AuBr3 mediated glycosidations: Synthesis of tetrasaccharide motif of the Leishmania donovani lipophosphoglycan

Article abstract of DOI:10.1007/s10719-012-9400-7

Tetrasaccharide cap present in lipophosphoglycan of the Leishmania donovani responsible for visceral Leishmaniaisis is synthesized as a fully protected propargyl glycoside. AuBr₃ mediated selective glycosylation of propargyl 1,2-orthoester in the presence of propargyl glycoside is employed as a key step to obtain propargyl containing oligomers. Further, propargyl tetrasaccharide is connected with a long chain hydrocarbon containing azidothiol functionality situated at two terminal ends via 'click' reaction.

Full text of DOI:10.1007/s10719-012-9400-7

Glycoconj J (2012) 29:221–230
DOI 10.1007/s10719-012-9400-7
AuBr3 mediated glycosidations: synthesis of tetrasaccharide motif
of the Leishmania donovani lipophosphoglycan
Gopalsamy Sureshkumar & Srinivas Hotha
Received: 4 April 2012 /Revised: 14 May 2012 /Accepted: 21 May 2012 /Published online: 3 June 2012
#
Springer Science+Business Media, LLC 2012
Abstract Tetrasaccharide cap present in lipophosphoglycan
of the Leishmania donovani responsible for visceral Leish-
maniaisis is synthesized as a fully protected propargyl gly-
coside. AuBr3 mediated selective glycosylation of propargyl
1,2-orthoester in the presence of propargyl glycoside is
employed as a key step to obtain propargyl containing
oligomers. Further, propargyl tetrasaccharide is connected
with a long chain hydrocarbon containing azidothiol func-
tionality situated at two terminal ends via ‘click’ reaction.
prerequisite in order to control and annihilate the spreading
of disease in human population.
The risky disease is caused by Leishmania donovani
which is a protozoan parasite and lives in the alimentary
tract of the sand fly [2]. The parasite penetrates in the
macrophages while sand fly feeding blood on the surface
of skin of the human body. After ingestion of parasite by
mammalian macrophages, the promastigote parasite enters
in phagolysosome compartment where they are supposed to
kill by oxidative toxic products and hydrolytic enzymes.
Instead, the parasite cleverly adapts the conditions and trans-
forms to amastigote form. Infected parasites after multiplica-
tion of amastigote start the infection to other macrophages and
organs [3–6]. So far, it has been understood that Leishmania
parasites exist in the form of promastigote fabricates lipophos-
phoglycan (LPG) on its entire cell surface. These LPGs are
further implicated in many biological functions to adhesion,
survival and infectivity of the parasites in both the sand fly and
human macrophages. On contrary, amastigote form of the
parasite can’t synthesize LPG but can participate in the human
macrophages to be infected [6].
Earlier reports on the structural analyses of Leishmania
donovani LPG [7–15] described that LPG is a heterogenous
glycolipid containing four domains: (i) a neutral oligosac-
charide cap at the terminal non-reducing end, (ii) a repeating
phosphoglycan unit, (iii) a phosphosaccharide core in which
an unusual galactofuranosyl unit is present, and (iv) glyco-
sylphosphatidylinositol (GPI) anchor as shown in Fig. 1.
Each fragment has been identified tentatively to play a
significant role in the sand fly as well as in human macro-
phages [7–20]. The foregoing discussion on the significance
of membrane-bound lipophosphoglycan prompted to devel-
op a route for immunogenic LPG fragments that could in turn
facilitate carbohydrate based vaccine development for Leish-
maniasis. Thus several research groups have synthesized
.
.
.
Keywords Glycosidation Leishmania Gold catalysis
.
.
Orthoester Lipophosphoglycan Tetrasaccharide
The human disease visceral Leishmaniasis is currently
found in nearly 88 countries where a few million people
are affected and surprisingly, 60000 people lose their lives
annually [1]. Unfortunately, no effective vaccine successful-
ly emerged yet to prevent the spreading of disease [2].
However, many drugs such as antimony compounds, dia-
midine were approved for the treatment of Leishmaniases.
These drugs are still having a series of disadvantages, as
they are capable of producing more side effects, high cost
and ineffective to patients who are residing in many parts of
the world. Thus, an effective therapy is still a question mark
to the Leishmaniasis affected patients and is a significant
Electronic supplementary material The online version of this article
(doi:10.1007/s10719-012-9400-7) contains supplementary material,
which is available to authorized users.
:
G. Sureshkumar S. Hotha (*)
Department of Chemistry,
Indian Insititute of Science Education & Research,
Pune 411 008, India
e-mail: s.hotha@iiserpune.ac.in

222
Glycoconj J (2012) 29:221–230
Fig. 1 General structure of Lipophosphoglycan of Leishmania Donovani
different portions of LPG [21–35]. Of which, Seeberger’s
spacer-equipped with amine and thiol functionality of the
tetrasaccharide cap for attaching carrier molecules is notewor-
thy for the future development of carbohydrate-based synthet-
ic vaccines against Leishmaniasis [28, 35]. However, the
introduction of a new spacer with a different functionality at
the reducing end needs refinement of the synthesis protocol
for the entire tetrasaccharide. In order to avoid multiple gly-
cosylations for the attachment of linkers, we thought to install
a stable and functionable protecting group early at the anome-
ric center of saccharide that enables synthesis of tetrasacchar-
ide library with different spacers. In this context, we
envisioned that the installation of the propargyl group as a
stable linker at the reducing end of tetrasaccharide would be
advantageous since (i) propargyl group can be ‘clicked’ effi-
ciently with azide bearing organic molecules and (ii) prop-
argyl group can be introduced at the anomeric position of
sugar directly by modified Fischer glycosidation.
were successfully activated in the presence of propargyl glyco-
sides facilitating the synthesis of 1,2-trans propargyl saccha-
rides [40]. Herein, we report the synthesis of a tetrasaccharide
cap of lipophosphoglycan present on the surface of Leishmania
donovani as a propargyl glycoside using gold catalyzed prop-
argyl 1,2-orthoester-based glycosyl donors.
To begin our investigation, we needed better strategy and
thought for the tetrasaccharide I, which can be prepared by
the deprotection of fully protected propargyl tetrasaccharide
II, which in turn can be disconnected into two building
blocks, namely, mannose propargyl 1,2-O-orthoester III
and propargyl trisaccharide IV in a linear sequence
(Scheme 1). These two fragments can be coupled by using
catalytic amount of AuBr3 in dichloromethane at room
temperature. The trisaccharide acceptor IV can be synthe-
sized by gold catalyzed selective glycosylation of mannose
propargyl 1,2-orthoester III in the presence of propargyl
disaccharide V, which in turn can be derived efficiently from
propargyl 1,2-orthoester of lactose VI. The synthetic en-
deavour for disaccharide acceptor 6 commenced from lac-
tose (Scheme 2). One pot conversion of lactose 1 to
lactopyranosyl bromide was accomplished under acetylation
conditions Ac2O/AcOH/Conc.H2SO4 followed by the
Gold catalysed glycosidations are explored recently for the
synthesis of oligosaccharides and glycoconjugates [36–48].
