Studies on the synthesis of Lewis-y oligosaccharides

Article abstract of DOI:10.1016/j.carres.2011.07.002

Lewis-y histo-blood group oligosaccharides are tumour-associated antigens prevalent in several different types of cancer, and they may also be secondary ligands for bacterial toxins from Escherichia coli and Vibrio cholerae. The key step in the synthesis

Full text of DOI:10.1016/j.carres.2011.07.002

Carbohydrate Research 346 (2011) 2113–2120
Contents lists available at ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
Studies on the synthesis of Lewis-y oligosaccharides
⇑
Pintu K. Mandal, W. Bruce Turnbull
School of Chemistry and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
Lewis-y histo-blood group oligosaccharides are tumour-associated antigens prevalent in several different
types of cancer, and they may also be secondary ligands for bacterial toxins from Escherichia coli and
Vibrio cholerae. The key step in the synthesis of these sterically congested oligosaccharides involves
difucosylation of partially protected lactosamine derivatives. Existing methods require either prolonged
reaction times or elaborate glycosyl donors to ensure high stereoselectivity. Herein we report an
optimised procedure for using a simple thioglycoside donor that leads to the desired products in high
yield and excellent stereoselectivity. It is found that initial glycosylation of the 30-hydroxy group of lac-
tosamine derivatives in dichloromethane solution can inhibit subsequent glycosylation at the 2-position;
however, reaction in toluene solution leads to Lewis-y oligosaccharides in high yield.
Received 28 May 2011
Received in revised form 4 July 2011
Accepted 6 July 2011
Available online 18 July 2011
Keywords:
Oligosaccharide synthesis
Fucosylation
Blood group antigen
Lewis-y
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
stereoselectivity if all of the fucosyl hydroxy groups are benzyl-
protected.18,19 Flowers was the first to observe that introducing
It is now half a century since the molecular features that distin-
guish blood groups were attributed to the histo-blood group oligo-
saccharides.1 More recently, it has become apparent that specific
members of this family of oligosaccharides can provide diagnostic
and prognostic markers for a variety of diseases.2,3 One such exam-
ple is the type II Lewis-y oligosaccharide (1; Fig. 1) which is a tu-
mour-associated antigen prevalent in several different types of
cancer.4 Furthermore, blood group A oligosaccharides 2 based on
the Lewis-y core tetrasaccharide have been identified as ligands
for the B-subunit of E. coli heat-labile toxin (LTB)5 and also a hybrid
protein derived from LTB and the analogous B-subunit of cholera
toxin (CTB).6 This discovery could provide insight to the blood
group dependence of diarrhoeal diseases, in which it has been ob-
served that patients with blood group O are more susceptible to
certain strains of cholera than those in blood groups A or B.7,8
Therefore, as part of our on-going studies into the thermody-
namics of bacterial toxin–ligand interactions,9–11 we sought an
efficient synthetic route to oligosaccharides with the Lewis-y core
structure. The key synthetic challenge is the difucosylaton reaction
leading to the sterically congested tetrasaccharide. Not surpris-
ingly, this important structure has attracted widespread attention
from synthetic chemists who favour a range of glycosylation meth-
ods. While Lemieux’s bromide anomerisation protocol provides
excellent stereoselectivity,12–17 it typically demands large excesses
of glycosyl donor14 and/or very prolonged reaction times.16,17
Alternative, more reactive glycosyl donors often show modest
ester groups at the 3- and 4-positions of a fucosyl donor could
improve stereoselectivity relative to a perbenzylated compound.20
Therefore, virtually all modern donors for this type of difucosyla-
tion reaction (e.g., fucosyl fluorides,21 phosphates,18 trichloroace-
timidates22 and thioglycosides19) incorporate ester groups at
either the 4-, or 3- and 4-positions. Although this strategy leads
to high stereoselectivity, it also significantly increases the length
of synthesis to prepare the fucosyl donors. Our aim was to employ
thioglycoside donors throughout the synthesis on account of their
high stability prior to activation.23 Therefore, we wondered if it
would be possible to optimise the reaction conditions to allow a
simple ethyl thioglycoside to provide rapid, efficient and highly
stereoselective glycosylation without proceeding through the less
reactive fucosyl bromide.24
2. Results and discussion
Two model disaccharide acceptors were synthesised as outlined
in Scheme 1. We chose to use a benzyloxycarbonyl-protected pro-
pyl amine as the aglycone as it would be suitable for subsequent
conjugation of the oligosaccharides to other molecules for bio-
chemical applications. Thus, glucosamine derivative 325 was gly-
cosylated with thioglycoside donors 426 and 827 under standard
conditions to provide disaccharides 5 and 9, respectively, in excel-
lent yield. Disaccharide 5 was then deacetylated to give triol 6 be-
fore selective benzoylation of the reactive 30-hydroxy group to
yield diol acceptor 7. Analogous deacetylation of disaccharide 9
was followed by reprotection of the 30,40-positions with an isopro-
pylidene acetal to give diol 10.
⇑
Corresponding author. Tel.: +44 (0) 113 343 7438; fax: +44 (0) 113 343 6565.
E-mail address: w.b.turnbull@leeds.ac.uk (W.B. Turnbull).
0008-6215/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2011.07.002

2114
P. K. Mandal, W. B. Turnbull / Carbohydrate Research 346 (2011) 2113–2120
trast, much higher yields of tri- and tetrasaccharides were obtained
OH
HO
when toluene was employed as the solvent. Reaction of acceptor 7
with 1.2 equiv of fucosyl donor 11 gave the 20-fucosyl trisaccharide
13 as the major product (65% yield), but also a small amount of tet-
rasaccharide 12. When the concentration of glycosyl donor was in-
creased to 2.4 equiv, the desired tetrasaccharide was obtained in
69% yield, with trisaccharide 13 providing most of the mass bal-
ance. No evidence for the formation of b-fucosides could be seen
upon inspecting the 1H NMR spectra of the products. Acceptor 10
(Table 2) gave even greater improvements in the yields of tetrasac-
charide 14 and trisaccharide 15 when the glycosylation reactions
were performed in toluene, leading to an impressive 85% yield of
the tetrasaccharide 14 when 2.4 equiv of donor was used. The im-
proved yields in toluene may be a consequence of the lower polar-
ity of the solvent which will affect the formation and distribution
of positively charged species present in the mixture (e.g.,
iodosulfonium vs oxacarbenium ions). However, the variation in
yields observed when using different acceptors indicates that the
effect of solvation on the acceptor alcohol may also be significant;
for example, toluene may stabilise a conformation of the acceptor
in which the less reactive 2-OH is more accessible for reaction with
the glycosyl donor. The high stereoselectivity of these reactions
probably arises from the sterically hindered nature of the acceptor.
Ley and co-workers have noted previously that fucosylation of
the more reactive 20-hydroxy group may inhibit further fucosyla-
tion at the 3-position.19 We were thus led to consider if further
improvements to the yield of the tetrasaccharide could be achieved
via a two step glycosylation procedure in which the 3-OH would be
glycosylated prior to unmasking the 20-position. Therefore, analo-
gous trisaccharide acceptors 18 and 20 were prepared as outlined
in Scheme 2. Disaccharide acceptors 5 and 9 were fucosylated at
the 3-position of the glucosamine ring to give fully protected
trisaccharides 16 and 19 in 69% and 73% yield, respectively. These
compounds were then deacetylated and reprotected in a manner
HO
O
OH
O
NHAc
O
HO
HO
O
O
O
1
O
OH
O
OH
OH
HO
OH
HO
OH
O
HO
HO
O
OH
O
R
HO
HO
O
AcHN
O
O
O
O
O
OH
O
OH
OH
HO
2
R = NHAc, OH
Figure 1. Lewis-y oligosaccharides.
Initial attempts to glycosylate acceptor 7 in dichloromethane
with 1.2 equiv of ethyl thiofucoside 1128 gave only a low yield of
the 20-fucosyl trisaccharide 13 (Table 1). Doubling the amount of
glycosyl donor had little impact on the reaction which failed to
give any of the desired tetrasaccharide 12. Thin layer chromatogra-
phy indicated that the glycosyl donor had been fully consumed
within 5 min of adding trifluoromethane sulfonic acid to the mix-
ture of donor, acceptor, N-iodosuccinimide and molecular sieves.
Similar results were obtained for acceptor 10 when glycosylated
under the same conditions in dichloromethane (Table 2). In con-
NPhth
HO
O
HO
O
OTBDPS
NHCbz
Ph
3
O
OBn
O
AcO
AcO
O
a
d
O
SEt
SEt
AcO
OAc
OAc
4
8
Ph
O
OBn
O
NPhth
O
NPhth
O
O
AcO
AcO
O
HO
HO
O
O
RO
O
O
OR
5 R = Ac
OAc
OTBDPS
NHCbz
OTBDPS
NHCbz
b
9
6
R = H
c
e
Ph
O
OBn
O
O
NPhth
O
O
O
NPhth
O
HO
HO
O
O
O
BzO
O
O
OH
OH
OTBDPS
NHCbz
OTBDPS
NHCbz
7
10
Scheme 1. Synthesis of disaccharide acceptors 7 and 10. Reagents and conditions: (a) NIS, TfOH, CH2Cl2, ꢀ40 °C, 30 min, 90%; (b) NaOMe, MeOH, 100%; (c) BzCl, CH2Cl2,
C5H5N, 84%; (d) NIS, TfOH, CH2Cl2, ꢀ40 °C, 30 min, 92%; (e) (i) NaOMe, MeOH; (ii) 2,2-dimethoxypropane, CSA, DMF, 82% over two steps.

