Efficient synthesis of oligosaccharyl 1,2-O-orthoesters from n-pentenyl glycosides and application to the pentaarabinofuranoside of the mycobacterial cell surface

Article abstract of DOI:10.1039/c4ob01395f

Complex oligosaccharide syntheses employ the use of more than one glycosyl donor and hence, methods for the interconversion of glycosyl donors are highly valuable for the overall synthesis plan. Herein, n-pentenyl glycosides are efficiently converted to g

Full text of DOI:10.1039/c4ob01395f

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DOI: 10.1039/C4OB01395F
ARTICLE
Efficient synthesis of oligosaccharyl 1,2-O-orthoesters
from n-pentenyl glycosides and application to the
pentaarabinofuranoside of mycobacterial cell surface
Cite this: DOI: 10.1039/x0xx00000x
Shivaji A. Thadke and Srinivas Hotha*
Received 00th January 2012,
Accepted 00th January 2012
Complex oligosaccharide syntheses employ the use of more than one glycosyl donor and
hence, methods for the interconversion of glycosyl donors are highly valuable for the overall
DOI: 10.1039/x0xx00000x
synthesis plan. Herein,
orthoesters in the presence of both acid and base sensitive functional groups. Identified
protocol was found to be suitable for the synthesis of trisaccharyl and tetrasaccharyl 1,2-
n-pentenyl glycosides are efficiently converted to glycosyl 1,2-O-
www.rsc.org/
O
-
orthoester as well. Furthermore, an iterative synthesis of pentaarabinofuranoside present in the
Mycobacterium tuberculosis cell surface was accomplished using this method.
Introduction
conditions would not be really encouraging for oligosaccharyl
bromide synthesis as they lead to the cleavage of the acid
Molecular glycobiology studies require pure and
structurally defined glycoconjugates or oligosaccharides which
are available in Nature as micro and heterogeneous forms.1
Oligosaccharide synthesis is still a challenging task even after
development of many elegant strategies.2 Oligosaccharides are
often synthesized from reducing end to the non-reducing end or
from the non-reducing end to the reducing end while employing
sensitive functional groups and/or interglycosidic bonds.
However, a rarely exploited but highly useful method for
the synthesis of glycosyl halides is the conversion of n-pentenyl
glycosides in the presence of molecular bromine.8 The
conversion of n-pentenyl glycosides to glycosyl bromide would
then assist its conversion to corresponding alkyl 1,2-orthoesters
in basic conditions. In particular, we got interested in
conversion of n-pentenyl glycosides into propargyl 1,2-
orthoesters as this switching would be beneficial: (i) for
increased reactivity and yield; (ii) as the glycosidation becomes
catalytic; (iii) since the leaving group becomes traceless; (iv)
affords 1,2-trans stereoselectivity; (v) for facilitated
purification; (vii) for orthogonal activation with glycosyl
donors, and (viii) for the convergent synthesis of
oligosaccharides.
the synthesis in
a convergent or linear fashion. Each
oligosaccharide is unique and hence its synthesis requires
optimization of glycosyl donor/acceptors and sometimes
strategies as well.3,4 Often, oligosaccharides are synthesized
with an alkyl group at the reducing end.5a,b The alkyl group is
chosen in such a way that it does not get affected during the
course of the entire synthesis. Recent developments in the field
of glycoconjugate chemistry have led to a renewed interest in
the use of glycosyl 1,2-O
-orthoesters5c-f with long shelf-life as
glycosyl donors. Current methods are suitable for the synthesis
of 1,2-orthoesters of the easily accessible saccharides.5
However, far too little attention has been paid to the synthesis
of 1,2-orthoester of an oligosaccharide with multiple protecting
groups.
Results and Discussion
Mindful of these advantages, conversion of
glycosides into propargyl 1,2-orthoesters was considered first.
Easily accessible -pentenyl 2,3,4,6-tetra- -benzoyl -D-
n-pentenyl
n
O

glucopyranoside (1a)9 was treated with molecular bromine in
the presence of 4 Å molecular sieves at 0 ºC in CH2Cl2 for 10
min to observe complete conversion of compound 1a into
anomeric bromide.8 The resulting glucosyl bromide was
quickly concentrated in vacuo and redissolved in CH2Cl2,
treated with propargyl alcohol, 2,6-lutidine, TBAI in the
presence of 4 Å MS powder at 60 ºC for 24 h to obtain
propargyl 1,2-orthoester 2a6 in 92% yield over two steps
(Scheme 1).10
Traditionally, 1,2-orthoesters are synthesized from
corresponding 2-
O-acylated glycosyl halides by the treatment
of an alcohol under basic conditions.6 Hence, oligosaccharyl
1,2-
the
O
-orthoester synthesis would require: (i) an acyl group at
C
-2 position of the sugar at the reducing end, (ii) a halide at
the reducing end of the oligosaccharide. Routinely employed
conditions for the synthesis of glycosyl bromides7 such as
HBr/AcOH7a,c or AcBr/MeOH7c are found to be more suitable
for monosaccharides and disaccharides. Further, these
This journal is © The Royal Society of Chemistry 2013
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Scheme 2. Synthesis of propargyl 1,2-orthobenzoates from n-
pentenyl furanosides, disaccharides and trisaccharides
Similarly, changing the nucleophile from propargyl alcohol
to 4-penten-1-ol afforded
-pentenyl orthoester 3a6 in 89%
yield under aforementioned conditions (Scheme 1). In this
endeavor, less reactive -pentenyl glucoside was converted into
a more reactive and stable -pentenyl or propargyl 1,2-
orthoesters in very high yield. In addition, the methodology has
been gauged by preparing methyl and cholesterol 1,2-
n
View Article Online
DOI: 10.1039/C4OB01395F
n
n
O
-
orthoesters 3b and 3c in 95% and 86% yields respectively using
methanol and cholesterol.10
Scheme 1. Conversion n-pentenyl glucoside into glucosyl 1,2-
orthoesters
OBz
O
BzO
BzO
ROH =
O
HO
O
92% over 2 steps
Ph
Ph
2a
O
Reagents. (a) Br2, 4 Å MS powder, 0 ºC, CH2Cl2, 10 min; (b)
propargyl alcohol, 2,6-lutidine, TBAI, 4 Å MS powder, 25 ºC,
CH2Cl2, 5 h; (c) propargyl alcohol, 2,6-lutidine, TBAI, 4 Å MS
powder, 60 ºC, CH2Cl2, 24 h.
OBz
O
BzO
BzO
HO
O
ROH =
O
89% over 2 steps
O
3a
Br2, 4 Å MS powder
0 °C, CH2Cl2, 10 min then
OBz
O
BzO
BzO
OBz
O
O
ROH, 2,6-lutidine, TBAI
4 Å MS powder, CH2Cl2
60 °C, 24 h
Accordingly, our investigation started with the successful
OBz
BzO
BzO
ROH = CH3OH
O
O
conversion of easily accessible
n-pentenyl furanoside 4 to the
Glycosyl Donor (1a)
95% over 2 steps
Ph
Ph
orthoester in 88% under above identified reaction conditions.
5
3b
OCH3
H3C
CH3
The glycosyl acceptor
deprotection of the
6
C
was synthesized from compound
-5-silyl ether Scheme 3. Iterative
4 by
OBz
H3C
CH3
O
O
BzO
BzO
H3C
H3C
H
ROH = Cholesterol
86% over 2 steps
O
conversion of
orthoesters for the synthesis of pentaarabinan of mycobacterial
cell wall using HF.Py to yield compound in 85% yields at
The protocol was found to be appropriate for furanosides as room temperature for 4 h. 1,2-Trans diastereoselective
well. For example, the -pentenyl 2,3,5-tri- -benzoyl -D- gold(III)-catalyzed glycosidation between the orthoester and
arabinofuranoside 1b11a was successfully converted into aglycon
afforded the disaccharide in 1 h. In continuation,
propargyl 1,2-orthobenzoate (2b) at room temperature in 90% propargyl 1,2-orthoester in very good yield was obtained and
yield over two steps. Similarly, per- -benzoyl derivatives of the deprotection of the silyl ether of compound resulted in the
pentenyl lactoside 1c7b and maltotrioside 1d were subjected to glycosyl acceptor
The furanosylation between glycosyl
the above delineated reaction conditions with only deviation donor and the glycosyl acceptor under gold(III)-catalyzed
n-pentenyl glycosides to propargyl 1,2-
Cholesterol =
H
H
HO
3c
O
6
n
O

