Towards a modular synthesis of well-defined chitooligosaccharides: Synthesis of the four chitodisaccharides

Article abstract of DOI:10.1016/j.carres.2010.05.010

The total chemical synthesis of the four well-defined chitodisaccharides is described using N-trichloroacetyl (TCA) and N-benzyloxycarbonyl (Z) as C-2 protecting groups for acetamido and free amino groups, respectively. The synthesis is carried out accord

Full text of DOI:10.1016/j.carres.2010.05.010

Carbohydrate Research 345 (2010) 1685–1697
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Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
Towards a modular synthesis of well-defined chitooligosaccharides: synthesis
of the four chitodisaccharides
*
Nadine Barroca-Aubry, Astrid Pernet-Poil-Chevrier, Alain Domard, Stéphane Trombotto
Laboratoire des Matériaux Polymères et des Biomatériaux, Ingénierie des Matériaux Polymères, UMR CNRS 5223, Université Lyon 1, Domaine scientifique de La Doua, Bât. ISTIL,
15 Bd Latarjet, F-69622 Villeurbanne Cedex, France
a r t i c l e i n f o
a b s t r a c t
Article history:
The total chemical synthesis of the four well-defined chitodisaccharides is described using N-trichloro-
acetyl (TCA) and N-benzyloxycarbonyl (Z) as C-2 protecting groups for acetamido and free amino groups,
respectively. The synthesis is carried out according to a strategy that paves way to the elaboration of var-
ious homo- and hetero-chitooligosaccharides, with perfect control of the number and the position of GlcN
and GlcNAc units along the oligomer chain.
Received 7 December 2009
Received in revised form 7 May 2010
Accepted 13 May 2010
Available online 19 May 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Chitooligosaccharides
Chitodisaccharides
Chitosan oligomers
Chitin oligomers
Chemical synthesis
1. Introduction
theses of COS with low DPs that involve multiple protection, cou-
pling and deprotection reactions have also been reported. Most of
Chitooligosaccharides (COS) are linear co-oligomers of (1?4)-
linked 2-acetamido-2-deoxy-b- -glucopyranose (GlcNAc) and
2-amino-2-deoxy-b- -glucopyranose (GlcN) units in varying
these syntheses are limited to the elaboration of homo-oligosaccha-
rides of GlcNAc or GlcN units,9 and only a few of them deal with the
preparation of hetero-COS10,11 or derivatives as precursors of Nod
factors.12 Recently, Kawada and Yoneda have reported the total
synthesis of two hetero-COS, that is, the disaccharide GlcN–GlcNAc
and the tetrasaccharide (GlcN–GlcNAc)2, using both phthalimido
and azido groups for the protection of the free amino groups.13
We have previously described an easy-access method for the
preparation of a homogeneous series of homo- and hetero-COS,
in controlling both the DA and DP.14 Our studies are now focused
on the development of a new chemical method for the synthesis
of COS, perfectly defined by their three-dimensional structural
parameters. We herein report on an original access of the four pos-
sible chitodisaccharides 17, 25, 32 and 38 (Fig. 1). We show that
the use of both N-trichloroacetyl (TCA) and N-benzyloxycarbonyl
(Z) groups for the C-2 protection of acetamido and free amino
groups, respectively, and the synthesis of convergent protected
chitodisaccharides 13, 20, 28 and 34 open way for the elaboration
of larger size COS such as the trisaccharide 39 (Fig. 1).
D
D
proportions. COS, also named chitin or chitosan oligomers, have
recently received considerable attention as functional materials for
many applications in the fields of medicine, the food industry, agri-
culture, cosmetics and pharmaceuticals.1 These molecules are water
soluble, nontoxic, biocompatible and biodegradable. They also exhi-
bit numerous interesting biological properties including anti-bacte-
rial, anti-fungal, anti-tumour and eliciting activities.1,2 Bioactivities
of COS have often been determined using heterogeneous and/or rel-
atively poorly characterized oligomer mixtures. There is, therefore,
an increasing interest in generating well-defined COS in order to
determine more precisely the relationship between their bioactivi-
ties and their three-dimensional structural parameters: (i) the
N-acetylation degree (DA) corresponding to the molar fraction of
GlcNAc units in the oligomer chain, (ii) the polymerization degree
(DP) and (iii) the N-acetylation pattern (PA) related to the intramo-
lecular distribution of N-acetyl groups along the oligomer chain.
