 Hz, 2H, ArH).; 13C-NMR
(75 MHz, CDCl3); δ 20.58 (CH3CO), 20.60 (CH3CO), 20.63
(CH3CO), 20.8 (CH3CO), 21.1 (CH3) 61.6, 67.2, 67.3, 72.0, 74.4,
86.9 (C1), 128.6, 129.6, 133.1, 138.4, 169.4 (C=O), 170.0 (C=O),
Ethyl 2,3,4,6-tetra-O-acetyl-1-thio-β-D-glucopyranoside (1c)20
Pure product 1b was isolated as white solid following elution
of the column with 25% EA/PE.; Yield 0.97 g, 89% (starting
from 1a, 500 mg, 2.8 mmol).; mp (EA/PE) 82-84 oC, [α]25D -26.7
(c 1.3, CHCl3) lit20 mp 84-86 °C and [α]23D -27.3 (c 2.00, CHCl3).;
1H-NMR (300 MHz, CDCl3); δ 1.22-1.27 (m, 3H, CH3), 1.98 (s,
3H, COCH3), 1.99 (s, 3H, COCH3), 2.03 (s, 3H, COCH3), 2.05 (s,
3H, COCH3), 2.64-2.75 (m, 2H, CH2), 3.69 (m, 1H, H5), 4.09-4.25
(m, 2H, H6, H6), 4.47 (d, J = 9.9 Hz, 1H, H1), 4.97-5.09 (m, 2H, H2,
H3), 5.19 (t, 1H, J = 9.3 Hz, H4).
170.2 (C=O), 170.3 (C=O).
p-Tolyl 2,3,4,6-tetra-O-acetyl-1-thio-β-D-glucopyranoside (1d)21
p-Methoxyphenyl 2,3,4,6-tetra-O-acetyl-1-thio-β-D-
galactopyranoside (2d)22
Pure product was isolated as white solid following elution of
the column with 20% EA/PE.; Yield 1.09 g, 87% (starting from Pure product was isolated as white solid following elution of
1a, 500 mg, 2.8 mmol).; mp (EA/PE) 114 oC, [α]25 -116.8 (c the column with 33% EA/PE.; Yield 1.08 g, 86% (starting from
D
1.00, CHCl3), lit21 mp 116 °C and [α]23 -114.3(c 1.00, CHCl3).; 2a, 500 mg, 2.8 mmol).; mp 112-114 °C, [α]25 +3.5 (c 1.00,
D
D
1
1H-NMR (300 MHz, CDCl3); δ 1.98 (s, 3H, COCH3), 2.01 (s, 3H, CHCl3), lit22 109-110 °C and [α]25 +3.2 (c 0.9, CHCl3).; H-NMR
D
COCH3), 2.08 (s, 3H, COCH3), 2.09 (s, 3H, COCH3), 2.35 (s, 3H, (300 MHz, CDCl3); δ 1.99 (s, 3H, COCH3), 2.04 (s, 3H, COCH3),
CH3), 3.70 (m, 1H, H5), 4.19-4.20 (m, 2H, H6, H6), 4.62 (d, J = 2.07 (s, 3H, COCH3), 2.17 (s, 3H, COCH3), 3.76 (s, 3H, OCH3),
10.0 Hz, 1H, H1), 4.92 (t, J = 9.9 Hz, 1H, H2), 5.01 (t, J = 9.8 Hz, 4.00 (apparent t, J = 6.4, 6.6 Hz, 1H, H5), 4.11-4.25 (m, 2H, H6,
1H, H3), 5.20 (t, J = 9.3 Hz, 1H, H4), 7.01-7.14 (d, J = 7.9 Hz, 2H, H6), 4.91 (d, J = 7.9 Hz, 1H, H1), 5.07 (dd, J = 3.2, 10.5 Hz, 1H,
ArH), 7.37-7.39 (d, J = 7.9 Hz, 2H, ArH).
H3), 5.42-5.47 (m, 2H, H2, H4), 6.79-6.82 (d, J = 8.9 Hz, 2H, ArH),
6.92-6.96 (d, J = 8.9 Hz, 2H, ArH).; 13C-NMR (75 MHz, CDCl3); δ
20.58 (CH3CO), 20.65 (CH3CO), 20.7 (CH3CO), 55.6 (OCH3), 61.3,
66.9, 68.8, 70.8, 100.8 (C1), 114.5, 118.6, 151.0, 155.7, 169.4
(C=O), 170.1 (C=O), 170.27 (C=O), 170.3 (C=O).
p-Methoxyphenyl 2,3,4,6-tetra-O-acetyl-1-thio-β-D-
glucopyranoside (1e)22
Pure product was isolated as white solid following elution of
the column with 33% EA/PE.; Yield 1.07 g, 85% (starting from
Phenyl 2,3,4,6-tetra-O-acetyl-1-thio-α-D-mannopyranoside (3b)6c
1a, 500 mg, 2.8 mmol).; mp 104-105 °C, [α]25 -9.3 (c 1.00,
D
6 | J. Name., 2012, 00, 1-3
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Journal Name
View Article Online
DOI: 10.1039/C6RA23198E
ARTICLE
Pure product was isolated as white solid following elution of NMR (300 MHz, CDCl3); δ 1.19 (d, J = 6.2 Hz, 3H, CH3), 2.01 (s,
the column with 22.5% EA/PE.; Yield 1.13 g, 93% (starting from 3H, COCH3), 2.05 (s, 3H, COCH3), 2.17 (s, 3H, COCH3), 3.73 (s,
3a, 500 mg, 2.8 mmol), scale up yield 10.6 g, 87% (starting 3H, OCH3), 4.00 (m, 1H, H5), 5.13 (t, J = 9.9 Hz, 1H, H4), 5.33 (bs,
o
from 3a, 5 g, 27.8 mmol).; mp (EA/PE) 84-86 C, [α]25D+77.1 (c 1H, H1), 5.41 (bs, 1H, H2), 5.48 (dd, J = 3.3, 10.0 Hz, 1H, H3),
1.2, CHCl3), lit6c mp 87 °C (Et2O/PE) and [α]22 +74.4 (c 1.5, 6.79-6.83 (d, J = 8.9 Hz, 2H, ArH), 6.97-7.00 (d, J = 8.9 Hz, 2H,
D
CHCl3).; 1H-NMR (300 MHz, CDCl3); δ 2.02 (s, 3H, COCH3), 2.05 ArH).; 13C-NMR (75 MHz, CDCl3); δ 17.4 (CH3), 20.7 (CH3CO),
(s, 3H, COCH3), 2.07 (s, 3H, COCH3), 2.15 (s, 3H, COCH3), 4.10 20.8 (CH3CO), 20.9 (CH3CO), 55.6 (OCH3), 66.9, 68.9, 69.8, 71.0,
(dd, J = 2.0, 12.2 Hz, 1H, H6,), 4.30 (dd, J = 5.9, 12.2 Hz, 1H, H6,), 96.5 (C1), 114.6, 117.6, 149.9, 155.2, 170.01 (C=O), 170.02
4.54 (m, 1H, H5), 5.32-5.34 (m, 2H, H3, H4), 5.49 (m, 2H, H1, H2), (C=O), 170.07 (C=O).
p-tolyl 2,3,4-tri-O-acetyl-1-thio-β-L-fucopyranoside (6b)6h
7.29-7.50 (m, 5H, ArH).; 13C-NMR (75 MHz, CDCl3); δ 20.6
(CH3CO), 20.7 (CH3CO), 20.8 (CH3CO), 62.5, 66.4, 69.4, 69.5,
70.9, 85.7 (C1), 128.1, 129.2, 132.1, 132.6, 169.7 (C=O), 169.8
Pure product was isolated as white solid following elution of
the column with 20% EA/PE.; Yield 1.04 g, 86% (starting from
o
5a, 500 mg, 3.05 mmol).; mp (EA/PE) 110-112 C, [α]25D -125.5
(C=O), 169.9 (C=O), 170.5 (C=O).