From our laboratory [36–44], we identified propargyl 1,2-
orthoesters as glycosyl donors in the presence of catalytic
amount of AuBr3 [38]. Subsequently, propargyl 1,2-orthoesters
OH
OH
OP
OP
OP
OH
O
O
HO
HO
PO
PO
O
PO
O
O
HO
PO
PO
P1
PO
PO
O
O
OP
O
HO
PO
O
PO
PO
PO
O
HO
OH
PO
OP
O
+
HO
HO
PO
PO
O
O
O
O
O
HO
PO
O
O
PO
PO
PO
O
O
O
O
O
O
O
HO
PO
III
IV
HO
PO
II
I
III
+
PO
PO
OP
O
PO
PO
OP
OH
OP
O
OP
O
O
O
D-Lactose
O
O
PO
PO
PO
O
PO
O
P1
VI
O
V
Scheme 1 Retrosynthetic analysis of tetrasaccharide

Glycoconj J (2012) 29:221–230
223
HO
HO
OH
O
AcO
AcO
OAc
O
OBn
O
BnO
BnO
OAc
O
OBn
O
OH
O
a,b
O
O
O
c,d
AcO
BnO
HO
BnO
AcO
HO
OH
O
O
O
O
OH
Me
Me
1
2
3
O
O
e
BnO
BnO
OBn
BnO
BnO
OBn
OBn
O
BnO
BnO
OBn
OBn
O
BnO
OH
O
O
O
O
g
O
O
O
O
O
O
f
BnO
BnO
BnO
BnO
BnO
BnO
OH
OAc
6
5
4
Scheme 2 Synthesis of disaccharide aglycone. Reagents and condi-
tions: (a) i) Ac2O, AcOH, Conc. H2SO4, 30 min; ii) HBr-AcOH, 5 h;
(b) 2,6-lutidine, TBAI, propargyl alcohol, CH2Cl2, 70 °C, 36 h, 55 %
(over two steps); (c) NaOMe, MeOH, 2 h, 100 %; (d) NaH, DMF,
BnBr, TBAI, 4 h, 0–25 °C, 83 %; (e) TMSOTf, CH2Cl2, propargyl
alcohol, 25 °C, 15 min, 85 %; (f) NaOMe, MeOH, 25 °C, 8 h, 90 %;
(g) i) DMSO, Ac2O, 24 h, 25 °C; ii) NaBH4, CH2Cl2 : CH3OH (1:1),
4 h, 0–25 °C, 82 % (over two steps)
addition of 33 % hydrobromic acid in glacial acetic acid
[49–51]. Subsequently, lactopyranosyl bromide is treated
with propargyl alcohol, 2,6-lutidine and catalytic amount
of tetra-n-butylammonium iodide (TBAI) in anhydrous
CH2Cl2 at 70 °C for 36 h to give the corresponding prop-
argyl 1,2-orthoacetate 2 in 55 % yield ([38] Supporting
Information). Further, O-acetyl groups of 1,2-orthoester 2
were deprotected under Zemplén conditions and the result-
ing hydroxyl groups were allowed to react with sodium
hydride, benzyl bromide and catalytic amount of TBAI in
anhydrous DMF at 0-25 °C for 4 h to obtain per-O-benzy-
lated lactose 1,2-orthoacetate 3 as a viscous oil in 83 % yield
(Supporting Information).
Thereafter, isomerization of lactosyl propargyl 1,2-
orthoacetate 3 to propargyl lactoside (4) with a O-acetyl
group at C-2 position was achieved efficiently in 85 % yield
by the use of a catalytic amount of TMSOTf and propargyl
alcohol in anhydrous CH2Cl2 at room temperature for
15 min (Supporting Information [52]). Propargyl lactoside
4 was then treated with a solution of sodium methoxide in
anhydrous methanol to deprotect acetate group and thus
obtained equatorial alcohol 5 was oxidized under conditions
DMSO/Ac2O/25 °C/24 h followed by reduction with sodi-
um borohydride in a mixture of anhydrous CH2Cl2 and
CH3OH (1:1) to obtain the required disaccharide acceptor
(6) in 82 % yield (Scheme 2) ([28, 53, 54] Supporting
Information). In parallel, mannose 1,2-orthoacetate 7 was
conveniently prepared from D-(+)-mannose as per the
sequences involved in the formation of per-O-benzylated
lactose 1,2-orthoester 3 (Supporting Information).
after 24 h. However, the reaction is completed when
20 mol% of AuBr3 is used and afforded propargyl trisac-
charide 8 in 48 % yield (Supporting Information). Further,
AuBr3 mediated glycosylation performed with more equiv-
alents of glycosyl donor 7 and glycosyl acceptor 6 did not
improve the overall performance of the reaction. Further-
more, glycosylation between the disaccharide acceptor 6
and per-O-benzylated mannose 1,2-orthobenzoate (9) under
20 mol% AuBr3/CH2Cl2/4 Å MS powder/25 °C/12 h result-
ing in the trisaccharide (10) as a propargyl glycoside in 46 %
yield (Supporting Information). Saponification of com-
pounds 8 and 10 under Zemplén conditions afforded prop-
argyl trisaccharide 11 (90 %) (Supporting Information).
Acceptor 11 was subsequently coupled with mannose 1,2-
orthoacetate 7 under aforementioned conditions to obtain
the desired propargyl tetrasaccharide 12 in 35 % yield
(Supporting Information). Furthermore, propargyl tetrasac-
charide 12 was allowed to react with S-acetyl-11-azido-
thioundecane 13 under CuI/DIPEA/CH3CN/25 °C for the
synthesis of a 1,2,3-triazole ‘clicked’ glycolipid (14) with
thioacetyl group at terminal end in excellent yield
(Scheme 3) (Supporting Information).
In conclusion, we have synthesized the tetrasaccharide
cap of Leishmania donovani lipophosphoglycan with a
propargyl group at the reducing end using gold mediated
selective activation of propargyl 1,2-orthoester in the pres-
ence of propargyl glycoside. Propargyl moiety was further
exploited for introducing a thiol containing long chain hy-
drocarbon via ‘click’ reaction. The immunological studies
with carrier proteins and the effect of triazole ring for further
development of vaccine are currently in progress. Besides,
propargyl tetrasaccharide is a valuable intermediate for syn-
thesizing various other orthogonal functional groups such as
alkene, aldehyde and carboxylic acid that are highly useful
for bioconjugation.
Having the glycosyl donor 7 and acceptor 6 in hand, the
glycosylation reaction was carried out in the presence of
10 mol% AuBr3/CH2Cl2/25 °C/4 Å MS powder in order to
get tri-saccharide 8 in good yield (Scheme 3). But, the
reaction proceeded very slowly and did not complete even

224
Glycoconj J (2012) 29:221–230
BnO
BnO
OBn
O
BnO
OH
O
O
O
OR
O
BnO
BnO
BnO
BnO
OH
O
BnO
6
BnO
OBn
BnO
BnO
b
BnO
BnO
+
a
BnO
BnO
BnO
O
OBn
R
O
O
BnO
O
O
O
O
BnO
BnO
O
O
O
BnO
O
BnO
O
O
O
BnO
BnO
BnO
7
8
, R = CH3
, R = Ac
10, R = Bz
11
9, R = Ph
c
BnO
OAc
O
BnO
OAc
O
BnO
BnO
BnO
BnO
BnO
O
d
BnO
O
O
N3
SAc
BnO
BnO
BnO
O
BnO
BnO
OBn
BnO
OBn
13
BnO
BnO
BnO
N
O
N
BnO
O
O
O
O
O
O
SAc
N
O
O
BnO
O
BnO
BnO
7
BnO
14
12
Scheme 3 Synthesis of propargyl tri- and tetrasaccharides. Reagents
and conditions: (a) AuBr3 (20 mol%), CH2Cl2, 25 °C, 4 Å MS powder
(1 h, 48 % for 8), (12 h, 46 % for 10); (b) NaOMe, MeOH, 25 °C, 8 h,
90 %; (c) 7, AuBr3 (20 mol%), CH2Cl2, 25 °C, 4 Å MS powder, 2 h,
35 %; (d) CuI, DIPEA, CH3CN, 25 °C, 1 h, 85 %
Experimental section
petroleum ether-ethyl acetate as the mobile phase to give
the corresponding lactose propargyl 1,2-orthoacetate 2
(10.35 g, 55 % (over 2 steps). Characterization data:
Synthesis of 3,6-di-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-β-
D-galactopyranosyl)-α-D-glucopyranose-1,2-(prop-2-ynyl
orthoacetate) (2)
25
[α]D (CHCl3, c 1.1)0+74.89; IR (ν, cm-1): 1218, 1749,
1
2879, 2972, 3302; H NMR (CDCl3, 200.13 MHz): δ 1.76
(3 H, s), 1.98 (3 H, s), 2.04 (3 H, s), 2.06 (3 H, s), 2.12 (6 H,
s), 2.18 (3 H, s), 2.43 (1 H, t, J02.41 Hz), 3.65 (1 H, d,
J09.61 Hz), 3.76–3.88 (1 H, m), 3.94 (1 H, t, J06.64 Hz),
4.05–4.17 (3 H, m), 4.19 (2 H, d, J02.38 Hz), 4.25 (1 H, dd,
J02.24, 12.05 Hz), 4.37 (1 H, dd, J02.54, 4.86 Hz), 4.61
(1 H, d, J07.81 Hz), 5.0 (1 H, dd, J03.4, 10.41 Hz), 5.19
(1 H, dd, J07.89, 10.29 Hz), 5.38 (1 H, d, J03.07 Hz), 5.55
(1 H, d, J02.73 Hz), 5.7 (1 H, d, J05.15 Hz); 13C NMR
(CDCl3, 50.32 MHz): δ 20.1, 20.4, 20.5, 20.5, 20.6, 20.7,
20.8, 51.7, 60.8, 63.2, 66.7, 66.9, 68.7, 69.6, 70.7, 70.8,
72.4, 73.8, 77.4, 79.5, 96.9, 102.3, 121.4, 168.9, 169.3,
169.9, 170.2, 170.3, 170.6; Mol. Wt. calculated for
C29H38O18: 674.20, Found: 697.52 (M+Na)+.
