Synthesis of a trisaccharide repeat of the zwitterionic Sp1 capsular polysaccharide utilizing 2-azido-4-benzylamino-4N,3-O-carbonyl-2,4,6-trideoxy-D- galactopyranosyl trichloroacetimidate

Article abstract of DOI:10.1016/j.carres.2013.05.005

2-Azido-4-benzylamino-4N,3-O-carbonyl-2,4,6-trideoxy-D-galactopyranosyl trichloroacetimidate 2 conveniently prepared in six steps from 6-deoxy-D-glucal glycosylated a selectively protected α1,3 linked methyl galabioside to afford the trisaccharide skeleto

Full text of DOI:10.1016/j.carres.2013.05.005

Carbohydrate Research 378 (2013) 26–34
Contents lists available at SciVerse ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
Synthesis of a trisaccharide repeat of the zwitterionic Sp1 capsular
polysaccharide utilizing 2-azido-4-benzylamino-4N,3-O-carbonyl-
2,4,6-trideoxy-D-galactopyranosyl trichloroacetimidate
⇑
Ithayavani Iynkkaran, David R. Bundle
Alberta Ingenuity Centre for Carbohydrate Science and Department of Chemistry, The University of Alberta, Gunning-Lemieux Chemistry Centre, Edmonton, AB, Canada T6G 2G2
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 8 April 2013
Received in revised form 6 May 2013
Accepted 11 May 2013
Available online 21 May 2013
2-Azido-4-benzylamino-4N,3-O-carbonyl-2,4,6-trideoxy-
veniently prepared in six steps from 6-deoxy-D-glucal glycosylated a selectively protected a1,3 linked
D
-galactopyranosyl trichloroacetimidate 2 con-
methyl galabioside to afford the trisaccharide skeleton of a repeating unit of the Sp1 zwitterionic capsular
polysaccharide. Lithium hydroxide hydrolysis of the 3,4-cyclic carbamate permitted the creation of a
2-acetamido-4-amino-2,4,6-trideoxygalactose residue. Selective cleavage of p-methoxybenzyl ethers by
trifluoroacetic acid gave a selectively deprotected trisaccharide with two hydroxymethyl groups that
were oxidized by the TEMPO reagent to afford access to trisaccharide glycoside 1 containing 2-acetam-
ido-4-amino-2,4,6-trideoxygalactose and two galacturonic acid residues.
This paper is dedicated to the memory of Dr.
Malcolm Perry and Professor Lennart Kenne.
Ó 2013 Published by Elsevier Ltd.
Keywords:
Zwitterionic trisaccharide
Type I pneumococcal polysaccharide repeat
2-Azido-4-benzylamino-4N,3-O-carbonyl
2,4,6-trideoxy-galactosyl donor
a-Glycosylation
Cyclic carbamate hydrolysis by lithium
hydroxide
Uronic acid via post assembly oxidation
1. Introduction
repeating units of these polymers.4 Zwitterionic polysaccharides
have also been used as non-protein carriers of oligosaccharide
Protein antigens are processed and presented to T-cells after
intracellular degradation into T-cell peptides that are bound in
the grove of a major histocompatibility protein (MHC I or MHC
II).1 Following recognition of the peptide complex with MHC by
the T-cell receptor, T-cells are triggered to release cytokines that
allow those B-cells with Ig receptors that bind the antigen to pro-
duce protein specific antibodies.1a Pure carbohydrate antigens are
T-cell independent antigens and do not produce a secondary im-
mune response that is augmented by T-cell help.1b A notable
exception to this generality are zwitterionic polysaccharides which
are degraded into ꢀ10 kDa fragments that can be presented by
T-cells.2 In fact processing of polysaccharide conjugate vaccines
employs a combination of this degradative pathway with that of
proteins.2c,3 The ability of zwitterionic polysaccharides to be taken
up and presented to T-cells has attracted considerable attention
and stimulated a number of synthetic efforts to construct the
haptens.5
The type I pneumococcal polysaccharide (Sp1) has the structure
shown (Fig. 1) and like the polysaccharide of Bacteroides fragilis uti-
lizes the major histocompatibility complex (MHC) class II pathway
in antigen-presenting cells (APCs) for processing and presenta-
tion.2a.d We have reported the synthesis of a mono- and dimeric
repeating units of the zwitterionic Sp1 capsular polysaccharide.4a
Christina et al. have prepared all three of the frame shifted mono-
meric repeating units of the same polysaccharide.4b Our work
avoids the use of uronic acid glycosyl donors by performing oxida-
tion of selectively protected hexose residues after oligosaccharide
assembly.4a The Dutch group of Marel and Codée demonstrated
an alternative approach by effective use of uronic acid building
blocks.4b
We recently reported a novel and concise synthesis of a glycosyl
donor that is well suited for introduction of 2-acetamido-4-amino-
2,4,6-trideoxy-a-D-galactopyranosyl repeating unit that contains
this sugar as a terminal residue.6 The synthesis of the trisaccharide
methyl glycoside 1 containing the diaminohexose as a terminal
⇑
Corresponding author. Tel.: +1 780 492 8808; fax: +1 780 492 7705.
E-mail address: dave.bundle@ualberta.ca (D.R. Bundle).
0008-6215/$ - see front matter Ó 2013 Published by Elsevier Ltd.
http://dx.doi.org/10.1016/j.carres.2013.05.005

I. Iynkkaran, D. R. Bundle / Carbohydrate Research 378 (2013) 26–34
27
PMP
H3N
O
OR2
O
O
O
R1O
BnO
O
O
SPh
R1O
AcHN
SPh
b
O
R1O
CO2
BnO
O
HO
5 R1 = H
7 R1 = H, R2 = PMB
3 R1 = Bz, R2 = PMB
CO2
HO
a
c
6 R1 = Bn
O
H3N
HO
O
O
HO
Scheme 1. Reagents and conditions: (a) BnBr, NaH, DMF, 85%; (b) NaCNBH3, TFA,
DCM, 75% (c) BzCl, Py, 92%.
O
AcHN
O
CO2
gave 6 and regioselective opening of the acetal provided the 6-O-p-
methoxybenzyl derivative 7, which was benzoylated to give 3
(Scheme 1).
O
HO
CO2
HO
O
HO
O
Methyl galactopyranoside was converted to the TBDPS deriva-
tive 88 in 92% yield on a 20 g scale. Dibutyltin oxide was used to
effect selective introduction of a 3-O-allyl ether to afford the diol
9. Benzylation of 9 gave the fully protected galactopyranoside 10
and after removal of the silyl ether, compound 11 was converted
to the p-methoxybenzyl ether 12. Selective removal of the allyl
ether gave the glycosyl acceptor 4 (Scheme 2).
HO
O
Figure 1. The structure of the type
polysaccharide.
I Streptococcus pneumoniae capsular
residue is reported utilizing this glycosyl donor 2 and monosaccha-
ride building blocks 3 and 4 (Fig. 2).
2.2. Oligosaccharide assembly
2. Results and discussion
The glycosidation of 3 by 4 was attempted under a variety of
conditions. Activation of 3 by Ph2SO–Tf2O gave disaccharide glyco-
side 13 in yields of 30% or less. NIS–TfOH at ꢁ30 °C gave a 57%
yield of disaccharide 13. The best yield 70% of 13 was obtained
with NIS–AgOTf. The disaccharide alcohol 14 was obtained by
transesterification of 13 (Scheme 3).
2.1. Monosaccharide building blocks
2-Azido-4-benzylamino-4N,3-O-carbonyl-2,4,6-trideoxy-
galactopyranosyl trichloroacetimidate 2 was prepared from
D-
D
-
glucal in seven steps as previously described.6 Assembly of the
target molecule was envisaged to proceed via the glycosidation
of phenylthiogalactoside 3 by methyl galactoside 4 followed by
glycosylation of the resulting galabioside by imidate 2. This ap-
proach requires the oxidation of a selectively deprotected trisac-
charide to create two uronic acid residues. As we have shown
before this avoids the challenges associated with glycosylation
reactions between relatively unreactive uronic acid acceptors
and donors.
Glycosylation of disaccharide 14 by imidate 26 was most effec-
tively carried out with a donor:acceptor molar ratio of 1.5:1.0
using TMSOTf as the Lewis acid promotor. The reaction was initi-
ated at 0 °C and allowed to warm to room temperature (Scheme 4).
Trisaccharide 15 was obtained in 70% yield exclusively as its
a
-anomer (3J1,2 homonuclear coupling constant).
2.3. Deprotection of trisaccharide 15
The most direct route to 3 from phenyl thiogalactopyranoside
involved the formation of the 4,6-O-p-methoxybenzylidene acetal
5, (although this compound has been previously reported its char-
acterization in several papers is rather sketchy).7 Benzylation of 5
Deprotection of trisaccharide 15 to give the target compound 1
required a series of carefully controlled steps to cleave the oxazo-
lidinone to afford the 2-acetamido-4-amino-2,4,6-tridoxyhexose
residue with the correct N-acyl protection pattern while also
H3N
O
HO
AcHN
O
CO2
O
HO
HO
CO2
O
HO
O
1
HO
OCH3
Bn
N
BzO
BnO
BnO
HO
OPMB
O
OPMB
O
O
O
SPh
O
N3
BnO
BnO
OCH3
O
CCl3
2
3
4
NH
Figure 2. Trisaccharide target 1 and monosaccharide synthons 2–4.

28
I. Iynkkaran, D. R. Bundle / Carbohydrate Research 378 (2013) 26–34
R3O
OR2
BnO
R1O
OTBDPS
O
O
R2O
R1O
BnO
OCH3
OCH3
8 R1 = R2 = R3 = H
11 R1= All, R2 = H
c
a
b
d
e
1 = R3 = H, R2 = All
12
4
1
R = All, R2 = PMB
9
R
R
1 = R3 = Bn, R2 = All
R1= H, R2 = PMB
10
Scheme 2. Reagents and conditions: (a) Bn2SnO, AllBr, TBAI, PhCH3, 60 °C, 60%; (b) BnBr, NaH, DMF, 87%; (c) TBAF, THF, 92%; (d) PMBBr, NaH, 89%; (e) PdCl2, HOAc, H2O,
NaOAc, 87%.