Ethyl 2,3,4,6-tetra-O-acetyl-1-thio-α-D-mannopyranoside (3c)24
(c 1.05, CHCl3).; 1H-NMR (300 MHz, CDCl3) δ 1.20 (d, J = 6.3 Hz,
Pure product was isolated as white solid following elution of 3H, CH3), 1.95 (s, 3H, COCH3), 2.06 (s, 3H, COCH3), 2.11 (s, 3H,
the column with 22.5% EA/PE.; Yield 0.99 g, 91% (starting from COCH3), 2.32 (s, 3H, CH3), 3.78 (m, 1H, H5), 4.61 (d, J = 9.8 Hz,
o
3a, 500 mg, 2.8 mmol).; mp (EA/PE) 160-162 C, [α]25D -64.8 (c 1H, H1), 5.01 (dd, J = 3.2, 9.8 Hz, 1H, H3), 5.14-5.23 (m, 2H, H2,
1.00, CHCl3), lit24 mp 162-164 °C and [α]23 -64.3 (c 0.90, H4), 7.09-7.12 (d, J = 7.7 Hz, 2H, ArH), 7.38-7.40 (d, J = 7.9 Hz,
D
CHCl3).; 1H-NMR (300 MHz, CDCl3); δ 1.25 (bs, 3H, CH3), 1.92 (s, 2H, ArH).; 13C-NMR (75 MHz, CDCl3); δ 16.5 (CH3), 20.62
3H, COCH3), 1.99 (s, 3H, COCH3), 2.02 (s, 3H, COCH3), 2.09 (s, (CH3CO), 20.63 (CH3CO), 20.9 (CH3CO), 21.1 (CH3), 67.4, 70.4,
3H, COCH3), 2.59 (bs, 2H, CH2), 4.04 (bs, 1H), 4.32 (bs, 2H), 5.22 72.5, 73.1, 86.8 (C1), 129.1, 129.6, 132.9, 138.2, 169.5 (C=O),
(bs, 4H).; 13C-NMR (75 MHz, CDCl3); δ 14.7, 20.5 (CH3CO), 20.6 170.1 (C=O), 170.6 (C=O).
Phenyl 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-1-thio-β-D-
(CH3CO), 20.8 (CH3CO), 25.3, 62.4, 66.3, 68.8, 69.4, 71.1, 82.2
glucopyranoside (7b)28
(C1), 169.6 (C=O), 169.7 (C=O), 169.8 (C=O), 170.4 (C=O).
Phenyl 2,3,4-tri-O-acetyl-1-thio-β-D-xylopyranoside (4b)25
To a suspension of 7a (500 mg, 1.6 mmol) and acetic anhydride
(4 equivalent, 6.5 mmol, 0.62 ml) was added Mg(OTf)2 (0.005
equivalent, 0.008 mmol, 2.6 mg), and the reaction mixture was
Pure product was isolated as white solid following elution of
the column with 20% EA/PE.; Yield 1.06 g, 86% (starting from
4a, 500 mg, 3.3 mmol).; mp (EA/PE) 78-80 oC, [α]25D-56.8 (c
o
allowed to stir at 80 C for 15 minutes. After the reaction was
1.00, CHCl3), lit25 mp 74-76 °C and [α]23 -55.3 (c 1.00, CHCl3).;
completed (checked by TLC), reaction mixture was cooled in
ice bath and to this thiophenol (1.1 equivalent, 1.78 mmol,
0.19 ml) followed by BF3.Et2O (1.2 equivalent, 1.94 mmol, 0.25
ml) were added, and the reaction mixture was kept on stirring
for overnight (8 hours) for complete conversion of starting
material. The reaction mixture was then worked up as
described under the general procedure. The crude product
was passed through a short pad of silica to give pure product
as white solid following elution of the column with 35% EA/PE;
D
1H-NMR (300 MHz, CDCl3); δ 2.04 (s, 3H, COCH3), 2.05 (s, 3H,
COCH3), 2.09 (s, 3H, COCH3), 3.43 (t, J = 11.5 Hz, 1H, H5a), 4.27
(dd, J = 4.8, 11.6 Hz, 1H, H5e), 4.79 (d, J = 8.3 Hz, 1H, H1), 4.88-
4.96 (m, 2H, H3, H4), 5.18 (apparent t, J = 7.9, 8.1 Hz, 1H, H2)
7.31-7.32(m, 3H, ArH), 7.46-7.48 (m, 2H, ArH).; 13C-NMR (75
MHz, CDCl3); δ 20.7 (CH3CO), 20.8 (CH3CO), 65.2, 69.8, 72.0,
86.2 (C1), 128.2, 129.0, 132.2, 132.7, 169.3 (C=O), 169.7 (C=O),
169.9 (C=O).
Phenyl 2,3,4-tri-O-acetyl-1-thio-α-L-rhamnopyranoside (5b)26
Yield 0.67 g, 78%.; mp (EA/PE) 144-146 oC, [α]25D +53.9 (c 1.00,
Pure product was isolated as white solid following elution of CHCl3), lit28 mp 145-146 °C and [α]25 +53.0 (c 1.0, CHCl3).; H-
1
D
the column with 30% EA/PE.; Yield 0.97 g, 84% (starting from NMR (300 MHz, CDCl3); δ 1.84 (s, 3H, COCH3), 2.04 (s, 3H,
5a, 500 mg, 3.05 mmol), scale up yield 9.30 g, 80% (starting COCH3), 2.10 (s, 3H, COCH3), 3.91 (m, 1H, H5), 4.18-4.30 (m, 2H,
from 5a, 5 g, 30.5 mmol).; mp (EA/PE) 120-122 oC, [α]25D -110.0 H6, H6’), 4.35 (t, J = 3.4 Hz, 1H, H2) 5.14 (apparent t, J = 9.6, 9.8
(c 1.5, CHCl3), lit26 mp 118 °C and [α]25 -107.0 (c 2.4, CHCl3).; Hz, 1H, H4), 5.71 (d, J = 10.6 Hz, 1H, H1), 5.79 (d, J = 7.9 Hz, 1H,
D
1H-NMR (300 MHz, CDCl3); δ 1.22 (d, J = 6.1 Hz, 3H, CH3), 1.99 H3), 7.26-7.88 (m, 9H, ArH).
p-Tolyl 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-1-thio-β-D-
(s, 3H, COCH3), 2.05 (s, 3H, COCH3), 2.11 (s, 3H, COCH3), 4.34
(m, 1H, H5), 5.12 (t, 1H, J = 9.7 Hz, H4), 5.26 (dd, J = 3.0, 9.9 Hz,
1H, H3), 5.39 (s, 1H, H1), 5.48 (bs, 1H, H2), 7.27-7.46 (m, 5H,
ArH).; 13C-NMR (75 MHz, CDCl3); δ 17.3 (CH3), 20.6 (CH3CO),
20.8 (CH3CO), 20.9 (CH3CO), 67.8, 69.4, 71.1, 71.3, 85.7 (C1),
127.9, 129.1, 131.8, 133.2, 169.8 (C=O), 169.9 (C=O), 170.2
(C=O).
glucopyranoside (7c)9d
Pure product was isolated as white solid following elution of
the column with 33% EA/PE; Yield 0.64 g, 73% (starting from
7a, 500 mg, 1.6 mmol).; mp (EA/PE) 162-164 oC, [α]25D +40.9 (c
0.70, CHCl3), lit9d mp 160-162 °C and [α]25 +40.0 (c 0.60,
D
1
CHCl3).; H-NMR (300 MHz, CDCl3); δ 1.83 (s, 3H, COCH3), 2.01
p-Methoxyphenyl 2,3,4-tri-O-acetyl-1-thio-α-L-rhamnopyranoside
(s, 3H, COCH3), 2.09 (s, 3H, COCH3), 2.32 (s, 3H, CH3), 3.87 (m,
1H, H5), 4.18-4.35 (m, 3H, H2, H6, H6’), 5.11 (t, J = 9.8 Hz, 1H, H4),
(5c)27
Pure product was isolated as white solid following elution of 5.64 (d, J = 10.5 Hz, 1H, H1), 5.77 (apparent t, J = 9.5, 9.9 Hz,
the column with 30% EA/PE.; Yield 1.05 g, 87% (starting from 1H, H3), 7.06-7.08 (d, J = 7.7 Hz, 2H, ArH), 7.28-7.31 (d, J = 7.9
5a, 500 mg, 3.05 mmol).; mp (EA/PE) 116-118 oC, [α]25D -64.0 (c Hz, 2H, ArH), 7.74-7.88 (m, 4H, ArH).; 13C-NMR (75 MHz,
1
1.5, CHCl3), lit27 mp 120 °C and [α]25 -65.0 (c 1.5, CHCl3).; H- CDCl3); δ 20.4 (CH3CO), 20.6 (CH3CO), 20.7 (CH3CO), 21.2 (CH3),
D
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
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DOI: 10.1039/C6RA23198E
ARTICLE
Journal Name
53.6, 62.2, 68.7, 71.7, 75.8, 83.1 (C1), 123.7, 126.9, 129.7, Pure product was isolated as white solid following elution of
131.2, 131.6, 133.9, 134.3, 134.5, 138.7, 166.9 (C=O), 167.8 the column with 33% EA/PE.; Yield 0.96 g, 91% (from D-
(C=O), 169.4 (C=O), 170.1 (C=O), 170.6 (C=O).