To a suspension of D-lactose (10 g, 27.8 mmol) in glacial
acetic acid (50 mL) was added acetic anhydride (24 mL,
249.8 mmol) followed by catalytic amount of conc. H2SO4
and the reaction mixture was stirred at room temperature for
30 min. Then a solution of 33 % hydrobromic acid in glacial
acetic acid (75 mL) was added at 0 °C and the resulting
solution was stirred for an additional 5 h at room tempera-
ture. After completion of the reaction as judged by TLC, the
reaction mixture was poured into ice and extracted with
dichloromethane (2×100 mL). Combined organic layers
were washed with water (3×200 mL), saturated NaHCO3
solution, water, dried over anhydrous sodium sulfate and
concentrated in vacuo to give hepta-O-acetyl-α-D-lactopyr-
anosyl bromide (18.3 g) that was redissolved in anhydrous
dichloromethane (50 mL). To that, 2,6-lutidine (10 mL),
propargyl alcohol (7.6 mL, 130.82 mmol) followed by a
catalytic amount of tetra-n-butylammonium iodide (0.2 g)
were added at room temperature under argon atmosphere.
The reaction mixture was stirred at 70 °C for 36 h under
argon atmosphere, quenched with a saturated solution of
oxalic acid and extracted with dichloromethane (2×
100 mL). Combined organic layers were washed with water,
brine, dried over anhydrous sodium sulfate and concentrated
in vacuo to obtain a brownish black residue, which was
purified by silica gel column chromatography using
Synthesis of 3,6-di-O-benzyl-4-O-(2,3,4,6-tetra-O-benzyl-
β-D-galactopyranosyl)-α-D-glucopyranose-1,2-(prop-2-
ynyl orthoacetate) (3)
To a solution of 3,6-di-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-
β-D-galactopyranosyl)-α-D-glucopyranose-1,2-(prop-2-
ynyl orthoacetate) 2 (6 g, 12.94 mmol) in anhydrous meth-
anol (75 mL) was added sodium metal (~50 mg) at room
temperature under argon atmosphere. The reaction mixture
was stirred for 2 h at the same temperature. After completion
of the reaction, the reaction mixture was concentrated under
reduced pressure to give deacetylated lactose 1,2-orthoester

Glycoconj J (2012) 29:221–230
225
(3.75 g, 100 %). To a solution of deacetylated product
(3.75 g, 8.88 mmol) in anhydrous DMF (25 mL) was added
NaH (2.48 g, 62.15 mmol) at 0 °C and the reaction mixture
was stirred for 1 h at room temperature. Benzyl bromide
(8 mL, 66.59 mmol) followed by a catalytic amount of
TBAI (0.1 g) were added at 0 °C under argon atmosphere
and the stirring was continued for an additional 4 h at room
temperature. After completion of the reaction as judged by
TLC, excess NaH was quenched by slow addition of meth-
anol followed by cold water and subsequently extracted
with diethyl ether (2x70mL). Combined organic layers were
washed with water, brine and dried over anhydrous sodium
sulfate. The solvent was evaporated under reduced pressure
and the resulting crude was purified by conventional silica
gel column chromatography using petroleum ether and ethyl
acetate as the mobile phase to give 3,6-di-O-benzyl-4-O-
(2,3,4,6-tetra-O-benzyl-β-D-galactopyranosyl)-α-D-gluco
pyranose-1,2-(prop-2-ynyl orthoacetate) 3 as a white amor-
purified by silica gel column chromatography using petroleum
ether-ethylacetate as the mobile phase to afford prop-2-ynyl
3,6-di-O-benzyl-4-O-(2,3,4,6-tetra-O-benzyl-β-D-galactopyra-
nosyl)-β-D-glucopyranoside 5 (1.79 g, 90 %) as a colourless
25
oil. Characterization data: [α]D (CHCl3, c 1.00)0-30.15; IR
(ν, cm−1): 1091, 1585, 1605, 2120, 2869, 2912, 3289, 3444.13;
1H NMR (CDCl3, 200.13 MHz): δ 2.45 (1 H, bs), 2.46 (1 H, t,
J02.35 Hz), 3.3–3.6 (7 H, m), 3.65–4.05 (5 H, m), 4.23–4.57
(9 H, m), 4.65–4.74 (3 H, m), 4.79 (2 H, d, J03.44 Hz),
4.96 (1 H, d, J011.51 Hz), 5.08 (1 H, d, J011.08 Hz),
7.1–7.4 (30 H, m); 13C NMR (CDCl3, 50.32 MHz): δ
55.6, 67.9, 68.0, 72.4, 72.9, 73.0, 73.1, 73.3, 73.4, 74.5,
74.7, 75.1, 75.1, 75.4, 75.9, 78.7, 79.8, 82.3, 82.5, 100.1,
102.6, 127.2–128.3, 137.9, 138.1, 138.4, 138.7, 138.8,
138.9; Mol. Wt. calculated for C57H60O11: 920.41, Found:
943.74 (M+Na)+.
25
Synthesis of prop-2-ynyl 3,6-di-O-benzyl-4-O-(2,3,4,6-tetra-
O-benzyl-β-D-galacto- pyranosyl)-β-D-mannopyranoside (6)
phous solid (7.1 g, 83 %). Characterization data: [α]D
(CHCl3, c 0.9)0+71.44; IR (ν, cm-1): 1099, 1605, 1585,
1
2867, 2921, 3289; H NMR (CDCl3, 200.13 MHz): δ 1.67
Propargyl lactoside 5 (1.7 g, 1.84 mmol) was dissolved
in 30 mL of DMSO and Ac2O mixture (2:1). The
resulting solution was stirred at room temperature for
24 h under argon atmosphere, concentrated directly
under reduced pressure and the resulting crude residue
was directly taken for the next step without further
purification. The disaccharide ketone (1.69 g,
1.83 mmol) was dissolved in 75 mL of CH2Cl2: MeOH
(1:1). To that, sodium borohydride (0.25 g, 6.43 mmol)
was added at 0 °C under argon atmosphere. The reac-
tion mixture was stirred at room temperature for 4 h,
quenched with water and extracted with dichloromethane
(2x100mL). Combined organic layers were washed with wa-
ter, brine, dried over anhydrous sodium sulfate and concen-
trated in vacuo to obtain a yellowish crude oil, which was
purified by flash silica gel (230-400 mesh) column chroma-
tography using petroleum ether-ethyl acetate as eluent to
afford prop-2-ynyl 3,6-di-O-benzyl-4-O-(2,3,4,6-tetra-O-ben-
zyl-β-D-galactopyranosyl)-β-D-mannopyranoside 6 (1.39 g,
82 % over two steps) as a white solid. Characterization data:
(3 H, s), 2.36 (1 H, t, J02.39 Hz), 3.35–3.57 (4 H, m), 3.60–
3.65 (2 H, m), 3.76 (2 H, dd, J07.82, 9.33 Hz), 3.87 (1 H, d,
J02.91 Hz), 3.98 (1 H, d, J09.18 Hz), 4.13–4.19 (1 H, m),
4.14 (2 H, d, J02.40 Hz), 4.23–4.45 (6 H, m), 4.5–4.78
(7 H, m), 4.93 (1 H, d, J011.52 Hz), 5.73 (1 H, d,
J05.24 Hz), 7.15–7.4 (30 H, m); 13C NMR (CDCl3,
50.32 MHz): δ 20.5, 51.5, 68.5, 68.9, 69.8, 71.7, 72.8,
73.1, 73.2, 73.3, 73.5, 73.5, 73.6, 74.6, 74.9, 75.5, 76.7,
79.1, 79.9, 81.9, 97.5, 105.3, 120.9, 127.4–128.3, 137.6,
138.0, 138.1, 138.3, 138.5, 138.5; Mol. Wt. calculated for
C59H62O12: 962.42, Found: 985.81 (M+Na)+.