Conventional methods described in the literature to prepare COS
are either enzymatic or chemical depolymerizations of chitin and
chitosan.1,3–8 In most cases, they lead to complex COS mixtures
with average DAs and DPs. Besides, some multi-step chemical syn-
2. Results and discussion
2.1. Synthetic strategy
The assembly of well-defined COS requires the preparation
of differentially protected glucosamine-based monosaccharide
* Corresponding author.
E-mail address: stephane.trombotto@univ-lyon1.fr (S. Trombotto).
0008-6215/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2010.05.010

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N. Barroca-Aubry et al. / Carbohydrate Research 345 (2010) 1685–1697
OH
OBn
O
OBn
O
NHR2
O
NHTCA
O
AcO
BnO
BnO
O
HO
HO
O
HO
O
OTBDMS
BnO
OH
O
NHR1
TCANH
TCANH
OBn
OH
39
Figure 1. Chemical structures of targeted chitodisaccharides and a protected chitotrisaccharide.
building blocks.15 The availability of these monosaccharide syn-
thons, which could build up convergent disaccharide synthons,
then upper size convergent synthons is a key point of our synthesis
strategy summarized in Scheme 1. Thus, each monosaccharide
building block should be able to be used as a GlcNAc/GlcN acceptor
(4 and 10, respectively) or a GlcNAc/GlcN donor (6 and 12, respec-
tively) with a minimum number of transformation steps from the
treatment of the known 1,3,4,6-tetra-O-acetyl-2-deoxy-2-
trichloroacetamido-D
-glucopyranose14 with hydrazine acetate in
N,N-dimethylformamide (DMF), followed by a silylation with tert-
butyldimethylsilyl chloride, afforded crystalline 1 in 60% overall
yield. The trans-esterification of 1 under Zemplèn conditions,18
followed by acetalation with 2,2-dimethoxybenzaldehyde and
camphorsulfonic acid, gave 2 in 83% yield. Protection at the 3-posi-
tion was then achieved by treatment with benzyl bromide and
sodium hydride in DMF to give crystalline 3 in 73% yield. No
N-benzylation reaction was observed under these conditions.
The regioselective reductive cleavage of the benzylidene acetal
in 3 with triethylsilane and trifluoroacetic acid19 gave the targeted
3,6-di-O-benzyl acceptor 4 in 81% yield. The use of boron trifluor-
ide diethyl etherate20 or the mixture of trifluoroacetic acid and tri-
fluoroacetic anhydride21 instead of trifluoroacetic acid did not
improve the yield nor decrease the reaction time of this reaction.
No 4-O-benzyl opening was detected under these conditions. The
acetylation of the GlcNAc acceptor 4 under conventional condi-
tions (acetic anhydride–pyridine) afforded 5. The 6-regioselective
reductive opening of the benzylidene acetal was confirmed from
5: its 1H NMR spectrum showed a chemical shift of the H-4 proton
from 3.7 to 5.06 ppm with two coupling constants J4,5 and J3,4
around 9 Hz.
commercial D-glucosamine hydrochloride. Compared to Kawada
and Yoneda13 different C-2 protecting groups were used in this
work. The N-trichloroacetyl (TCA) and N-benzyloxycarbonyl (Z)
groups were, respectively, selected for the protection of acetamido
and free amino groups based on their easy attachment, subsequent
transformation and cleavage.
This was emphasized by their enhanced capability to form b-gly-
cosidic linkages and their compatibility with various protecting
groups.16,17 Therefore, we report the involvement of tert-butyldi-
methylsilyl (TBDMS) and acetyl (Ac) groups, respectively, for the
protection of both positions: 1-O at the reducing end and 4-O at the
non-reducing end of our synthons.12 Owing to these two orthogonal
protecting groups, every protected chitooligosaccharide can be easily
convertedasa newbuilding block acceptorordonor without affecting
other protecting groups present on the skeleton, so as to make possi-
ble the growth of the oligosaccharide chain in each direction.