OPMB
O
R4N
R3O
RO
BnO
O
BnO
OPMB
O
R2
BnO
a
OR1
O
3
4
+
O
a
15
O
BnO
OCH3
BnO
OR1
BnO
BnO
13
R = Bz
O
b
14 R = H
O
BnO
Scheme 3. Reagents and conditions: (a) NIS, AgOTf, DCM 4 Å MS, ꢁ30 °C, 70%; (b)
MeONa, MeOH, DCM 45 °C 10 h, 94%.
OCH3
16 R1 = PMB, R2 = N3, R3 = H, R4 = BnH
b
c
R
R
1 = PMB, R2 = N3, R3 = Bn, R4 = BnH
1 = H, R2 = N3, R3 = Bn, R4 = BnH
17
18
Bn
N
19 R1 = H, R2 = NHAc, R3 = Bn, R4 = BnH
d
O
O
O
Scheme 5. Reagents and conditions: (a) 2 M LiOH, LiI, THF/EtOH (2:1) reflux 2 days
95%; (b) BnBr, NaH, DMF, 80%; (c) TFA, DCM, 20 min, 75%; (d) (i) H2S, Py/H2O/Et3N,
20 h rt, (ii) Ac2O, MeOH, 72%.
a
N3
OPMB
O
2
14
+
O
BnO
BnO
OPMB
O
be seen neither Cs2CO3–THF nor KOTMS–THF afforded product and
1 M NaOH–THF–EtOH gave only moderate yield (Scheme 5).
In order to protect the newly revealed hydroxyl group, 16 was
initially benzylated with excess benzyl bromide to give a dibenzy-
lated tertiary amine. Although reduction of the azide and acetyla-
tion of the resulting amine proceeded in excellent yield subsequent
attempts to selectively remove the two PMB ethers using DDQ and
CAN resulted in a mixture of products that included incompletely
hydrolysed PMB ethers and a series of partially N-debenzylated
products. We reasoned that a dibenzylamine created an electron
rich environment that was prone to oxidation and we sought to
avoid N-benzylation of 16. By employing a limited amount of
benzyl bromide regioselective benzylation at the 300 OH group
was achieved in 80% yield to afford 17.
BnO
O
BnO
15
OCH3
Scheme 4. Reagents and conditions: (a) TMSOTf, DCM, 4 Å MS, 70%.
permitting selective deprotection of the hydroxymethyl groups of
the two galactopyranoside residues as a prelude to their oxidation
to provide the galacturonic acid residues.
Of the several methods available in the literature for the cleav-
age of the oxazolidinone ring we elected to use base hydrolysis.9
After screening a series of reaction conditions, varying the inor-
ganic base, solvent system, temperature and reaction time, we
found that the cleavage of oxazolidinone could be achieved by
choosing a small and strongly Lewis acid; lithium cation. Treat-
ment of 15 with LiOH and a catalytic amount of LiI in a mixture
of THF and ethanol under reflux for 4 days gave the 4N-benzylgal-
atosamine derivative 16 in excellent yield (Table 1, entry 8). As can
Attempts to oxidatively cleave the PMB groups using DDQ/CAN
gave only a trace amount of the desired diol 18. However mild acid
PhCH
N
O
Table 1
BnO
Conditions for controlled hydrolysis of the oxazolidinone 16 to provide access to a 2-
acetamido-4-amino-2,4,6-tridoxyhexose residue
AcHN
b
a
O
1
19
CO2H
Entry
Reaction condition
Temperature (°C)
Yield (%)
O
BnO
1
2
3
4
5
6
7
8
Cs2CO3–THF
Cs2CO3–THF
rt
—
—
—
—
50
—
80
95
BnO
CO2H
BnO
Varying from 40 to 80
rt
Varying from 40 to 80
80
80
80
80
O
1 M NaOH–THF
1 M NaOH–THF
1 M NaOH–THF–EtOH
KOTMS–THF
2 M LiOH–THF–EtOH
2 M LiOH–LiI–THF–EtOH
O
BnO
OCH3
20
Scheme 6. Reagents and conditions: (a) TEMPO/NaOCl, Me2CO, NaHCO3/KBr/H2O,
10 min; (b) H2, Pd(OH)2/C, H2O/AcOH, 53% over two steps from 19.

I. Iynkkaran, D. R. Bundle / Carbohydrate Research 378 (2013) 26–34
29
hydrolysis of 17 using 5% TFA in DCM gave 18 in excellent yield.
Selective reduction of the azide and acetylation of the resulting
amine gave the N-acetylated diol 19. This diol was oxidized by
TEMPO-NaOCl-KBr10 to give the di-acid 20 in which the secondary
amine group had been oxidized to an imine Scheme 6. Global
deprotection to afford 1 was then accomplished by hydrogenolysis.
Gel permeation chromatography on Bio-gel P2 was used to purify
the highly polar zwitterionic target molecule 1. The three bond
analytical services in the department. Optical rotations were deter-
mined with a Perkin-Elmer, model 241, polarimeter at room tem-
perature using the sodium D-line and are reported in units of
deg mL gꢁ1 dmꢁ1. Elemental analysis was performed by analytical
services of this department.
3.2. Methyl 2-acetamido-4-amino-2,4,6-trideoxy-
galactopyranosyl-(1?4)- -galactopyranosiduronate-(1?3)-
a-D-galactopyranosiduronate (1)
a-D-
a
-D
proton homonuclear coupling constants establish the
a-anomeric
configuration of each pyranose ring of 1 and it is note worthy that
1H and 13C NMR chemical shifts were similar to those reported for
a related oligosaccharide synthesized as its glycerol glycoside.4b
Although glycosyl donor 2 was previously shown to be effective
Crude 20 was dissolved in a mixture of H2O–AcOH (4:1, 3 mL)
and 20% Pd(OH)2/C (0.015 g) was added to the resulting solution.
The reaction mixture was shaken under a hydrogen atmosphere
at 60 psi for 2 days. The catalyst was filtered off through cotton
wool and then through a microfilter. The filtrate was concentrated
(1 mL) under reduced pressure. Purification was performed on a
Bio-gel P2 column (1.6 ꢂ 35 cm) using NH4OH (1 mL/L) in water
as eluent and with monitoring by a Waters R403 refractive index
detector. Subsequent lyophilization of the purified fractions affor-
in yielding
a
-glycosides with model acceptors,6 the application
here demonstrates its utility for the synthesis of oligosaccharide
sequences that require C2 and C4 amino groups that can be readily
differentiated.
2.4. Biological evaluation
ded the final trisaccharide 1 (0.004 g,þ53%) as a white solid. [
a]
D
Trisaccharide glycoside 1 was tested for its ability to stimulate
interleukin 10 (IL-10) and Interferon-gamma (IFN-c) (unpublished
+49.1 (c 0.2, H2O); 1H NMR of the NH4 salt form (600 MHz, D2O)
d 5.22 (d, 1H, J1 ,2 = 3.7 Hz, H-10), 4.92 (d, 1H, J1 ,2 = 3.3 Hz, H-100),
0
0
00 00
00 00
results, Kasper and co-workers at Harvard Medical School). Each of
these responses is representative of the T-cell activating ability of
zwitterionic antigens.11 Unfortunately, this trisaccharide, as well
as a previously frame-shifted trisaccharide and its corresponding
hexasaccharide were not active.4a Published data describing the
molecular weight required for activity2d that appeared after
synthetic work was initiated is consistent with this result. Based
on this data, it appears that at least six repeating units are required
for activity.
4.86 (d, 1H, J1,2 = 3.8 Hz, H-1), 4.64 (qd, 1H, J4 ,5 = 1.6 Hz,
J5 ,6 = 6.5 Hz, H-500), 4.55 (app s, 1H, H-50), 4.49 (d, 1H,
00 00
0
0
J3,4 = 3.1 Hz, J4,5 = 1.2 Hz, H-4), 4.33 (d, 1H, J3 ,4 = 3.1 Hz,
J4 ,5 = 0.9 Hz, H-40), 4.22 (d, 1H, J4,5 = 1.1 Hz, H-5), 4.10 (dd, 1H,
0
0
J2 ,3 = 10.9 Hz, J3 ,4 = 3.3 Hz, H-30), 4.08 (dd, 1H, J2 ,3 = 9.0 Hz,
0
0
0
0
00 00
J3 ,4 = 3.7 Hz, H-300), 4.06 (dd, 1H, J1 ,2 = 3.5 Hz, J2 ,3 = 11.2 Hz, H-
00 00
00 00
00 00
200), 4.00 (dd, 1H, J2,3 = 10.3 Hz, J3,4 = 3.2 Hz, H-3), 3.94 (dd, 1H,
0
0
J1,2 = 3.8 Hz, J2,3 = 10.2 Hz, H-2), 3.89 (dd, 1H, J1 ,2 = 3.9 Hz,
J2 ,3 = 10.7 Hz, H-20), 3.41 (s, 3H, OCH3), 3.37 (dd, 1H, J3 ,4 = 4.1 Hz,
0
0
00 00
J4 ,5 = 1.5 Hz, H-400), 2.09 (s, 3H, COCH3), 1.24 (d, 3H, J5 ,6 = 6.7 Hz,
H-600 CH3). 13C NMR of the NH4þ salt form (125 MHz, D2O) d 176.4,
175.9, 175.5, 100.3, 99.8, 96.7, 81.0, 76.2, 72.1, 71.9, 69.6, 68.9,
68.4, 67.3, 67.0, 65.7, 56.1, 55.6, 50.1, 23.2, 16.5. ESI HRMS calcd
for C21H33N2O16 (MꢁH): 569.1837, found 569.1839.