5
6
7
8
O
n
-
7
9
.
8
9
being the reaction was needed to be conducted at 60 ºC to glycosidation conditions afforded the tetrasaccharide 10
.
obtain corresponding propargyl 1,2-orthobenzoates 2c6 and 2d Tetrasaccharide 10 was again successfully converted to the 1,2-
in 88% and 89% yield respectively (Scheme 2).10 Conversion orthoester 11 under aforementioned mild conditions in 88%
of a less reactive glycosyl donor to a more reactive and stable yield.
glycosyl donor will be an interesting strategy for the synthesis
It is gratifying to note that the current method enabled
of oligosaccharides.12 In this regard, mycobacterial arabinan synthesis of 1,2-orthoester of oligosaccharides (2d and 11) as
synthesis has been considered in order to illustrate the benefits well in a facile manner without affecting any functionality on
of converting n-pentenyl glycosides to 1,2-orthoesters.
the glycan. The formation of tetrasaccharide 1,2-orthoester 11
1
Mycobacterium tuberculosis (Mtb) is the etiological agent was confirmed on the NMR spectral analysis. In the H NMR
for the tuberculosis which kills more than ~2 million lives spectrum of tetrasaccharide 11, anomeric proton of the
annually.13 Two main oligosaccharides (arabinogalactan and furanoside at the reducing end was noticed at
lipoarabinomanan) are identified on the cell surface of Mtb in Hz) ppm and acetylenic methine was found at
which arabinose and galactose exists in furanoside form.14a the 13C NMR spectrum, the presence of alkyne was confirmed
Ethambutol, a frontline drug, was proven to act by inhibiting based on the resonances at 52.0, 73.7 and 79.3 ppm along
the arabinan biosynthesis.14b As a result, arabinan synthesis has with quaternary carbon of 1,2-orthoester at 122.5 ppm which
been a subject of intense investigation15 and herein, the utility confirmed the successful formation of tetrasaccharyl 1,2-


6.35 (d,
2.36 ppm. In
J 4.3
of
n
-pentenyl furanoside conversion into propargyl 1,2- orthoester 11. Further orthoester 11 was treated with one molar
to afford the pentaarabinan 12
orthoester strategy to synthesize a pentasaccharide in an equivalent of glycosyl acceptor
6
iterative fashion was demonstrated.
in the presence of 7 mol% of AuCl3; however, the conversion
was found to be slow and less yielding (50%).
2 | J. Name., 2012, 00, 1‐3
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Journal Name
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ARTICLE
Scheme 2. Synthesis of Pentaarabinofuranoside of
mycobacterium cell surface
Addition of 7 mol% each of AuCl3 and AgOTf was found to
be highly beneficial for the successful synthesis of
View Article Online
pentasaccharide 12 (Scheme 3).16a Gold trichloride upon
DOI: 10.1039/C4OB01395F
reaction with silver triflate is known to form gold(III) triflate
which in turn was found to be better in gold-catalyzed
reactions.16 Pentasaccharide 12 displayed five singlets for the
five anomeric protons around 5.16-5.59 ppm as in the 1H
NMR spectrum, five anomeric carbons were identified at