P. K. Mandal, W. B. Turnbull / Carbohydrate Research 346 (2011) 2113–2120
2115
Table 1
Fucosylation of acceptors 7 and 18a
Ph
Fuc =
O
O
NPhth
O
O
SEt
OBn
O
R2
O
O
O
OBn
O
BzO
O
OBn
BnO
OBn
BnO
11
R1
OTBDPS
NHCbz
Acceptor
R1
Solvent
Equiv donor 11
Yieldb
R2
12 R1 = Fuc; R2 = Fuc
13 R1 = Fuc; R2 = H
7
7
7
7
18
18
H
H
H
H
H
H
H
H
H
H
Fuc
Fuc
CH2Cl2
CH2Cl2
Toluene
Toluene
CH2Cl2
Toluene
1.2
2.4
1.2
2.4
1.2
1.2
0
0
11
69
41
69
25
39
65
25
nac
nac
a
b
c
Reagents and conditions: donor 11, NIS (1.44 or 2.88 equiv), TfOH, 4 Å molecular sieves, ꢀ30 °C, 2 h.
Isolated yields.
Not applicable.
Table 2
Fucosylation of acceptors 10 and 20a
Fuc =
OBn
O
O
NPhth
R2
O
SEt
OBn
O
O
O
OBn
O
O
O
OBn
BnO
OBn
BnO
R1
O
11
OTBDPS
NHCbz
Acceptor
R1
Solvent
Equiv donor 11
Yieldb
R2
14 R1 = Fuc; R2 = Fuc
15 R1 = Fuc; R2 = H
10
10
10
10
20
20
H
H
H
H
H
H
H
H
H
H
Fuc
Fuc
CH2Cl2
CH2Cl2
Toluene
Toluene
CH2Cl2
Toluene
1.2
2.4
1.2
2.4
1.2
1.2
0
0
10
85
47
71
30
33
83
15
nac
nac
a
b
c
Reagents and conditions: donor 11, NIS (1.44 or 2.88 equiv), TfOH, 4 Å molecular sieves, ꢀ30 °C, 2 h.
Isolated yields.
Not applicable.
analogous to the synthesis of disaccharide acceptors 7 and 10, to
yield the benzoate 18 and isopropylidene acetal 20.
the converse may be true in toluene. Nevertheless, a one step
difucosylation reaction in toluene was found to be superior to
a two step strategy for the production of Lewis-y tetrasaccha-
rides, or to any strategy employing dichloromethane as solvent.
This optimised method provides efficient access to a range of
protected tri- and tetrasaccharides that are suitable for further
elaboration to synthesise blood group A and B derivatives of
the Lewis-y core structure. The synthesis of such compounds
and their evaluation as ligands for bacterial toxins will be
described elsewhere.
Glycosylation of the trisaccharide acceptors 18 and 20 in dichlo-
romethane yielded tetrasaccharide products 12 and 14, respec-
tively, in moderate yields (Tables 1 and 2). Nevertheless the
ability to access these products in dichloromethane solution is a
marked improvement on the previous experiments employing
disaccharide acceptors 7 and 10. Therefore, these results support
the Ley hypothesis19 that fucosylation at the 20-position signifi-
cantly inhibits further glycosylation at the 3-position of the gluco-
samine residue. Once again, higher yields of the tetrasaccharide
products could be achieved by performing the glycosylation reac-
tions in toluene. However, in these cases, no improvements in yield
were seen relative to the one step difucosylation reaction in tolu-
ene. Indeed, the isopropylidene-protected trisaccharide acceptor
20 gave a reduced yield (71%) relative to difucosylation of analo-
gous disaccharide acceptor 10 (85%). Therefore, in toluene solution,
it may actually be advantageous to glycosylate the 30-position be-
fore glycosylation of the 2-OH group.
3. Experimental
3.1. General methods
All solvents were dried prior to use, according to standard
methods. All solvents used for flash chromatography were of GPR
grade, except hexane and ethyl acetate, when HPLC grade was
used. All concentrations were performed in vacuo, unless other-
wise stated. All reactions were performed in oven dried glassware
under a N2(g) atmosphere, unless otherwise stated. Analytical TLC
was performed on Silica Gel 60-F254 (Merck) with detection by
fluorescence and/or charring following immersion in a 5% H2SO4/
MeOH solution, unless otherwise stated. Optical rotations were
measured at the sodium D-line with an Optical Activity AA-1000
In conclusion, while dichloromethane is typically the solvent
of choice when working with thioglycoside donors, switching
to toluene has a very dramatic effect on the yields of these gly-
cosylation reactions. In dichloromethane solution, initial glyco-
sylation of the 30-hydroxy group of a lactosamine derivative
can inhibit subsequent glycosylation at the 2-position; however,

2116
P. K. Mandal, W. B. Turnbull / Carbohydrate Research 346 (2011) 2113–2120
5
9
a
d
OBn
N
OBn
BnO
BnO
Ph
BnO
BnO
O
O
O
OBn
O
NPhth
O
AcO
AcO
O
O
O
O
O
O
O
AcO
O
O
OAc
OAc
OTBDPS
NHCbz
OTBDPS
NHCbz
19
16 R = Ac
b
17
R = H
c
e
OBn
OBn
BnO
BnO
Ph
BnO
BnO
O
O
O
OBn
O
O
NPhth
O
O
NPhth
O
O
O
O
O
O
BzO
O
O
O
OH
OH
OTBDPS
NHCbz
OTBDPS
NHCbz
18
20
Scheme 2. Synthesis of trisaccharide acceptors 18 and 20. Reagents and conditions: (a) donor 11, NIS, TfOH, toluene, ꢀ15 °C, 7 h, 69%; (b) NaOMe, MeOH, 100%; (c) BzCl,
CH2Cl2, C5H5N, 74%; (d) donor 11, NIS, TfOH, toluene, ꢀ15 °C, 7 h, 73%; (e) (i) NaOMe, MeOH; (ii) 2,2-dimethoxypropane, CSA, DMF, 77% over two steps.
polarimeter. [
a
]
values are given in units of 10ꢀ1 deg cm2 gꢀ1
.
OCH2R, H-6abA, H-3A, H-4A), 3.56–3.49 (m, 2H, H-5B, H-5A), 3.11–
3.10 (m, 2H, NCH2), 2.07 (s, 3H, COCH3), 1.85 (s, 3H, COCH3),
1.66–1.60 (m, 2H, –CH2–), 1.09 (s, 9H, SiC(CH3)3); 13C NMR
(75 MHz, CDCl3): d 170.6 (COCH3), 169.0 (COCH3), 168.5, 168.1
(CO Phth), 156.3 (COOCH2Ph), 137.0–123.0 (Ar-C), 101.2 (PhCH),
101.0 (C-1B), 98.0 (C-1A), 80.5 (C-3A), 74.8 (C-5B), 73.2 (C-5A),
71.8 (C-3B), 69.5 (C-4B), 68.7 (C-2B), 68.4 (–OCH2R), 67.1 (C-6B),
66.8 (C-4A), 66.4 (COOCH2Ph), 61.8 (C-6A), 56.3 (C-2A), 38.4
(NCH2), 29.5 (–CH2–), 26.9 (SiC(CH3)3), 20.9 (COCH3), 20.5 (COCH3),
19.5 (SiC(CH3)3); ESI-MS: C58H64N2NaO16Si requires m/z
1095.3917; found: m/z 1095.3955 [M+Na]+.
D
Infra-red spectra were recorded on a Perkins–Elmer Spectrum
One FT-IR spectrometer. 1H NMR spectra were acquired at
500 MHz on a Bruker Avance 500 instrument or at 300 MHz on a
Bruker Avance 300 instrument. 13C NMR spectra were acquired
at 75 MHz on a Bruker Avance 300 instrument. Chemical shifts
are given in parts per million downfield from tetramethylsilane.
Electrospray (ES+) ionisation mass spectra were obtained on a Bru-
ker HCT-Ultra mass spectrometer, and high resolution ES+ were
performed on a Bruker Daltonics MicroTOF mass spectrometer.