Synthesis of prop-2-ynyl 3,6-di-O-benzyl-4-O-(2,3,4,6-tetra-
O-benzyl-β-D-galacto- pyranosyl)-β-D-glucopyranoside (5)
To a solution of propargyl 1,2-orthoester of lactose 3 (1.8 g,
1.869 mmol), propargyl alcohol (0.11 mL, 1.869 mmol) and
freshly activated 4 Å molecular sieves powder (0.5 g) in
dichloromethane (15 mL) was added a catalytic amount of
TMSOTf (2 drops) at room temperature under argon atmo-
sphere. The reaction mixture was stirred for 15 min., filtered
through a celite pad and the filtrate was concentrated in vacuo.
The resulting crude residue was purified by silica gel column
chromatography using petroleum ether-ethyl acetate as eluent
to give prop-2-ynyl 2-O-acetyl-3,6-di-O-benzyl-4-O-(2,3,4,6-
tetra-O-benzyl-β-D-galactopyranosyl)-β-D-glucopyranoside 4
as a colourless liquid (1.54 g, 85 %). Prop-2-ynyl lactoside
(2.08 g, 2.16 mmol) was dissolved in anhydrous methanol
(25 mL). Sodium metal (~50 mg) was added at room temper-
ature under argon atmosphere and the reaction mixture was
stirred till the consumption of starting material. The solvent was
concentrated in vacuo and the resulting crude residue was
[α]D (CHCl3, c 1.00)0-30.91; IR (ν, cm−1): 1099, 1585,
25
1605, 2868, 2920, 3285, 3510; 1 H NMR (CDCl3,
200.13 MHz): δ, 2.43 (1 H, t, J02.33 Hz), 2.5 (1 H, bs)
3.37–3.6 (6 H, m), 3.72 (1 H, d, J07.83 Hz), 3.79 (2 H, d,
J03.31 Hz), 3.91 (1 H, d, J02.56 Hz), 4.11 (2 H, d, J0
7.74 Hz), 4.25–4.85 (15 H, m), 4.96 (1 H, d,
J011.52 Hz), 7.11–7.4 (30 H, m); 13C NMR (CDCl3,
50.32 MHz): δ 55.4, 68.3, 68.5, 68.6, 72.4, 72.5, 72.9, 73.1,
73.4, 73.4, 74.1, 74.5, 75.0, 75.1, 75.3, 78.7, 79.1, 79.8, 82.4,
96.9, 103.1, 127.4–128.4, 137.9, 138.3, 138.4, 138.4, 138.6,
138.9; Mol. Wt. calculated for C57H60O11: 920.41,Found:
943.81 (M+Na)+.

226
Glycoconj J (2012) 29:221–230
Synthesis of 3,4,6-tri-O-benzyl-β-D-mannopyranose-1,2-
(prop-2-ynyl orthoacetate) (7)
21.1, 55.4, 67.9, 68.5, 68.7, 68.9, 70.9, 71.9, 72.1, 72.4,
72.6, 73.0, 73.0, 73.1, 73.2, 73.3, 74.3, 74.4, 74.8, 74.8,
74.9, 75.1, 75.7, 78.6, 78.9, 79.8, 80.0, 82.6, 97.0, 98.9,
103.1, 126.5–128.3, 138.0, 138.3, 138.4, 138.4, 138.5,
138,7, 138.7, 138.8, 138.9, 169.8; Mol. Wt. calculated for
C86H90O17: 1394.62, Found: 1418.26 (M+Na)+.
Preparative protocol is same as delineated above for com-
25
pounds 2 and 3. Characterization data: [α]D (CHCl3,
c
1.00)0+28.54; IR (ν, cm−1): 1588, 1605, 2126, 2869,
1
2923, 3284; H NMR (CDCl3, 200.13 MHz): δ 1.77 (3 H,
s), 2.41 (1 H, t, J02.42 Hz), 3.43 (1 H, ddd, J02.61, 4.1,
9.25 Hz), 3.71 (1 H, d, J02.72 Hz), 3.73 (2 H, dd, J04.0,
6.8 Hz), 3.91 (1 H, t, J09.23 Hz), 4.18 (2 H, d, J02.39 Hz),
4.44 (1 H, dd, J02.66, 3.91 Hz), 4.57 (2 H, d, J03.26 Hz),
4.59 (1 H,d, J011.47 Hz), 4.79 (2 H, s), 4.88 (1 H, d,
J010.74 Hz), 5.37 (1 H, d, J02.61 Hz), 7.19–7.45 (15 H,
m); 13C NMR (CDCl3, 50.32 MHz): δ 24.6, 50.6, 68.9,
72.3, 73.3, 73.4, 74.0, 74.2, 75.2, 76.9, 78.8, 79.8, 97.6,
123.7, 127.5–128.5, 137.7, 138.1, 138.1; Mol. Wt. calculat-
ed for C32H34O7: 530.23, Found: 553.47 (M+Na)+.
Synthesis of 3,4,6-tri-O-benzyl-β-D-mannopyranose-1,2-
(prop-2-ynyl orthobenzoate) (9)
To a solution of 3,4,6-tri-O-benzoyl-β-D-mannopyranose-
1,2-(prop-2-ynyl orthobenzoate) (2.5 g, 3.94 mmol) in an-
hydrous THF (20 mL) was added a solution of sodium
methoxide in methanol at room temperature under argon
atmosphere. The resulting solution was stirred for 1 h at
room temperature and concentrated in vacuo to obtain a
yellowish crude oil which was purified by flash silica gel
(230-400 mesh) column chromatography using dichlorome-
thane followed by a mixture of ethyl acetate and acetone
solvent to get the triol of mannose 1,2-orthobenzoate
(1.17 g, 92 %) as a viscous liquid. The triol prepared vide
supra was dissolved in anhydrous DMSO (10 mL). Pow-
dered KOH (1.83 g, 32.59 mmol) followed by benzyl chlo-
ride (2.5 mL, 21.72 mmol) were added at room temperature
under argon atmosphere. The reaction mixture was stirred
for 4 h, quenched with water and extracted with diethyl
ether (2×50 mL). Combined organic layers were washed
with water, brine, dried over anhydrous sodium sulfate and
concentrated in vacuo to obtain a dark yellow oil, which was
purified by silica gel column chromatography using petro-
leum ether-ethyl acetate as the mobile phase to give 3,4,6-
tri-O-benzyl-β-D-mannopyranose-1,2-(prop-2-ynyl ortho-
benzoate) 9 (1.89 g, 88 %) as a colourless viscous liquid.