105.6, 105.7, 105.8, 105.9 and 105.9 ppm in the 13C NMR
spectrum and gave very good mass spectral matching (m/z
calcd. for C116H108NaO31Si: 2047.6542, found: 2047.6522).
Silyl ether deprotection of 12 was carried out using HF.Py and
global deprotection of benzoates was performed under Zemplén
conditions to obtain fully deprotected pentaarabinan (13) as n-
pentenyl glycoside.10
Conclusions
In conclusion, a facile protocol for the synthesis of 1,2-
orthoesters from -pentenyl glycosides has been found.
n
Identified method is shown to be compatible for pyranosides,
furanosides and oligosaccharides as well. Furthermore, the
utility of the methodology is shown by the successful synthesis
of pentaarabinofuranoside present in the cell surface of
Mycobacterium tuberculosis in an iterative fashion.
Experimental section
General Methods. Unless otherwise noted, materials were
obtained from commercial suppliers and were used without
further purification. Unless otherwise reported all reactions
were performed under argon atmosphere. Removal of solvent
in vacuo refers to distillation using a rotary evaporator attached
to an efficient vacuum pump. Products obtained as solids or
syrups were dried under high vacuum. AuCl3 and AgOTf were
purchased from multinational commercial vendors. Analytical
thin-layer chromatography was performed on pre-coated silica
plates (F254, 0.25 mm thickness); compounds were visualized
by UV light or by staining with anisaldehyde spray. Optical
rotations were measured on a digital polarimeter. IR spectra
were recorded on a FT-IR spectrometer. NMR spectra were
recorded either on a 400 or a 500 MHz with CDCl3 as the
solvent and TMS as the internal standard. High resolution mass
spectroscopy (HRMS) was performed using an ESI mass
analyzer. Low resolution mass spectroscopy (LRMS) was
performed on UPLC-MS.
General procedure for the synthesis of 1,2-O-orthoesters
from -pentenyl glycosides: Pent-4-enyl pyranoside (1a) (1.00
n
g, 1.5 mmol) in anhydrous CH2Cl2 (10 mL) containing 4 Å
molecular sieves powder (0.50 g) and cooled to 0 oC. Bromine
(0.078 mL, 1.5 mmol) in CH2Cl2 (1 mL) was added drop-wise
o
Reagents. (a) Br2, 4 Å MS powder, 0 ºC, CH2Cl2, 10 min; (b)
propargyl alcohol, 2,6-lutidine, TBAI, 4 Å MS powder, 25 ºC,
CH2Cl2, 10 h; (c) HF.Py, 4: 1 THF-Py, 0 ºC-25 ºC, 4 h, (d) 7 mol%
AuCl3, 4 Å MS powder, 25 ºC, CH2Cl2, 1 h; (e) 7 mol% each of
AuCl3 and AgOTf, 4 Å MS powder, 25 ºC, CH2Cl2, 2 h; (f) NaOMe,
MeOH, 24 h, 25 ºC.
to the reaction mixture and was stirred at 0 C for 10 min. The
reaction mixture was concentrated under reduced pressure to
afford 2,3,4,6-tetra-O-benzoyl glucopyranosyl bromide as a
solid along with 4 Å molecular sieves powder which was
immediately used in the next step without any additional
purification.
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The crude pyranosyl bromide prepared vide supra was acetonitrile:water as mobile phase to get fully deprotected 13 as
redissolved in 10 mL anhydrous CH2Cl2 and propargyl alcohol a colourless fluffy solid (29 mg, 78% over two steps).
(0.13 mL, 2.3 mmol) and 2,6-lutidine (0.35 mL, 3.0 mmol) Pent-4-enyl 2,3,6-tri-
O
-benzoyl-4-
O DOI: 10.103O9-/bC4eOnBzo01y3l9-45F-
-(2,3,6-tri-View Article Online
-D-gluco-
were added. Catalytic amount of tetra -butyl ammonium -(2,3,4,6-tetra- -benzoyl-
n
O
O
-D-glucopyranosyl)-
iodide was added to the reaction and stirred for 24 h at 60 °C. pyranosyl)--D-glucopyranoside (1d): This compound is
After completion of reaction (judged by TLC), the reaction prepared by the known procedure8,9 using maltotriose (0.50 g,
mixture was filtered through a bed of celite and the filtrate was 0.99 mmol) as the starting material, Yield: (1.10 g, 68% over
0.8 in CHCl3); IR(cm-1, CHCl3): 3065,
25
diluted with CH2Cl2 (100 mL) and water (100 mL) and the two steps); []D +76.0 (
c
1
aqueous layer was extracted with CH2Cl2 (2x50 mL) and the 2927, 1725, 1594, 1451, 1265, 1098, 706; H NMR (399.78,
organic extract was washed with saturated oxalic acid solution, CDCl3): δ 1.58 (2 H, dt,
saturated sodium bicarbonate solution. The organic phase was 3.48 (1 H, dt, 9.6, 6.7), 3.85 (1 H, dt,
collected, dried over sodium sulphate and concentrated in ddd, 9.4, 4.5, 2.0), 4.22 (1 H, d, 9.5), 4.33 – 4.50 (6 H, m),
vacuo. The crude residue of orthoester was purified by silica 4.60 (1 H, dd, 12.4, 2.8), 4.66 (1 H, dd, 12.2, 4.8), 4.72 (1
gel column chromatography (EtOAc:Petroleum ether 20:80) to H, d, 7.5), 4.56 – 4.82 (1 H, m), 4.77 – 4.83 (1 H, m), 4.98 (1
obtain 2a (0.88 g, 92% over two steps) as a white solid. H, dd, 12.0, 1.8), 5.08 (1 H, dd, 10.0, 3.9), 5.22 – 5.29 (2 H,
Similar procedure was applied for the synthesis of 3a 6
m), 5.50 – 5.72 (4 H, m), 5.74 (1 H, d, 3.9), 5.92 (1 H, dd,
3c 18 2a 6,7b 2b,11a 2c,6 2d
, and 11 9.7, 8.5), 6.09 (1 H, t, 10.1), 7.06 – 7.63 (30 H, m), 7.51 –
General procedure for deprotection of -silyl ethers: To a 7.63 (6 H, m), 7.69 – 7.76 (4 H, m), 7.79 – 7.89 (4 H, m), 7.91
solution of -TBDPS protected saccharide C
(1.50 g, 2.26 – 7.98 (2 H, m), 8.02 – 8.08 (2 H, m), 8.14 – 8.21 (2 H, m,); 13
J
16.2, 7.9), 1.92 (2 H, quintet,
J 6.7),
J
J
9.7, 6.2), 4.05 (1 H,
J
J
J
J
J
J
J
,
3b 18
,
J
J
,
,
,
5
,
7
.
J
O
O
4
mmol) in 20 mL of THF:Py (10:2) was added HF.Py (2 mL) at NMR (100.53 MHz, CDCl3): δ 28.5, 29.7, 62.2, 63.0, 63.2,
0 °C and the reaction mixture was stirred for 4 h at room 69.0, 69.1, 69.1, 70.0, 70.0, 70.7, 70.8, 71.7, 72.3, 72.8, 73.6,
temperature. The reaction mixture was treated with sat solution 73.7, 75.0, 96.4, 96.7, 100.5, 114.8, 127.8-129.9 (50C), 132.9
of aq. sodium bicarbonate and the compound was extracted (4C), 133.0 (2C), 133.1, 133.2, 133.3 (2C), 137.7, 164.7, 164.9,
with EtOAc (2 x 50 mL) from the aqueous layer. The EtOAc 165.0, 165.1, 165.3, 165.5(2C), 165.7, 165.8, 166.1; HRMS
layer was dried over anhydrous sodium sulphate and (ESI) : m/z calcd for [C93H80O26+Na]+: 1636.4869; Found:
concentrated in vacuo to obtain a crude residue which was 1636.4886.
purified by flash silica gel column chromatography (EtOAc:pet 3,6-Di-
O
-benzoyl-4-
O
-(2,3,6-tri-O-benzoyl-4-O-(2,3,4,6-tetra
-D-glucopyranosyl)- -D
ether, 25:75) to give required saccharide
yellow gum.
6
(0.82 g, 85%) as a -O-benzoyl- -D-glucopyra-nosyl)-