3.2. 3-(Benzyloxycarbonylamino)propyl 6-O-t-butyldiphenyl-
si lyl-2-deoxy-4-O-(2,3-di-O-acetyl-4,6-O-benzylidene-b-
D
-ga-
3.3. 3-(Benzyloxycarbonylamino)propyl 4-O-(4,6-O-benzyli-
lac topyranosyl)-2-phthalimido-b- -glucopyranoside (5)
D
dene -b-
2-phthalimido-b-
D
-galactopyranosyl)-6-O-t-butyldiphenylsilyl-2-deoxy-
-glucopyranoside (6)
D
To
butyldiphenylsilyl-2-deoxy-2-phthalimido-b-
(5.0 g, 6.77 mmol) and ethyl 2,3-di-O-acetyl-4,6-O-benzylidene-
1-thio-b-
-galactopyranoside 426 (3.2 g, 8.13 mmol) in dry CH2Cl2
(50 mL) was added MS-4 Å (3 g) and the reaction mixture was al-
lowed to stir under N2 at room temperature for 1 h. N-Iodosuccin-
imide (NIS; 2.2 g, 9.7 mmol) was added to the reaction mixture and
a
solution of 3-(benzyloxycarbonylamino)propyl 6-O-t-
D
-glucopyranoside 325
A solution of disaccharide 5 (2.5 g, 2.3 mmol) in 0.1 M MeONa/
MeOH (90 mL) was allowed to stir at room temperature for
30 min before neutralisation with Amberlite-IR 120 (H+) resin.
The reaction mixture was filtered and evaporated to dryness to
give the crude product which was passed through a short column
of SiO2 using toluene–EtOAc (1:1) as eluant to give triol 6 (2.3 g,
D
which was then cooled to ꢀ40 °C before adding TfOH (50
l
L) and
quantitative); ½a D25
ꢁ
ꢀ37 (c 1.5, CHCl3); IR: 3430, 2932, 1712,
the reaction mixture was allowed to stir at same temperature for
30 min. When TLC showed complete consumption of the acceptor
3, the reaction mixture was diluted with CH2Cl2 (100 mL) and fil-
tered through a CeliteÒ bed. The organic layer was washed with
5% aq Na2S2O3, satd NaHCO3 and water, dried (Na2SO4) and evap-
orated to dryness. The crude product was purified over SiO2 using
hexane–EtOAc (4.5:1) as eluent to furnish disaccharide 5 (6.60 g,
1641, 1391, 1159, 1040, 753 cmꢀ1 1H NMR (500 MHz, CDCl3): d
;
7.78–7.66 (m, 7H, Ar-H), 7.43–7.25 (m, 17H, Ar-H), 5.45 (s, 1H,
PhCH), 5.21 (d, J = 8.6 Hz, 1H, H-1A), 5.01–4.97 (m, 2H, COOCH2Ph),
4.95–4.90 (m, 1H, NHCbz), 4.48 (d, J = 8.1 Hz, 1H, H-1B), 4.42 (dd,
J = 9.0 , 1.7 Hz, 1H, H-2A), 4.24–4.16 (m, 3H, H-4B, H-5A, H-5B),
4.13–4.09 (m, 2H, H-6abB), 3.96 (dd, J = 10, 3.2 Hz, 2H, H-3B, H-
3A), 3.82 (m, 2H, OCH2R), 3.71–3.67 (m, 1H, H-2B), 3.58–3.53 (m,
2H, H-6abA), 3.42 (br s, 1H, H-4A), 3.10–3.09 (m, 2H, NCH2), 1.69–
1.66 (m, 2H, –CH2–), 1.07 (s, 9H, SiC(CH3)3); 13C NMR (75 MHz,
CDCl3): d 168.5, 168.1 (CO Phth), 156.3 (COOCH2Ph), 137.0–123.0
(Ar-C), 103.6 (C-1B), 101.4 (PhCH), 98.1 (C-1A), 81.8 (C-4A), 75.2
(C-5A), 74.9 (C-4B), 72.8 (C-2B), 71.5 (C-3B), 69.8 (C-3A), 68.7
(OCH2R), 67.2 (C-6B), 66.9 (C-5B), 66.5 (COOCH2Ph), 62.8 (C-6A),
56.3 (C-2A), 38.4 (NCH2), 29.5 (–CH2–), 26.9 (SiC(CH3)3, 19.4
90%); yellow oil; ½a D25
ꢁ
+45 (c 1.5, CHCl3); IR: 3434, 2932, 1751,
1711, 1640, 1389, 1218, 1042, 753, 668 cmꢀ1
;
1H NMR (500 MHz,
CDCl3): d 7.78–7.27 (m, 24H, Ar-H), 5.44 (s, 1H, PhCH), 5.40 (dd,
J = 8.1, 2.5, 1H, H-2B), 5.25 (d, J = 8.5 Hz, 1H, H-1A), 4.99–4.97 (m,
2H, COOCH2Ph), 4.92 (dd, J = 10.5, 3.6 Hz, 1H, H-3B), 4.74 (d,
J = 8.0 Hz, 1H, H-1B), 4.46–4.44 (m, 1H, H-4B), 4.34–4.29 (m, 2H,
H-6abB), 4.20 (dd, J = 8.7, 2.1 Hz, 1H, H-2A), 4.00–3.90 (m, 6H,

P. K. Mandal, W. B. Turnbull / Carbohydrate Research 346 (2011) 2113–2120
2117
(SiC(CH3)3); ESI-MS: C54H60N2NaO14Si requires m/z 1011.3706;
found: m/z 1011.3737 [M+Na]+.
SiC(CH3)3); 13C NMR (75 MHz, CDCl3): d 170.6 (COCH3), 170.5
(COCH3), 170.0 (COCH3), 168.9, 168.3 (CO Phth), 156.7
(COOCH2Ph), 137.7–123.5 (Ar-C), 101.6 (C-1B), 98.4 (C-1A), 81.5
(C-4A), 75.2 (C-5A), 73.9 (PhCH2), 72.7 (C-3B), 71.4 (C-5B), 70.1 (C-
2B), 69.4 (C-4B), 67.6 (C-3A) 67.5 (2 C, OCH2R, C-6B), 66.8
(COOCH2Ph), 62.4 (C-6A), 56.6 (C-2A), 38.8 (NCH2), 29.8 (–CH2–),
27.3 (SiC(CH3)3, 21.1 (COCH3), 21.0 (COCH3), 20.7 (COCH3), 19.8
(SiC(CH3)3); ESI-MS: C60H68N2NaO17Si requires m/z 1140.1131;
found: m/z 1140.1152 [M+Na]+.
3.4. 3-(Benzyloxycarbonylamino)propyl 4-O-(3-O-benzoyl-4,6-
O-benzylidene-b-
D-galactopyranosyl)-6-O-t-butyldiphenylsilyl-
2-deoxy-2-phthalimido-b-
D-glucopyranoside (7)
A solution of triol 6 (5.0 g, 5.1 mmol) and pyridine (532
6.07 mmol) in dry CH2Cl2 (50 mL) was cooled to ꢀ40 °C allowed
to stir. Benzoyl chloride (502 L, 5.56 mmol) was added and the
lL,
l
reaction mixture was allowed to stir at same temperature for 1 h.
When TLC showed complete consumption of the starting material,
the reaction mixture was diluted with CH2Cl2 (100 mL) and
washed with 1 M HCl, satd NaHCO3 and water. The solution was
then dried (Na2SO4) and evaporated. The crude product was puri-
fied over SiO2 using hexane–EtOAc (4.5:1) as eluent to furnish pure
3.6. 3-(Benzyloxycarbonylamino)propyl 4-O-(6-O-benzyl-3,4-O-
isopropylidene-b-
D-galactopyranosyl)-6-O-t-butyldiphenylsilyl-
2-deoxy-2-phthalimido-b-
D
-glucopyranoside (10)
A solution of disaccharide 9 (2.50 g, 2.24 mmol) in 0.1 M MeO-
Na/MeOH (150 mL) was allowed to stir at room temperature for
30 min. The reaction mixture was neutralised with Amberlite-IR
120 (H+) resin, filtered, and concentrated. To a solution of the
deacetylated product in anhydrous DMF (30 mL) were added 2,2-
dimethoxypropane (0.4 mL, 3.3 mmol) and camphorsulfonic acid
(0.5 g), and the reaction mixture was allowed to stir at room tem-
perature for 12 h. The reaction mixture was neutralized with Et3N
(1.5 mL) and evaporated to dryness. The crude mass was purified
over SiO2 using hexane–EtOAc (5:1) as eluant to furnish disaccha-
benzoate 7 (4.7 g, 84%); ½a D25
ꢁ
ꢀ25 (c 1.5, CHCl3); IR: 3428, 2931,
1715, 1452, 1390, 1276, 1113, 1045, 822, 756, 709 cmꢀ1
;
1H
NMR (500 MHz, CDCl3): d 8.15–8.12 (m, 2H, Ar-H), 7.87–7.63 (m,
9H, Ar-H), 7.53–7.34 (m, 18H, Ar-H), 5.50 (s, 1H, PhCH), 5.27 (d,
J = 8.6 Hz, 1H, H-1A), 5.08 (dd, J = 10.3, 3.6 Hz, 1H, H-3B), 5.04 (br
s, 2H, OCH2Ph), 4.94–4.92 (m, 1H, NHCbz), 4.65 (d, J = 8.6 Hz, 1H,
H-1B), 4.51–4.46 (m, 2H, H-4B, H-2B), 4.34–4.31 (m, 1H, H-6aB),
4.25 (dd, J = 8.8, 2.1 Hz, 1H, H-2A), 4.17–4.11 (m, 2H, H-6bB. H-
3A), 4.08–4.05 (m, 2H, H-6abA), 3.90–3.84 (m, 2H, H-5A, H-5B),
3.66–3.62 (m, 2H, OCH2R), 3.56–3.52 (m, 1H, H-4A), 3.19–3.15
(m, 2H, NCH2), 1.80–1.71 (m, 2H, –CH2–), 1.14 (s, 9H, SiC(CH3)3);
13C NMR (75 MHz, CDCl3): d 168.3, 168.1 (CO Phth), 166.8 (COPh),
156.5 (COOCH2Ph), 137.7–126.3 (Ar-C), 104.1 (C-1B), 100.9 (PhCH),
98.3 (C-1A), 82.1 (C-5A), 75.5 (C-4A), 74.5 (C-3B), 73.6 (C-2B), 70.2
(C-3A), 69.1 (C-4B), 69.0 (OCH2R), 67.5 (C-6B), 67.2 (C-5B), 66.8
(COOCH2Ph), 63.4 (C-6A), 56.5 (C-2A), 38.7 (NCH2), 29.8 (–CH2–),
27.2 (SiC(CH3)3, 19.7 (SiC(CH3)3); ESI-MS: C61H64N2NaO15Si re-
quires m/z 1115.3732; found: m/z 1115.3753 [M+Na]+.