Synthesis of prop-2-ynyl 2-O-(2-O-acetyl-3,4,6-tri-O-benzyl-
α-D-mannopyranosyl)-3,6-di-O-benzyl-4-O-(2,3,4,6-tetra-O-
benzyl-β-D-galactopyranosyl)-β-D-mannopyranoside (8)
To a solution of mannose 1,2-orthoester 7 (0.1 g,
0.188 mmol) and disaccharide acceptor 6 (0.173 g,
0.188 mmol) in anhydrous dichloromethane (5 mL) was
added freshly activated 4 Å molecular sieves powder
(50 mg) followed by solid AuBr3 (16 mg, 0.038 mmol) at
room temperature under argon atmosphere. The reaction
mixture was stirred for 1 h at room temperature. After
completion of the reaction as judged by TLC, the reaction
mixture was filtered through a celite pad and the filtrate was
concentrated in vacuo. The resulting crude residue was purified
by flash silica gel column chromatography using petroleum
ether-ethyl acetate as eluent to obtain propargyl trisaccha-
ride 8 (125 mg, 48 %) as a thick syrup. Characterization
25
Characterization data: [α]D (CHCl3, c 1.2)0-36.43; IR
(ν, cm−1): 1100, 1588, 1605, 2869, 2925, 3287; 1H (CDCl3,
200.13 MHz): δ 2.4 (1 H, t, J02.42 Hz), 3.46–3.6 (2 H, m),
3.67 (1 H, dd, J04.91, 10.74 Hz), 3.9 (1 H, d, J03.83 Hz),
3.91 (1 H, ABq, J09.17 Hz), 4.09 (2 H, d, J02.44 Hz), 4.42
(2 H, s), 4.62 (1 H, d, J010.81 Hz), 4.75–4.94 (4 H, m),
5.53 (1 H, d, J03.04 Hz), 7.2–7.45 (18 H, m), 7.65–7.75
(2 H, m); 13C NMR (CDCl3, 50.32 MHz): δ 52.3, 69.1,
71.9, 73.2, 73.7, 74.2, 75.0, 75.2, 76.0, 78.1, 79.7, 98.0,
122.2, 126.8–129.4, 135.6, 137.7, 138.2, 138.3; Mol. Wt.
calculated for C37H36O7: 592.25, Found: 615.60 (M+Na)+.
data: [α]D (CHCl3, c 0.9)0-15.57; IR (ν, cm−1): 1100,
25
1588, 1605, 1746, 2867, 2928, 3297; 1H NMR (CDCl3,
500.13 MHz): δ 2.03 (3 H, s), 2.35(1 H, t, J02.33 Hz), 3.38
(2 H, ddd, J04.9, 8.49, 19.73 Hz), 3.44 (1 H, dd,
J02.82, 9.78 Hz), 3.46–3.51 (1 H, m), 3.51 (1 H, t,
J08.49 Hz), 3.57 (1 H, dd, J02.83, 8.78 Hz), 3.66 (1 H,
dd, J01.67, 10.76 Hz), 3.70 (1 H, dd, J07.77, 9.57 Hz),
3.77 (1 H, dd, J05.44, 10.99 Hz), 3.79–3.90 (4 H, m), 4.02
(1 H, dd, J03.33, 9.58 Hz), 4.14 (1 H, t, J08.94 Hz), 4.2
(1 H, d, J02.65 Hz), 4.21 (1 H, d, J011.74 Hz), 4.29–4.35
(5 H, m), 4.38 (1 H, d, J012.02 Hz), 4.41 (1 H, d, J0
5.59 Hz), 4.44 (1 H, d, J07.10 Hz), 4.5 (1 H, t,
J011.54 Hz), 4.52 (1 H, d, J06.81 Hz), 4.54 (1 H, d,
J 02.35 Hz), 4.59–4.68 (5 H, m), 4.71 (2 H, d,
J011.57 Hz), 4.79 (2 H, dd, J04.15, 10.97 Hz), 4.86
(1 H, d, J011.56 Hz), 4.93 (1 H, d, J012.13 Hz), 5.16
(1 H, d, J01.14 Hz), 5.61 (1 H, dd, J01.71, 3.28 Hz),
7.10–7.35 (45 H, m); 13C NMR (CDCl3, 125.76 MHz): δ
Synthesis of prop-2-ynyl 2-O-(2-O-benzoyl-3,4,6-tri-O-
benzyl-α-D-mannopyranosyl)-3,6-di-O-benzyl-4-O-
(2,3,4,6-tetra-O-benzyl-β-D-galactopyranosyl)-β-D-
mannopyranoside (10)
To a solution of propargyl 1,2-orthoester of mannose 9
(100 mg, 0.169 mmol) and disaccharide acceptor 6 (0.156 g,
0.169 mmol) in anhydrous dichloromethane (7 mL) was

Glycoconj J (2012) 29:221–230
227
added freshly activated 4 Å molecular sieves powder
(100 mg) followed by solid AuBr3 (15 mg, 0.034 mmol) at
room temperature under argon atmosphere. The reaction mix-
ture was stirred for 12 h at same temperature, filtered through a
celite pad and the filtrate was concentrated in vacuo to obtain a
gummy residue, which was purified by flash silica gel column
chromatography (230-400 mesh) using petroleum ether-ethyl
acetate as eluent to afford propargyl trisaccharide 10 (0.113 g,
46 %) as a colourless viscous liquid. Characterization data:
79.9, 79.9, 80.1, 82.5, 97.2, 100.1, 102.9, 127.2–128.5,
138.0, 138.2, 138.4, 138.5, 138.5, 138.7, 138.7, 138.7,
138.8; Mol. Wt. calculated for C84H88O16: 1352.61, Found:
1376.39 (M+Na)+.
Synthesis of prop-2-ynyl 2-O-(2-O-(2-O-acetyl-3,4,6-tri-O-
benzyl-α-D-mannopyranosyl)-3,4,6-tri-O-benzyl-α-D-man
nopyranosyl)-3,6-di-O-benzyl-4-O-(2,3,4,6-tetra-O-benzyl-
β-D-galactopyranosyl)-β-D-mannopyranoside (12)
[α]D (CHCl3, c 1.00)0-53.83; IR (ν, cm-1): 1070, 1269,
25
1585, 1602, 1724, 2867, 2923, 3301; 1H NMR (CDCl3,
500.13 MHz): δ 2.36 (1 H, t, J02.46 Hz), 3.4 (1 H, dd,
J03.44, 8.56 Hz), 3.43–3.55 (4 H, m), 3.58 (1 H, m), 3.69–
3.95 (6 H, m), 4.07 (1 H, td, J03.5, 9.59 Hz), 4.14–4.22 (3 H,
m), 4.24 (1 H, dd, J03.59, 11.68 Hz), 4.31–4.37 (3 H, m),
4.38 (2 H, t, J03.98 Hz), 4.41 (1 H, d, J03.24 Hz), 4.46–4.82
(14 H, m), 4.85 (1 H, dd, J03.39, 11.56 Hz), 4.94 (1 H, dd,
J03.4, 12.17 Hz), 5.32 (1 H, s), 5.82–5.85 (1 H, m), 6.98–
7.54 (48 H, m), 8.0–8.07 (2 H, m); 13C NMR (CDCl3,
125.76 MHz): δ 55.4, 67.9, 68.9, 69.0, 69.1, 71.4, 71.6,
72.4, 72.5, 72.6, 73.1, 73.2, 73.2, 73.3, 73.7, 74.4, 74.5,
74.8, 74.9, 75.0, 75.2, 75.8, 78.6, 78.9, 79.7, 79.9, 82.5,
97.0, 98.8, 103.1, 126.7–129.9, 132.7, 138.1, 138.3, 138.4,
138.5, 138.6, 138.7, 138.7, 138.8, 138.9, 165.1; Mol. Wt.
calculated for C91H92O17: 1456.63, Found: 1480.37
(M+Na)+.