00 00
00 00
3. Experimental
3.1. General methods
All chemical reagents were of analytical grade and used as ob-
tained from commercial sources unless otherwise indicated. Sol-
vents used in water-sensitive reactions were purified by
successive passage through columns of alumina and copper under
nitrogen, except for DMSO, which was distilled under vacuum and
collected over 4 Å molecular sieves. Unless otherwise noted, reac-
tions were carried out at room temperature, and water-sensitive
reactions were performed under an atmosphere of argon. Molecu-
lar sieves were flame dried and then allowed to cool to room tem-
perature under argon before use. Reactions were monitored by
analytical thin-layer chromatography (TLC) performed on Silica
Gel 60-F254 (E. Merck). Plates were visualized under UV light,
and/or by treatment with 5% sulphuric acid in ethanol followed
by heating. Organic solvents were removed under vacuum at
<40 °C. Medium-pressure chromatography was conducted using
silica gel (230–400 mesh, Silicycle, Montreal) at flow rates between
5 and 10 mL minꢁ1. Following deprotection, final compounds were
purified by HPLC (Flow rate = 3.0 mL/min, Diameter = 7.8 mm)
with 70% CH3CN–30% H2O as eluent on a TSK-GEL Amide-80 col-
umn, concentrated under reduced pressure to remove acetonitrile,
and then lyophilized. 1H NMR spectra were recorded at 498 or
600 MHz, and chemical shifts, reported in d (ppm), were referenced
to internal residual protonated solvent signals or to external ace-
tone (0.1% ext. acetone d 2.225 ppm) in the case of D2O. 13C NMR
spectra were recorded at 125 MHz, and chemical shifts are refer-
enced to internal CDCl3 (d 77.23) or external acetone (d 31.07). First
order chemical shifts of 1H and 13C are reported to the second and
first decimal place, respectively. High resolution mass spectra were
obtained on a Micromass Zabspec TOF-mass spectrometer by
3.3. Phenyl 4-O-benzoyl-2,3-di-O-benzyl-6-O-p-methoxybenzyl-
1-thio-b-D-galactopyranoside (3)
Compound 7 (1.71 g, 2.98 mmol) was dissolved in dry pyridine
(25 mL) under an argon atmosphere. Benzoyl chloride (0.50 mL,
3.58 mmol, 1.2 equiv) was added at room temperature and after
7 h the reaction mixture was quenched by addition of MeOH. After
stirring for 25 min the solution was concentrated under reduced
pressure. The residue was dissolved in DCM, washed with satu-
rated NaHCO3 solution and brine. Then, the DCM solution was
dried over Na2SO4, filtered and concentrated to dryness. Chroma-
tography of the residue using hexanes–EtOAc (17:3) afforded the
benzoylated galactoside 3 (1.86 g, 92%). [a] +7.2 (c 1.3, CH2Cl2);
D
1H NMR (498 MHz, CDCl3) d 8.11 (d, 1H, J = 7.4 Hz, ArH), 8.02–
7.96 (m, 2H, ArH), 7.67–7.55 (m, 3H, ArH), 7.53–7.41 (m, 3H,
ArH), 7.41–7.18 (m, 13H, ArH), 6.81–6.75 (m, 2H, ArH), 5.89 (dd,
1H, J3,4 = 2.1 Hz, J4,5 = 0.4 Hz, H-4), 4.85 (d, 1H, Jgem = 11.2 Hz,
PhCH2), 4.73 (s, 2H, PhCH2), 4.70 (d, 1H, J1,2 = 9.5 Hz, H-1), 4.52
(d, 1H, Jgem = 11.2 Hz, PhCH2), 4.45 (d, 1H, Jgem = 11.4 Hz, PhCH2),
4.37 (d, 1H, Jgem = 11.4 Hz, PhCH2), 3.88 (app t, 1H, J5,6a = 6.3 Hz,
J5,6b = 6.3 Hz, H-5), 3.78–3.73 (dd, H, J2,3 = 9.0 Hz, J3,4 = 3.2 Hz, H-
3), 3.74 (s, 3H, OCH2C6H4OCH3), 3.71 (app t, 1H, J1,2 = 9.3 Hz,
J2,3 = 9.3 Hz, H-2), 3.68–3.63 (dd, 1H, J5,6a = 5.9 Hz, J6a,6b = 9.5 Hz,
H-6a), 3.55 (dd, 1H, J5,6b = 5.9 Hz, J6a,6b = 9.3 Hz, H-6b). 13C NMR
(125 MHz, CDCl3) d 165.6, 159.3, 138.3, 137.6, 133.1, 132.9,
132.8, 130.0, 129.8, 129.7, 129.6, 128.8, 128.3, 128.2, 128.1,
127.7, 127.6, 113.8, 87.2, 81.5, 76.5, 76.2, 75.7, 73.3, 71.8, 67.9,
67.3, 55.2. ESI HRMS calcd for C41H40O7SNa (M+Na): 699.2387,

30
I. Iynkkaran, D. R. Bundle / Carbohydrate Research 378 (2013) 26–34
found 699.2394. Anal. Calcd for C41H40O7S: C, 72.76; H, 5.96; O,
16.55, S, 4.74. Found: C, 73.10; H, 6.12; O, 16.87, S, 3.91.
3.7. Phenyl 2,3-di-O-benzyl-6-O-p-methoxybenzyl-1-thio-b-D-
galactopyranoside (7)
3.4. Methyl 2,4-di-O-benzyl-6-O-p-methoxybenzyl-
galactopyranoside (4)
a
-
D
-
TFA (0.78 mL, 7.01 mmol, 5 equiv) was added dropwise to a
cooled (0 °C) solution of 6 (0.8 g, 1.40 mmol) and NaCNBH3
(0.44 g, 7.01 mmol, 5 equiv) in dry THF (10 mL) containing acti-
vated 4 Å molecular sieves (0.20 g). The solution was then stirred
at room temperature until TLC showed complete consumption of
starting material. The reaction was quenched with TEA and then
it was diluted with EtOAc (20 mL). Molecular sieves were removed
by filtering through Celite. The filtrate was washed with an equal
volume of saturated aqueous NaHCO3 solution and brine. The com-
bined organic phase was dried over Na2SO4, filtered and concen-
trated under reduced pressure. The residue was purified by silica
To a solution of 12 (0.48 g, 0.91 mmol) in acetic acid (10 mL)
and water (10 drops) were added PdCl2 (0.32 g, 1.82 mmol,
2 equiv) and NaOAc (0.32 g, 3.91 mmol, 4.3 equiv) at room tem-
perature with stirring. After 7 h the reaction mixture was filtered
through Celite. The filtrate was diluted with EtOAc (15 mL) and
then washed with an equal volume of saturated aqueous NaH-
CO3 solution, brine and water. The organic phase was dried over
Na2SO4, filtered and then concentrated to dryness. The residue
was chromatographed using hexanes–EtOAc (7:3) as eluent to
gel column chromatography (hexanes–EtOAc, 8:2) to give
7
give 4 (0.39 g, 87%) as a syrup. [
a]
+63.7 (c 1.3, CH2Cl2); 1H
(0.60 g, 75%) as a white solid. [
a]
D
+0.5 (c 1.5, CH2Cl2); 1H NMR
D
NMR (600 MHz, CDCl3) d 7.39–7.25 (m, 11H, ArH), 7.24–7.18
(m, 2H, ArH), 6.88–6.83 (m, 2H, ArH), 4.80 (d, 1H, Jgem = 11.6 Hz,
PhCH2), 4.70 (d, 1H, Jgem = 9.1 Hz, PhCH2), 4.69 (s, 1H, H-1), 4.66
(d, 1H, Jgem = 12.0 Hz, PhCH2), 4.61 (d, 1H, Jgem = 11.6 Hz, PhCH2),
4.46 (d, 1H, Jgem = 11.4 Hz, PhCH2), 4.37 (d, 1H, Jgem = 11.4 Hz,
PhCH2), 4.04 (ddd, 1H, J2,3 = 10.0 Hz, J3,3OH = 4.8 Hz, J3,4 = 3.3 Hz,
H-3), 3.92.
(600 MHz, CDCl3) d 7.61–7.56 (m, 2H, ArH), 7.44–7.39 (m, 2H,
ArH), 7.38–7.22 (m, 13H, ArH), 6.91–6.85 (m, 2H, ArH), 4.84 (d,
1H, Jgem = 10.3 Hz, PhCH2), 4.76 (d, 1H, Jgem = 10.3 Hz, PhCH2),
4.73 (d, 1H, Jgem = 11.6 Hz, PhCH2), 4.69 (d, 1H, Jgem = 10.3 Hz,
PhCH2), 4.64 (d, 1H, J1,2 = 9.8 Hz, H-1), 4.51 (s, 2H, PhCH2), 4.11
(d, 1H, J = 3.2 Hz, H-4), 3.81 (s, 3H, OCH2C6H4OCH3), 3.81–3.73
(m, 3H, H-2, H-6), 3.58 (m, 2H, H-5, H-3). 13C NMR (125 MHz,
CDCl3) d 159.3, 138.2, 137.7, 133.9, 131.8, 130.0, 129.5, 128.9,
128.5, 128.4, 128.3, 128.0, 127.9, 127.8, 127.3, 113.8, 87.7, 82.6,
77.3, 75.8, 73.4, 72.1, 69.1, 66.9, 55.3. ESI HRMS calcd for
3.5. Phenyl 4,6-O-p-methoxybenzylidene-1-thio-b-D-
galactopyranoside (5)
C
C
34H36O6SNa (M+Na): 595.2125, found 595.2123. Anal. Calcd for
34H36O6S: C, 71.30; H, 6.34. Found: C, 70.85; H, 6.34.
Phenyl-1-thio-b-D-glucopyranoside (4.97 g, 18.4 mmol) was
dissolved in dry CH3CN (30 mL). p-Anisaldehyde dimethyl acetal
(4.10 mL, 22.08 mmol, 1.2 equiv) and a catalytic amount of cam-
phorsulphonic acid were added. The reaction was stirred at room
temperature for 3 h. Then the reaction mixture was quenched by
addition of TEA and concentrated under reduced pressure. The
yellow residue was purified by column chromatography (5%
MeOH in DCM) to afford 5 (6.61 g, 92%) as a white crystalline so-
lid. NMR chemical shifts and coupling constants were in excel-
3.8. Methyl 6-O-tert-butyldiphenylsilyl-a-D-galactopyranoside
(8)
Methyl
a-D-galactopyranoside (20.00 g, 103.1 mmol) was dis-
solved in DMF (50 mL) with stirring under argon. Imidazole
(8.41 g, 123.72 mmol, 1.2 equiv) and then by tert-butylchlorodi-
phenylsilane (31.16 mL, 113.53 mmol, 1.1 equiv) were added to
the solution. After 5 h the reaction was quenched by adding MeOH.