ride 10 (1.90 g, 82%); ½a D25
ꢁ
+33 (c 1.5, CHCl3); IR: 2931, 1714,
1454, 139, 1243, 1070, 753, 699 cmꢀ1
;
1H NMR (500 MHz, CDCl3):
d
7.79–7.66 (m, 8H, Ar-H), 7.41–7.15 (m, 16H, Ar-H), 5.13 (d,
J = 8.5 Hz, 1H, H-1A), 4.99 (br s, 2H,COOCH2Ph), 4.89–4.86 (m, 1H,
NHCbz), 4.48–4.39 (m, 4H, PhCH2, H-4B, H-3B), 4.30 (d, J = 8.3
Hz, 1H, H-1B), 4.18 (dd, J = 8.9 Hz, 1H, H-2A), 4.09 (dd, J = 8.4,
1.2 Hz, 1H, H-5A), 4.03–3.94 (m, 4H, H-6abA, H-4A, H-5B), 3.84–
3.79 (m, 1H, H-3A), 3.75–3.64 (m, 3H, H-6aB, –OCH2R), 3.57–3.55
(m, 1H, H-6bB), 3.49–3.45 (m, 2H, H-4A, H-2B), 3.12–3.09 (m, 2H,
–NCH2), 1.69–1.67 (m, 2H, –CH2–), 1.50 (s, 3H, C(CH3)2), 1.32 (s,
3H, C(CH3)2), 1.06 (s, 9H, SiC(CH3)3); 13C NMR (75 MHz, CDCl3): d
168.9, 168.2 (CO Phth), 156.7 (COOCH2Ph), 137.9–123.6 (Ar-C),
110.8 (C(CH3)2), 103.7 (C-1B), 98.6 (C-1A), 83.6 (C-3B), 79.3
(C-4A), 75.5 (C-5A), 74.0 (C-2B), 73.9 (PhCH2), 73.8 (C-4B), 72.8
(C-5B), 70.4 (C-3A), 69.5 (COOCH2Ph), 67.5 (C-6B), 66.8 (–OCH2R),
63.9 (C-6A), 56.4 (C-2A), 38.8 (NCH2), 29.9 (–CH2–), 28.5
(C(CH3)2), 27.3 (SiC(CH3)3), 26.7 (C(CH3)2), 19.7 (SiC(CH3)3);
ESI-MS: C57H66N2NaO14Si requires m/z 1053.3981; found: m/z
1053.3992 [M+Na]+.
3.5. 3-(Benzyloxycarbonylamino)propyl 6-O-t-butyldiphenyl
silyl-2-deoxy-2-phthalimido-4-O-(2,3,4-tri-O-acetyl-6-O-ben
zyl-b-D-galactopyranosyl)-b-D-glucopyranoside (9)
To
a
solution of 3-(benzyloxycarbonylamino)propyl 6-O-t-
-glucopyranoside
325 (6.00 g, 8.13 mmol) and ethyl 2,3,4-tri-O-acetyl-6-O-benzyl-1-
thio-b-
-galactopyranoside 827 (5.73 g, 9.75 mmol) in dry CH2Cl2
butyldiphenylsilyl-2-deoxy-2-phthalimido-b-
D
D
(70 mL) was added MS-4 Å (3.00 g) and the reaction mixture was
allowed to stir under N2 at room temperature for 1 h. N-Iodosuc-
cinimide (NIS; 2.6 g, 11.7 mmol) was added to the reaction mixture
3.7. 3-(Benzyloxycarbonylamino)propyl 4-O-[3-O-benzoyl-4,6-
O-benzylidene-2-O-(2,3,4-tri-O -benzyl-
galactopyranosyl]-6-O-t-butyldiphenylsilyl-2-deoxy-2-phthal-
imido-3-O-(2,3,4-tri-O -benzyl- -fucopyranosyl)-b- -glucopy-
ra noside (12) and 3-(benzyloxycarbonylamino)propyl 4-O-[3-
O-benzoyl-4,6-O-benzylidene-2-O-(2,3,4-tri-O-benzyl- -fucopy-
ranosyl)-b- -galactopyranosyl]-6-O-t-butyldiphenylsilyl-2-deoxy
-2-phthalimido-b- -glucopyranoside (13)
a-L-fucopyranosyl)-b-D-
and it was cooled to ꢀ40 °C before adding TfOH (50
lL). The reac-
tion mixture was allowed to stir at same temperature for 30 min.
When TLC showed complete consumption of the acceptor 3 the
reaction mixture was diluted with CH2Cl2 (100 mL) and filtered
through a CeliteÒ bed. The organic layer was washed with 5% aq
Na2S2O3, satd NaHCO3 and water, dried (Na2SO4) and evaporated
to dryness. The crude product was purified over SiO2 using hex-
ane–EtOAc (5:1) as eluent to furnish disaccharide 9 (8.40 g, 92%);
a
-L
D
a-L
D
D
To a solution of disaccharide 7 (2.30 g, 2.10 mmol) and ethyl
2,3,4-tri-O-benzyl-1-thio-
-fucopyranoside 1128 (2.40 g, 5.0 mmol)
yellow oil; ½a 2D5
ꢁ
+5 (c 1.5, CHCl3); IR: 2933, 2111, 1751, 1644,
a-L
1508, 1370, 1220, 1126, 1080, 770, 699 cmꢀ1
;
1H NMR (500 MHz,
in anhydrous toluene (40 mL) was added MS-4 Å (2.00 g) and the
reaction mixture was allowed to stir under N2 at room temperature
for 1 h. The reaction mixture was cooled to ꢀ30 °C and N-iodosuc-
CDCl3): d 7.81–7.79 (m, 2H, Ar-H), 7.75–7.71 (m, 4H, Ar-H), 7.68–
7.66 (m, 2H, Ar-H), 7.43–7.18 (m, 16H, Ar-H), 5.40 (d, J = 3.4 Hz,
1H, H-4B), 5.19 (d, J = 8.6 Hz, 1H, H-1A), 5.18–5.15 (m, 1H, H-3B),
4.99–4.95 (m, 3H, COOCH2Ph, 1H, H-2B), 4.66 (d, J = 8.1 Hz, 1H,
H-1B), 4.44 (d, J = 11.9 Hz, 1H, PhCH2), 4.31 (d, J = 11.9 Hz, 1H,
PhCH2), 4.20 (dd, J = 8.6, 1.3 Hz, 1H, H-2A), 4.03, (br s, 1H, H-5A),
3.97–3.95 (m, 1H, H-6aA), 3.88–3.82 (m, 4H, H-6bA, H-3A, –OCH2R),
3.58–3.46 (m, 3H, H-6abB, H-4A), 3.39 (dd, J = 6.2 Hz, 1H, H-5A),
3.11–3.08 (m, 2H, NCH2), 2.02 (s, 3H, COCH3), 1.97 (s, 3H, COCH3),
1.74–1.67 (m, 2H, –CH2–), 1.66 (s, 3H, COCH3), 1.08 (s, 9H,
cinimide (1.35 g, 6.0 mmol) and TfOH (30 lL) were added in
succession. The reaction mixture was allowed to stir at same tem-
perature for 2 h before dilution with CH2Cl2 (70 mL). The reaction
mixture was filtered through a CeliteÒ bed and the organic layer