-(prop-2-yn-1-yl)-1,2-orthobenzoate (2d): This compound is
prepared using the above mentioned general procedure using 1d
Similar procedure was applied for the synthesis of 9.
General procedure for gold(III
furanosylation: To a CH2Cl2 solution (25 mL) containing 89%); []D +89.0
)
catalyzed 1,2-trans (1.00 g, 0.62 mmol) as the starting material, Yield: (0.873 g,
1.2 in CHCl3); IR(cm-1, CHCl3): 3301,
25

(
c
glycosyl donor
5
(1.19 g, 1.88 mmol) and glycosyl acceptor
6
3065, 2970, 2114, 1728, 1640, 1451, 1267, 1101, 707; 1H NMR
(0.80 g, 1.88 mmol) with 4 Å molecular sieves powder (1.00 g) (399.78 MHz, CDCl3): δ 2.18 (1 H, d,
was added a catalytic amount of AuCl3 (40 mg, 0.13 mmol) [for m), 3.11 – 3.19 (1 H, m), 3.89 (1 H, d,
J
J
1.9), 2.91 – 3.01 (1 H,
7.8), 4.09 – 4.17 (2 H,
compound 12: Silver triflate (7 mol%) as an additive] and m), 4.22 – 4.59 (7 H, m), 4.78 (2 H, q,
stirred at room temperature. After 2 h at room temperature, the 10.3, 3.9), 5.22 (1 H, dd, 10.6, 3.9), 5.32 – 5.39 (1 H, m), 5.65
reaction mixture was neutralized by the addition of Et3N and (1 H, t, 9.8), 5.83 (1 H, d, 3.7), 5.94 (1 H, d, 5.2), 6.01 –
filtered through celite and concentrated in vacuo. The resulting 6.19 (3 H, m), 6.79 – 7.57 (32 H, m), 7.55 – 8.11 (18 H, m); 13
J 8.4), 5.07 (1 H, dd, J
J
J
J
J
C
residue was purified by silica gel column chromatography using NMR (100.53 MHz, CDCl3): δ 51.8, 62.3, 63.3, 63.6, 67.5,
ethyl acetate-petroleum ether to obtain 1,2-trans glycoside as a 67.9, 68.9, 69.1, 69.2, 69.8, 70.8, 71.0, 71.7, 72.4, 72.9, 73.0,
fluffy solid
7
(1.58 g, 84%).
73.7, 78.9, 94.0, 97.0, 97.6, 121.3, 126.7-130.2 (50C), 132.8,
133.0, 133.0, 133.1, 133.2, 133.2, 133.2, 133.3, 133.6, 133.6,
Similar procedure was applied for the synthesis of 10
,
12.
Deprotection under Zemplén conditions: Silyl ether of 12 (100 164.7, 164.8, 165.0, 165.5, 165.7, 165.7, 165.9, 166.0, 166.1;
mg, 0.049 mmol) was carried out under aforementioned HRMS (ESI) : m/z calcd for [C91H74O26+Na]+: 1605.4366;
conditions using HF.Py which was directly used in the next step Found: 1605.4384.
for the saponification of benzoates.
redissolved in methanol and sodium methoxide (0.049 mmol, D-arabinofuranoside (4): This compound is prepared using
freshly prepared) and stirred at 25
C. After 24 h, the reaction the known procedure10,15 using arabinose (4.00 g, 26.64 mmol)
The residue was (Pent-4-enyl) 2,3-di-O-benzoyl-5-O-(t-butyldiphenylsilyl)--
⁰
mixture was treated with Amberlite IR-120 and filtered. The as the starting material, Yield: (5.67 g, 32% over three steps);
c
1.4 in CHCl3); IR(cm-1, CHCl3): 3070, 2927,
25
filtrate was concentrated and diluted with a solution containing []D +11.0 (
1:1 mixture of water-ethyl acetate and the compound 13 in 1725, 1594, 1268, 1109, 700; 1H NMR (399.78, CDCl3): δ
aqueous layer was washed with ethyl acetate (10 mL) and was 1.05 (9 H, s), 1.66 – 1.90 (2 H, m), 2.18 (2 H, dt, 13.1, 6.8),
concentrated in vacuo The crude was purified by reverse 3.53 (1 H, dt, 9.5, 6.2), 3.78 (1 H, dt, 9.5, 6.7), 4.01 (2 H,
phase C18-silica gel column chromatography using dABq, 11.1, 5.0), 4.37 (1 H, q, 4.8), 4.93 – 5.10 (2 H, m),
5.21 (1 H, s), 5.21 (1 H, s), 5.45 (1 H, d, 1.4), 5.84 (1 H, ddt,
J
.
J
J
J
J
J
J
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ARTICLE
16.9, 10.1, 6.7), 7.14 – 7.83 (16 H, m), 7.94 – 8.23 (4 H, m); HRMS (ESI) : m/z calcd for [C59H60O31Si+Na]+: 1027.3701;
13C NMR (100.53, CDCl3): δ 19.3, 26.7, 26.7, 26.7, 28.7, 30.3, Found: 1027.3711.
63.6, 66.6, 77.4, 82.3, 82.9, 105.7, 114.9, 127.6, 127.6, 127.7, 3-
128.3, 128.3, 128.4, 129.2, 129.5, 129.6, 129.6, 129.6, 129.8, yl)-
129.9, 129.9, 129.9, 133.1, 133.2, 133.3, 133.3, 134.8, 135.6, yn-1-yl)-1,2-
135.6, 135.6, 135.6, 138.1, 165.4, 165.5; HRMS (ESI) : m/z using the above mentioned general procedure using
O