The second targeted synthon, that is, GlcNAc donor 6, was ob-
tained by removing the TBDMS group by treatment with tetrabu-
tylammonium fluoride and acetic acid in tetrahydrofuran (THF).
A subsequent reaction with trichloroacetonitrile in the presence
of 1,8-diaza[5.4.0]bicycloundec-7-ene (DBU) as a base afforded
2.2. Synthesis of differentially protected glucosamine-based
monosaccharide building blocks
The preparation of the GlcNAc acceptor
4 was achieved
in a straightforward manner as illustrated in Scheme 2. The
the
a
-imidate 6 in 94% overall yield. The
a
-anomeric configuration
OH
OH
O
NHR
O
HO
O
HO
O
HO
HO
O
OH
OH
NHR
H
NH2·HCl
OH
n ≥ 1
D-Glucosamine hydrochloride
Targeted chitoligosaccharides (R = H or Ac)
OBn
OBn
O
O
HO
BnO
HO
BnO
OTBDMS
OTBDMS
NHTCA
NHZ
OBn
NHR2
4
6
10
12
O
BnO
O
O
OBn
OR1
BnO
OBn
O
NHR2
R3
O
O
OBn
AcO
BnO
AcO
BnO
n ≥ 1
TCAHN
ZHN
O
NH
Protected chitoligosaccharides (R1 = TBDMS, R2 = Z or
TCA, R3 = Ac) can be easily converted as new building
block acceptors (R1 = TBDMS, R2 = Z or TCA, R3 = OH)
or donors (R1 = C(NH)CCl3, R2 = Z or TCA, R3 = Ac)
O
NH
CCl3
CCl3
Protected glucosamine-based monosaccharide building blocks
Scheme 1. Synthesis strategy for the assembly of both homo- and hetero-chitooligosaccharides.

N. Barroca-Aubry et al. / Carbohydrate Research 345 (2010) 1685–1697
1687
OR6
OBn
O
OBn
O
O
R4O
R3O
AcO
BnO
f
AcO
BnO
OTBDMS
OTBDMS
NHR1
NHR1
R1NH
O
NH
CCl3
a
b
c
d
a
e
c
d
Scheme 2. Preparation of GlcNAc/GlcN acceptor (4, 10) and donor (6, 12) monosaccharide synthons. Reagents and conditions: (a) (i) NaOMe, MeOH; (ii) PhCH(OMe)2, CSA,
CH3CN; (b) (i) NaH, DMF, 0 °C; (ii) BnBr, DMF; (c) Et3SiH, TFA, CH2Cl2, 0 °C; (d) Ac2O, pyridine; (e) BnBr, BaO, Ba(OH)2ꢀ8H2O, DMF; (f) (i) Bu4NFꢀ3H2O, AcOH, THF; (ii) CCl3CN,
DBU, CH2Cl2.
was deduced from the 1H NMR spectrum: doublet for H-1
6.47 ppm, J1,2 = 3.4 Hz.
a
at
isolated in a yield of 26%. Compared to these results, it appears that
the use of the couple TCA/Z as acetamido/free amino protecting
groups at the C-2 position leads to a significant increase of the gly-
cosylation yield. This is likely due to a better selectivity for the b
glycoside, since in our glycosylation conditions, we exclusively ob-
serve the formation of the b glycoside. The b-glycosidic linkage of
disaccharides 13 and 20 was confirmed by 1H NMR spectroscopy:
The two other targeted synthons, that is, GlcN acceptor 10 and
GlcN donor 12, were obtained according to a similar synthetic
route (Scheme 2) from the known 1,3,4,6-tetra-O-acetyl-2-(ben-
zyloxycarbonyl)amino-2-deoxy-D
-glucopyranose.22 However, the
3-O-protection could not be carried out by treatment with benzyl
bromide and sodium hydride in DMF due to the instability of the
N-benzyloxycarbonyl group under these drastic basic conditions.