Then the solvent was removed under reduced pressure. The resi-
due was purified by column chromatography on silica gel using a
mixture of hexanes/EtOAc (7:3) as eluent to afford 8 (41.00 g,
92%) as a syrup. NMR chemical shifts and coupling constants were
in general agreement with the literature.8 Our observed values are
lent agreement with the literature.7
(lit. [
ꢁ7.5).
[a
]
D
ꢁ7.5 (c 1.5, CHCl3)
a
]
D
3.6. Phenyl 2,3-di-O-benzyl-4,6-O-p-methoxybenzylidene-1-
thio-b- -galactopyranoside (6)
D
To a solution of diol 57 (6.34 g, 16.25 mmol) in dry DMF
(25 mL) at 0 °C was added NaH (dispersion in mineral oil; 60%
by mass; 1.18 g, 16.25 mmol, 3 equiv) in portions under an inert
argon atmosphere. After 1 h, BnBr (8.45 mL, 16.25 mmol, 3 equiv)
was slowly added to the above mixture, which was then
warmed to room temperature and stirred for a further 5 h. The
reaction mixture was then quenched by careful addition of
MeOH. The solution was diluted with DCM (100 mL) and washed
with an equal volume of water and brine. The organic extract
was dried over Na2SO4, filtered and the filtrate was concentrated.
Chromatography on silica gel with toluene–EtOAc (13:1) as elu-
reported since there are some differences; [a]D +75.7 (c 0.3, CHCl3);
1H NMR (498 MHz, CDCl3) d 7.70 (m, 4H, ArH), 7.48–7.35 (m, 6H,
ArH), 4.79 (d, 1H, J1,2 = 3.9 Hz, H-1), 4.11 (s, 1H, H-4), 3.93 (dd,
1H, J5,6a = 6.1 Hz, J6a,6b = 10.6 Hz, H-6a), 3.90–3.85 (dd, 1H,
J5,6b = 5.3 Hz, J6a,6b = 10.6 Hz, H-6b), 3.85–3.81 (dd, 1H,
J1,2 = 3.9 Hz, J2,3 = 9.4 Hz, H-2), 3.77 (t, 1H, J5,6 = 5.7 Hz, H-5), 3.74
(dd, 1H, J2,3 = 9.4 Hz, J3,4 = 3.3 Hz, H-3), 3.37 (s, 3H, OCH3), 2.52 (s,
4H, OH), 1.07 (s, 9H, C(CH3)3). 13C NMR (125 MHz, CDCl3) d
135.6, 135.6, 133.3, 133.2, 129.7, 127.7, 99.6, 71.0, 70.4, 69.6,
69.4, 63.4, 55.1, 26.8, 19.2. ESI HRMS calcd for C23H32O6SiNa
(M+Na): 455.1860, found 455.1853. Anal. Calcd for C23H32O6Si: C,
63.86; H, 7.46. Found: C, 63.56; H, 7.45.
ent gave 6 (7.95 g, 85%). [
a]
+3.2 (c 0.6, CH2Cl2); 1H NMR
D
(498 MHz, CDCl3) d 7.77–7.71 (m, 2H, ArH), 7.51–7.41 (m, 4H,
ArH), 7.41–7.19 (m, 11H, ArH), 6.94 (t, 2H, J = 5.6 Hz, ArH),
5.47 (s, 1H, CHPhOCH3), 4.78–4.67 (m, 4H, PhCH2), 4.64 (d, 1H,
J1,2 = 9.6 Hz, H-1), 4.37 (d, 1H, J6a,6b = 12.2 Hz, H-6a), 4.16 (d,
1H, J3,4 = 3.3 Hz, H-4), 4.00–3.96 (d, 1H, J6a,6b = 3.3 Hz, H-6b),
3.93 (app t, 1H, J1,2 = 9.4 Hz, J2,3 = 9.4 Hz, H-2), 3.86 (s, 3H,
CHPhOCH3), 3.64 (dd, 1H, J2,3 = 9.2 Hz, J3,4 = 3.4 Hz, H-3), 3.40
(s, 1H, H-5). 13C NMR (125 MHz, CDCl3) d 160.2, 138.6, 138.2,
132.9, 132.7, 130.6, 128.9, 128.4, 128.3, 128.2, 127.9, 127.9,
127.8, 127.8, 127.7, 127.5, 113.5, 101.3, 86.6, 81.4, 73.7, 71.8,
3.9. Methyl 3-O-allyl-6-O-tert-butyldiphenylsilyl-a-D-
galactopyranoside (9)
A mixture of 8 (0.51 g, 1.18 mmol) and dibutyltin oxide (0.32 g,
1.30 mmol, 1.1 equiv) in toluene (15 mL) was heated at reflux for
3 h with azeotropic removal of water. The solution was concen-
trated to 10 mL by continued evaporation and was cooled to
60 °C. TBAI (0.47 g, 1.30 mmol, 1.1 equiv) and allyl bromide
(0.16 mL, 1.30 mmol, 1.1 equiv) were added to the solution. The
reaction mixture was heated at 60 °C overnight and the solution
was then evaporated under reduced pressure. The residue was
69.9, 69.4, 55.4. ESI HRMS calcd for
593.1968, found 593.1970.
C34H34O6SNa (M+Na):

I. Iynkkaran, D. R. Bundle / Carbohydrate Research 378 (2013) 26–34
31
purified by silica gel column chromatography using a stepped gra-
Jgem = 12.1 Hz, PhCH2), 4.61 (d, 1H, Jgem = 11.2 Hz, PhCH2), 4.33
(ddt, 1H, Jgem = 13.0 Hz, Jvic = 5.6 Hz, 4J = 1.4 Hz, OCH2CH@CH2),
dient (20–30% EtOAc in hexanes) to give compound 9 (0.33 g, 60%).
[
a]
D
+88.8 (c 0.4, CH2Cl2); 1H NMR (600 MHz, CDCl3) d 7.73–7.67
4.23
(ddt,
1H,
Jgem = 13.0 Hz,
Jvic = 5.6 Hz,
4J = 1.4 Hz,
(m, 4H, ArH), 7.46–7.36 (m, 6H, ArH), 5.97 (m, 1H, OCH2CH@CH2),
5.37–5.28 (ddd, 1H, Jtrans = 17.2 Hz, Jgem = 3.1 Hz, 4J = 1.5 Hz,
OCH2CH = CH), 5.26–5.19 (ddd, 1H, Jcis = 10.3 Hz, Jgem = 2.8 Hz,
4J = 1.2 Hz, OCH2CH = CH), 4.81 (d, 1H, J1,2 = 4.0 Hz, H-1), 4.20 (m,
2H, OCH2CH = CH2), 4.15–4.12 (m, 1H, H-4), 3.99–3.92 (m, 2H, H-
2, H-6), 3.87 (dd, 1H, J5,6b = 5.8 Hz, J6a,6b = 10.4 Hz, H-6b), 3.77
(app t, 1H, J4,5 = 5.9 Hz, J5,6b = 5.9 Hz, H-5), 3.54 (dd, 1H,
J2,3 = 9.7 Hz, J3,4 = 3.2 Hz, H-3), 3.39 (s, 3H, OCH3), 2.48–2.45 (s,
1H, 4-OH), 2.07 (s, 1H, 2-OH), 1.10–1.05 (s, 9H, C(CH3)3). 13C
NMR (125 MHz, CDCl3) d 135.6, 135.6, 134.6, 133.3, 133.2, 129.7,
129.7, 127.8, 117.8, 99.4, 78.2, 70.9, 70.1, 68.5, 66.8, 63.3, 55.2,
26.8, 19.2. ESI HRMS calcd for C26H36O6SiNa (M+Na): 495.2173,
found 495.2176.
OCH2CH@CH2), 4.00 (dd, 1H, J1,2 = 3.7 Hz, J2,3 = 10.1 Hz, H-2), 3.89
(d, 1H J4,5 = 2.7 Hz, H-5), 3.83 (dd, 1H, J2,3 = 10.1 Hz, J3,4 = 2.9 Hz,
H-3), 3.77–3.69 (m, 2H, H-4, H-6a), 3.55–3.46 (m, 1H, H-6b), 3.37
(s, 3H, OCH3), 1.68 (dd, 1H, J6a,6OH = 9.0 Hz, J6b,6OH = 2.8 Hz, 2-OH).
13C NMR (125 MHz, CDCl3) d 138.5, 138.2, 135.1, 128.6, 128.5,
128.3, 128.1, 128.0, 127.7, 116.6, 98.9, 78.7, 76.2, 74.8, 74.4, 73.6,
72.1, 70.2, 62.5, 55.3. ESI HRMS calcd for C24H30O6Na (M+Na):
437.1935, found 437.1935.