To a solution of mannose 1,2-orthoester 7 (78 mg,
0.148 mmol), trisaccharide acceptor 11 (0.2 g, 0.148 mmol)
and freshly activated 4 Å molecular sieves powder (100 mg)
in anhydrous dichloromethane (5 mL) was added solid
AuBr3 (13 mg, 0.03 mmol) at room temperature under argon
atmosphere. The reaction mixture was stirred at room tem-
perature for 2 h. After completion of the reaction as judged
by TLC, the reaction mixture was filtered through a celite
pad and the filtrate was concentrated in vacuo. The resulting
crude was purified by flash silica gel column chromatogra-
phy using petroleum ether-ethyl acetate as eluent to obtain
propargyl tetrasaccharide 12 (94 mg, 35 %) as a colourless
25
viscous liquid. Characterization data: [α]D (CHCl3,
c
0.9)0-15.20; IR (ν, cm−1): 1096, 1585, 1605, 1742, 2866,
2917, 3285; H NMR (CDCl3, 400.13 MHz): δ 2.06 (3 H,
1
s), 2.34 (1 H, t, J02.27 Hz), 3.32–3.45 (5 H, m), 3.48 (1 H,
d, J010.4 Hz), 3.53–3.63 (2 H, m), 3.68 (1 H, dd, J01.29,
11.34 Hz), 3.73 (2 H, dd, J07.65, 9.63 Hz), 3.76–3.83 (3 H,
m), 3.85 (1 H, d, 0 J 9.54 Hz), 3.87–3.92 (2 H, m), 3.94
(1 H, d, J02.5 Hz), 3.98 (1 H, dd, J03.18, 9.03 Hz), 4.01
(1 H, d, J02.07 Hz), 4.04 (1 H, t, J02.14 Hz), 4.08 (1 H, t,
J08.71 Hz), 4.21 (2 H, ABq, J011.56 Hz), 4.25 (1 H, d,
J01.23 Hz), 4.26 (1 H, d, J011.1 Hz), 4.30 (2 H, t,
J02.90 Hz), 4.36 (1 H, d, J010.75 Hz), 4.4 (2 H, dd,
J02.28, 11.81 Hz), 4.41 (1 H, d, J010.88 Hz), 4.45–4.72
(14 H, m), 4.74 (2 H, d, J05.23 Hz), 4.8 (2 H, dd, J02.81,
10.85 Hz), 4.91 (1 H, d, J01.46 Hz), 4.93 (1 H, d,
J011.55 Hz), 5.19 (1 H, s), 5.5 (1 H, dd, J00.99,
1.78 Hz), 7.07–7.38 (60 H, m); 13C NMR (CDCl3,
100.61 MHz): δ 21.1, 55.2, 68.1, 68.8, 68.8, 69.0, 69.2,
71.6, 71.7, 71.8, 71.9, 72.4, 72.6, 72.6, 73.1, 73.1, 73.2,
73.3, 74.1, 74.3, 73.3, 74.5, 74.6, 74.7, 74.8, 74.9, 74.9,
75.2, 75.5, 75.7, 78.2, 79.1, 79.5, 79.5, 79.9, 82.5, 97.1,
99.3, 100.0, 102.6, 127.0–128.4, 137.9, 138.1, 138.4, 138.4,
138.5, 138.6, 138.7, 138.7, 138.7, 138.8, 138.9, 139.0,
170.0; Mol. Wt. calculated for C113H118O22: 1826.81,
Found: 1849.79 (M+Na)+ [MALDI-TOF].
Synthesis of prop-2-ynyl 2-O-(3,4,6-tri-O-benzyl-α-D-
mannopyranosyl)-3,6-di-O-benzyl-4-O-(2,3,4,6-tetra-O-
benzyl-β-D-galactopyranosyl)-β-D-mannopyranoside (11)
Preparative procedure is same as described in the prepara-
tion of compound 5, which provided trisaccharide acceptor
11 as a colourless viscous liquid. Characterization data:
[α]D (CH3OH, c 1.00)0+1.72; IR (ν, cm−1): 1099, 1585,
25
1603, 2867, 2917, 3296, 3447; 1 H NMR (CDCl3,
500.13 MHz): δ 2.25 (1 H, bs), 2.34 (1 H, t, J02.37 Hz),
3.37–3.44 (3 H, m), 3.44 (1 H, dd, J02.9, 9.92 Hz), 3.50–
3.57 (2 H, m), 3.67 (1 H, dd, J01.8, 10.78 Hz), 3.71–3.79
(2 H, m), 3.78 (1 H, dd, J03.85, 10.74 Hz), 3.84 (1 H, dd,
J04.95, 11.37 Hz), 3.86-3. 91 (3 H, m), 4.05 (1 H, s), 4.15
(1 H, t, J08.91 Hz), 4.21 (1 H, d, J02.76 Hz), 4.25 (1 H, d,
J011.8 Hz), 4.30 (2 H, t, J02.74 Hz), 4.38 (2 H, d,
J011.92 Hz), 4.43 (2 H, d, J02.54 Hz), 4.46 (1 H, d,
J05.18 Hz), 4.48 (1 H, d, J06.67 Hz), 4.51 (1 H, d,
J07.62 Hz), 4.54 (1 H, d, J011.54 Hz), 4.59 (1 H, d,
J 012.05 Hz), 4.61–4.72 (5 H, m), 4.7 (1 H, d,
J03.90 Hz), 4.76 (1 H, d, J010.6 Hz), 4.76 (2 H, ABq,
J011.03 Hz), 4.85 (1 H, d, J012.05 Hz), 4.93 (1 H, d,
J011.37 Hz), 5.27 (1 H, d, J01.22 Hz), 7.10–7.38 (45 H,
m); 13C NMR (CDCl3, 125.76 MHz): δ 55.3, 68.5, 68.6,
68.7, 68.8, 70.7, 71.8, 72.6, 72.8, 73.1, 73.2, 73.3, 73.3,
73.4, 73.6, 74.3, 74.4, 74.5, 74.8, 74.9, 75.2, 75.9, 78.9,
Synthesis of S-acetyl-11-azido-thioundecane (13)
A solution of 10-undecen-1-ol (1 g, 5.87 mmol) in anhy-
drous dioxane (5 mL) was purged with argon balloon. To
that was added excess of thioacetic acid (6.1 mL,

228
Glycoconj J (2012) 29:221–230
25
117.4 mmol) followed by AIBN (50 mg) at room tempera-
ture. The reaction mixture was purged once again with
argon balloon, stirred at 75 °C for 24 h under argon atmo-
sphere, concentrated in vacuo and the resulting crude was
purified by silica gel column chromatography using petro-
leum ether-ethylacetate as eluent to afford 11-thioacetyl-
undecan-1-ol (0.37 g, 26 %) as a dark liquid that was
redissolved in anhydrous dichloromethane (15 mL). To that
was added carbon tetrabromide (1.0 g, 3.00 mmol) followed
by a dropwise solution of triphenylphosphine (0.79 g,
3.00 mmol) in dichloromethane (5 mL) at 0 °C under argon
atmosphere. The reaction mixture was stirred for 1 h at room
temperature, quenched with water and extracted with
dichloromethane (2x20mL). Combined organic layers were
washed with water, dried over anhydrous sodium sulfate and
concentrated in vacuo. The resulting crude residue was
purified by silica gel column chromatography using petro-
leum ether-ethyl acetate as the mobile phase to obtain 11-
thioacetyl-undecylbromide (0.38 g, 83 %) as dark oil. To a
solution of 11-thioacetyl-undecylbromide (0.36 g,
1.16 mmol) in anhydrous DMF (5 mL) was added carefully
NaN3 (0.38 g, 5.82 mmol) at room temperature under argon
atmosphere. The reaction mixture was stirred for 20 h at
same temperature, quenched with water and extracted with
diethyl ether (2x20mL). Combined organic layers were
washed with water, dried over anhydrous sodium sulfate
and concentrated in vacuo. The resulting crude was purified
by silica gel column chromatography using petroleum ether
and ethyl acetate as the mobile phase to give S-acetyl-11-
azido-thioundecane 13 (0.28 g, 90 %) as a brown coloured
liquid. Characterization data: IR (ν, cm−1): 1693, 2096,
Characterization data: [α]D (CHCl3, c 1.10)0-(2-6); IR
(ν, cm−1): 1098, 1688, 1740, 2856, 2926; 1H NMR (CDCl3,
400.13 MHz): δ 1.05–1.35 (14 H, m), 1.51–1.63 (4 H, m),
2.05 (3 H, s), 2.31 (3 H, s), 2.85 (2 H, t, J07.34 Hz), 3.33–
3.43 (4 H, m), 3.45 (3 H, d, J010.74 Hz), 3.54 (2 H, dd,
J03.26, 11.12 Hz), 3.60 (1 H, t, J07.8 Hz), 3.7–3.8 (1 H, m),
3.74 (1 H, ABq, J07.66 Hz), 3.81–3.92 (7 H, m), 3.94 (1 H, t,
J03.02 Hz), 3.99 (1 H, dd, J02.53, 9.53 Hz), 4.03 (1 H, d,
J02.09 Hz), 4.05 (1 H, t, J01.88 Hz), 4.1 (1 H, t, J08.84 Hz),
4.22 (2 H, d, J011.86 Hz), 4.23 (2 H, ABq, J011.63 Hz),
4.30–4.57 (12 H, m), 4.60–4.82 (11 H, m), 4.91 (2 H, dd,
J01.89, 3.72 Hz), 4.94 (1 H, d, J05.25 Hz), 5.23 (1 H, s), 5.49
(1 H, dd, J00.93, 1.88 Hz), 7.02–7.32 (60 H, m), 7.45 (1 H, s);
13C NMR (CDCl3, 100.61 MHz): δ 21.1, 26.4, 28.8, 29.0,
29.1, 29.1, 29.4, 29.4, 29.4, 29.5, 30.2, 30.6, 49.9, 62.5, 68.2,
68.8, 68.9, 69.0, 69.1, 71.5, 71.7, 71.8, 71.8, 72.5, 72.5, 72.6,
73.1, 73.1, 73.2, 73.3, 73.3, 73.8, 74.2, 74.4, 74.6, 74.8, 74.9,
75.1, 75.2, 75.2, 75.6, 78.2, 79.8, 79.9, 80.0, 82.6, 98.8, 99.3,
99.6, 102.7, 122.9, 127.0–128.3, 137.9, 138.1, 138.4, 138.4,
138.5, 138.5, 138.6, 138.7, 138.7, 138.8, 138.8, 138.9, 144.4,
170.0, 196.1; Mol. Wt. calculated for C126H143N3O23S:
2097.98, Found: 2120.96 (M+Na)+ [MALDI-TOF].