maltose 10a, 500 mg, 1.46 mmol), scale up yield 3.7 g, 87%
(from 10a, 2 g, 5.84 mmol).; mp 90-92 °C, [α]25 +56.3 (c 1.00,
Typical procedure for phenyl 2,3,4,6-tetra-O-acetyl-β-D-
D
0
1
CHCl3), lit29 mp 92-94 C and [α]25 +57.0 (c 1.00, CHCl3).; H-
glucopyranosyl-(1→4)-2,3,6-tri-O-acetyl-1-thio-β-D-
D
glucopyranoside (8b)29
NMR (300 MHz, CDCl3); δ 1.98 (s, 3H, COCH3), 2.01 (s, 3H,
COCH3), 2.02 (s, 6H, COCH3), 2.05 (s, 3H, COCH3), 2.08 (s, 3H,
COCH3), 2.11 (s, 3H, COCH3), 3.72 (m, 1H, H5), 3.89-3.93 (m, 2H,
H4, H5’), 4.03 (m, 1H, H6/H6’), 4.17-4.24 (m, 2H, H6/H6’, H6’),
4.53 (m, 1H, H6), 4.69-4.85 (m, 3H, H1, H2’, H3’), 5.03 (t, J = 9.8
Hz, 1H, H2), 5.24-5.33 (m, 2H, H3, H4’), 5.37 (d, J = 4.1 Hz, 1H,
H1’), 7.17-7.47 (m 5H, ArH).; 13C-NMR (75 MHz, CDCl3); δ 20.57
(CH3CO), 20.66 (CH3CO), 20.7 (CH3CO), 20.8 (CH3CO), 20.9
(CH3CO), 61.5, 62.8, 68.0, 68.5, 69.3, 69.9, 70.7, 72.5, 76.1,
76.4, 85.0 (C1), 95.4 (C1’), 128.5, 128.9, 129.0, 131.2, 133.4,
169.4 (C=O), 169.5 (C=O), 169.9 (C=O), 170.1 (C=O), 170.3
To a suspension of D-cellobiose 8a (500 mg, 1.46 mmol) and
acetic anhydride (8 equivalent, 11.7 mmol, 1.1 ml) was added
Mg(OTf)2 (0.005 equivalent, 0.007 mmol, 2.4 mg) and the
reaction mixture was allowed to stir at 80 oC for 5 minutes.
After the reaction was completed (checked by TLC), reaction
mixture was cooled in ice bath and to this thiophenol (1.1
equivalent, 1.6 mmol, 0.16 ml), followed by BF3.Et2O (1.2
equivalent, 1.75 mmol, 0.22 ml) were added, and the reaction
mixture was kept on stirring for overnight (8 hours). When TLC
showed complete conversion of starting material, the reaction
mixture was diluted with ethyl acetate, and the mixture was
washed subsequently with cold 5% NaOH solution followed by
brine solution. The organic layer was dried over anhydrous
Na2SO4. The solvent was removed under reduced pressure,
and the crude product was passed through a short pad of silica
to give the product. Pure product was isolated as white solid
following elution of the column with 33% EA/PE.; Yield 0.82 g,
(C=O), 170.5 (C=O).
p-Methoxyphenyl 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl-
(1→4)-2,3,6-tri-O-acetyl-β-D-glucopyranoside (10c)30
Pure product was isolated as white solid following elution of
the column with 40% EA/PE.; Yield 0.89 g, 83% (from D-
maltose 10a, 500 mg, 1.46 mmol).; mp 130-132 °C, [α]25D +54.3
(c 1.00, CHCl3), lit30 mp 130-132 °C and [α]24 +49.8 (c 1.0,
D
1
o
77%.; mp (EA/PE) 214-216 C, [α]25D -16.8 (c 1.00, CHCl3), lit29
CHCl3).; H-NMR (400 MHz, CDCl3); δ 2.00 (s, 3H, COCH3), 2.02
1
mp 217 °C and [α]20 -13.2(c 1.05, CHCl3).; H-NMR (300 MHz,
(s, 3H, COCH3), 2.03 (s, 3H, COCH3), 2.04 (s, 3H, COCH3), 2.05
(s, 3H, COCH3), 2.10 (s, 3H, COCH3), 2.11 (s, 3H, COCH3), 3.77
(s, 3H, OCH3), 3.80 (m, 1H, H5), 3.96 (m, 1H, H5’), 4.05 (dd, J =
1.6, 12.0 Hz, 1H, H6), 4.18 (t, J = 9.2Hz, 1H, H4), 4.23-4.28 (m,
2H, H6’, H6’), 4.48 (dd, J = 2.8, 12.0 Hz, 1H, H6), 4.86 (dd, J = 3.8,
10.6 Hz, 1H, H2’), 4.98 (d, J = 7.6 Hz, 1H, H1), 5.02-5.08 (m, 2H,
H2, H3’), 5.30 (m, 1H, H4’), 5.36 (t, J = 10.0 Hz, 1H, H3), 5.43 (d, J
D
CDCl3); δ 1.96 (s, 3H, COCH3), 1.99 (s, 6H, COCH3), 2.00 (s, 3H,
COCH3), 2.05 (s, 3H, COCH3), 2.06 (s, 3H, COCH3), 2.09 (s, 3H,
COCH3), 3.62-3.74 (m, 3H, H4, H5, H5’), 3.99-4.18 (m, 2H, H6, H6),
4.36 (dd, J = 3.7, 12.3 Hz, 1H, H6’), 4.47-4.56 (m, 2H, H2’, H6’),
4.65 (d, J = 10.0 Hz, 1H, H1), 4.86-4.92 (m, 2H, H2, H1’), 5.01-
5.21 (m, 3H, H3, H3’, H4’), 7.26-7.29 (m, 3H, ArH), 7.44-7.66 (m,
2H, ArH).; 13C-NMR (75 MHz, CDCl3); δ 20.5 (CH3CO), 20.6
(CH3CO), 20.7 (CH3CO), 20.8 (CH3CO), 61.5, 62.0, 67.8, 70.2,
= 4.0 Hz, 1H, H1’), 6.81-6.94 (m, 4H, ArH).
General procedure for 4,6-O-arylidenation of monosaccharides
71.6, 71.9, 72.9, 73.6, 76.3, 85.5 (C1), 100.7 (C1’), 128.3, 128.9, To a solution of unprotected monosaccharide glycosides (200
129.1, 131.7, 133.1, 168.9 (C=O), 169.3 (C=O), 169.5 (C=O), mg) and benzaldehyde dimethylacetal or p-
169.7 (C=O), 170.1 (C=O), 170.2 (C=O), 170.4 (C=O).
methoxybenzaldehyde dimethylacetal (1.1 equivalent with
respect to sugr) in dry acetonitrile (10 ml), 10 mole % Mg(OTf)2
was added at ambient temperature. After completion of
reaction (indicated by TLC), the reaction mixture was diluted
with ethyl acetate, and the mixture was washed subsequently
with saturated NaHCO3 followed by brine solution; finally the
organic extract was dried over anhydrous Na2SO4. The solvent
was removed under reduced pressure and the crude product
was either crystallized or passed through a short pad of silica
to give pure arylidenated product.