-Benzoyl-5-
-D-arabinofuranosyl)-
-orthobenzoate (8): This compound is prepared
O
-(2,3-di-
O
-benozyl-5-OD-(Ot-I:b1u0.t1y0l3Vd9iei/pwCh4ArOetincBl0ey1lOs3ni9lli5n-Fe
-D-arabinofuranoside (prop-2-

O
7
(0.80 g,
calcd for [C40H44O7Si+Na]+: 687.2754; Found: 687.2750.
3- -Benzoyl-5- -(t-butyldiphenylsilyl)- -D-arabinofurano-
side (prop-2-yn-1-yl)-1,2- -orthobenzoate (5):
compound is prepared using the above mentioned general δ 1.01 (9 H, s), 2.37 (1 H, t,
procedure using (1.5 g, 2.26 mmol) as the starting material, 3.72 – 3.80 (1 H, m), 3.90 – 3.96 (1 H, m), 3.96 – 4.02 (1 H,
Yield: (1.26 g, 88%); []D
CHCl3): 3293, 3066, 2939, 1727, 1595, 1453, 1266, 1106, 704; m), 4.61 (1 H, t,
1H NMR (399.78 MHz, CDCl3): δ 0.99 (9 H, s), 2.37 (1 H, t,
5.45 (1 H, m), 5.50 – 5.68 (2 H, m), 6.36 (1 H, d,
2.2), 3.63 (2 H, dd,
t, 7.5), 5.09 (1 H, d,
6.97 – 7.86 (18 H, m), 8.09 (2 H, d,
0.80 mmol) as the starting material, Yield: (0.66 g, 85%); []D
25
O
O


18.9 (
c
1.2 in CHCl3); IR(cm-1, CHCl3): 3434, 3070, 2931,
1
O
This 1721, 1588, 1264, 1107, 706; H NMR (399.78 MHz, CDCl3):
J
2.5), 3.51 (1 H, dd, J 10.4, 7.5),
4
1.2, CHCl3); IR(cm-1, m), 4.26 (1 H, q,
J
4.4), 4.34 (1 H, d,
J 2.2), 4.44 – 4.56 (1 H,
25

20.0 (
c
J
7.4), 5.05 (1 H, s), 5.12 (1 H, d,
J
J
4.3), 5.34 –
4.3), 7.10 –
J
J
7.5, 4.1), 3.84 – 4.02 (2 H, m), 4.46 (1 H, 7.75 (24 H, m), 7.86 – 8.22 (6 H, m); 13C NMR (100.53 MHz,
J
J
4.3), 5.67 (1 H, s), 6.33 (1 H, d,
J 4.3), CDCl3): δ 19.3, 26.8, 26.8, 26.8, 52.0, 63.2, 66.8, 73.8, 77.2,
J
7.9); 13C NMR (100.53 77.9, 79.4, 82.2, 83.2, 85.0, 85.4, 105.9, 106.8, 122.6, 126.5,
MHz, CDCl3): δ 19.1, 26.7, 26.7, 26.7, 51.9, 63.4, 73.7, 77.5, 126.5, 127.7, 127.7, 127.7, 127.7, 127.8, 128.0, 128.0, 128.3,
79.3, 85.0, 87.2, 106.5, 122.4, 126.3, 126.3, 127.5, 127.6, 128.4, 128.4, 128.5, 128.5, 128.5, 128.6, 128.6, 129.7, 129.7,
127.6, 127.6, 128.2, 128.3, 128.4, 128.4, 129.2, 129.6, 129.6, 129.9, 129.9, 130.0, 130.0, 130.0, 130.0, 130.0, 133.2, 133.3,
129.6, 129.8, 129.8, 133.1, 133.1, 133.4, 134.2, 135.3, 135.4, 133.5, 133.6, 135.6, 135.7, 135.7, 135.7, 135.7, 136.0, 165.3,
135.4, 135.4, 165.1; HRMS (ESI)
[C38H38O7Si+Na]+: 657.2284; Found: 657.2281.
(Pent-4-enyl) 2,3-di- -benzoyl-
This compound is prepared using the above mentioned general arabinofuranosyl)-
:
m/z calcd for 165.4, 165.7; HRMS (ESI) : m/z calcd for [C57H54O13Si+Na]+:
997.3231; Found: 997.3238.
O

-D-arabinofuranoside (6): (Pent-4-enyl)-2,3-di-O-benzoyl-5-O-(2,3-di-O-benozyl-
-D-

-D-ara-binofuranoside (9):
This
procedure using
Yield: (0.818 g, 85%); []D
CHCl3): 3512, 3071, 2931, 1723, 1601, 1451, 1265, 1176, 710; Yield: (0.43 g, 80%); []D
4
(1.5 g, 2.26 mmol) as the starting material, compound is prepared using the above mentioned general
1.0 in CHCl3); IR(cm-1, procedure using
7
(0.70 g, 0.70 mmol) as the starting material,
25