3.12. Methyl 3-O-allyl-2,4-di-O-benzyl-6-O-p-methoxybenzyl-
a-
D-galactopyranoside (12)
Alcohol 11 (0.28 g, 0.68 mmol) was dissolved in DMF (5 mL) and
treated with NaH (dispersion in mineral oil; 60% by mass; 0.03 g,
0.75 mmol, 1.1 equiv) in portions at 0 °C. The reaction was stirred
at room temperature for 1 h and then PMBBr (0.15 mL, 0.75 mmol,
1.1 equiv) was added drop wise and stirring was continued at room
temperature for a further 5 h. Unreacted NaH was quenched by
slow addition of MeOH at 0 °C. The reaction mixture was diluted
with DCM (10 mL), and the organic phase was washed with water,
brine, and the organic phase was dried over MgSO4. The filtrate
was concentrated under reduced pressure and the residue was
purified by column chromatography (hexanes–EtOAc, 9:1) to give
3.10. Methyl 3-O-allyl-2,4-di-O-benzyl-6-O-tert-
butyldiphenylsilyl-a-D-galactopyranoside (10)
To a stirred solution of 9 (0.40 g, 0.85 mmol) in dry DMF (7 mL),
NaH (dispersion in mineral oil; 60% by mass; 0.073 g, 1.78 mmol,
2.1 equiv) was added in portions at 0 °C and stirring was continued
until the evolution of gas had ceased. After 1 h, BnBr (0.30 mL,
1.78 mmol, 2.1 equiv) was slowly added to the above mixture,
which was then warmed to room temperature and stirred for
4 h. The reaction mixture was then quenched with MeOH. The
solution was diluted with DCM (20 mL) and washed with an equal
volume of water and brine. The organic extract was dried over
Na2SO4, filtered and concentrated to a light yellow residue. Chro-
matography on silica gel with hexanes–EtOAc (4:1) as eluent gave
12 (0.31 g, 89%) as a colourless syrup. [a] +38.3 (c 2.2, CH2Cl2);
D
1H NMR (600 MHz, CDCl3) d 7.40–7.27 (m, 8H, ArH), 7.27–7.00
(m, 5H, ArH), 6.93–6.82 (m, 2H, ArH), 5.96 (m, 1H, OCH2CH = CH2),
5.35 (ddd, 1H, Jtrans = 17.2 Hz, Jgem = 3.5 Hz, 4J = 1.7 Hz,
OCH2CH@CH), 5.18 (ddd, 1H, Jcis = 10.4 Hz, Jgem = 3.2 Hz,
4J = 1.4 Hz, OCH2CH@CH), 4.93 (d, 1H, Jgem = 11.4 Hz, PhCH2), 4.83
(d, 1H, Jgem = 12.1 Hz, PhCH2), 4.69 (d, 1H, Jgem = 15.2 Hz, PhCH2),
4.67 (s, 1H, H-1), 4.56 (d, 1H, Jgem = 11.4 Hz, PhCH2), 4.43 (d, 1H,
Jgem = 11.4 Hz, PhCH2), 4.34 (d, 1H, Jgem = 11.4 Hz, PhCH2), 4.28
(ddt, 1H, Jgem = 13.0 Hz, Jvic = 5.1 Hz, 4J = 1.6 Hz, OCH2CH@CH2),
10 (0.48 g, 87%) as a white solid. [a]
D +76.2 (c 0.4, CH2Cl2); 1H NMR
(600 MHz, CDCl3) d 7.66–7.60 (m, 4H, ArH), 7.47–7.20 (m, 16H,
ArH), 6.03–5.95 (m, 1H, OCH2CH@CH2), 5.37 (ddd, 1H,
Jtrans = 17.2 Hz, Jgem = 3.5 Hz, 4J = 1.7 Hz, OCH2CH = CH), 5.20 (ddd,
1H, Jcis = 10.6 Hz, Jgem = 3.2 Hz, 4J = 1.4 Hz, OCH2CH@CH), 4.95 (d,
1H, Jgem = 11.4 Hz, PhCH2), 4.82 (d, 1H, Jgem = 12.1 Hz, PhCH2),
4.67 (d, 1H, Jgem = 12.1 Hz, PhCH2), 4.63 (d, 1H, J1,2 = 3.7 Hz, H-1),
4.61 (d, 1H, Jgem = 11.4 Hz, PhCH2), 4.31 (ddt, 1H, Jgem = 13.0 Hz,
4.20
(ddt,
1H,
Jgem = 13.0 Hz,
Jvic = 5.5 Hz,
4J = 1.5 Hz,
OCH2CH@CH2), 3.97 (dd, 1H, J1,2 = 3.7 Hz, J2,3 = 10.1 Hz, H-2),
3.94–3.90 (dd, 1H, J3,4 = 3.0 Hz, J4,5 = 1.1 Hz, H-4), 3.88 (ddd, 1H,
J4,5 = 1.1 Hz, J5,6a = 6.5 Hz, J5,6b = 6.5 Hz, H-5), 3.81 (dd, H,
J2,3 = 10.1 Hz, J3,4 = 2.9 Hz, H-3), 3.80 (s, 3H, OCH2C6H4OCH3), 3.53
(dd, 1H, J5,6a = 7.0 Hz, J6a,6b = 9.3 Hz, H-6a), 3.49 (dd, 1H,
J5,6b = 5.9 Hz, J6a,6b = 9.3 Hz, H-6b), 3.39–3.31 (m, 3H, OCH3). 13C
NMR (125 MHz, CDCl3) d 159.3, 138.8, 138.6, 135.1, 130.1, 129.5,
128.3, 128.2, 128.2, 128.0, 127.6, 127.5, 116.3, 113.8, 98.9, 78.6,
76.2, 75.0, 74.78, 73.6, 73.2, 71.8, 69.2, 68.7, 55.3, 55.3. ESI HRMS
calcd for C32H38O7Na (M+Na): 557.2510, found 557.2510.
Jvic = 5.1 Hz,
4J = 1.5 Hz,
OCH2CH@CH2),
4.23
(ddt,
1H,
Jgem = 13.0 Hz, Jvic = 5.5 Hz, 4J = 1.4 Hz, OCH2CH@CH2), 3.97 (d, 1H,
J3,4 = 2.9 Hz, H-4), 3.95 (dd, 1H, J1,2 = 3.7 Hz, J2,3 = 10.1 Hz, H-2),
3.80 (dd, 1H, J2,3 = 10.1 Hz, J3,4 = 2.9 Hz, H-3), 3.75–3.68 (m, 3H,
H-6, H-5), 3.28 (s, 3H, OCH3), 1.10–1.03 (m, 9H, C(CH3)3). 13C
NMR (125 MHz, CDCl3) d 138.7, 138.6, 135.5, 135.3, 133.4, 129.7,
129.68, 128.3, 128.1, 128.0, 127.7, 127.68, 127.6, 127.4, 116.3,
98.7, 78.8, 76.3, 74.8, 74.7, 73.5, 71.8, 70.7, 62.7, 55.0, 26.9, 19.2.
ESI HRMS calcd for
675.3113.
C40H48O6SiNa (M+Na): 675.3112, found
3.13. Methyl 4-O-benzoyl-2,3-di-O-benzyl-6-O-p-
methoxybenzyl-
O-p-methoxybenzyl-a-D
a
-
D
-galactopyranosyl-(1?3)-2,4-di-O-benzyl-6-
-galactopyranoside (13)
3.11. Methyl 3-O-allyl-2,4-di-O-benzyl-
a
-D
-galactopyranoside
(11)
Acceptor 4 (0.44 g, 0.88 mmol) and phenyl thiogalactoside 3
(0.77 g, 1.15 mmol, 1.3 equiv) were combined and concentrated
from a toluene solution and the residue was then dried in vacuo
overnight. The residue was dissolved in freshly distilled DCM
(25 mL) and the mixture was stirred under argon at room temper-
ature in the presence of powdered 4 Å molecular sieves for 30 min
before being cooled to ꢁ30 °C. NIS (0.28 g, 1.01 mmol, 1.2 equiv)
was then added and stirring was continued for 30 min. After addi-
tion of AgOTf (0.02 g, 0.09 mmol, 0.1 equiv) the reaction mixture
turned deep purple, and the reaction mixture was then stirred
for a further 1 h at ꢁ30 °C at which point the reaction was com-
plete. The mixture was made basic by addition of TEA and stirred
for an additional 20 min. The mixture was diluted, filtered through
Celite and washed with 5% Na2S2O3 solution and dried over
A solution of silyl ether 10 (0.48 g, 0.73 mmol) in dry THF
(10 mL) was reacted with TBAF (1.0 M in THF; 0.23 mL, 0.88 mmol,
1.2 equiv) under stirring at room temperature for 6 h. The solution
was then diluted with EtOAc (15 mL), washed with water, brine
and the organic phase was dried over sodium sulphate, filtered
and the filtrate concentrated in vacuo. The residue was purified
by silica gel column chromatography to give compound 11
(0.28 g, 92%) as a colourless oil. [
a]
+71.1 (c 2.3, CH2Cl2); 1H
D
NMR (600 MHz, CDCl3) d 7.42–7.25 (m, 10H, ArH), 6.00 (m, 1H,
OCH2CH@CH2), 5.37 (ddd, 1H, Jtrans = 17.2 Hz, Jgem = 3.3 Hz,
4J = 1.6 Hz, OCH2CH@CH), 5.21 (ddd, 1H, Jcis = 10.6 Hz, Jgem = 3.3 Hz,
4J = 1.4 Hz, OCH2CH@CH), 4.98 (d, 1H, Jgem = 11.2 Hz, PhCH2), 4.84
(d, 1H, Jgem = 12.1 Hz, PhCH2), 4.70 (s, 1H, H-1), 4.67 (d, 1H,

32
I. Iynkkaran, D. R. Bundle / Carbohydrate Research 378 (2013) 26–34
anhydrous MgSO4. The filtrate was concentrated to a residue that
was subjected to silica gel column chromatography using 8% EtOAc
in toluene as eluent to obtain the disaccharide 13 as a white crys-
toluene and dried in vacuo overnight. The residue was dissolved
in freshly distilled DCM (15 mL) and the mixture was stirred under
argon at room temperature in the presence of powdered 4 Å
molecular sieves for 30 min before being cooled to 0 °C. TMSOTf
talline solid (exclusively a, 0.7 g, 70%). [a] +202.7 (c 0.4, CH2Cl2);
D
1H NMR (600 MHz, CDCl3) d 8.15–7.99 (m, 3H, ArH), 7.65–7.10 (m,
27H, ArH), 6.94–6.64 (m, 5H, ArH), 5.77 (d, 1H, J = 2.0 Hz, H-40),
(5.0 lL, 0.09 mmol, 0.05 equiv) was added and the reaction mix-
ture was stirred for 1 h at 0 °C and then it was allowed to warm
to room temperature. The reaction mixture was quenched by addi-
tion of TEA and stirred for an additional 20 min, the mixture was
diluted, filtered through Celite and the filtrate was concentrated.