was washed with 5% aq Na2S2O3, satd NaHCO3 and water, dried
(Na2SO4) and evaporated to dryness. The crude product was puri-
fied over SiO2 using hexane–EtOAc (4:1) as eluent to furnish tetra-
saccharide 12 (2.80 g, 69%); yellow oil; ½a D25
ꢁ
+21 (c 1.5, CHCl3); IR:

2118
P. K. Mandal, W. B. Turnbull / Carbohydrate Research 346 (2011) 2113–2120
3779, 3405, 2922, 1591, 1354, 1066, 762 cmꢀ1; 1H NMR (500 MHz,
CDCl3): d 7.73–7.51 (m, 8H, Ar-H), 7.49–6.92 (m, 51H, Ar-H), 5.60
(d, J = 3.6 Hz, 1H, H-1D), 5.51 (s, 1H, PhCH), 5.07 (d, J = 7.8 Hz, 1H,
H-1A), 5.05 (dd, J = 11.3, 2.3 Hz, 1H, H-3B), 4.95 (d, J = 3.4 Hz, 1H,
H-1C), 4.91–4.87 (m, 3H, COOCH2Ph, PhCH2), 4.82–4.80 (m, 1H,
H-5C), 4.72–4.70 (m, 1H, NHCbz), 4.61–4.51 (m, 3H, H-4B, H-1B,
PhCH2), 4.48 (br s, 2H, PhCH2), 4.45–4.40 (m, 3H, H-2A, PhCH2),
4.37–4.31 (m, 4H, H-3A, PhCH2), 4.25 (dd, J = 11.6 Hz, 2H, PhCH2),
4.20 (d J = 11.6 Hz, 1H PhCH2), 4.14–4.11 (m, 2H, H-6aA, H-5D),
3.96–3.88 (m, 4H, H-6bA, H-5B, H-5A, H-6aB), 3.72–3.68 (m, 1H,
H-6bB), 3.56 (dd, J = 11.3, 3.1 Hz, H-4C), 3.49 (dd, J = 8.4 , 1.2 Hz,
H-3D), 3.41–3.37 (m, 2H, H-2B, H-2C), 3.27–3.25 (m, 1H, H-3C),
3.19 (br s, 1H, H-4A), 3.12–3.10 (m, 1H, H-2D), 3.02–3.00 (m, 3H,
H-4D, NCH2), 1.69–1.61 (m, 2H, –CH2–), 1.21 (d, J = 6.4 Hz. 3H,
CH3), 1.12 (d, J = 6.4 Hz, 3H, CH3) 1.02 (s, 9H, SiC(CH3)3); 13C NMR
(75 MHz, CDCl3): d 168.6, 168.1 (CO Phth), 165.6 (COPh), 156.4
(COOCH2Ph), 139.6–123.7 (Ar-C), 99.9 (PhCH), 99.8 (C-1B), 98.5
(C-1C), 98.4 (2C-1A, C-1D), 79.4 (C-3D), 79.2 (C-3C), 78.5 (C-2B),
78.2 (C-2D), 77.4 (C-4C), 77.2 (C-5A), 76.0 (C-4D), 75.9 (C-2C), 75.0
(PhCH2), 74.6 (PhCH2), 73.4 (C-5B), 73.3 (C-3A), 73.2 (2 C, PhCH2),
73.9 (PhCH2), 72.9 (C-4A), 72.5 (C-3B), 71.4 (PhCH2), 69.3 (–OCH2R),
67.5 (C-4B), 66.7 (C-5D), 66.6 (COOCH2Ph), 66.5 (C-6B), 61.6 (C-6A),
56.5 (C-2A), 38.5 (NCH2), 29.7 (–CH2–), 26.9 (SiC(CH3)3), 19.8
(SiC(CH3)3), 16.3 (2 C, CH3); ESI-MS: C115H120N2NaO23Si requires
m/z 1947.6052; found: m/z 1947.6075 [M+Na]+.
succinimide (942 mg, 4.18 mmol) and TfOH (20 lL) were added in
succession. The reaction mixture was allowed to stir at same tem-
perature for 2 h before dilution with CH2Cl2 (50 mL). The reaction
mixture was filtered through a CeliteÒ bed and the organic layer
was washed with 5% aq Na2S2O3, satd NaHCO3 and water, dried
(Na2SO4) and evaporated to dryness. The crude product was purified
over SiO2 using hexane–EtOAc (5:1) as eluent to furnish tetrasaccha-
ride 14 (2.30 g, 85%); yellow oil; ½a D25
ꢁ
+45 (c 1.5, CHCl3); IR: 2933,
1777, 1716, 1454, 1384, 1219, 1051, 697 cmꢀ1; 1H NMR (500 MHz,
CDCl3): d 7.75–7.49 (m, 8H, Ar-H), 7.39–7.18 (m, 35H, Ar-H), 7.02–
6.90 (m, 11H, Ar-H), 5.56 (d, J = 3.8 Hz, 1H, H-1D), 5.01 (d,
J = 7.7 Hz, Hz, 1H, H-1A), 5.02–5.49 (m, 2H, COOCH2Ph), 4.95 (d,
J = 11.6 Hz, 1H, PhCH2), 4.91 (d, J = 3.6 Hz, H-1C), 4.90 (d,
J = 12.0 Hz, 1H, PhCH2), 4.81 (d, J = 12.0 Hz, 1H, PhCH2), 4.77–4.65
(m, 7H H-1B, H-5C, PhCH2), 4.60 (ABq, J = 11.8 Hz, 2H, PhCH2),
4.51–4.47 (dd, J = 11.8 Hz, 2H, PhCH2), 4.46–4.41 (m, 4H, H-2A, H-
4B, PhCH2), 4.28–4.19 (m, 4H, H-3B, H-5A, H-6abA), 4.16–4.13 (m,
1H, H-2D), 4.11–4.08 (m, 2H, H-2C, H-3C), 4.03–4.01 (m, 2H, H-5B,
H-5D), 3.80–3.72 (m, 4H, OCH2R, H-3A, H-3D), 3.66–3.63 (m, 1H, H-
2B), 3.59–3.55 (m, 2H, H-6abB), 3.44–3.40 (m, 2H, H-4D, H-4C),
3.14–3.10 (m, 3H, H-4A, NCH2), 1.70–1.60 (m, 2H, –CH2–), 1.45 (s,
3H, C(CH3)2), 1.34 (s, 3H, C(CH3)2), 1.19 (d, J = 6.4 Hz, 3H, CH3), 1.09
(d, J = 6.4 Hz, 3H, CH3), 1.03 (s, 9H, SiC(CH3)3); 13C NMR (75 MHz,
CDCl3): d 168.6, 168.1 (CO Phth), 156.7 (COOCH2Ph), 138.4–123.0
(Ar-C), 110.0 (C(CH3)2), 100.1 (C-1B), 98.4 (C-1D), 98.1 (C-1C), 97.7
(C-1A), 80.3 (C-3D), 80.1 (C-3C), 78.9 C-2D), 78.2 (C-2B), 78.1 (C-2C),
77.9 (C-5A), 76.9 (C-4A), 76.2 (C-4C), 75.1 (PhCH2), 75.0 (PhCH2),
74.5 (C-5B), 74.4 (C-3B), 73.8 (2 C, C-4A, C-3A), 73.5 (2 C, PhCH2)
73.2 (PhCH2), 72.7 (C-5D), 72.6 (2 C, PhCH2) 71.5 (C-4B), 68.8
(OCH2R), 67.1 (C-5C), 66.7 (COOCH2Ph), 66.6 (C-6B), 61.5 (C-6A),
56.8 (C-2A), 38.7 (NCH2), 29.6 (–CH2–), 28.7 (C(CH3)2), 27.1
(SiC(CH3)3), 26.9 (C(CH3)2), 19.8 (SiC(CH3)3), 17.1 (CH3), 16.8 (CH3);
ESI-MS: C111H122N2NaO22Si requires m/z 1886.8166; found: m/z
1886.8195 [M+Na]+.