32.8 (
c
19.0 (c
1.0 in CHCl3); IR(cm-1,
25
1H NMR (399.78, CDCl3): δ 1.60 – 1.94 (2 H, m), 2.08 – 2.31 CHCl3): 3422, 3070, 2928, 1724, 1598, 1451, 1264, 1110, 712;
(2 H, m), 2.43 (1 H, br s), 3.54 (1 H, dt,
9.5, 6.2), 3.79 (1 H, 1H NMR (399.78 MHz, CDCl3): δ 1.40 – 1.90 (2 H, m), 2.07 –
dt, 9.5, 6.6), 3.99 (2 H, d, 11.7), 4.32 (1 H, q, 4.1), 4.89 – 2.34 ( 2 H, m), 2.39 (1 H, br s), 3.51 (1 H, dt, 9.5, 6.1), 3.77
5.08 (2 H, m), 5.23 (1 H, s), 5.40 – 5.48 (1 H, m), 5.53 (1 H, d, (1 H, dt, 9.5, 6.6), 3.96 (2 H, dd, 11.2, 2.9), 4.02 (1 H, dd,
1.3), 5.82 (1 H, ddt, 16.9, 10.2, 6.6), 7.24 – 7.77 (6 H, m), 12.1, 3.5), 4.20 (1 H, dd, 11.2, 4.6), 4.44 (1 H, td, 4.6, 3.0),
7.79 – 8.35 (4 H, m); 13C NMR (100.53 MHz, CDCl3): δ 28.7, 4.51 (1 H, q,
4.0), 4.88 – 5.08 (2 H, m), 5.22 (1 H, s), 5.42 (1
30.2, 62.3, 66.7, 77.8, 81.7, 83.6, 105.5, 114.9, 128.4, 128.4, H, s), 5.43 – 5.45 (1 H, m), 5.51 (1 H, d, 1.2), 5.62 (1 H, d,
128.5, 128.5, 129.0, 129.1, 129.7, 129.8, 129.9, 129.9, 133.5, 5.0), 5.66 (1 H, d, 1.3), 5.82 (1 H, ddt, 16.9, 10.2, 6.7), 7.04
133.5, 138.0, 165.3, 166.1; HRMS (ESI) : m/z calcd for – 7.73 (12 H, m), 7.75 – 8.30 (8 H, m); 13C NMR (100.53 MHz,
J
J
J
J
J
J
J
J
J
J
J
J
J
J
J
J
J
[C24H26O7+Na]+: 449.1576; Found: 449.1573.
(Pent-4-enyl)-2,3-di- -benzoyl-5- -(2,3-di-
t-butyldiphenylsilyl)- -D-arabinofuranosyl)-
CDCl3): δ 28.7, 30.2, 62.2, 66.1, 66.6, 77.3, 77.7, 81.6, 81.7,
81.8, 83.6, 105.5, 105.7, 114.9, 128.3, 128.3, 128.4, 128.4,
128.5, 128.5, 128.5, 128.5, 128.9, 129.0, 129.0, 129.2, 129.7,
O

O
O
-benozyl-5-
-D-arabino-
O-
(
furanoside (7): This compound is prepared using the above 129.7, 129.8, 129.8, 129.8, 129.8, 129.8, 129.8, 133.3, 133.4,
mentioned general procedure using (1.19 g, 1.88 mmol) and 133.4, 133.5, 138.0, 165.1, 165.4, 165.7, 166.1; HRMS (ESI) :
5
6
(0.80 g, 1.88 mmol) as the starting material, Yield: (1.58 g, m/z calcd for [C43H42O13+Na]+: 789.2523; Found: 789.2520.
1.0 in CHCl3); IR(cm-1, CHCl3): 3070, Pent-4-enyl-2,3-di-
O
-benzoyl-5-
-(2,3-di- -benzoyl-5-
-D-arabinofuranosyl)- -D-arabinofuranosyl)-
-D-arabinofuranosyl)- -D-arabino-furanoside (10) : This
compound is prepared using the above mentioned general
O-(2,3-di-O
-benzoyl-5-O-
25
84%); []D

12.4 (
c
1
2927, 1727, 1594, 1451, 1268, 1115, 715; H NMR (399.78 (2,3-di-
O
-benzoyl-5-
O
O
O-(t-butyldi-
MHz, CDCl3): 1.02 (9 H, s), 1.68 – 1.80 (2 H, m), 2.12 – 2.23 phenylsilyl)-
(2 H, m), 3.52 (1 H, dt, 9.0, 5.9), 3.79 (1 H, dt, 9.2, 6.5),
3.93 (1 H, dd, 11.2, 2.5), 3.99 (1 H, d, 4.4), 4.20 (1 H, dt,
11.1, 6.5), 4.33 (1 H, d, 2.3), 4.48 (1 H, d, 3.9), 4.51 (1 H, procedure using
dd,
s), 5.51 (1 H, s), 5.58 (1 H, s), 5.63 (1 H, s), 5.64 (1 H, s), 5.81 
(1 H, ddt,
(8 H, m); 13C NMR (100.53 MHz, CDCl3):
26.7, 28.7, 30.3, 63.3, 66.1, 66.6, 77.4, 77.5, 81.7, 81.8, 82.1, (1 H, dt,
83.2, 105.6, 105.9, 114.9, 127.5-133.3 (30C), 135.6, 135.6, m), 4.17 (3 H, ddd,


J
J


J
J
J
J
J
9
(0.42 g, 0.55 mmol) and
8
(0.53 g, 0.55
25
J
10.5, 5.9), 4.92 – 5.06 (2 H, m), 5.22 (1 H, s), 5.38 (1 H, mmol) as the starting material, Yield: (0.78 g, 84%); []D
(
c
1.2 in CHCl3); IR(cm-1, CHCl3): 3068, 2933, 1724,
1
J
16.8, 10.1, 6.5), 7.14 – 7.80 (22 H, m), 7.87 – 8.19 1599, 1452, 1266, 1109, 708; H NMR (399.78 MHz, CDCl3):

19.2, 26.7, 26.7, δ 0.99 (9 H, s), 1.79 – 1.65 (2 H, m), 2.21 – 2.09 (2 H, m), 3.50
9.5, 6.2),3.76 (1 H, dt, 9.5, 6.6), 3.98 – 3.85 (5 H,
14.7, 7.9, 3.2), 4.42 (1 H, dd, 7.6, 4.5),
J
J
J
J
135.6, 135.7, 135.9, 135.9, 138.1, 165.2, 165.4, 165.5, 165.6; 4.47 (1 H, q,
J
4.5), 4.64 – 4.56 (2 H, m), 5.04 – 4.90 (2 H, m),
This journal is © The Royal Society of Chemistry 2012
J. Name., 2012, 00, 1‐3 | 5