→4)
-2,3,6-
Phenyl 2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl-(1
tri-O-acetyl-1-thio-β-D-glucopyranoside (9b)29
Pure product was isolated as white solid following elution of
the column with 33% EA/PE.; Yield 0.90 g, 85% (from D-lactose
9a, 500 mg, 1.46 mmol), scale up yield 3.5 g, 83% (from 9a, 2
g, 5.84 mmol).; mp (EA/PE) 168-170 °C, [α]25 -15.3 (c 1.00,
D
1
CHCl3), lit29 mp 169-170 0C and [α]25 -12.7 (c 1.00, CHCl3).; H-
D
NMR (300 MHz, CDCl3); δ 1.95 (s, 3H, COCH3), 2.03 (s, 9H,
COCH3), 2.08 (s, 3H, COCH3), 2.09 (s, 3H, COCH3), 2.14 (s, 3H,
COCH3), 3.65 (m, 1H, H5), 3.74 (t, J = 9.3 Hz, 1H, H4), 3.85 (bt, J
= 6.7 Hz, 1H, H5’), 4.02-4.12 (m, 3H, H6, H6/H6’, H6’), 4.45-4.54
Typical procedure for phenyl 4,6-O-benzylidene-1-thio-β-D-
glucopyranoside (11b)31
(m, 2H, H3, H6/H6’), 4.66 (d, J = 10.0 Hz, 1H, H1), 4.86-4.96 (m, To a solution of 11a (200 mg, 0.74 mmol) and benzaldehyde
2H H1’, H3’), 5.08 (apparent t, J = 9.3 Hz, 1H, H2), 5.21 (t, J = 9.0 dimethylacetal (1.1 equivalent, 0.81 mmol, 0.12 ml) in dry
Hz, 1H, H2’), 5.33 (d, J = 2.5 Hz, 1H, H4’), 7.31-7.48 (m 5H, ArH).; acetonitrile (10 ml), Mg(OTf)2 (0.1 equivalent, 0.074 mmol,
13C-NMR (75 MHz, CDCl3); δ 20.5 (CH3CO), 20.6 (CH3CO), 20.7 23.8 mg) was added at ambient temperature. After completion
(CH3CO), 20.8 (CH3CO), 60.8, 62.1, 66.6, 69.1, 70.2, 70.7, 70.9, of reaction (indicated by TLC), the reaction mixture was diluted
73.8, 76.1, 85.5 (C1), 101.0 (C1’), 128.3, 128.9, 131.7, 133.0, with ethyl acetate, and the mixture was washed subsequently
162.3, 169.4 (C=O), 169.6 (C=O), 169.7 (C=O), 170.0 (C=O), with saturated NaHCO3 followed by brine solution; finally the
170.1 (C=O), 170.2 (C=O), 170.3 (C=O).
organic extract was dried over anhydrous Na2SO4. The solvent
was removed under reduced pressure. The crude material was
crystallized from EtOH to isolate pure product as white solid.
→4)
-2,3,6-tri-
Phenyl 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl-(1
O-acetyl-1-thio-β-D-glucopyranoside (10b)29
8 | J. Name., 2012, 00, 1-3
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Yield 230 mg, 87% (2.17 g, 82%).; mp (EtOH) 172-174 oC, [α]22
The crude mass was crystallized from EtOH to isolate pure
D
1
-28.1 (c 1.00, CHCl3), lit31 174 0C and [α]25D -26.9.; H-NMR (300 product as white solid. Yield 205 mg, 81% (starting from 15a
,
MHz, CDCl3); δ 2.17 (bs, 2H, OH), 3.45-3.54 (m, 3H, H2, H3, H5), 200 mg, 0.66 mmol).; mp 180-182 ˚C, [α]25 -38.7 (c 1.00,
D
3.75-3.88 (m, 2H, H4, H6a), 4.38 (m, 1H, H6e), 4.62 (d, J = 9.7 Hz, CHCl3), lit16g mp 182-184 ˚C and [α]25D -38.8 (c 0.89, CHCl3).; 1H-
1H, H1), 5.54 (s, 1H, PhCH), 7.33-7.56 (m, 10H, ArH).
NMR (400 MHz, CDCl3); δ 2.71 (bs, 1H, OH), 2.84 (bs, 1H, OH),
3.49-3.67 (m, 2H, H2/H3, H5), 3.77-3.84 (m, 2H, H3/H2, H6a), 3.92
(m, 1H, H4), 4.37 (m, 1H, H6e), 4.99 (d, J = 7.6 Hz, 1H, H1), 5.57
(s, 1H, PhCH), 6.93-6.95 (d, J = 8.8 Hz, 2H, ArH), 7.38-7.51 (m,
4-Tolyl 4,6-O-benzylidene-1-thio-β-D-glucopyranoside (12b)32
The crude product was crystallized from EtOH to isolate pure
product as white solid. Yield 209 mg, 80% (starting from 12a
,
7H, ArH).
200 mg, 0.699 mmol), scale up yield, 2.0 g, 77% (starting from
2'-Napthyl 4,6-O-benzylidene-β-D-glucopyranoside (16b)36
12a, 2.09 g, 6.99 mmol).; mp 170-172 ˚C, [α]25 -40.1 (c 1.0,
D
CHCl3), lit32 mp 171-172 ˚C and [α]25D -34.4 (c 1.0, CHCl3).; 1H- The crude product was crystallized from EtOH to isolate pure
NMR (500 MHz, CDCl3); δ 2.28 (s, 3H, CH3), 2.61 (s, 1H, OH), product as white solid. Yield 214 mg, 83% (starting from 16a
,
2.76 (s, 1H, OH), 3.35 (t, J = 9.0 Hz, 1H, H3), 3.39-3.44 (m, 2H, 200 mg, 0.65 mmol).; mp 202-204 ˚C, [α]25 -36.0 (c 1.00,
D
H2, H5), 3.69 (m, 1H, H6a), 3.75 (t, J = 8.5 Hz, 1H, H4), 4.29 (dd, J CHCl3), lit36 mp 202-205 ˚C and [α]25D -37.1 (c 1.00, CHCl3).; 1H-
= 4.3, 10.3 Hz, 1H, H6e), 4.48 (d, J = 10 Hz, 1H, H1), 5.44 (s, 1H, NMR (300 MHz, CDCl3); δ 2.83 (bs, 1H, OH), 2.92 (bs, 1H, OH),
PhCH), 7.07-7.08 (d, J = 8.0 Hz, 2H, ArH), 7.28-7.31 (m, 3H, 3.68-3.90 (m, 4H, H2, H3, H5, H6a), 3.95 (m, 1H, H4), 4.44 (m, 1H,
ArH), 7.35 -7.40 (m, 4H, ArH).; 13C-NMR (125 MHz, CDCl3); δ H6a), 5.19 (d, J = 7.5 Hz, 1H, H1), 5.59 (s, 1H, PhCH), 7.28-7.52
21.2, 68.6, 70.6, 72.5, 74.6, 80.2, 88.7 (C1), 101.9 (PhCH), (m, 9H, ArH), 7.75-7.82 (m, 3H, ArH).; 13C-NMR (75 MHz,
126.3, 127.2, 128.4, 129.3, 129.9, 133.7, 136.9, 138.9.
CDCl3); δ 66.6, 68.6, 73.2, 74.4, 80.3, 101.3, 102.0, 111.6,
118.8, 124.7, 126.3, 126.6, 127.2, 127.7, 128.4, 129.4, 129.8,
Ethyl 4,6-O-benzylidene-1-thio-β-D-glucopyranoside (13b)33
130.2, 134.1, 136.8.
The crude product was crystallized from EtOH to isolate pure
Methyl 2-O-benzyl-4,6-O-benzylidene-α-D-glucopyranoside (17b)37
product as white solid. Yield 228 mg, 82% (starting from 13a
,
200 mg, 0.89 mmol), scale up yield, 2.2 g, 79% (starting from The pure product was isolated as white solid following elution
13a
,
2.09 g, 8.9 mmol).; mp 146-148 ˚C, [α]22 -64.0 (c 1.4, of the column with 22.5% EA/PE.; Yield 217 mg, 83% (starting
D
CHCl3), lit33 145 ˚C, and [α]25D -65.0 (c 1.0, CHCl3).; 1H-NMR (300 from 17a, 200 mg, 0.7 mmol).; mp 126-128 ˚C, [α]25D +35.5 (c
MHz, CDCl3); δ 1.33-1.38 (t, J = 7.4 Hz, 3H, CH3), 2.75-2.82 (q, J 5.0, CHCl3), lit37 mp 129-130 ˚C and [α]25D +35.0 (c 5.0, CHCl3).;
= 7.4 Hz, 3H, SCH2, OH), 2.93 (bs, 2H, OH), 3.49-3.63 (m, 3H, H2, 1H-NMR (300 MHz, CDCl3); δ 3.37 (s, 3H, OCH3), 3.44-3.52 (m,
H3, H5), 3.76-3.88 (m, 2H, H4, H6a), 4.37 (m, 1H, H6e), 4.48 (d, J = 2H, H2, H3), 3.69 (apparent t, J = 10.1, 10.2 Hz, 1H, H6a), 3.80
9.7 Hz, 1H, H1), 5.56 (s, 1H, PhCH), 7.28-7.52 (m, 5H, ArH).
Phenyl 4,6-O-(4-methoxybenzylidene)-1-thio-β-D-glucopyranoside
(m, 1H, H5), 4.16 (t, J = 9.3 Hz, 1H, H4), 4.26 (dd, J = 4.9, 9.9 Hz,
1H, H6e), 4.61 (d, J = 3.1 Hz, 1H, H1), 4.67-4.81 (m, 2H, BnH),
5.51 (s, 1H, PhCH), 7.30-7.39 (m, 8H, ArH), 7.49-7.53 (m, 2H,
(11c)34
ArH).