The residue was subjected to silica gel column chromatography
using a stepped gradient eluent (20–30% EtOAc in hexanes) to ob-
5.26 (d, 1H, J1 ,2 = 3.3 Hz, H-10), 4.99 (d, 1H, Jgem = 11.5 Hz, PhCH2),
4.83 (d, 2H, J = 11.6 Hz, PhCH2), 4.72 (d, 1H, Jgem = 12.0 Hz, PhCH2),
4.69–4.62 (m, 2H, PhCH2), 4.61–4.50 (m, 3H, H-50, H-1, PhCH2),
4.43 (d, 1H, Jgem = 11.5 Hz, PhCH2), 4.37 (d, 1H, Jgem = 11.5 Hz,
PhCH2), 4.33 (d, 1H, Jgem = 11.5 Hz, PhCH2), 4.30 (d, 1H,
Jgem = 11.5 Hz, PhCH2), 4.27 (d, 1H, Jgem = 11.5 Hz, PhCH2), 4.18
(dd, 1H, J2,3 = 10.2 Hz, J3,4 = 2.5 Hz, H-3), 4.14 (dd, 1H,
0
0
tain the trisaccharide 15 as a colourless syrup (exclusively
a,
0.40 g, 70%). [
a
]
D
+90.8 (c 1.0, CH2Cl2); 1H NMR (498 MHz, CDCl3)
J2 ,3 = 10.0 Hz, J3 ,4 = 3.1 Hz, H-30), 4.01 (dd, 1H, J1,2 = 3.6 Hz,
d 7.38–7.09 (m, 31H, ArH), 7.09 (s, 1H, ArH), 6.92–6.76 (m, 4H,
0
0
0
0
J2,3 = 10.0 Hz, H-2), 3.99 (dd, 1H, J1 ,2 = 3.3 Hz, J2 ,3 = 8.8 Hz, H-20),
3.95 (d, 1H, J3,4 = 1.4 Hz, H-4), 3.85 (t, 1H, J = 6.8 Hz, H-5), 3.81 (s,
3H, OCH2C6H4OCH3), 3.72 (s, 3H, OCH2C6H4OCH3), 3.50 (dd,
ArH), 5.13 (s, 1H, H-10), 5.03 (d, 1H, J1 ,2 = 4.2 Hz, H-100), 4.93 (d,
0
0
0
0
00 00
1H, Jgem = 11.7 Hz, PhCH2) 4.91 (d, 2H, Jgem = 15.5 Hz, PhCH2), 4.75
(d, 1H, Jgem = 8.0 Hz, PhCH2), 4.72 (d, 1H, Jgem = 7.0 Hz, PhCH2),
J5 ,6a = 6.1 Hz, 1H, J6a ,6b = 9.8 Hz, H-6a0), 3.47 (d, 2H, J = 6.3 Hz, H-
4.64–4.57 (m, 4H, H-1, PhCH2), 4.53 (dd, 1H, J2 ,3 = 6.3 Hz,
0
0
0
0
00 00
6), 3.39 (dd, J5 ,6a = 6.8 Hz, 1H, J6a ,6b = 9.6 Hz, H-6b0), 3.31 (s, 3H,
OCH3). 13C NMR (125 MHz, CDCl3) d 165.8, 159.2, 159.0, 139.0,
138.6, 138.2, 138.2, 132.9, 130.2, 130.2, 130.1, 129.9, 129.8,
129.4, 129.4, 128.5, 128.4, 128.3, 128.3, 128.2, 128.2, 128.1,
128.1, 128.0, 128.0, 127.9, 127.8, 127.8, 127.7, 127.6, 127.4,
127.2, 113.8, 113.5, 98.5, 96.9, 76.4, 76.0, 75.8, 75.6, 74.8, 74.8,
74.3, 73.2, 73.0, 72.7, 71.3, 69.2, 68.7, 68.7, 67.9, 67.8, 55.3, 55.2,
55.1. ESI HRMS calcd for C64H68O14Na (M+Na): 1083.4501, found
1083.4503.
J3 ,4 = 7.8 Hz, H-300), 4.46 (d, 1H, Jgem = 12.2 Hz, PhCH2), 4.41 (d,
0
0
0
0
00 00
1H, Jgem = 11.5 Hz, PhCH2), 4.36–4.17 (m, 7H, H-500, H-40, H-50, H-
30, 3 ꢂ PhCH2), 4.07 (dd, 1H, J2,3 = 10.0 Hz, J3,4 = 2.8 Hz, H-3), 4.05
(d, 1H, Jgem = 15.0 Hz, PhCH2), 3.92 (dd, 1H, J1,2 = 3.7 Hz,
J2,3 = 10.2 Hz, H-2), 3.91–3.88 (m, 2H, PhCH2, H-20), 3.87 (d, 1H,
J4,5 = 2.3 Hz, H-4), 3.81–3.77 (m, 7H, H-5, 2 OCH3), 3.76 (dd, 1H,
J1 ,2 = 3.9 Hz, J2 ,3 = 6.2 Hz, H-200), 3.66 (dd, 1H, J3 ,4 = 8.0 Hz,
00 00
00 00
00 00
J4 ,5 = 3.0 Hz, H-400), 3.50 (t, 1H, J6a ,6b = 9.0 Hz, H-6a0), 3.47–3.41
00 00
0
0
(m, 3H, 2 H-6, H-6b0), 3.28 (s, 3H, OCH3), 1.03 (d, 3H, J5 ,6 = 6.8 Hz,
00 00
H-600 CH3). 13C NMR (125 MHz, CDCl3) d 159.3, 159.2, 158.7, 139.0,
138.6, 138.5, 138.1, 135.7, 130.1, 130.0, 129.6, 129.3, 129.0, 128.4–
127.1 (m), 113.9, 113.8, 98.5, 96.5, 96.5, 76.6, 76.1, 75.8, 75.5, 74.9,
74.7, 73.9, 73.7, 73.1, 73.0, 72.9, 72.5, 72.0, 69.2, 68.6, 68.6, 66.7,
64.9, 58.4, 55.3, 55.2, 48.7, 17.4. ESI HRMS calcd for C71H78O16N4Na
(M+Na): 1265.5305, found 1265.5305.
3.14. Methyl 2,3-di-O-benzyl-6-O-p-methoxybenzyl-
galactopyranosyl-(1?3)-2,4-di-O-benzyl-6-O-p-
methoxybenzyl-a-D-galactopyranoside (14)
a-D-
Disaccharide 13 (0.90 g, 0.85 mmol) was dissolved in a mixture of
freshly distilled DCM and MeOH (4:1; v/v, 15 mL). Then 1.5 M MeO-
Na/MeOH (0.3 mL) was added drop wise. The solution was heated at
45 °C for 10 h then it was neutralized with Amberlite resin IR-120
(H+), filtered and concentrated under reduced pressure. Chromatog-
raphy over silica gel using a gradient eluent (25–35% EtOAc in hex-
3.16. Methyl 2-azido-4-benzylamino-2,4,6-trideoxy-a-D-
galactopyranosyl-(1?4)-2,3-di-O-benzyl-6-O-p-
methoxybenzyl-
O-p-methoxybenzyl-
a
-
D
-galactopyranosyl-(1?3)-2,4-di-O-benzyl-6-
-galactopyranoside (16)
a-D
anes) gave 14 (0.76 g, 94%) as a colourless syrup. [a] +64.1 (c 0.8,
D
CH2Cl2); 1H NMR (600 MHz, CDCl3) d 7.38–7.33 (m, 2H, ArH),
7.33–7.14 (m, 22H, ArH), 7.12 (m, 2H, ArH), 6.88–6.81 (m, 4H,
To a solution of oxazolidinone derivative 15 (0.32 g, 0.26 mmol)
in a mixture of THF and EtOH (2:1, v/v, 12 mL) were added 2 M
LiOH (4 mL), and a catalytic amount of LiI. The mixture was heated
under reflux for 4 days. It was then concentrated to dryness under
reduced pressure. The residue was dissolved in DCM (15 mL) and
washed with an equal volume of water and brine. The extract
was dried over Na2SO4, filtered and the filtrate was concentrated.
Column chromatography on silica gel using hexanes and EtOAc
(3:1) afforded the title compound 16 (0.30 g, 95%) as a colourless
ArH), 5.21 (d, 1H, J1 ,2 = 3.5 Hz, H-10), 4.99 (d, 1H, Jgem = 11.4 Hz,
PhCH2), 4.83 (d, 1H, Jgem = 11.5 Hz, PhCH2), 4.71–4.66 (m, 3H,
PhCH2), 4.64 (s, 1H, H-1), 4.63 (d, 1H, Jgem = 8.7 Hz, PhCH2), 4.53 (d,
1H, Jgem = 11.9 Hz, PhCH2), 4.46 (d, 1H, Jgem = 11.6 Hz, PhCH2), 4.41
(d, 1H, Jgem = 11.5 Hz, PhCH2), 4.33 (m, 3H, PhCH2), 4.24 (t, 1H,
J = 5.2 Hz, H-50), 4.14 (dd, 1H, J2,3 = 10.2 Hz, J3,4 = 2.7 Hz, H-3), 4.01
(m, 2H, H-40, H-20), 3.97 (dd, 1H, J1,2 = 3.6 Hz, J2,3 = 10.2 Hz, H-2),
0
0
3.92 (app s, 1H, H-4), 3.90 (dd, 1H, J2 ,3 = 9.9 Hz, J3 ,4 = 3.2 Hz, H-
syrup. [
a
]
+150.1 (c 0.5, CH2Cl2); 1H NMR (600 MHz, CDCl3) d
D
0
0
0
0
30), 3.84 (t, 1H, J = 6.8 Hz, H-5), 3.80 (s, 3H, OCH2C6H4OCH3), 3.78
7.49–7.05 (m, 31H, ArH), 6.88–6.79 (m, 4H, ArH), 5.22 (d, 1H,
0
0
0
0
0
0
(s, 3H, OCH2C6H4OCH3), 3.60 (dd, 1H, J5 ,6a = 5.4 Hz, J6a ,6b = 10.3 Hz,
J1 ,2 = 3.3 Hz, H-10), 4.95 (d, 1H, Jgem = 11.3 Hz, PhCH2), 4.86–4.79
(m, 2H, H-100, PhCH2), 4.74 (d, 1H, Jgem = 12.5 Hz, PhCH2), 4.70 (d,
1H, Jgem = 11.5 Hz, PhCH2), 4.67 (d, 1H, Jgem = 11.5 Hz, PhCH2),
4.63 (d, 1H, Jgem = 12.3 Hz, PhCH2), 4.56 (d, 1H, J1,2 = 3.6 Hz, H-1),
H-6a0), 3.52 (dd, 1H, J5 ,6b = 5.2 Hz, J6a ,6b = 10.3 Hz, H-6b0), 3.46 (dd,
2H, J = 6.7, J = 1.4 Hz, H-6), 3.30 (s, 3H, OCH3), 2.90 (s, 1H, 40-OH). 13C
NMR (125 MHz, CDCl3) d 139.0, 138.5, 138.3, 138.2, 130.1, 129.4,
129.3, 128.4, 128.3,, 128.1, 128.0, 127.9, 127.7, 127.6, 127.6, 127.2,
113.8, 113.7, 98.4, 96.5, 77.7, 76.0, 75.8, 75.7, 74.8, 74.7, 74.2, 73.1,
73.0, 72.9, 71.8, 69.5, 69.2, 68.6, 68.3, 68.1, 55.3, 55.2, 55.2. ESI HRMS
calcd for C57H64O13Na (M+Na): 979.4239, found 979.4239.