Acknowledgements S.H. thanks Department of Science & Technol-
ogy, New Delhi for SwarnaJayanti Fellowship. G.S.K thanks Council
of Science & Industrial Research, New Delhi for research fellowship.
Authors thank National Chemical Laboratory, Pune for infrastructural
support during initial stages of this work.
References
1
2855, 2928; H NMR (CDCl3, 200.13 MHz): δ 1.20–1.43
(14 H, m), 1.56 (4 H, quintet, J07.1 Hz), 2.32 (3 H, s), 2.86
(2 H, t, J07.37 Hz), 3.26 (2 H, t, J06.89 Hz); 13C NMR
(CDCl3, 50.32 MHz): δ 26.6, 28.7, 28.8, 29.0, 29.1, 29.1,
29.3, 29.3, 29.3, 29.4, 30.6, 51.4, 196.0; Mol. Wt. calculat-
ed for C13H25N3OS: 271.17, Found: 294.28 (M+Na)+.
1. Herwaldt, B.L.: Leishmaniasis. Lancet 354, 1191–1199 (1999)
2. http://www.who.int/topics/leishmaniasis/en/
3. Sacks, D.L.: Metacyclogenesis in Leishmania promastigotes. Exp.
Parasitol. 69, 100–103 (1989)
4. McNeely, T.B., Tolson, D.L., Pearson, T.W., Turco, S.J.: Charac-
terization of Leishmania donovani variant clones using anti-
lipophosphoglycan monoclonal antibodies. Glycobiology 1, 63–
69 (1990)
Synthesis of a triazole ‘clicked’ glycolipid (14)
5. Beverley, S.M., Turco, S.J.: Lipophosphoglycan (LPG) and the
identification of virulence genes in the protozoan parasite Leish-
mania. Trends Microbiol. 6, 35–40 (1998)
6. Turco, S.J., Descoteaux, A.: The Lipophosphoglycan of Leishman-
ia Parasites. Annu. Rev. Microbiol. 46, 65–92 (1992)
7. Ferguson, M.A.J., Homans, S.W., Dwek, R.A., Rademacher, T.W.:
Glycosyl-phosphatidylinositol moiety that anchors Trypanosoma
brucei variant surface glycoprotein to the membrane. Science 239,
753–759 (1988)
8. Homans, S.W., Ferguson, M.A.J., Dwek, R.A., Rademacher, T.W.,
Anand, R., Williams, A.F.: Complete structure of the glycosyl
phosphatidylinositol membrane anchor of rat brain Thy-1 glyco-
protein. Nature 333, 269–272 (1988)
9. Ferguson, M.A.J., Williams, A.F.: Cell-surface anchoring of pro-
teins via glycosyl-phosphatidylinositol structures. Annu. Rev. Bio-
chem. 57, 285–320 (1988)
To a solution of propargyl tetrasaccharide 12 (0.3 g,
0.16 mmol), S-acetyl-11-azido-thioundecane 13 (45 mg,
0.16 mmol) and DIPEA (57μL, 0.33 mmol) in CH3CN
(5 mL) was added CuI (33 mg, 0.17 mmol) at room tem-
perature. The reaction mixture was stirred for 1 h at room
temperature, quenched with a saturated solution of ammo-
nium chloride and extracted with ethyl acetate (2×20 mL).
Combined organic layers were washed with water, dried
over anhydrous Na2SO4 and the solvent was concentrated
in vacuo. The resulting crude residue was purified by silica
gel column chromatography using petroleum ether and ethyl
acetate as the mobile phase to afford a 1,2,3-triazole ‘clicked’
glycolipid 14 (0.29 g, 85 %) as a colourless viscous oil.
10. Low, M.G.: Biochim. Biophys. Acta 988, 427–454 (1989)

Glycoconj J (2012) 29:221–230
229
11. Thomas, J.R., Dwek, R.A., Rademacher, T.W.: Structure, biosyn-
thesis, and function of glycosylphosphatidylinositols. Biochemis-
try 29, 5413–5422 (1990)
31. Ruhela, D., Vishwakarma, R.A.: Efficient synthesis of the antigen-
ic phosphoglycans of the Leishmaniaparasite. Chem. Commun.
2024–2025 (2001)
12. Cross, G.A.M.: Glycolipid anchoring of plasma membrane pro-
teins. Annu. Rev. Cell. Bio. 6, 1–39 (1990)
32. Gandolfi-Donadio, L., Gallo-Rodriguez, C., de Lederkremer,
R.M.: Synthesis of α-D-Galp-(1→3)-β-D-Galf-(1→3)-D-man, a
terminal trisaccharide of Leishmania type-2 glycoinositolphospho-
lipids. J. Org. Chem. 67, 4430–4435 (2002)
33. Ruhela, D., Vishwakarma, R.A.: A facile and novel route to the
antigenic branched phosphoglycan of the protozoan Leishmania
major parasite. Tetrahedron Lett. 45, 2589–2592 (2004)
34. Higson, A.P., Ross, A.J., Tsvetkov, Y.E., Routier, F.H., Sizova,
O.V., Ferguson, M.A.V., Nikolaev, M.A.V.: Synthetic fragments of
antigenic lipophosphoglycans from Leishmania major and Leish-
mania mexicana and their use for characterisation of the Leish-
mania elongating α-D-mannopyranosylphosphate transferase.
Chem. Eur. J. 11, 2019–2030 (2005)
13. McConville, M.J.: Glycosylated-phosphatidylinositols as virulence
factors in Leishmania. Cell Bio. Intl. Rep. 15, 779–798 (1991)
14. McConville, M.J., Ferguson, M.A.J.: The structure, biosynthesis
and function of glycosylated phosphatidylinositols in the parasitic
protozoa and higher eukaryotes. Biochem. J. 294, 305–324 (1993)
15. Englund, P.T.: The structure and biosynthesis of glycosyl phospha-
tidylinositol protein anchors. Annu. Rev. Biochem. 62, 121–138
(1993)
16. Saltiel, A.R., Fox, J.A., Sherline, P., Cuatrecasas, P.: Insulin-
stimulated hydrolysis of a novel glycolipid generates modulators
of cAMP phosphodiesterase. Science 233, 967–972 (1986)
17. Tolsen, D.J., Turco, S.J., Beecroft, R.P., Pearson, T.W.: The im-
munochemical structure and surface arrangement of Leishmania
donovani lipophosphoglycan determined using monoclonal anti-
bodies. Mol. Biochem. Parasitol. 35, 109–118 (1989)
35. Liu, X.Y., Siegrist, S., Amacker, M., Zurbriggen, R., Pluschke, G.,
Seeberger, P.H.: Enhancement of the immunogenicity of synthetic
carbohydrates by conjugation to virosomes: a Leishmaniasis vac-
cine candidate. ACS Chem. Bio. 1, 161–164 (2006)
18. Chan, B.L., Chao, M.V., Saltiel, A.R.: Nerve growth factor stim-
ulates the hydrolysis of glycosylphosphatidylinositol in PC-12
cells: a mechanism of protein kinase C regulation. Proc. Natl.