11c was isolated as white solid following elution of the column
Methyl 3-O-benzyl-4,6-O-benzylidene-α-D-glucopyranoside (18b)37
with 45% EA/PE; Yield 224 mg, 78% (starting from 11a, 200
mg, 0.74 mmol).; mp (EtOH) 170-172 ˚C, [α]25 -31.5 (c 1.0,
The pure product was isolated as white solid following elution
of the column with 22.5% EA/PE.; Yield 222 mg, 85% (starting
from 18a, 200 mg, 0.7 mmol).; mp 184-186 ˚C, [α]25D +77.8 (c
5.0, CHCl3), lit37 mp 185-187 ˚C and [α]25D +80.0 (c 5.0, CHCl3).;
1H-NMR (300 MHz, CDCl3); δ 3.46 (s, 3H, OCH3), 3.58-3.89 (m,
5H, H2, H3, H4, H6a, H6e), 4.33 (m, 1H, H5), 4.80 (d, J = 3.7 Hz, 1H,
H1), 4.80-4.84 (m, 1H, BnH), 4.98 (dd, J = 3.1, 11.6 Hz, 1H, BnH),
5.59 (s, 1H, PhCH), 7.29-7.41 (m, 8H, ArH), 7.51-7.54 (m, 2H,
ArH).
D
CHCl3), lit34 mp(EtOH) 173-176 ˚C and [α]25 -38.8 (c 0.19,
D
1
CHCl3).; H-NMR (500 MHz, CDCl3); δ 2.66 (s, 1H, OH), 2.82 (s,
1H, OH), 3.36-3.44 (m, 3H, H2, H3, H5), 3.66-3.76 (m, 5H, OCH3,
H4, H6a), 4.27 (m, 1H, H6e), 4.54 (d, J = 9.5 Hz, 1H, H1), 5.40 (s,
1H, PhCH), 6.79-6.81 (d, J = 8.5 Hz, 2H, ArH), 7.26 (bs, 3H, ArH),
7.31-7.33 (d, J = 8.5 Hz, 2H, ArH), 7.46 (bs, 2H, ArH).; 13C-NMR
(125 MHz, CDCl3); δ 55.3 (OCH3), 68.6, 70.6, 72.6, 74.6, 80.2,
88.6 (C1), 101.9 (PhCH), 113.8, 127.6, 128.5, 129.1, 129.4,
131.3, 133.4.
Allyl 4,6-O-benzylidene-2-deoxy-2-phthalimido-1-thio-β-D-
4-Methoxyphenyl 4,6-O-benzylidene-β-D-glucopyranoside (14b)35
glucopyranoside (19b)38
The crude material was crystallized from MeOH to isolate pure Pure product was isolated as white solid following elution of
product as white solid. Yield 214 mg, 82% (starting from 14a the column with 33% EA/PE and crystallized from DCM and
,
200 mg, 0.699 mmol).; mp 212 ˚C, [α]25 -28.1 (c 1.0, PE.; Yield 220 mg, 88% (starting from 19a
,
200 mg, 0.57
D
CH3OH/CHCl3 1:1), lit35 mp 213-214 ˚C and [α]25 -35.0 (c 1.0, mmol).; mp 182-184 ˚C, [α]25D -39.0 (c 1.0, CHCl3), lit38 mp 185-
D
DMF).; 1H-NMR (300 MHz, D6-DMSO); δ 3.48 (d, J = 8.9 Hz, 187 ˚C and [α]25 -40.0 (c 1.0, CHCl3).; 1H-NMR (300 MHz,
D
1H), 3.57 (bs, 2H), 3.70 (s, 4H), 4.20 (d, J = 5.2 Hz, 1H), 4.97 (d, CDCl3); δ 2.89 (bs, 1H, OH), 3.58-3.60 (m, 2H), 3.81 (m, 1H, H3),
J = 7.3 Hz, 1H, H1), 5.44 (d, J = 3.7 Hz, 1H), 5.59 (s, 1H, PhCH), 4.00 (m, 1H, H6), 4.23-4.39 (m, 3H, H2, H4, H6), 4.61 (m, 1H, H5),
6.85-6.87 (d, J = 8.5 Hz, 2H, ArH), 6.98-7.00 (d, J = 8.4 Hz, 2H, 5.02-5.16 (m, 2H, AllCH2), 5.28 (d, J = 8.4 Hz, 1H, H1), 5.56 (s,
ArH), 7.37-7.45 (m, 5H, ArH).; 13C-NMR (75 MHz, D6-DMSO); δ 1H, PhCH), 5.69 (m, 1H, AllCH), 7.36-7.37 (d, J = 3.0 Hz, 3H,
55.8 (OCH3), 66.2, 68.3, 73.3, 74.7, 80.9 (C1), 101.2 (PhCH), ArH), 7.49-7.50 (d, J = 3.3 Hz, 2H, ArH), 7.69-7.71 (d, J = 2.9 Hz,
102.2 (C1), 114.9, 118.3, 126.8, 128.5, 129.3, 138.2, 151.5, 2H, ArH), 7.82-7.84 (m, 2H, ArH).; 13C-NMR (75 MHz, CDCl3); δ
154.9.
56.7, 66.2, 68.6, 68.7, 70.1, 82.2, 98.0 (C1), 101.9 (PhCH),
4-Bromophenyl 4,6-O-benzylidene-β-D-glucopyranoside (15b)16g
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 9
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117.6, 123.5, 126.4, 128.4, 129.3, 131.6, 133.4, 137.1, 168.1 CDCl3); δ 21.3, 68.7, 69.3, 69.9, 73.7, 75.5, 87.1 (C1), 101.9
(C=O), 168.2 (C=O).
(PhCH), 126.6, 126.9, 128.2, 129.0, 129.3, 129.7, 129.8, 134.2,
134.5, 136.4, 137.7, 138.4.
Phenyl 3-O-benzyl-4,6-O-benzylidene-1-thio-β-D-
Phenyl 4,6-O-benzylidene-2-deoxy-2-phthalimido-1-thio-β-D-
glucopyranoside (20b)39
galactopyranoside (25b)
Pure product was isolated as foam following elution of the
column with 40% EA/PE.; Yield 200 mg, 82% (starting from The crude mass was crystallized from DCM and PE to isolate
20a, 200 mg, 0.5 mmol).; [α]25D +30.7 (c 1.0, CHCl3), lit39 [α]25
pure product as white solid.; Yield 209 mg, 84% (starting from
D
+34.2 (c 1.3, CHCl3).; 1H-NMR (300 MHz, CDCl3); δ 3.61 (m, 1H, 25a, 200 mg, 0.55 mmol), scale up yield, 2.04 g, 82% (starting
H3), 3.70 (m, 1H, H6a), 3.83 (apparent t, J = 9.8, 10.1 Hz, 1H, H2), from 25a, 2.0 g, 5.5 mmol).; mp 159-160 ˚C and [α]25D +13.1 (c
4.30-4.43 (m, 2H, H4, H6e), 4.64 (m, 1H, H5), 5.56 (s, 1H, PhCH), 1.0, CHCl3).; H-NMR (300 MHz, CDCl3); δ 2.51 (bs, 1H, OH),
1
5.69 (d, J = 10.3 Hz, 1H, H1), 7.17-7.89 (m, 14H, ArH).