Thus, 9 could be afforded from 8 by reaction with benzyl bromide
in a milder basic medium using barium oxide and barium hydrox-
ide octahydrate.23 Under these conditions, 9 was obtained in 69%
yield, and no N-benzylation reaction was observed. The regioselec-
tive reductive cleavage of the benzylidene acetal under the same
conditions as 3 allowed the targeted GlcN acceptor 10 to be ob-
tained in 75% yield. The acetylation of 10, then, TBDMS group re-
moval followed by the trichloroacetimidoylation, afforded the
targeted GlcN donor 12 in 86% overall yield.
for 13,
d 4.96 ppm, J1,2 = 8.3 Hz, H-1b; for 20, d 4.87 ppm,
J1,2 = 8.4 Hz, H-1b. In the case of the protected disaccharides 28
and 34, the doublet signal of the b-anomeric proton was over-
lapped with the singlet signal of CH2 protons of the benzyloxycar-
bonyl group. In addition, it was not possible to determine the b
coupling constant J1,2 from neither the H-2b signal nor the 2D COSY
spectrum. Therefore, it was difficult to certify the b-configuration
at this stage of the synthesis. However, owing to the well-known
anchimeric assistance of carbamates, there was not much doubt
for the b-configuration of the new 1,2-linkage, as we shall see
below.
2.3. Protected chitodisaccharide preparation
2.4. Targeted chitodisaccharide deprotections
All combinations of donors 6 and 12 with acceptors 4 and 10 led
to the four possible protected disaccharides 13, 20, 28 and 34 in
good to excellent yields: 90%, 73%, 70% and 70%, respectively
(Scheme 3). Glycosylations were carried out in dry dichlorometh-
ane using indifferently trimethylsilyl trifluoromethanesulfonate
(TMSOTf) or boron trifluoride diethyl etherate (BF3ꢀEt2O). As men-
tioned by Belot and Jacquinet24 BF3ꢀEt2O may be used instead of
TMSOTf to prevent the intermolecular aglycon transfer of the
TBDMS group in trichloroacetimidate glycosylation conditions. In-
deed, BF3ꢀEt2O allowed the aglycon transfer to decrease from 30%
to 3%, thus enhancing the glycosylation yield of 20, for example,
from 43% to 73%. In the synthesis of the disaccharide GlcN–GlcNAc,
Kawada and Yoneda reported that the glycosylation reaction be-
tween the phthalimido derivative of the acceptor 4 (or 10) and
According to our initial strategy, after the assembly of the oligo-
saccharide skeleton under perfect control, the next stage consisted
in the complete deprotection of protected chitodisaccharides to af-
ford four targeted chitodisaccharides 17, 25, 32 and 38 (Scheme 4).
First, the N-trichloroacetyl groups in compounds 13, 20 and 28
were readily transformed into their corresponding N-acetyl groups
by free-radical reduction14 with tributyltin hydride and azobisi-
sobutyronitrile (AIBN) to give acetamides 14, 21 and 29 in good
to excellent yields: 97%, 82% and 75%, respectively. Note that the
conversion yields of the N-trichloroacetyl group into the N-acetyl
moiety are significantly improved compared to the 53% yield ob-
tained for the same conversion from the phthalimido group on
analogous structures.12 Furthermore, the conversion of the N-tri-
chloroacetyl group into the N-acetyl moiety requires only one reac-
tion step, under milder reaction conditions instead of two for the
phthalimido group.
the azido derivative of the donor 6 (or 12) affords a mixture of
a
and b glycosides.12 Under their best conditions, the b glycoside is
OBn
TMSOTf
or BF3.Et2O
NHR2
O
O
6 or 12
+
4 or 10
BnO
AcO
O
BnO
OTBDMS
CH2Cl2
NHR1
OBn
Scheme 3. Preparation of protected chitodisaccharides 13, 20, 28 and 34.