0
0
0
0
4.53 (q, 1H, J5 ,6 = 6.5 Hz, H-500), 4.46 (d, 1H, Jgem = 12.3 Hz, PhCH2),
00 00
4.41 (d, 1H, Jgem = 11.5 Hz, PhCH2), 4.35–4.26 (m, 4H, PhCH2), 4.23
(dd, 1H, J5 ,6a = 5.8 Hz, J5 ,6b = 9.1 Hz, H-50), 4.15 (app s, 1H, H-40),
4.10 (dd, 1H, J2,3 = 9.1 Hz, J3,4 = 5.7 Hz, H-3), 4.03 (d, 1H,
0
0
0
0
0
0
0
0
Jgem = 12.6 Hz, PhCH2), 3.99 (dd, 1H, J1 ,2 = 3.3 Hz, J2 ,3 = 10.3 Hz,
H-20), 3.95–3.85 (m, 4H, H-30, H-4, H-2, H-300), 3.82 (m, 1H, H-5),
3.80 (s, 3H, OCH2C6H4OCH3), 3.78–3.68 (m, 5H, OCH2C6H4OCH3,
3.15. Methyl 2-azido-4-benzylamino-4-N,3-O-carbonyl-2,4,6-
trideoxy-
methoxybenzyl-
O-p-methoxybenzyl-
a
-
D
-galactopyranosyl-(1?4)-2,3-di-O-benzyl-6-O-p-
-galactopyranosyl-(1?3)-2,4-di-O-benzyl-6-
-galactopyranoside (15)
a
-D
PhCH2, H-6a0), 3.50 (dd, 1H, J5 ,6b = 5.7 Hz, J6a ,6b = 9.0 Hz, H-6b0),
3.43 (d, 2H, J = 7.5 Hz, H-6), 3.27 (s, 3H, OCH3), 2.90 (dd, 1H,
0
0
0
0
a-D
J1 ,2 = 3.7 Hz, J2 ,3 = 10.0 Hz, H-200), 2.78 (dd, 1H, J = 4.3, 1.0 Hz,
00 00
00 00
The acceptor 14 (0.44 g, 0.46 mmol) and imidate 26 (0.31 g,
H-400), 1.00 (d, 3H, J5 ,6 = 6.5 Hz, H-600 CH3). 13C NMR (125 MHz,
00 00
0.69 mmol, 1.5 equiv) were combined and concentrated from dry
CDCl3) d 159.2, 140.0, 139.0, 138.6, 138.1, 130.2, 130.0, 129.7,

I. Iynkkaran, D. R. Bundle / Carbohydrate Research 378 (2013) 26–34
33
129.3, 128.7, 128.3, 128.0, 127.9, 127.6, 127.5, 127.4, 127.2, 127.2,
113.8, 113.7, 98.5, 98.3, 96.4, 76.9, 76.2, 76.0, 75.5, 74.9, 74.7, 73.9,
73.8, 73.1, 73.0, 72.5, 72.3, 69.2, 68.9, 68.6, 67.4, 66.5, 66.5, 62.4,
61.5, 55.5, 55.3, 55.2, 55.1, 17.3. ESI HRMS calcd for C70H81N4O15
(M+H): 1217.5693, found 1217.5687.
1H, Jgem = 11.3 Hz, PhCH2), 4.69 (d, 1H, Jgem = 11.5 Hz, PhCH2),
4.54 (s, 2H, PhCH2), 4.40 (d, 1H, Jgem = 11.5 Hz, PhCH2), 4.38–
4.20 (m, 4H, PhCH2, H-500), 4.15 (dd, 1H, J2,3 = 10.2 Hz,
J3,4 = 2.5 Hz, H-3), 4.04 (app t, 1H, J5 ,6 = 6.6 Hz, H-50), 3.98 (dd,
1H, J1,2 = 3.5 Hz, J2,3 = 10.2 Hz, H-2), 3.96–3.70 (m, 6H, H-4, H-
0
0
20, H-30, H-40, H-300, PhCH2) 3.76 (d, 1H, J2 ,3 = 10.3 Hz, H-200),
00 00
0
0
0
0
3.17. Methyl 2-azido-3-benzyl-4-benzylamino-2,4,6-trideoxy-
-galactopyranosyl-(1?4)-2,3-di-O-benzyl-6-O-p-
methoxybenzyl- -galactopyranosyl-(1?3)-2,4-di-O-benzyl-6-
O-p-methoxybenzyl- -galactopyranoside (17)
a
-
3.72–3.66 (m, 2H, H-5, H-6a), 3.60 (dd, 1H, J5 ,6a = 6.9 Hz, J6a , 6b =
D
10.7 Hz, H-6a0), 3.52 (dd, 1H, J5,6b = 4.6 Hz, J6a,6b = 10.8 Hz, H-6b),
0
0
0
0
a
-D
3.47 (dd, 1H, J5 ,6a = 6.8 Hz, J6a ,6b = 10.8 Hz, H-6b0), 3.34 (s, 3H,
00 00
a-
D
OCH3), 3.13 (d, 1H, J = 2.8 Hz, H-400), 1.11 (d, 3H, J5 ,6 = 5.6 Hz,
H-600 CH3). 13C NMR (125 MHz, CDCl3) d 138.5, 138.3, 138.0,
138.0, 136.7, 129.5, 129.0, 128.5, 128.4, 128.3, 128.1, 128.1,
127.7, 127.4, 98.3, 98.2, 96.0, 76.3, 75.6, 75.4, 75.1, 75.0, 74.6,
74.1, 73.0, 72.5, 71.8, 70.7, 70.3, 62.4, 60.7, 59.7, 59.5, 57.2,
55.3, 38.1, 31.2, 29.7, 17.5. ESI HRMS calcd for C61H71N4O13
(M+H): 1067.5012, found 1067.5015.