3.45 (bs, 1H, H5), 3.52 (dd, J = 3.3, 9.3 Hz, 1H, H3), 3.91-4.00 (m,
2H, H2, H6a), 4.15 (d, J = 3.2 Hz, 1H, H4), 4.35 (dd, J = 1.4, 12.4
Hz, 1H, H6e), 4.52 (d, J = 9.5 Hz, 1H, H1), 4.72-4.77 (m, 2H, BnH),
5.43 (s, 1H, PhCH), 7.20-7.43 (m, 13H, ArH), 7.66-7.69 (m, 2H,
ArH).; 13C-NMR (75 MHz, CDCl3); δ 67.2, 69.4 70.1, 71.7, 73.3,
80.3, 87.1 (C1), 101.1 (PhCH), 126.5, 127.9, 128.0, 128.1, 128.5,
4-Methoxyphenyl 4,6-O-benzylidene-2-deoxy-2-phthalimido-β-D-
glucopyranoside (21b)40
Pure product was isolated as foam following elution of the
column with 33% EA/PE.; Yield 206 mg, 85% (starting from
21a, 200 mg, 0.48 mmol), scale up yield, 1.96 g, 81% (starting
,
2.0 g, 4.8 mmol).; [α]25 +12.3 (c 1.0, CHCl3), lit40
D
128.9, 129.1, 129.8, 130.8, 132.6, 133.7, 137.9, 138.0.
from 21a
[α]20D +11.4 (c 0.67, CHCl3).; 1H-NMR (300 MHz, CDCl3); δ 3.67-
3.69 (m, 2H), 3.72 (s, 3H, OCH3), 3.87 (m, 1H), 4.39 (m, 1H),
4-Methoxyphenyl 4,6-O-benzylidene-β-D-galactopyranoside
(26b)42
4.50 (m, 1H), 4.70 (m, 1H), 5.59 (s, 1H, PhCH), 5.80 (d, J = 8.4 The crude mass was crystallized from MeOH to isolate pure
Hz, 1H, H1), 6.72-6.75 (d, J = 9.0 Hz, 2H, ArH), 6.83-6.86 (d, J = product as white solid.; Yield 201 mg, 77% (starting from 26a
,
9.1 Hz, 2H, ArH), 7.37-7.86 (m, 9H, ArH).
200 mg, 0.699 mmol).; mp 230-232 ˚C, [α]25 -79.8 (c 1.0,
D
CH3OH/CHCl3 1:1), lit42 mp 230-232 ˚C and [α]25 -80.4 (c 1.0,
3-(N-Carboxybenzyl)propyl 4,6-O-benzylidene-2-deoxy-2-
D
phthalimido-1-thio-β-D-glucopyranoside (22b)16e
CH3OH / CHCl3 1:1).; 1H-NMR (300 MHz, D6-DMSO); δ 3.59 (bs,
2H, OH), 3.69 (s, 4H), 4.05 (bs, 2H), 4.12 (s, 1H), 4.83 (d, J = 5.9
Hz, 1H), 5.05 (s, 1H), 5.27 (s, 1H), 5.57 (s, 1H, PhCH), 6.84-6.87
(d, J = 8.9 Hz, 2H, ArH), 6.99-7.02 (d, J = 8.9 Hz, 2H, ArH), 7.36-
7.46 (m, 5H, ArH).; 13C-NMR (75 MHz, D6-DMSO); δ 55.8
(OCH3), 66.5, 68.9, 70.2, 72.2, 76.3, 101.2 (PhCH), 102.0 (C1),
114.9, 118.1, 126.7, 128.4, 129.1, 139.1, 151.8, 154.8.
Pure product was isolated as foam following elution of the
column with 50% EA/PE.; Yield 205 mg, 87% (starting from
22a, 200 mg, 0.4 mmol).; [α]25D -38.7 (c 1.2, CHCl3), lit16e [α]20
D
1
-39.8 (c 1.48, CHCl3).; H-NMR (300 MHz, CDCl3); δ 1.62-1.69
(m, 2H, CH2), 2.87 (bs, 1H, OH), 3.02-3.12 (m, 2H, NCH2), 3.47
(m, 1H), 3.59 - 3.65 (m, 3H, OCH2, H6), 3.75-3.87 (m, 2H, H3, H5),
4.23 (dd, J = 8.5, 10.4 Hz, 1H, H2), 4.35 (dd, J = 3.7, 10.6 Hz, 1H,
H6), 4.60 (apparent t, J = 8.9, 9.1 Hz, 1H, H4), 4.94 (m, 1H, NH),
5.01 (bs, 2H, BnH), 5.24 (d, J = 8.5 Hz, 1H, H1), 5.54 (s, 1H,
2-Allylphenyl 4,6-O-benzylidene-β-D-galactopyranoside (27b)
The crude mass was crystallized from MeOH to isolate pure
product as white solid. Yield 197 mg, 76% (starting from 27a
,
200 mg, 0.68 mmol).; mp 230-232 ˚C.; 1H-NMR (300 MHz, D6-
DMSO); δ 3.59-3.68 (m, 2H), 3.72 (bs, 2H, OH), 4.06 (s, 2H),
4.15 (s, 1H), 4.90 (d, J = 7.3 Hz, 1H, H1), 4.99 (d, J = 9.9 Hz, 1H),
5.06-5.12 (m, 2H), 5.26 (d, J = 5.0 Hz, 1H), 5.58 (s, 1H, PhCH),
5.97-6.06 (m, 1H), 6.95 (m, 1H, ArH), 7.11-7.16 (m, 3H, ArH),
7.36-7.48 (m, 5H, ArH).; 13C-NMR (75 MHz, D6-DMSO); δ 66.5,
68.9, 70.4, 72.3, 76.3, 100.3 (C1), 101.9 (PhCH), 115.6, 116.1,
122.4, 126.7, 127.7, 128.4, 129.1, 129.7, 129.9, 137.7, 139.1,
155.5.
PhCH), 7.34-7.81 (m, 14H, ArH).
Phenyl 4,6-O-benzylidene-1-thio-β-D-galactopyranoside (23b)41
The crude product was crystallized from EtOH to isolate pure
product as white solid.; Yield 233 mg, 88% (starting from 23a
,
200 mg, 0.74 mmol), scale up yield, 2.25 g, 82% (starting from
23a
,
2.0 g, 7.4 mmol).; mp 116-118 ˚C, [α]25 -41.2 (c 1.0,
D
CHCl3), lit41 mp 118˚C and [α]25 -34.5 (c 1.2, CHCl3).; H-NMR
1
D
(300 MHz, CDCl3); δ 3.55 (s, 1H, OH), 3.68-3.72 (m, 3H, H2, H3,
H5), 4.03 (d, J = 10.6 Hz, 1H, H6), 4.21(s, 1H, H4), 4.38 (d, J =
12.4 Hz, 1H, H6), 4.51 (d, J = 8.8 Hz, 1H, H1), 5.51 (s, 1H, PhCH),
7.27-7.31 (m, 3H, ArH), 7.38 (bs, 5H, ArH), 7.68-7.70 (d, J = 6.3
Phenyl 4,6-O-benzylidene-1-thio-α-D-mannopyranoside (28b)43
Isolated as white solid following elution of the column with EA
and crystallized from CH3OH.; Yield 180 mg, 68% (starting from
28a, 200 mg, 0.74 mmol).; mp 210-212 ˚C, [α]25D +281.0 (c 1.0,
CH3OH/CHCl3 1:1), lit43 mp 213-214 ˚C and [α]20D -289.0 (c 0.50,
Hz, 2H, ArH).
4-Tolyl 4,6-O-benzylidene-1-thio-β-D-galactopyranoside (24b)32
The crude mass was crystallized from EtOH to isolate pure
product as white solid.; Yield 225 mg, 86% (starting from 24a
1
CH3OH/CHCl3 1:1).; H-NMR (300 MHz, D6-DMSO); δ 3.77-3.81
,
(m, 2H, 2OH), 3.93-4.08 (m, 4H, H4, H5, H6a, H6e), 5.24 (d, J = 6.0
Hz, 1H, H3), 5.47 (s, 1H, H2), 5.57 (d, J = 3.8 Hz, 1H, H1), 5.63 (s,
1H, PhCH), 7.30-7.49 (m, 10H, ArH).; 13C-NMR (75 MHz, D6-
DMSO); δ 65.8, 68.1, 68.6, 72.9, 78.9, 89.7 (C1), 101.7 (PhCH),
126.9, 127.9, 128.5, 129.3, 129.7, 131.8, 134.1, 138.3.
200 mg, 0.699 mmol), scale up yield, 2.09 g, 80% (starting from
24a
,
2.0 g, 6.9 mmol).; mp 152-154 ˚C, [α]25 -65.1 (c 1.0,
D
CHCl3), lit32 mp 154-155 ˚C and [α]25 -72.8 (c 1.0, CHCl3).; 1H-
D
NMR (300 MHz, CDCl3); δ 2.36 (s, 3H, CH3), 2.96 (bs, 2H, OH),
3.44 (bs, 1H), 3.63-3.65 (m, 2H), 3.95 (d, J = 12.4 Hz, 1H, H6),
4.12 (bs, 1H, H4), 4.33 (d, J = 12.4 Hz, 1H, H1), 4.43 (m, 1H, H6),
5.47 (s, 1H, PhCH), 6.98-7.12 (d, J = 7.6 Hz, 2H, ArH), 7.37-7.39
(m, 5H, ArH), 7.58 (d, J = 7.9 Hz, 2H, ArH).; 13C-NMR (75 MHz,
General procedure for one-pot 4,6-O-benzylidation acetylation of
carbohydrates
10 | J. Name., 2012, 00, 1-3
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Journal Name
View Article Online
DOI: 10.1039/C6RA23198E
ARTICLE
Phenyl 2,3-di-O-acetyl-4,6-O-benzylidene-β-D-galactopyranosyl-
(1→4)-2,3,6-tri-O-acetyl-1-thio-β-D-glucopyranoside (33)45
To a solution of unprotected glycosides (100 mg) and
benzaldehyde dimethylacetal (1.1 mmol) in dry acetonitrile (5
ml), 10 mole % Mg(OTf)2 was added at room temperature.