Organic & Biomolecular Chemistry
Page 6 of 7
Journal Name
ARTICLE
5.21 (1 H, s), 5.35 (1 H, s), 5.39 (1 H, s), 5.40 (1 H, s), 5.48 (1 (56C), 133.0, 133.1, 133.1, 133.1, 133.1, 133.2, 133.2, 133.3,
H, t,
ddt,
J 2.1), 5.53 (1 H, t, J 4.0), 5.65 – 5.59 (6 H, m), 5.80 (1 H, 133.3, 133.3, 133.4, 133.4, 135.6, 135.6, 135.6, 135.6, 138.1,
View Article Online
J
16.9, 10.2, 6.7), 7.59 – 7.19 (30 H, m), 7.67 (4 H, m), δ 165.1, 165.1, 165.1, 165.1, 165.4, 165.4D, O1I6: 150.5.1,03196/C54.5O,B1016359.56F,
8.06 – 7.86 (16 H, m); 13C NMR (100.53 MHz, CDCl3): δ 19.4, 165.6; HRMS (ESI) : m/z calcd for [C116H108O31Si+Na]+:
26.9, 26.9, 26.9, 28.9, 30.4, 60.6, 63.4, 65.8, 65.9, 66.0, 66.8, 2047.6542; Found: 2047.6532.
66.8, 77.3, 77.4, 81.7, 81.7, 81.9, 81.9, 82.1, 82.1, 82.3, 83.2, Pent-4-enyl [5-O-(5-O-(5-O-(5-O-α-D-arabinofuranosyl)-α-
105.7, 105.9, 106.0, 106.0, 115.0, 127.8-130.1 (50C), 133.2, D-arabinofuranosyl)-α-D-arabinofuranosyl)-α-D-arabinofu-
133.3, 133.3, 133.3, 133.5, 133.5, 133.5, 133.5, 135.8, 135.8, ranosyl]-α-D-arabinofuranoside (13):
138.2, 165.3, 165.3, 165.4, 165.6, 165.6, 165.7, 165.7, 165.8; This compound is prepared using the known procedure15 using
HRMS (ESI): m/z calcd for [C97H92O25Si+Na]+: 1708.5628; (0.1 g, 0.049 mmol) as the starting material, Yield: (29 mg,
Found: 1708.5620.
78% over two steps); [α]20 +77.5 (
KBr): 3295, 2922, 2848, 1640, 1402, 1069, 1035; H NMR
(399.78 MHz, D2O): 1H NMR (399.78 MHz, D2O): δ 1.70 (2 H,
c
1.7 in H2O); IR(cm-1,
D
1
3-
5-
O
O
-Benzoyl-5-
-(2,3-di- -benzoyl-5-
-D-arabinofuranosyl)-
-D-arabinofuranoside (prop-2-yn-1-yl)-1,2-
orthobenzoate (11): This compound is prepared using the 5.9, 3.2), 3.65 – 4.25 (22 H, m), 5.01 (1 H, s), 4.99 – 5.13 (2 H,
O
-(2,3-di-
O
O
-benozyl-5-
-( -butyldiphenylsilyl)-
-D-arabinofura-
O
-(2,3-di-
O

-benzoyl-
-D-ara-
O
t
binofuranosyl)-
nosyl)-


quintet,
J
6.8), 2.13 (2 H, q,
J
7.0), 3.71 (1 H, dd,
J 12.3, 5.8),

O
-
3.81 (2 H, s), 3.87 (1 H, td,
J
10.9, 10.2, 4.7), 3.95 (1 H, dd, J
above mentioned general procedure using 10 (0.70 g, 0.42 m), 5.08 (4 H, s), 5.89 (1 H, ddt,
J
13.4, 10.2, 6.7);13C NMR
2.1 (100.53 MHz, CDCl3): δ 27.8, 29.5, 61.1, 61.1, 66.7, 66.8, 66.9,
25
mmol) as the starting material, Yield: (0.61 g, 88%); []D
(c
1.0 in CHCl3); IR(cm-1, CHCl3): 3302, 3071, 2927, 2105, 67.8, 76.4, 76.5, 76.5, 76.7, 76.7, 80.7, 80.8, 80.8, 80.9, 80.9,
1
1725, 1596, 1454, 1265, 1107, 708; H NMR 399.78 MHz, 81.7, 82.3, 82.3, 83.9, 83.9, 107.2, 107.4, 107.4, 107.5, 107.5,
CDCl3): δ 1.00 (9 H, s), 2.36 (1 H, t, 2.5), 3.51 (1 H, dd,
114.8, 138.7; HRMS (ESI) : m/z calcd for [C30H50O21+Na]+:
10.3, 7.2), 3.67 (1 H, dd, 11.2, 2.7), 3.78 (1 H, dd, 10.3, 769.2742; Found: 769.2731.
7.7), 3.88 (1 H, dd, 9.5, 2.5), 3.92 (2 H, dd, 5.2, 2.4), 3.96 (2
H, d, 4.5), 4.07 (1 H, dd, 11.2, 4.0), 4.17 (1 H, dd, 11.3,
7.4, 3.9), 4.49 (1 H, q, 4.6), 4.58-4.62 (2
1.3), 5.61-5.63 (3 H, m), 5.11 (1 H, d,
1.2), 5.52 (1 H, s), 5.06 (1
H, s), 5.38 (1 H, s), 5.60 (1 H, s), 6.35 (1 H, d, 4.3), 7.21-7.70
J
J
J
J
J
J
J
J
J
Acknowledgements
4.1), 4.28 (1 H, dd,
H, m), 5.56 (1 H, d,
4.3 Hz), 5.30 (1 H, s), 5.45 (1 H,
J
J
J
SAT thanks the CSIR New Delhi and SH thanks the DST New
Delhi for the financial assistance in the form of SwarnaJayanthi
Fellowship.
J =
J
J
(36 H, m), 7.87-8.05 (14 H, m); 13C NMR (100.53 MHz,
CDCl3): δ 19.2, 26.7 (3C), 52.0, 63.3, 65.5, 65.7, 66.4, 76.7,
77.2, 77.3, 77.7, 81.4, 81.5, 82.0, 82.1, 82.1, 82.1, 83.1, 84.8,
85.3, 105.4, 105.8, 105.9, 106.7, 122.5, 126.4 (2C), 127.6-135.6
(59C), 165.0, 165.1, 165.2 (2C), 165.4, 165.6 (2C); HRMS
(ESI): m/z calcd for [C95H86O25Si+Na]+: 1678.5159; Found:
1678.5206.
Notes and references
†Electronic Supplementary Information (ESI) available: Copies of 1H, 13
C
and DEPT NMR spectra for all new compounds. See
DOI: 10.1039/b000000x/
1.
2.
3.
4.
(a) O. J. Planet, E. R. Palace and P. H. Seeberger, Science, 2001, 291,
1523; (b) A. Varki, Glycobiology, 1993, 3, 97; (c) C. R. Bertozzi, L.
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(a) G.-J. Boons, Tetrahedron, 1996, 52, 1095; (b) R. W. Friesen and
S. J. Danishefsky, J. Am. Chem. Soc., 1989, 111, 6656; (c) P. Fugedi,
W. Birberg; P. J. Garegg, and A. Pilotti, Carbohydrate Res., 1987,
164, 297-312.
(a) H. Paulsen, Angew. Chem. Int. Ed. Engl., 1982, 21, 155; (b) K.
Pachamuthu, and R. R. Schmidt, Chem. Rev., 2006, 106, 160; (c) A.
V. Demchenko, In Handbook of Chemical Glycosidation, Ed. A. V.
Demchenko, Wiley-VCH, Weinheim, Germnay, 2008.
(a) B. Fraser-Reid, J. C. López, A. M. Gómez, and C. Uriel, Eur. J.
Org. Chem., 2004, 1387; (b) J. C. López, A. Agocs, C. Uriel, A. M.
Gómez, and B. Fraser-Reid, Chem. Commun., 2005, 5088; (c) B.
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1990, 55, 6068.
Pent-4-enyl-2,3-di-
(2,3-di- -benzoyl-5-
benzoyl-5- -( -butyldiphenylsilyl)-
-D-arabinofuranosyl)- -D-arabinofuranosyl)-
arabinofuranosyl)- -D-arabinofuranoside
compound is prepared using the above mentioned general
O
O
-benzoyl-5-
-(2,3-di- -benzoyl-5-
-D-arabinofuranosyl)-
-D-
(12): This
O
-(2,3-di-
O
O
-benzoyl-5-O-
O
O
-(2,3-di-
O-
O
t