Further elution with the same solvents provided trisaccharide
13 (0.79 g, 25%); yellow oil; ½a D25
ꢁ
+11 (c 1.5, CHCl3); IR: 3759,
3325, 2902, 1791, 1454, 1234, 1066, 762 cmꢀ1
;
1H NMR
(500 MHz, CDCl3): d 8.21–8.19 (m, 2H, Ar-H), 7.99–7.95 (m, 2H,
Ar-H), 7.52–6.87 (m, 40H, Ar-H), 5.46 (d, J = 3.8 Hz. 1H, H-1D),
5.45 (s, 1H, PhCH), 5.26 (d, J = 3.7, 10.2 Hz, 1H, H-3B), 5.22
(d, J = 8.2 Hz, 1H, H-1A), 5.13–5.03 (m, 3H, H-2A, COOCH2Ph), 4.94
(d, J = 8.2 Hz, 1H, H-1B), 4.90 (d, J = 11.7 Hz, 2H, PhCH2), 4.81–
4.79 (m, 1H, NHCbz), 4.62–4.60 (m, 1H, PhCH2), 4.56
(d, J = 11.6 Hz, 1H, PhCH2), 4.47–4.39 (m, 5H, PhCH2, H-5D,
H-4B), 4.28–4.22 (m, 3H, H-5A H-3D, H-3A), 4.16–3.88 (m, 4H,
H-5B, H-4D, H-6abB), 3.74–3.72 (m, 1H, H-2B), 3.66–3.51 (m, 2H,
H-2D, H-6aA), 3.47–3.39 (m, 4H, H-4A,H-6bA OCH2R), 3.17–3.16
(m, 2H, NCH2), 1.76–1.70 (m, 2H, –CH2–), 1.09 (s, 9H, SiC(CH3)3),
1.03 (d, J = 6.5 Hz, 3H, CH3); 13C NMR (75 MHz, CDCl3): d 168.3,
168.1 (CO Phth), 166.4 (COPh), 156.4 (COOCH2Ph), 139.5–123.8
(Ar-C), 101.6 (H-1B), 99.8 (PhCH), 98.3 (H-1D), 98.2 (H-1A), 79.3
(C-3D), 78.7 (C-3A), 77.5 (C-2D), 76.1 (C-4D), 75.3 (C-5A), 74.7
(PhCH2), 74.3 (C-4B), 73.6 (C-3B), 72.9 (PhCH2), 72.6 (C-2B), 71.6
(PhCH2), 69.3 (C-5B), 66.7 (C-6B), 66.6 (2 C, OCH2R, OCH2Ph), 66.5
(2 C, C-5D, C-4A), 61.9 (C-6A), 56.7 (C-2A), 38.5 (NCH2), 29.7
(–CH2–), 26.9 (SiC(CH3)3), 19.8 (SiC(CH3)3), 16.5 (CH3); ESI-MS:
Further elution with the same solvents provided trisaccharide
15 (0.31 g, 15%); yellow oil; ½a D25
ꢁ
+33 (c 1.5, CHCl3); IR: 2932,
2879, 1776, 1717, 1454, 1387, 1218, 1068, 963, 753, 699 cmꢀ1
;
1H NMR (500 MHz, CDCl3): d 7.71–7.24 (m, 39H, Ar-H), 5.56 (d,
J = 3.8 Hz, 1H, H-1D), 5.11 (d, J = 8.0 Hz, 1H, H-1A), 5.01 (br s, 2H,
COOCH2Ph), 4.94 (d, J = 11.7 Hz, 1H, PhCH2), 4.84 (d, J = 11.4 Hz,
2H, PhCH2), 4.74 (d, J = 8.2 Hz, 1H, H-1B), 4.72 (d, J = 11.5 Hz, 1H,
PhCH2), 4.62 (d, J = 11.2 Hz, 2H, PhCH2), 4.53 (dd, J = 11.6, 3.2 Hz,
1H, H-4B), 4.45 (d, J = 11.6 Hz, 1H, PhCH2), 4.38–4.35 (m, 2H, H-
3B, PhCH2), 4.24–4.18 (m, 2H, H-2A, H-5D), 4.15–4.05 (m, 2H, H-
2B, H-5B), 4.03–3.86 (m, H-6abA, H-3D, H-3A, H-5A), 3.78–3.66 (m,
H-6abB, OCH2R, H-2D), 3.43–3.37 (m, 1H, H-4D), 3.33–3.31 (m, 1H,
H-4A), 3.11–3.09 (m, 2H, NCH2), 1.72–1.69 (m, 2H, –CH2–), 1.51
(s, 3H, C(CH3)2), 1.32 (s, 3H, C(CH3)2), 1.12 (d, J = 6.4 Hz, 3H, CH3),
1.02 (s, 9H, SiC(CH3)3); 13C NMR (75 MHz, CDCl3): d 168.6, 168.1
(CO Phth), 156.4 (COOCH2Ph), 138.1–127.4 (Ar-C), 110.3
(C(CH3)2), 100.6 (C-1B), 98.0 (C-1A), 96.8 (C-1D), 80.0 (C-3B), 78.9
(2 C, C-3D, C-2B) 78.1 (C-2D), 76.7 (C-4A), 76.1 (C-4D), 75.4 (C-3A)
74.8 (PhCH2), 73.8 (2 C, C-5A, C-5D), 73.6 (PhCH2), 73.4 (PhCH2),
72.7 (PhCH2), 72.2 (C-5B), 69.4 (C-4B), 68.8 (OCH2R), 66.8 (C-6B),
66.5 (COOCH2Ph), 61.9 (C-6A), 56.6 (C-2A), 38.5 (NCH2), 29.6 (–
CH2–), 28.1 (C(CH3)2), 26.8 (SiC(CH3)3), 26.5 (C(CH3)2), 19.6
(SiC(CH3)3), 16.7 (CH3); ESI-MS: C84H94N2NaO18Si requires m/z
1469.4269; found: m/z 1469.4274 [M+Na]+.
C
88H92N2NaO19Si requires m/z 1531.4063; found: m/z 1531.4072
[M+Na]+.
3.8. 3-(Benzyloxycarbonylamino)propyl 4-O-[6-O-benzyl-3,4-O-
isopropylidene-2-O-(2,3,4-tri-O-benzyl-
galactopyranosyl]-6-O-t-butyldiphenylsilyl-2-deoxy-2-phthal-
imido-3-O-(2,3,4-tri-O -benzyl- -fucopyranosyl)-b- -glucopy
ranoside (14) and 3-(Benzyloxycarbonylamino)propyl 4-O-[6-
O-benzyl-3,4-O-isopropylidene-2-O-(2,3,4-tri-O-benzyl-
fucopyranosyl)-b- -galactopyranosyl]-6-O-t -butyldiphenylsilyl-
2-deoxy-2-phthalimido-b- -glucopyranoside (15)
a-L-fucopyranosyl)-b-D-
a
-L
D
a-L-
D
D
3.8.2. Monofucosylation of trisaccharide 18
3.8.1. Fucosylation of disaccharide 10
To a solution of disaccharide 10 (1.50 g, 1.45 mmol) and ethyl
2,3,4-tri-O-benzyl-1-thio-
-fucopyranoside 1128 (1.70 g, 3.49
A solution of diol 17 (2.4 g, 1.71 mmol) and pyridine (180
2.05 mmol) in dry CH2Cl2 (40 mL) was cooled to ꢀ40 °C allowed
to stir. Benzoyl chloride (173 L, 1.88 mmol) was added and the
lL,
a
-
L
l
mmol) in anhydrous toluene (20 mL) was added MS-4 Å (1 g) and
the reaction mixture was allowed to stir under N2 at room temper-
ature for 1 h. The reaction mixture was cooled to ꢀ30 °C and N-iodo-
reaction mixture was allowed to stir at same temperature for 1 h.
When TLC showed complete consumption of the starting material,
the reaction mixture was diluted with CH2Cl2 (80 mL) and washed

P. K. Mandal, W. B. Turnbull / Carbohydrate Research 346 (2011) 2113–2120
2119
with 1 M HCl, satd. NaHCO3 and water. The solution was then dried
(Na2SO4) and evaporated. The crude product was purified over SiO2
using hexane–EtOAc (6.5:1) as eluent to provide benzoate 18
(1.95 g, 74%); 1H NMR (500 MHz, CDCl3): d 8.19–8.17 (m, 2H, Ar-
H), 7.78–6.84 (m, 42H, Ar-H), 5.55 (s, 1H, PhCH), 5.11–5.08 (m,
1H, H-3B), 5.07 (d, J = 7.9 Hz, 1H, H-1A), 5.03 (d, J = 8.1 Hz, 1H, H-
1B), 5.02–5.01 (m, 2H, COOCH2Ph), 4.84–4.76 (m, 3H, H-2A, H-4B ,
NHCbz), 4.68 (d, J = 3.7 Hz, 1H, H-1C), 4.58 (ABq, 2H, PhCH2),
4.49–4.36 (m, 4H, PhCH2, H-5C), 4.23 (d, J = 11.3 Hz, 1H, PhCH2),
4.13–4.04 (m, 4H, H-3C, H-5A, H-2C, H-5B), 4.03–3.96 (m, 2H, H-
(C-4C), 74.8 (2 C, C-5A, C-4B), 73.5 (2 C, PhCH2), 72.9 (C-3B), 72.2
(C-2B), 71.8 (2 C, PhCH2), 69.1 (C-6B), 68.9 (C-5C), 66.7 (OCH2R),
66.6 (OCH2Ph), 66.5 (2 C, C-5B, C-4A), 61.5 (C-6A), 56.6 (C-2A),
38.4 (NCH2), 29.6 (–CH2–), 26.9 (SiC(CH3)3, 21.0 (COCH3), 20.7
(COCH3), 19.7 (SiC(CH3)3), 16.2 (CH3); ESI-MS: C85H92N2NaO20Si re-
quires m/z 1511.5905; found: m/z 1511.5918 [M+Na]+.