After completion of reaction (indicated by TLC), solvent was
concentrated in vacuum and in the same reaction vessel acetic
anhydride (1.0 equivalent per hydroxyl group) was added.
After completion of the reaction (indicated by TLC), the
reaction mixture was diluted with ethyl acetate, and the
mixture was washed subsequently with saturated NaHCO3
followed by brine solution; the organic extract was finally dried
over anhydrous Na2SO4. The solvent was removed under
reduced pressure and the crude product was either crystallized
The crude product was crystallized from EA and PE to isolate
pure product as white solid.; Yield 141.7 mg, 84% (starting
from 32, 100 mg, 0.23 mmol).; mp 254-256 ˚C, [α]25D +23.5 (c
0.50, CHCl3), lit45 mp 257 ˚C and [α]25 +24.5 (c 0.70, CHCl3).;
D
1H-NMR (300 MHz, CDCl3); δ 2.03 (s, 9H, COCH3), 2.08 (s, 3H,
COCH3), 2.10 (s, 3H, COCH3), 3.45 (s, 1H), 3.65-3.77 (m, 2H),
4.01-4.14 (m, 2H), 4.26-4.33 (m, 2H), 4.44 (d, J = 7.8 Hz, 1H,
H1), 4.56 (m, 1H), 4.68 (d, J = 10.0 Hz, 1H), 4.85-4.96 (m, 2H,
H1’), 5.19-5.28 (m, 2H,), 5.46 (s, 1H, PhCH), 7.29-7.31 (m, 3H,
ArH), 7.36-7.38 (m, 3H, ArH), 7.41-7.49 (m, 4H, ArH).; 13C-NMR
(75 MHz, CDCl3); δ 20.6 (CH3CO), 20.7 (CH3CO), 20.8 (CH3CO),
22.7 (CH3CO), 29.7 (CH3CO), 62.1, 62.4, 66.5, 68.1, 68.4, 69.0,
69.7, 70.1, 70.4, 72.1, 73.1, 73.4, 73.6, 74.4, 75.9, 76.9, 85.5,
or passed through a short pad of silica to give pure product.
Typical procedure for 4-tolyl 2,3-di-O-acetyl-4,6-O-benzylidene-1-
thio-β-D-glucopyranoside (29)44
To a solution of glycoside 12a (100 mg, 0.35 mmol) and 101.1, 101.4, 126.5, 128.2, 128.9, 129.0, 129.2, 129.7, 131.9,
benzaldehyde dimethylacetal (1.1 equivalent, 0.39 mmol, 0.06 133.0, 134.5, 137.4, 168.9 (C=O), 169.4 (C=O), 169.6 (C=O),
ml) in dry acetonitrile (5 ml), Mg(OTf)2 (0.1 equivalent, 0.4 170.2 (C=O), 170.3 (C=O), 170.4 (C=O), 170.7 (C=O).
Methyl 2,3-di-O-acetyl-4,6-O-benzylidene-β-D-galactopyranosyl-
→4)
(1 -2,3,6-tri-O-acetyl-β-D-glucopyranoside (35)
mmol, 12.8 mg) was added at ambient temperature. After
completion of reaction (indicated by TLC), solvent was
concentrated in vacuum and in the same reaction vessel acetic
anhydride (2.0 equivalent, 0.7 mmol, 0.06 ml) was added.
After completion of the reaction (indicated by TLC), the
reaction mixture was worked up as described under the
general procedure, and the crude product was crystallized
from EA and PE to isolate 29 as white solid.; Yield 123.4 mg,
77%.; mp 170-172 ˚C, [α]25D -38.0 (c 1.00, CHCl3), lit44 mp 172-
46
The crude product was purified by column chromatography on
silica gel and the white solid mass was crystallized from EtOH
to give 35.; Yield 78% (starting from 34, 100 mg, 0.28 mmol).;
mp 220–222 ˚C, [α]25D +36.5 (c 1.46, CHCl3), lit32 mp 225 ˚C and
[α]25 +36.5 (c 0.70, CHCl3).; 1H-NMR (300 MHz, CDCl3); δ 2.03
D
(s, 12H, 4×COCH3), 2.11 (s, 3H, COCH3), 3.45 (s, 1H), 3.47 (s, 3H,
OCH3), 3.59-3.63 (m, 1H), 3.79 (t, J = 9.5 Hz, 1H), 4.03 (d, J =
12.4 Hz, 1H), 4.12 (dd, J = 4.8,11.9 Hz, 1H), 4.27-4.33 (m, 2H),
4.39 (d, J = 7.9 Hz, 1H), 4.45-4.54 (m,2H), 4.85-4.93 (m, 2H),
5.26 (d, J = 10.5 Hz 1H), 5.19 (d, J = 9.7 Hz, 1H), 5.46 (s, 1H,
CHPh), 7.36-7.38 (m, 3H, ArH), 7.44-7.46 (m, 2H, ArH).
174 ˚C and [α]25 -34.1 (c 1.00, CHCl3).; 1H-NMR (500 MHz,
D
CDCl3); δ 1.95 (s, 3H, COCH3), 2.03 (s, 3H, COCH3), 2.28 (s, 3H,
CH3), 3.48 (m, 1H, H5), 3.56 (t, J = 9.5 Hz, 1H, H6a), 3.70 (t, J =
10.0 Hz, 1H, H4), 4.29 (dd, J = 5.0, 10.5 Hz, 1H, H6e), 4.65 (d, J =
10.0 Hz, 1H, H1), 4.89 (apparent t, J = 9.0, 10.0 Hz, 1H, H2), 5.25 4-Methoxyphenyl 2,3-di-O-acetyl-4,6-O-benzylidene-α-D-
(apparent t, J = 9.0, 9.5 Hz, 1H, H3), 5.42 (s, 1H, PhCH), 7.06-
7.07 (d, J = 8.0 Hz, 2H, ArH), 7.26-7.35 (m, 7H, ArH).;13C-NMR
(125 MHz, CDCl3); δ 20.7 (CH3CO), 20.8 (CH3CO), 21.2 (CH3),
68.5, 70.6, 70.8, 72.9, 78.1, 86.8 (C1), 101.5 (PhCH), 126.2,
127.7, 128.3, 129.2, 133.7, 136.8, 138.8, 169.5 (C=O), 170.1
(C=O).