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We thus confirmed the b-linked configuration of disaccharide
ylation of protected disaccharides 13, 20, 28 and 34 with methano-
lic sodium methoxide led to acceptor synthons 18, 26, 33 and 35,
respectively, in very good yields. Corresponding donor synthons,
29 which could not be clearly identified at the previous stage for
28. The 1H NMR spectrum of 29 showed a signal for H-1b at
4.59 ppm with a large coupling constant J1,2 = 8.8 Hz, in agreement
with a newly established 1,2-trans interglycosidic linkage. The
orthogonal 4-O-protection was then removed by treatment with
methanolic sodium methoxide to give the disaccharides 15, 22,
30 and 35 in good to excellent yields: 83%, 87%, 95% and 79%,
respectively. At this stage, it was not yet possible to confirm the
b-linkage of 35 due to the overlapping of the anomeric proton H-
1b signal with the CH2 proton signal of the benzyloxycarbonyl
group. Treatment with tetrabutylammonium fluoride and acetic
acid in THF led to the reductive disaccharides 16, 23, 31 and 36
in very good yields: 89%, 87%, 86% and 89%, respectively. Fortu-
nately, after two reaction steps, the 1H NMR spectrum showed
for disaccharide 36 a signal for H-1b at 4.72 ppm with a large cou-
pling constant J1,2 = 7.9 Hz, confirming the unique presence of a b-
(1?4) glycosidic linkage.
that is,
a-imidates 19 and 27, could be obtained, respectively, in
89% and 84% overall yields, (i) by removal of the TBDMS group
by treatment with tetrabutylammonium fluoride and acetic acid
in THF and (ii) by a subsequent reaction with trichloroacetonitrile
in the presence of DBU.
In order to test our new synthetic route for the well-defined
COS elaboration, we decided to elongate the disaccharide 13 up
to a trisaccharide. Thus, glycosylation of the acceptor 18, previ-
ously obtained from 13, with the imidate donor 6 under BF3ꢀEt2O
catalysis in dry dichloromethane afforded the targeted b-linked tri-
saccharide 39 in 76% yield (Scheme 6). By this result, we confirmed
that this strategy is potentially applicable to build up well-defined
chitosan fragments with higher molecular sizes.
3. Conclusions
The final deprotection, consisting of the removal of all benzyl
groups by hydrogenolysis in the presence of Pd–C in aqueous
methanol, afforded the target chitodisaccharides 17, 25, 32 and
38 in moderate to good yields: 75%, 62%, 75% and 58%, respectively.
A significant increase in the yields could be obtained for chitodi-
saccharides 25 and 38 when the two last deprotection reaction
steps were inverted (Scheme 4, route B). First, the hydrogenolysis
of disaccharides 22 and 35 in aqueous methanol with Pd–C led
to disaccharides 24 and 37 in good yields: 75% and 74%, respec-
tively. Then, the TBDMS group was removed by treatment with tet-
rabutylammonium fluoride and acetic acid in THF to give targeted
chitodisaccharides 25 and 38 in excellent yields 92% and 90%,
respectively. Therefore, chitodisaccharides 25 and 38 were pre-
pared from disaccharides 22 and 35, in 69% and 67% overall yields
for route B, compared to 54% and 50% for the route A, respectively.
In this study, N-trichloroacetyl (TCA) and N-benzyloxycarbonyl
(Z) groups were used, respectively, for the protection of acetamido
and free amino groups in glucosamine-based glycosyl donors and
acceptors. The combination of these building blocks allowed us
to synthesize efficiently the four possible chitodisaccharide struc-
tures, with a perfect control of the architecture. As also illustrated
by the synthesis of a protected chitotrisaccharide, the synthetic
route developed herein can give a ready access to various homo-
or hetero-chitooligosaccharides. This strategy takes advantage of
the possibility to easily convert every protected chitooligosaccha-
ride as a new acceptor or donor, so as to build up the oligosaccha-
ride chain in each direction. Thus, the way is now open for the
elaboration of higher molecular sized, well-defined chitooligosac-
charides, which is currently being investigated in our group.