To a solution of 16 (0.125 g, 0.123 mmol) in dry DMF (4 mL)
at 0 °C was added NaH (dispersion in mineral oil; 60% by mass;
0.006 g, 0.18 mmol, 1.5 equiv) in portions under an atmosphere
of argon. After 1 h, BnBr (26.34 lL, 0.18 mmol, 1.5 equiv) was
slowly added to the above mixture, which was then warmed
to room temperature and stirred for 5 h. The reaction was then
quenched by careful addition of MeOH. The solution was diluted
with DCM (6 mL) and washed with an equal volume of water
and brine. The organic extract was dried over Na2SO4, filtered
and the filtrate was concentrated. Chromatography of the resi-
due on silica gel with hexanes–EtOAc (17:3) as eluent gave 17
3.19. Methyl 2-acetamido-3-benzyl-4-benzylamino-2,4,6-
trideoxy-a-D-galactopyranosyl-(1?4)-2,3-di-O-benzyl-a-D-
galactopyranosyl-(1?3)-2,4-di-O-benzyl-a-D-galactopyranoside
(19)
(0.107 g, 80%). [
a]
D
+47.0 (c 0.3, CH2Cl2); 1H NMR (600 MHz,
Trisaccharide 18 (0.09 g, 0.086 mmol) was dissolved in a solu-
tion of pyridine, water and TEA (10:1:0.3, 11.3 mL). The solution
was saturated with H2S by bubbling gas into the solution for 1 h
at 0 °C, followed by stirring at room temperature for 20 h. Solvent
was evaporated under reduced pressure and the residue was fur-
ther dried in vacuo for 5 h. The crude amine was dissolved in dry
MeOH and acetic anhydride (0.1 mL) was added to the resulting
mixture. After 30 min at room temperature the reaction mixture
was concentrated. The residue was subjected to silica gel column
chromatography using a stepped gradient eluent (DCM–MeOH
CDCl3) d 7.42–6.96 (m, 36H, ArH), 6.88–6.81 (m, 4H, ArH), 5.23
(d, 1H, J1 ,2 = 3.2 Hz, H-10), 4.95 (s, 1H, H-100), 4.93 (s, 1H, PhCH2),
4.80 (d, 1H, Jgem = 11.7 Hz, PhCH2), 4.77 (d, 1H, Jgem = 12.7 Hz,
PhCH2), 4.71 (d, 1H, Jgem = 11.6 Hz, PhCH2), 4.67 (d, 1H,
Jgem = 12.7 Hz, PhCH2), 4.64 (d, 1H, Jgem = 12.3 Hz, PhCH2), 4.56
(d, 1H, J1,2 = 3.5 Hz, H-1), 4.49–4.40 (m, 4H, PhCH2), 4.35 (q,
0
0
1H, J5 ,6 = 6.4 Hz, H-500), 4.33–4.28 (m, 4H, H-40, PhCH2), 4.22
00 00
(dd, 1H, J5 ,6a = 6.0 Hz, J5 ,6b = 6.1 Hz, H-50), 4.18 (s, 1H, PhCH2),
0
0
0
0
4.11 (dd, 1H, J2,3 = 10.1 Hz, J3,4 = 2.5 Hz, H-3), 3.97 (dd, 1H,
0
0
0
0
0
0
J1 ,2 = 3.3 Hz, J2 ,3 = 10.3 Hz, H-2 ), 3.92 (m, 5H, H-2, H-4, H-3 ,
1?3) to obtain the acetamide derivative 19 (0.067 g, 72%). [a]
D
H-300, PhCH2), 3.84–3.74 (m, 9H, H-5, H-6a0, PhCH2,
+89.4 (c 0.1, CH2Cl2); 1H NMR (600 MHz, CDCl3) d 7.41–7.07 (m,
30H, ArH), 5.13 (d, 1H, J1 ,2 = 3.3 Hz, H-10), 4.98 (d, 1H,
00 00
00 00
0
0
2 ꢂ OCH2C6H4OCH3), 3.56 (dd, 1H, J1 ,2 = 3.7 Hz, J2 ,3 = 10.8 Hz,
H-200), 3.51 (dd, 1H, J5 ,6b = 5.8 Hz, J6a ,6b = 9.1 Hz, H-6b0), 3.44
(dd, 2H, J = 6.7, 1.8 Hz, H-6), 3.28 (s, 3H, OCH3), 3.01 (d, 1H,
Jgem = 12.8 Hz, PhCH2), 4.89 (d, 1H, J1 ,2 = 3.0 Hz, H-100), 4.87 (d,
0
0
0
0
00 00
1H, Jgem = 11.5 Hz, PhCH2), 4.79 (d, 1H, Jgem = 12.5 Hz, PhCH2),
4.74 (d, 1H, J1,2 = 3.4 Hz, H-1), 4.70 (d, 1H, Jgem = 11.5 Hz, PhCH2),
4.67 (d, 1H, Jgem = 12.5 Hz, PhCH2), 4.53 (app s, 2H, PhCH2), 4.39
J = 3.4 Hz, H-400), 1.06 (d, 3H, J5 ,6 = 6.6 Hz, H-600 CH3). 13C NMR
00 00
(125 MHz, CDCl3) d 159.2, 139.0, 138.6, 138.3, 137.6, 130.2,
130.0, 129.6, 129.3, 128.5, 128.4, 128.3, 128.2, 128.1, 128.0,
127.9, 127.8, 127.6, 127.4, 127.3, 127.2, 127.1, 113.8, 113.7,
98.6, 98.4, 96.5, 77.0, 76.6, 76.1, 76.1, 75.5, 74.9, 74.7, 73.8,
73.6, 73.2, 73.0, 72.6, 71.1, 69.2, 68.6, 67.0, 66.7, 59.8, 57.6,
55.3, 55.2, 55.2, 55.0, 17.8. ESI HRMS calcd for C77H87N4O15
(M+H): 1307.6162, found 1307.6161.
(m, 3H, PhCH2, H-200, H-4), 4.26 (q, 1H, J5 ,6 = 6.4 Hz, H-500), 4.10
00 00
(dd, 1H, J2,3 = 10.2 Hz, J3,4 = 2.8 Hz, H-3), 4.02 (app t, 1H,
J = 6.5 Hz, H-50), 3.98 (dd, 1H, J1,2 = 3.5 Hz, J2,3 = 10.3 Hz, H-2),
3.91–3.82 (m, 5H, H-20, H-30, H-40, PhCH2), 3.73–3.64 (m, 3H, H-6,
PhCH2), 3.56 (dd, 1H, J2 ,3 = 10.4 Hz, J3 ,4 = 2.9 Hz, H-300), 3.49 (d,
00 00
00 00
1H, J = 9.7 Hz, H-5), 3.37–3.29 (m, 4H, OCH3, H-6a0), 3.20 (dd, 1H,
J5 ,6a = 6.4 Hz, J6a ,6b = 10.7 Hz, H-6b0), 3.01 (app s, 1H, H-400), 1.90
0
0
0
0
(s, 3H, COCH3), 1.17 (d, 3H, J5 ,6 = 5.6 Hz, H-600 CH3). 13C NMR
00 00
3.18. Methyl 2-azido-3-benzyl-4-benzylamino-2,4,6-trideoxy-
a-
D
-galactopyranosyl-(1?4)-2,3-di-O-benzyl-
a
-
D
-
(125 MHz, CDCl3) d 171.8, 138.5, 138.2, 138.1, 138.0, 128.7,
128.5, 128.4, 128.3, 128.3, 128.2, 128.1, 128.0, 127.9, 127.6,
127.6, 98.2, 96.8, 76.2, 76.1, 75.8, 75.1, 74.6, 74.3, 73.0, 72.2,
70.9, 70.3, 62.3, 60.6, 59.5, 55.3, 53.6, 49.1, 38.1, 31.2, 29.7, 23.3,
17.5. ESI HRMS calcd for C63H75N2O14Na (M+Na): 1083.5213, found
1083.5211.
galactopyranosyl-(1?3)-2,4-di-O-benzyl-a-D-galactopyranoside
(18)
Trisaccharide 17 (0.125 g, 0.0.096 mmol) was dissolved in
DCM (5 mL) stirring at room temperature. To the resulting solu-
tion 5% TFA (0.25 mL) was added drop wise and the reaction was
monitored by TLC (5% MeOH in DCM). After 20 min the reaction
was quenched by adding saturated NaHCO3 solution (10 mL). The
reaction mixture was diluted with DCM (10 mL), and the DCM
solution was washed with water and brine. The organic phase
was dried over MgSO4, filtered and the filtrate was concentrated
under reduced pressure. Purification of the residue via column
chromatography (3% MeOH in DCM) gave the titled compound
3.20. Methyl 2-acetamido-3-benzyl-4-benzylideneamino-2,4,6-
trideoxy-a-D-galactopyranosyl-(1?4)-2,3-di-O-benzyl-a-D-
galactopyranosiduronate-(1?3)-2,4-di-O-benzyl-
a-
D-
galactopyranosiduronate (20)
To a stirred solution of 6,60 diol 19 (0.015 g, 13.8
lmol) in ace-
tone (1 mL) at 0 °C was added 5% NaHCO3 aqueous solution
(0.5 mL) followed by KBr (0.003 g, 0.03 mmol, 2 equiv) and TEMPO
(0.003 g, 0.004 mmol, 3 equiv) at 0 °C. After 10 min, NaOCl
(0.027 mL, 0.055 mmol, 4 equiv) was slowly added to the above
mixture at the same temperature and it was stirred for further
10 min. The solution was concentrated under reduced pressure.
18 (0.08 g, 75%) as a colourless syrup. [a] +91.5 (c 0.2, CH2Cl2);
D
1H NMR (600 MHz, CDCl3) d 7.40–7.09 (m, 30H, ArH), 5.19 (d,
1H, J1 ,2 = 3.3 Hz, H-10), 5.00 (d, 1H, Jgem = 11.5 Hz, PhCH2), 4.94
0
0
(d, 1H, J1 ,2 = 3.1 Hz, H-100), 4.80 (d, 1H, Jgem = 11.5 Hz, PhCH2),
00 00
4.75 (d, 1H, Jgem = 12.8 Hz, PhCH2), 4.74 (s, 1H, H-1), 4.73 (d,

34
I. Iynkkaran, D. R. Bundle / Carbohydrate Research 378 (2013) 26–34
The crude product was carried to the next step without purifica-
tion. A small portion of crude 20 was purified by Sephadex G-10
column using H2O–NH4OH as eluent monitored by Pharmacia UV
detector. Subsequent lyophilization of the purified fractions affor-
ded 20 as a white solid. 1H NMR of the NHþ4 salt form (600 MHz,
D2O) d 7.49–7.27 (m, 27H, ArH, PhCH2), 7.19 (m, 2H, ArH), 5.50
References
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2. (a) Duan, J. Y.; Avci, F. Y.; Kasper, D. L. Proc. Natl. Acad. Sci U.S.A. 2008, 105,
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(d, 1H, J1 ,2 = 3.4 Hz, H-10), 4.93 (d, 1H, J1 ,2 = 3.4 Hz, H-100), 4.89
(d, 1H, Jgem = 10.7 Hz, PhCH2), 4.81–4.63 (m, 7H, H-1, H-5, PhCH2),
4.58–4.49 (m, 4H, H-4, H-40, H-50, PhCH2), 4.45 (m, 3H, PhCH2),
0
0
00 00
4.22–4.17 (m, 3H, H-3, H-500, PhCH2), 4.15 (dd, 1H, J1 ,2 = 3.7 Hz,
00 00
J2 ,3 = 10.8 Hz, H-200), 3.93 (dd, 1H, J1 ,2 = 3.6 Hz, J2 ,3 = 11.3 Hz, H-
00 00
0
0
0
0
20) 3.88 (dd, 1H, J1,2 = 3.7 Hz, J2,3 = 10.3 Hz, H-2), 3.81 (dd, 1H,
J2 ,3 = 10.5 Hz, J3 ,4 = 2.4 Hz, H-30), 3.63 (dd, 1H, J2 ,3 = 10.9 Hz,
0
0
0
0
00 00
J3 ,4 = 3.7 Hz, H-300), 3.32 (s, 3H, OCH3), 3.11 (app s, 1H, H-400),
00 00
6. Iynkkaran, I.; Bundle, D. R. Carbohydr. Res. 2010, 345, 2323–2327.
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2039–2048.
2.04 (s, 3H, COCH3), 0.99 (d, 3H, J5 ,6 = 7.2 Hz, H-600 CH3). ESI HRMS
00 00
calcd for C63H66O16N2Na3 (M+Na): 1175.4100, found 1175.4100.
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525–532; Arias-Perez, M. S.; Lopez, M. S.; Santos, M. J. J. Chem. Soc., Perkin Trans.
2 2002, 1549–1552.
Supplementary data
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Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.carres.2013.05.
005.