→4)
glucopyranosyl-(1
-2,3,6-tri-O-acetyl-β-D-glucopyranoside
(37)16g
The crude product was purified by column chromatography on
silica gel and the white solid mass was crystallized from EtOH
to give 37.; Yield 131.5 mg, 79% (starting from 36
, 100 mg,
0.35 mmol).; mp 180-182 °C, [α]25D +25.5 (c 0.49, CHCl3), lit16g
Phenyl 2,3-di-O-acetyl-4,6-O-benzyledene-β-D-glucopyranosyl-
mp 182–184 ˚C and [α]25 +24.5 (c 0.60, CHCl3).; H-NMR (300
1
D
45
→4)
(1
-2,3,6-tri-O-acetyl-1-thio-β-D-glucopyranoside (31)
MHz, CDCl3); δ 2.04 (s, 3H, COCH3), 2.05 (s, 3H, COCH3), 2.05 (s,
3H, COCH3), 2.06 (s, 3H, COCH3), 2.08 (s, 3H, COCH3), 3.64 (t, J
= 9.5 Hz, 1H, H4), 3.70-3.77 (m, 4H, OCH3, H4’), 3.80-3.91 (m,
2H, H5’, H6’), 4.08 (t, J = 9.4 Hz, 1H, H3), 4.24-4.32 (m, 2H, H5,
H2’), 4.54 (dd, J = 2.7, 12.5 Hz, 1H, H6’), 4.89 (dd, J = 4.1, 10.1
Hz, 1H, H6), 4.97 (d, J = 7.6 Hz, 1H, H1), 5.06 (t, J = 7.7 Hz, 1H,
H2), 5.31 (t, J = 8.8 Hz, 1H, H6), 5.38 (d, J = 4.1 Hz, 1H, H1’),
5.43–5.50 (m, 2H, H3’, PhCH), 6.79-6.84 (m, 2H, ArH), 6.90-6.95
The crude product was crystallized from EA and PE to isolate
pure product as white solid.; Yield 123.2 mg, 73% (starting
from 30, 100 mg, 0.23 mmol).; mp 264-266 ˚C, [α]25D -42.5 (c
0.50, CHCl3), lit45 mp 267 ˚C and [α]25D -45.3 (c 1.00, CHCl3).; 1H-
NMR (300 MHz, CDCl3); δ 2.01 (s, 3H, COCH3), 2.02 (s, 3H,
COCH3), 2.04 (s, 3H, COCH3), 2.08 (s, 3H, COCH3), 2.11 (s, 3H,
COCH3), 3.47 (m, 1H, H5), 3.62-3.77 (m, 4H, H4, H6’, H5’, H6’),
4.07 (dd, J = 5.0, 11.8 Hz, 1H, H6), 4.33 (dd, J = 4.5, 10.0 Hz, 1H,
H6’), 4.48-4.59 (m, 2H, H3, H4’), 4.66 (d, J = 10.0 Hz, 1H, H1)
4.85-4.94 (m, 2H, H1’, H2), 5.16-5.28 (m, 2H, H2’, H3’), 5.47 (s,
1H, PhCH), 7.26-7.48 (m, 10H, ArH).; 13C-NMR (75 MHz, CDCl3);
δ 20.6 (CH3CO), 20.7 (CH3CO), 20.8 (CH3CO), 20.9 (CH3CO), 30.9
(CH3CO), 61.9, 62.2, 62.3, 66.4, 68.5, 69.2, 70.2, 70.3, 71.7,
71.9, 72.6, 74.2, 74.4, 75.8, 76.1, 76.3, 76.8, 77.9, 85.3, 100.5,
101.5, 126.1, 128.3, 128.9, 129.0, 129.8, 133.0, 133.3, 134.5,
136.6, 169.4 (C=O), 169.5 (C=O), 170.2 (C=O), 170.3 (C=O),
171.5 (C=O).
(m, 2H, ArH), 7.33-7.36 (m, 3H, ArH), 7.40-7.44 (m, 2H, ArH).;
2'-Azidoethyl 2,3-di-O-acetyl-4,6-O-benzylidene-α-D-
glucopyranosyl-(1→4)-2,3,6-tri-O-acetyl-β-D-glucopyranoside
(39)16g
The crude product was purified by column chromatography on
silica gel and the white solid mass was crystallized from EtOH
to give 39.; Yield 135.8 mg, 79% (starting from 38
, 100 mg,
0.24 mmol).; mp 184-186 °C, [α]25 +2.3 (c 2.25, CHCl3), lit16g
D
mp 186-188 °C and [α]25 +2.0 (c 2.25, CHCl3).; H-NMR (400
1
D
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 11
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DOI: 10.1039/C6RA23198E
ARTICLE
Journal Name
6
(a) C. Limousin, J. Cleophax, A. Petit, A. Loupy and G. Lukacs,
J. Carbohydr. Chem.,1997, 16, 327.; (b) F. Dasgupta, P. P. Sing
and H. C. Srivastava, Carbohydr. Res., 1980, 80, 346.; (c) G.
Agnihotri, P. Tiwari and A. K. Misra, Carbohydr. Res., 2005,
340, 1393.; (d) C.-A. Tai, S. S. Kulkarni and S.-C. Hung, J. Org.
Chem., 2003, 68, 8719.; (e) J. C. Lee, C. -A. Tai and S. -C.
Hung, Tetrahedron Lett., 2002, 43, 851.; (f) N. P. Bizier, S. R.
Atkins, L. C. Helland, S. F. Colvin, J. R. Twitchell and M. J.
Cloninger, Carbohydr. Res., 2008, 343, 1814.; (g) G. Bartoli, R.
Dalpozzo, A. D. Nino, L. Maiuolo, M. Nardi, A. Procopio and
MHz, CDCl3); δ 2.01 (s, 3H, COCH3), 2.02 (s, 3H, COCH3), 2.04 (s,
3H, COCH3), 2.05 (s, 3H, COCH3), 2.11 (s, 3H, COCH3), 3.26 (m,
1H, NCH), 3.47 (m, 1H, NCH), 3.60-3.76 (m, 4H), 3.83-3.89 (m,
1H), 3.97-4.05 (m, 2H), 4.22-4.27 (m, 2H, H6), 4.57-4.61 (m, 2H,
H6, H3’), 4.82-4.89 (m, 2H, H1, H2’), 5.26 (apparent t, J = 8.8,
9.2 Hz, 1H, H2), 5.36 (d, J = 4.0 Hz, 1H, H1’), 5.44 (d, J = 9.6 Hz,
1H, H3), 5.48 (s, 1H, PhCH), 7.33-7.42 (m, 5H, ArH).
Methyl 2,3-di-O-acetyl-4,6-O-benzylidene-β-D-glucopyranoside
(41)47
A. Tagarelli, Green Chem., 2004, 6, 191.; (h) S. San, N. Ding,
W. Zhang, P. Wang, Y. Li and M. Li, J. Carbohydr. Chem.,
2012, 31, 571.; (i) K.-C. Lu, S.-Y. Hsieh, L. N. Patkar, C.-T. Chen
and C.-C. Lin, Tetrahedron, 2004, 60, 8967.; (j) L. Shi, G.
Zhang and F. Pan, Tetrahedron, 2008, 64, 2572.; (k) N. K.
Jalsa, Cat. Commun., 2012, 18, 32.
The crude product was crystallized from EA and PE to isolate
pure product as white solid.; Yield 145 mg, 77% (starting from
40, 100 mg, 0.52 mmol).; mp 106-108 ˚C, [α]28D -100.6 (c 2.10,
CHCl3), lit47 mp 110-112 ˚C and [α]24 -95.2 (c 5.24, CHCl3).; 1H-
D
NMR (300 MHz, CDCl3); δ 2.05 (s, 3H, COCH3), 2.07 (s, 3H,
COCH3), 3.52 (s, 3H, OCH3), 3.56 (m, 1H, H5), 3.70 (t, J = 9.5 Hz,
1H, H4), 3.80 (t, J = 10.2 Hz, 1H, H6), 3.83 (dd, J = 4.9, 10.5 Hz,
1H, H6), 4.51 (d, J = 7.8 Hz, 1H, H1), 4.99 (apparent t, J = 8.0, 9.0
Hz, 1H, H2), 5.32 (apparent t, J = 9.4, 11.5 Hz, 1H, H3), 5.51 (s,
1H, CHPh), 7.35-7.44 (m, 5H, ArH).
7
8
(a) J. A. Hyatt and G. W. Tindall, Heterocycles, 1993, 35, 227.;
(b) R. H. Furneaux, P. M. Rendle and I. M. Sims, J. Chem. Soc.,
Perkin Trans. 1, 2000, 2011.; (c) C.-S. Chao, M.-C. Chen, S.-C.
Lin and K.-K. T. Mong, Carbohydr. Res., 2008, 343, 957.
(a) P. M. Bhaskar and D. Loganathan, Tetrahedron Lett.,
1998, 39, 2215.; (b) P. M. Bhaskar and D. Loganathan,
Synlett, 1999, 129.; (c) G. Fan, C. Liao, T. Fang, S. Luo and G.
Song, Carbohydr. Polym., 2014, 112, 203.; (d) J. Zhang, B.
Zhang, J. Zhou, J. Li, C. Shi, T. Huang, Z. Wang and J. Tang, J.
Carbohydr. Chem., 2011, 30, 165.; (e) A. K. Misra, P. Tiwari
and S. K. Madhusudan, Carbohydr. Res., 2005, 340, 1075.; (f)
L. Cai, C. Rufty and M. Liquois, Assian. J. Chem., 2014, 26,
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Acknowledgements
Financial support from DST-SERB (Scheme No. SR/S1/OC-
61/2012), New Delhi, India to RG, from CAS-UGC and FIST-DST,
India, to the Department of Chemistry, Jadavpur University are
acknowledged. MMM (SRF) is grateful to UGC, India for
fellowship.
341, 339.; (h) L. Wu and Z. Yin, Carbohydr. Res., 2013, 365
,
14.; (i) A. Santra, G. Guchhait and A. K. Misra, Green Chem.,
2011, 13, 1345.
9
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