3.10. 3-(Benzyloxycarbonylamino)propyl 4-O-(4,6-O-benzyli-
de ne-b-D-galactopyranosyl)-6-O-t-butyldiphenylsilyl-2-deoxy-
2-phthalimido-3-O-(2,3,4-tri-O-benzyl-a-L-fucopyranosyl)-b-D-
6abB), 3.85–3.76 (m, 2H, H-2B, H-4C), 3.63–3.54 (m, 2H, H-6abA),
glucopyranoside (17)
3.43–3.40 (m, 2H, OCH2R), 3.37 (br s, 1H, H-4A), 3.19–3.18 (m,
1H, H-3A), 3.04–3.02 (m, 2H, NCH2), 1.64–1.59 (m, 2H, –CH2–),
1.13 (s, 9H, SiC(CH3)3), 1.06 (d, J = 6.5 Hz, 3H, CH3); ESI-MS:
A solution of trisaccharide 16 (3.00 g, 2.01 mmol) in 0.05 M
MeONa/MeOH (80 mL) was allowed to stir at room temperature
for 30 min before neutralisation with Amberlite-IR 120 (H+) resin.
The reaction mixture was filtered and evaporated to dryness to
give the crude product, which was passed through a short column
of SiO2 using hexane–EtOAc (2:1) as eluant to give diol 17 (2.90 g,
C
88H92N2NaO19Si requires m/z 1531.4055; found: m/z 1531.4078
[M+Na]+.
To a solution of trisaccharide 18 (1.2 g, 0.79 mmol) and ethyl
2,3,4-tri-O-benzyl-1-thio- -fucopyranoside (456 mg,
1128
a-L
0.95 mmol) in anhydrous toluene (28 mL) was added MS-4 Å
(0.6 g) and the reaction mixture was allowed to stir under N2 at
room temperature for 1 h. The reaction mixture was cooled to
ꢀ30 °C and N-iodosuccinimide (256 mg, 1.14 mmol) and TfOH
quantitative); colourless syrup; ½a D25
ꢀ10 (c 1.2, CHCl3); IR: 3423,
ꢁ
3009, 2931, 1776, 1700, 1453, 1388, 1097, 997, 752, 698 cmꢀ1
;
1H NMR (500 MHz, CDCl3): d 7.76–7.73 (m, 4H, Ar-H), 7.50–6.85
(m, 30H, Ar-H), 5.59 (s, 1H, PhCH), 5.03 (d, J = 8.5 Hz, 1H, H-1A),
5.00 (br s, 2H, COOCH2Ph), 4.92 (d, J = 4.4 Hz, 1H, H-4B), 4.82–
4.76 (m, 2H, H-2A, NHCbz), 4.66 (d, J = 3.6 Hz, 1H, H-1C), 4.56 (br
s, 2H, PhCH2), 4.48 (d, J = 8.6 Hz, 1H, H-1B), 4.45 (d, J = 12.0 Hz,
1H, PhCH2), 4.46–4.44 (m, 1H, H-5C), 4.39 (dd, J = 12.0 Hz, 2H,
PhCH2), 4.34–4.32 (m, 1H, H-3B), 4.23 (d, J = 12.0 Hz, 1H, PhCH2),
4.14–4.12 (m, 2H, H-6abA), 4.05–4.00 (m, 2H, H-2B, H-3C), 3.97–
3.94 (m, 1H, H-3A), 3.77–3.73 (m, 1H, H-2C), 3.63–3.47 (m, 5H, H-
4A, H-6abB, OCH2R), 3.42–3.40 (m, 1H, H-4C), 3.28–3.22 (m, 2H, H-
5A, H-5B), 3.03–3.02 (m, 2H, NCH2), 1.66–1.60 (m, 2H, –CH2–),
1.10 (br s, 12H, CH3, SiC(CH3)3); 13C NMR (75 MHz, CDCl3): d
168.4, 168.1 (CO Phth), 156.3 (COOCH2Ph), 136.1–125.8 (Ar-C),
101.5 (PhCH), 100.1 (C-1B), 98.1 (C-1C), 98.0 (C-1A), 79.1 (C-3C),
78.6 (C-3A), 75.9 (C-2C), 75.3 (4C), 74.9 (C-5A), 74.8 (PhCH2), 73.5
(C-4B), 72.9 (PhCH2), 72.3 (PhCH2), 72.0 (C-3B), 71.5 (C-2B), 69.4
(OCH2R), 66.8 (C-5C), 66.7 (COOCH2Ph), 66.6 (C-6B), 66.5 (H-4A),
66.4 (C-5B), 61.9 (C-6A), 56.7 (C-2A), 38.4 (NCH2), 29.6 (–CH2–),
26.9 (SiC(CH3)3, 19.8 (SiC(CH3)3), 16.5 (CH3); ESI-MS:
(18 lL) were added in succession. The reaction mixture was al-
lowed to stir at same temperature for 2 h before dilution with
CH2Cl2 (60 mL). The reaction mixture was filtered through a CeliteÒ
bed and the organic layer was washed with 5% aq Na2S2O3, satd
NaHCO3 and water, dried (Na2SO4) and evaporated to dryness.
The crude product was purified over SiO2 using hexane–EtOAc
(6:1) as eluent to furnish tetrasaccharide 14 (1.06 g, 69%); analytical
data identical to those quoted above.
3.9. 3-(Benzyloxycarbonylamino)propyl 6-O-t-butyldiphenylsil
yl-2-deoxy-4-O-(2,3-di-O-acetyl-4,6-O-benzylidene-b-
lacto pyranosyl)-2-phthalimido-3-O-(2,3,4-tri-O-benzyl-
fucopyr anosyl)-b- -glucopyranoside (16)
D-ga-
a-L-
D
To a solution of disaccharide 5 (4.5 g, 4.19 mmol) and ethyl 2,3,4-
tri-O-benzyl-1-thio-
-fucopyranoside 1128 (2.6 g, 5.45 mmol) in
a-L
anhydrous toluene (20 mL) was added MS-4 Å (2.00 g) and the
reaction mixture was allowed to stir under N2 at room temperature
for 1 h. The reaction mixture was cooled to ꢀ15 °C and N-iodosuc-
C
81H88N2NaO18Si requires m/z 1427.5694; found: m/z 1427.5718
[M+Na]+.
cinimide (1.50 g, 6.54 mmol) and TfOH (30 lL) were added in suc-
cession. The reaction mixture was allowed to stir at same
temperature for 7 h before dilution with CH2Cl2 (80 mL). The reac-
tion mixture was filtered through a CeliteÒ bed and the organic
layer was washed with 5% aq Na2S2O3, satd NaHCO3 and water,
dried (Na2SO4) and evaporated to dryness. The crude product
was purified over SiO2 using hexane–EtOAc (4:1) as eluent to fur-
3.11. 3-(Benzyloxycarbonylamino)propyl 6-O-t-butyldiphenyl-
silyl-2-deoxy-2-phthalimido-4-O-(2,3,4-tri-O-acetyl-6-O-benzyl
-b-
D-galactopyranosyl)-3-O-(2,3,4-tri-O-benzyl-a-L-fucopy-
rano syl)-b-
D-glucopyranoside (19)
To a solution of disaccharide 9 (1.0 g, 0.89 mmol) and ethyl 2,3,4-
tri-O-benzyl-1-thio-
-fucopyranoside 1128 (0.51 g, 1.07 mmol) in
nish trisaccharide 16 (4.3 g, 69%); yellow oil; ½a D25
ꢁ
+27 (c 1.5,
a-L
CHCl3); IR (neat): 3427, 2934, 1715, 1638, 1386, 1217, 1058, 749,
anhydrous toluene (25 mL) was added MS-4 Å (0.5 g) and the reac-
tion mixture was allowed to stir under N2 at room temperature for
1 h. The reaction mixture was cooled to ꢀ15 °C and N-iodosuccin-
698 cmꢀ1 1H NMR (500 MHz, CDCl3): d 7.79–6.84 (m, 39H, Ar-
;
H), 5.56 (s, 1H, PhCH), 5.39 (dd, J = 8.4, 2.0 Hz , 1H, H-2B), 5.11 (d,
J = 8.5 Hz, 1H, H-1A), 5.03 (d, J = 8.6 Hz, 1H, H-1B), 5.01 (br s, 2H,
COOCH2Ph), 4.88 (dd, J = 10.1, 3.5 Hz, 1H, H-3B), 4.82–4.81 (m,
1H, H-4B), 4.72 (dd, J = 10.0 Hz, 1.9 Hz, H, H-2A), 4.64 (d,
J = 3.6 Hz, 1H, H-1C), 4.55 (br s, 2H, PhCH2), 4.83–4.42 (m, 3H, H-
5C, PhCH2), 4.33–4.29 (m, 1H, H-4C), 4.64–4.22 (m, 1H, H-3C),
4.16–4.14 (m, 1H, H-6aA), 4.07–4.04 (m, 1H, H-6bA), 4.00 (d,
J = 11.4 Hz, 2H, PhCH2), 3.94–3.79 (m, 2H, H-6abB), 3.60 (dd,