Acad. Sci. U.S.A. 86, 1756–1760 (1989)
19. Eardley, D.D., Koshland, M.E.: Glycosylphosphatidylinositol: a
candidate system for interleukin-2 signal transduction. Science
251, 78–81 (1991)
20. Pimento, P.F.P., Saraiva, E.M.B., Sacks, D.L.: The comparative
fine structure and surface glycoconjugate expression of three life
stages of Leishmania major. Exp. Parasitol. 72, 191–204 (1991)
21. Nikolaev, A.V., Rutherford, T.J., Ferguson, M.A.J., Brimacombe,
J.S.: The chemical synthesis of Leishmania donovani phosphogly-
can fragments. Bioorg. Med. Chem. Lett. 4, 785–788 (1994)
22. Nikolaev, A.V., Chudek, J.A., Ferguson, M.A.: The chemical
synthesis of Leishmania donovani phosphoglycan via polyconden-
sation of a glycobiosyl hydrogenphosphonate monomer. Carbo-
hydr. Res. 272, 179–189 (1995)
36. Hotha, S., Kashyap, S.: Propargyl glycosides as stable glycosyl
donors: anomeric activation and glycoside syntheses. J. Am.
Chem. Soc. 128, 9620–9621 (2006)
37. Hotha, S., Kashyap, S.: Stereoselective synthesis of α-glucosides
from 3-O-propargyl protected glucal exploiting the alkynophilicity
of AuCl3. Tetrahedron Lett. 47, 2021–2023 (2006)
38. Sureshkumar, G., Hotha, S.: Propargyl 1,2-orthoesters as glycosyl
donors: stereoselective synthesis of 1,2-trans glycosides and dis-
accharides. Tetrahedron Lett. 48, 6564–6568 (2007)
39. Kashyap, S., Vidadala, S.R., Hotha, S.: Synthesis of C-2 methy-
lene glycosides from C-2 propargyloxymethyl glycals exploiting
the alkynophilicity of AuCl3. Tetrahedron Lett. 48, 8960–8962
(2007)
40. Sureshkumar, G., Hotha, S.: Gold mediated glycosylations: selec-
tive activation of propargyl 1,2-orthoesters in the presence of
aglycones containing a propargyl moiety Chem. Commun. 4282–
4284 (2008)
23. Arasappan, A., FraserReid, B.: n-Pentenyl glycoside methodology
in the stereoselective construction of the tetrasaccharyl cap portion
of Leishmania lipophosphoglycan. J. Org. Chem. 61, 2401–2406
(1996)
24. Nikolaev, A.V., Watt, G.M., Ferguson, M.A.J., Brimacombe, J.S.:
Parasite glycoconjugates. Part 6.1 Chemical synthesis of phosphor-
ylated penta- and hepta-saccharide fragments of Leishmania major
antigenic lipophosphoglycan. J. Chem. Soc., Perkin Trans 1, 969–
980 (1997)
41. Vidadala, S.R., Hotha, S.: Methyl glycosides are identified as
glycosyl donors for the synthesis of glycosides, disaccharides
and oligosaccharides Chem. Commun. 2505–2507 (2009)
42. Vidadala, S.R., Thadke, S.A., Hotha, S.: Orthogonal activation of
propargyl and n-pentenyl glycosides and 1,2-orthoesters. J. Org.
Chem. 74, 9233–9236 (2009)
43. Kayastha, A.K., Hotha, S.: Gold-catalyzed glycosidations: unusual
cleavage of the interglycosidic bond while studying the armed/
disarmed effect of propargyl glycosides. Tetrahedron Lett. 51,
5269–5272 (2010)
44. Thadke, S.A., Hotha, S.: Gold-catalyzed glycosidations: synthesis
of 1,6-anhydro saccharides. Tetrahedron Lett 51, 5912–5914
(2010). Other papers on gold catalyzed glycosidations
45. Li, Y., Yang, Y., Yu, B.: An efficient glycosylation protocol with
glycosyl ortho-alkynylbenzoates as donors under the catalysis of
Ph3PAuOTf. Tetrahedron Lett. 49, 3604–3608 (2008)
46. Li, Y., Tank, P., Chen, Y., Yu, B.: Gold(I)-catalyzed glycosidation
of 1,2-anhydrosugars. J. Org. Chem. 73, 4323–4325 (2008)
47. Götze, S., Fitzner, R., Kunz, H.: Gold catalysis in glycosylation
reactions. Synlett 3346–3348 (2009)
48. Mamidyala, S.K., Finn, M.G.: Glycosylation using unprotected
alkynyl donors. J. Org. Chem. 74, 8417–8420 (2009)
49. Kartha, K.P.R., Jennings, H.J.: A simplified, one-pot preparation of
acetobromosugars from reducing sugars. J. Carbohydr. Chem. 9,
777–781 (1990)
25. Higson, A.P., Tsvetkov, Y.E., Ferguson, M.A.J., Nikolaev, A.V.:
The synthesis of Leishmania major phosphoglycan fragments.
Tetrahedron Lett. 40, 9281–9284 (1999)
26. Ruda, K., Lindberg, J., Garegg, P.J., Oscarson, S., Konradsson, P.:
Synthesis of the Leishmania LPG Core Heptasaccharyl myo-
Inositol. J. Am. Chem. Soc 122, 11067–11072 (2000)
27. Upreti, M., Ruhela, D., Vishwakarma, R.A.: Synthesis of the
tetrasaccharide cap domain of the antigenic lipophosphoglycan of
Leishmania donovani parasite. Tetrahedron 56, 6577–6584 (2000)
28. Hewitt, M.C., Seeberger, P.H.: Solution and solid-support synthe-
sis of a potential Leishmaniasis carbohydrate vaccine. J. Org.
Chem. 66, 4233–4243 (2001)
29. Hewitt, M.C., Seeberger, P.H.: Automated solid-phase synthesiso f
a branched Leishmania cap tetrasaccharide. Org Lett. 3, 3699–
3702 (2001)
30. Yashunsky, D.V., Higson, A.P., Ross, A.J., Nikolaev, A.V.: An
efficient and stereoselective synthesis of β-D-Arap-(1→2)-β-D-
Galp-(1→3)-β-D-Galp-(1→4)-α-D-Manp, a tetrasaccharide frag-
ment of Leishmania majorlipophosphoglycan. Carbohydr. Res.
336, 243–248 (2001)
50. Larsen, K., Olsen, C.E., Motawia, M.S.: A facile protocol for direct
conversion of unprotected sugars into phenyl 4,6-O-benzylidene-per-
O-acetylated-1,2-trans-thioglycosides. Carbohydr. Res. 338, 199–
202 (2003)

230
Glycoconj J (2012) 29:221–230
51. Hunsen, M., Long, D.A., D’Ardenne, C.R., Smith, A.L.: Mild one-
pot preparation of glycosyl bromides. Carbohydr. Res. 340, 2670–
2674 (2005)
52. Mach, M., Schlueter, U., Mathew, F., Fraser-Reid, B., Hazan,
K.C.: Comparing n-pentenyl orthoesters and n-pentenyl glyco-
sides as alternative glycosyl donors. Tetrahedron 58, 7345–
7354 (2002)
53. Warren, C.D., Augé, C., Laver, M.L., Suzuki, S., Power, D.,
Jeanloz, R.W.: The synthesis of O-β-D-mannopyranosyl-(1→4)-
O-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-(1→4)-2-acet-
amido-2-deoxy-D-glucopyranose. Carbohydrate Res. 82, 71–83
(1980)
54. Liu, K.K.-C., Danishefsky, S.J.: Route from glycals to mannose
β-glycosides. J. Org. Chem 59, 1892–1894 (1994)