procedure using 11 (0.50 g, 0.30 mmol) and
mmol) as the starting material, Yield: (0.50 g, 82%); []D +5.7
6
(0.13 g, 0.30
25
(
c
1.0 in CHCl3); IR(cm-1, CHCl3): 3070, 2927, 1727, 1591,
1451, 1268, 1113, 714; 1H NMR (399.78, CDCl3): δ 0.95 (9 H,
s), 1.69 (2 H, dd, 12.7, 6.3), 2.12 (2 H, dt, 11.5, 6.9), 3.46 (1
H, dt, 9.4, 6.2), 3.72 (1 H, dt, 9.3, 6.6), 3.79 – 3.99 (6 H, m),
4.05 – 4.23 (4 H, m), 4.38 (1 H, q, 4.4), 4.43 (1 H, q, 4.5),
J
J
J
J
5.
(a) R. R. Schmidt and J. Michel, Angew. Chem. Int. Ed. Engl., 1980,
19, 731; (b) P. J. Garegg, Adv. Carbohydrate Chem. Biochem., 1997,
52, 179; (c) K. N. Jayaprakash, J. Lu, and B. Fraser-Reid, Angew.
Chem. Int. Ed. 2005, 44, 5894; (d) F. Kong, Carbohydr. Res., 2007,
342, 345; (e) A. Y. Shaikh, G. Sureshkumar, D. Pati, S. S. Gupta, and
S. Hotha, Org. Biomol. Chem., 2011, 9, 5951; (f) G. Sureshkumar
and S. Hotha Glycoconjugate J., 2012, 29, 221.
J
J
4.48 – 4.61 (3 H, m), 4.81 – 5.04 (2 H, m), 5.16 (1 H, s), 5.32
(1 H, s), 5.34 (2 H, s), 5.35 (1 H, s), 5.46 (1 H, s), 5.51 (1 H, s),
5.53 – 5.64 (8 H, m), 5.77 (1 H, ddt,
J 16.9, 10.2, 6.7), 7.12 –
7.57 (36 H, m), 7.64 (4 H, ddd, 7.6, 3.7, 1.3), 7.79 – 8.08 (20
J
H, m); 13C NMR (100.53, CDCl3): δ 19.2, 26.7, 26.7, 26.7,
28.7, 30.3, 63.3, 65.7, 65.7, 65.8, 65.9, 66.6, 77.1, 77.2, 77.2,
77.3, 81.4, 81.5, 81.5, 81.7, 81.7, 81.8, 82.0, 82.0, 82.0, 82.0,
82.1, 83.1, 105.6, 105.7, 105.8, 105.9, 114.9, 126.2-129.9
6.
7.
S. R. Vidadala, S. A. Thadke, and S. Hotha, J. Org. Chem., 2009, 74,
9233.
(a) A. F. Bochkov and N. K. Kochetkov, Carbohydrate Res., 1975,
39, 355; (b) G. Sureshkumar and S. Hotha, Tetrahedron Lett., 2007,
6 | J. Name., 2012, 00, 1‐3
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Page 7 of 7
Organic & Biomolecular Chemistry
Journal Name
ARTICLE
48, 6564; (c) C. V. S. Ramamurty, P. Ganney, C. S. Rao, and B.
Fraser-Reid, J. Org. Chem., 2011, 76, 2245; (d) N. M. Podvalnyy, S.
L. Sedinkin, P. I. Abronina, A. I. Zinin, K. G. Fedina, V. I. Torgov,
and L. O. Kononov, Carbohydrate Res., 2011, 346, 7; (e) M. Ginisty,
C. Gravier-Pelletier, and Y. L.Merrer, Tetrahedron: Asymmetry,
2006, 17, 142.
View Article Online
DOI: 10.1039/C4OB01395F
8.
9.
P. Konradsson, and B. Fraser-Reid, J. Chem. Soc., Chem. Commun.,
1989, 1024.
B. Fraser-Reid, U. E. Udodong, Z. Wu, H. Ottoson, J. R. Merrit, C. S.
Rao, C. Roberts, and R. Madsen, Synlett, 1992, 927.
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