4. Experimental
2.5. Towards the preparation of larger size COS
4.1. General methods
A key point of our synthetic strategy for the preparation of lar-
ger size COS was to easily convert any protected chitooligosaccha-
rides previously synthesized into new donors or acceptors with a
minimum number of reaction steps (Scheme 5). Thus, the deacet-
All solvents and reagents were purchased from Sigma–Aldrich,
Acros Chemicals or SDS, and used without further purification.
Reactions were monitored by analytical thin-layer chromatography
OBn
OBn
NHR2
NHR2
Bu3SnH, AIBN
O
O
BnO
AcO
O
BnO
BnO
AcO
O
BnO
OTBDMS
OTBDMS
O
O
NHR1
NHR1
Benzene, 80˚C
OBn
OBn
NaOMe, MeOH
OBn
O
NHR2
route B
BnO
HO
O
BnO
OTBDMS
O
NHR1
H2, Pd/C
EtOAc/MeOH/H2O
OBn
Bu4NF, AcOH, THF
route A
OBn
O
OH
O
NHR2
NHR2
BnO
HO
O
BnO
HO
HO
O
HO
OTBDMS
OH
O
O
NHR1
NHR1
OBn
OH
H2, Pd/C, MeOH/H2O
Bu4NF, AcOH, THF
OH
O
NHR2
HO
HO
O
HO
OH
O
NHR1
OH
Scheme 4. Deprotection reaction pathways leading to chitodisaccharides 17, 25, 32 and 38.
a–d
yields determined from 23, 24, 36, 37, respectively.

N. Barroca-Aubry et al. / Carbohydrate Research 345 (2010) 1685–1697
1689
OBn
O
NHR2
NaOMe, MeOH
BnO
HO
O
BnO
OTBDMS
O
NHR1
OBn
OBn
O
NHR2
O
BnO
AcO
O
BnO
OTBDMS
NHR1
OBn
OBn
O
NHR2
1) Bu4NF, AcOH, THF
2) CCl3CN, DBU, CH2Cl2
BnO
AcO
O
BnO
O
R1NH
NH
CCl3
O
OBn
Scheme 5. Chemical conversions of protected chitodisaccharides into new acceptors (18, 26, 33 and 35) and donors (19 and 27).
OBn
O
OBn
O
NHTCA
BF3.Et2O
CH2Cl2
BnO
O
O
AcO
BnO
18
+ 6
OTBDMS
BnO
O
NHTCA
NHTCA
OBn
39 (76%)
Scheme 6. Synthesis of the protected chitotrisaccharide 39.
(TLC) using aluminum-backed E. Merck Silica Gel plates (60 F254). A
solution of 10% (v/v) H2SO4 in EtOH was used to develop the TLC
plates. Flash-chromatography separations were performed using
5.30 (dd, 1H, J3,4 9.2, J2,3 10.9, H-3), 5.09 (dd, 1H, J4,5 10.0, H-4),
0
4.88 (d, 1H, J1,2 7.9, H-1), 4.23 (dd, 1H, J5,6 5.7, J6,6 12.2, H-6),
4.15 (dd, 1H, J5,6 2.7, H-60), 3.95 (m, 1H, H-2), 3.74 (m, 1H, H-5),
0
E. Merck Silica Gel 60H (40–63
l
m) under 1 bar pressure. NMR
2.08 (s, 3H, CH3CO), 2.04 (s, 3H, CH3CO), 2.03 (s, 3H, CH3CO), 0.88
(s, 9H, (CH3)3CSi), 0.13 (s, 3H, CH3Si), 0.10 (s, 3H, CH3Si); 13C
NMR (75 MHz, CDCl3): d 171.3 (CO, Ac), 170.7 (CO, Ac), 169.4
(CO, Ac), 161.9 (CONH), 95.9 (C-1), 92.4 (CCl3), 72.1 (C-3), 71.8
(C-5), 68.9 (C-4), 62.5 (C-6), 57.9 (C-2), 25.6 ((CH3)3CSi), 20.8
(CH3CO), 20.8 (CH3CO), 20.7 (CH3CO), 17.9 ((CH3)3CSi), ꢃ4.1
(CH3Si), ꢃ5.1 (CH3Si); ESIMS: m/z 604 [M+K+], 588 [M+Na]+; Anal.