J = 10.5, 3.5 Hz, 1H, H-4A), 3.41–3.38 (m, 3H, OCH2R, H-2C), 3.31
(br s, 1H, H-5B), 3.11–3.10 (m, 1H, H-5A), 3.05–3.01 (m, 2H,
NCH2), 2.15 (s, 3H, COCH3), 1.91 (s, 3H, COCH3), 1.66–1.60 (m,
2H, –CH2), 1.12 (br s, 12H, CH3, SiC(CH3)3); 13C NMR (75 MHz,
CDCl3): d 170.6 (COCH3), 168.8 (COCH3), 168.3, 168.1 (CO Phth),
156.3 (COOCH2Ph), 139.0–123.7 (Ar-C), 99.9 (2 C, PhCH, H-1B),
98.2 (H-1A), 97.9 (H-1C), 79.2 (C-3C), 78.9 (C-3A), 77.4 (C-2C), 75.9
imide (288 mg, 1.28 mmol) and TfOH (15 lL) were added in suc-
cession. The reaction mixture was allowed to stir at same
temperature for 7 h before dilution with CH2Cl2 (50 mL). The reac-
tion mixture was filtered through a CeliteÒ bed and the organic
layer was washed with 5% aq Na2S2O3, satd NaHCO3 and water,
dried (Na2SO4) and evaporated to dryness. The crude product
was purified over SiO2 using hexane–EtOAc (4:1) as eluent to fur-
nish trisaccharide 19 (1.0 g, 73%); yellow oil; ½a D25
ꢁ
+15 (c 1.5,
CHCl3); IR (neat): 2930, 2011, 1851, 1562, 1407, 1220, 1126,
1025, 779, 699 cmꢀ1 1H NMR (500 MHz, CDCl3): d 7.78–6.83 (m,
;
39H, Ar-H), 5.38 (d, J = 3.4 Hz, 1H, H-4B), 5.02–4.97 (m, 4H, H-1A,
COOCH2Ph, H-3B), 4.95 (d, J = 3.4 Hz, 1H, H-1C), 4.75 (d, J = 8.1 Hz,
1H, H-1B), 4.74–4.67 (m, 3H, H-2A, H-2B, H-5C), 4.58 (d,
J = 11.2 Hz, 1H, PhCH2), 4.51 (d, J = 11.2 Hz, 1H, PhCH2), 4.44

2120
P. K. Mandal, W. B. Turnbull / Carbohydrate Research 346 (2011) 2113–2120
(d, J = 11.2 Hz, 1H, PhCH2), 4.41–4.38 (m, 2H, H-4C, H-3C), 4.35 (d,
J = 11.2 Hz, 2H, PhCH2), 4.22 (d, J = 11.2 Hz, 1H, PhCH2), 4.19 (d,
J = 11.1 Hz, 1H, PhCH2), 4.15 (d, J = 11.1 Hz, 1H, PhCH2), 4.02–3.99
(m, 1H, H-6aA), 3.94–3.92 (m, 1H, H-6bA), 3.88–3.86 (m, 1H, H-
3A), 3.78–3.73 (m, 2H, H-5B, H-2C), 3.66–3.58 (m, 2H, H-6abB),
3.53–3.51 (m, 1H, H-5A), 3.38–3.36 (m, 1H, H-4A), 3.35–3.28 (m,
2H, –OCH2R), 3.01–2.99 (m, 2H, NCH2), 1.93 (s, 3H, COCH3), 1.80
(s, 3H, COCH3), 1.71 (s, 3H, COCH3), 1.66–1.54 (m, 2H, –CH2–),
1.16 (d, J = 6.5 Hz, 3H, CH3), 1.05 (s, 9H, SiC(CH3)3); 13C NMR
(75 MHz, CDCl3): d 170.6 (COCH3), 170.4 (COCH3), 168.9 (COCH3),
168.5, 168.2 (CO Phth), 136.7–123.9 (Ar-C), 100.1 (C-1B), 98.3 (C-
1A), 97.5 (C-1C), 80.2 (C-3C), 77.7 (C-2C), 76.1 (C-3A), 74.9 (3 C, C-
4C, C-5A, C-5B), 74.4 (PhCH2), 73.6 (PhCH2), 73.2 (PhCH2), 73.1
(PhCH2), 72.1 (C-3B), 71.7 (C-2B), 71.5 (C-5C), 69.6 (C-4A), 67.5 (C-
4B), 66.9 (OCH2R), 66.7 (C-6B), 66.6 (COOCH2Ph), 61.5 (C-6A), 56.6
(C-2A), 38.5 (NCH2), 29.7 (–CH2–), 27.1 (SiC(CH3)3), 21.1 (COCH3),
20.9 (COCH3), 20.6 (COCH3), 19.9 (SiC(CH3)3), 16.8 (CH3); ESI-MS:
(C-4B), 69.9 (OCH2R), 67.1 (C-6B), 66.6 (OCH2Ph), 62.6 (C-6A), 56.4
(C-2A), 38.4 (NCH2), 29.6 (–CH2), 28.4 (C(CH3)2), 26.9 (SiC(CH3)3,
26.4 (C(CH3)2), 19.7 (SiC(CH3)3), 16.9 (CH3); ESI-MS: C60H68N2-
NaO17Si requires m/z 1469.6163; found: m/z 1469.6187 [M+Na]+.
Acknowledgments
The authors thank the Royal Society for funding this research
through a Newton International Fellowship awarded to P.K.M.
and a Royal Society University Research Fellowship awarded to
W.B.T.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.carres.2011.07.002.
C
60H68N2NaO17Si requires m/z 1555.4273; found: m/z 1555.4295
References
[M+Na]+.
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D
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D
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117, 5701–5711.
A solution of trisaccharide 19 (2.0 g, 1.42 mmol) in 0.1 M MeO-
Na/MeOH (80 mL) was allowed to stir at room temperature for
30 min. The reaction mixture was neutralised with Amberlite-IR
120 (H+) resin, filtered, and concentrated. To a solution of the
deacetylated product in anhydrous DMF (40 mL) were added 2,2-
dimethoxypropane (0.3 mL, 2.13 mmol) and camphorsulfonic acid
(0.5 g), and the reaction mixture was allowed to stir at room tem-
perature for 12 h. The reaction mixture was neutralized with Et3N
(3.0 mL) and evaporated to dryness. The crude mass was purified
over SiO2 using hexane–EtOAc (5:1) as eluant to furnish trisaccha-
ride 20 (1.6 g, 77%); yellow oil; ½a D25
ꢁ
+45 (c 1.5, CHCl3); IR (neat):
2903, 2031, 1951, 1764, 1548, 1330, 1126, 1090, 790, 689 cmꢀ1
;
1H NMR (500 MHz, CDCl3): d 7.71–7.57 (m, 8H, Ar-H), 7.40–6.92
(m, 31H, Ar-H), 5.05 (d, J = 8.4 Hz, 1H, H-1A), 4.98 (br s, 2H,
COOCH2Ph), 4.82–4.79 (m, 1H, NHCBz), 4.78 (d, J = 11.2, 1H,
PhCH2), 4.74 (d, J = 3.4 Hz, 1H, H-1C), 4.69–4.65 (dd, J = 9.9 Hz,
1H, H-2A), 4.62 (d, J = 8.3 Hz, 1H, H-1B), 4.57–4.51 (ABq, 2H, PhCH2),
4.46 (d, J = 11.3 Hz, 1H, PhCH2), 4.43 (d, J = 11.3 Hz, 1H, PhCH2),
4.39 (d, J = 11.2 Hz, 2H, PhCH2), 4.38–4.35 (m, 1H, H-5C), 4.31 (d,
J = 12.0 Hz, 1H, PhCH2), 4.23–4.19 (m, 2H, H-4B, H-3B), 4.11–4.09
(m, 1H, H-2B), 3.99–3.95 (m, 2H, H-6abA), 3.92–3.89 (m, 2H, H-3A,
H-5B), 3.87–3.83 (m, 1H, H-3C), 3.78–3.75 (m, 1H, H-4A), 3.72–
3.69 (m, 3H, H-4C, H-2C, H-6aB), 3.57–3.55 (m, 1H, H-6bB), 3.53–
3.50 (m, 1H, H-5A), 3.43–3.38 (m, 2H, OCH2R), 3.06–3.03 (m,
NCH2), 1.68–1.57 (m, 2H, –CH2–), 1.43 (s, 3H, –C(CH3)2), 1.33 (s,
3H, –C(CH3)2), 1.06 (s, 9H, SiC(CH3)3), 1.02 (d, J = 6.5 Hz, 3H, CH3);
22. Windmueller, R.; Schmidt, R. R. Tetrahedron Lett. 1994, 35, 7927–7930.
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13C NMR (75 MHz, CDCl3):
d 168.4, 168.1 (CO Phth), 156.4
(COOCH2Ph), 139.1–123.6 (Ar-C), 110.1 (C(CH3)2), 100.4 (H-1B),
98.7 (H-1A), 98.1 (H-1C), 79.5 (C-3C), 79.1 (C-2C), 78.1 (C-3A), 75.7
(C-4C), 75.8 (C-3B), 75.2 (C-5A), 75.1 (PhCH2), 74.9 (C-4A), 74.7 (C-
5B), 74.4 (C-2B), 73.6 (PhCH2), 73.4 (PhCH2), 73.1 (PhCH2), 72.0