Calcd for C20H32Cl3NO9Si: C, 42.52; H, 5.71; N, 2.48. Found: C,
42.89; H, 5.76; N, 2.42.
spectra were recorded on a Bruker DRX 300 or DRX 500 spectrom-
eter, respectively, at 300 or 500 MHz for 1H and 75 or 125 MHz for
13C. The signal of the residual protonated solvent was taken as a ref-
erence. Chemical shift (d) and coupling constants (J) are reported in
parts per million (ppm) and Hz, respectively. For NMR assignments,
sugar units are identified by letters (a, b, or c) starting from the
reducing end to the non-reducing end. ESI mass spectra (ESIMS)
were recorded with a Micromass LCT mass spectrometer from
Waters, Inc. Optical rotations were measured with a Perkin–Elmer
241 polarimeter using a sodium lamp at 20 °C. Elemental analyses
were performed by the ‘Service Central d’Analyses du CNRS’ in Sola-
ize (69, France).
4.3. tert-Butyldimethylsilyl 4,6-O-benzylidene-2-deoxy-2-
trichloroacetamido-b-D-glucopyranoside (2)
A suspension of 1 (10.7 g, 18.9 mmol) in MeOH (100 mL)
was treated for 1 h at rt with methanolic NaOMe (1 M, 3 mL). The
solution was deionized with an Amberlite IR-120 (H+) resin, filtered
and concentrated to give the corresponding triol. Camphorsulfonic
acid (88 mg, 0.4 mmol) was added to a solution of the resulting triol
in CH3CN (120 mL) and 2,2-dimethoxybenzaldehyde (3.4 mL,
4.2. tert-Butyldimethylsilyl 3,4,6-tri-O-acetyl-2-deoxy-2-
trichloroacetamido-b-D-glucopyranoside (1)
Hydrazine acetate (4.7 g, 50.6 mmol) was added to a solution of
1,3,4,6-tetra-O-acetyl-2-deoxy-2-trichloroacetamido- -glucopy-
D
ranoside14 (16.2 g, 32.9 mmol) in dry DMF (100 mL). The solution
was stirred for 30 min at room temperature (rt), poured into cold
water and extracted with EtOAc (3 ꢁ 250 mL). The organic extracts
were washed with water, satd aq NaHCO3 and water, dried
(MgSO4) and concentrated. A mixture of the obtained hemiacetal
with imidazole (9.0 g, 132.0 mmol) and tert-butyldimethylsilyl
chloride (9.9 g, 65.9 mmol) in dry DMF (120 mL) was stirred 8 h
at rt, diluted with EtOAc (3 ꢁ 250 mL), washed with water, 5% (v/
v) aq HCl and water, dried (MgSO4) and concentrated. The residue
was chromatographed on a column of silica gel with 1:1 heptane–
EtOAc and crystallized from EtOAc–heptane to give 1 as a white
22.6 mmol). The mixture was stirred 1 h at rt. Et3N (160 lL) was
added, and the solvent was removed under vacuum. The residue
was chromatographed on a column of silica gel with 2:1 heptane–
EtOAc to afford 2 as a colourless oil (8.8 g, 88% from 1); ½a D20
ꢃ32 (c
ꢂ
1.03, CHCl3); 1H NMR (300 MHz, CDCl3): d 7.65–7.36 (m, 5H, Ph),
6.94 (d, 1H, J2,NH 7.4, NH), 5.53 (s, 1H, PhCH), 5.09 (d, 1H, J1,2 7.7,
0
H-1), 4.31 (dd, 1H, J5,6 4.6, J6,6 10.5, H-6), 4.26 (m, 1H, J3,4 8.6, J2,3
10.1, H-3), 3.77 (dd, 1H, J5,6 9.6, H-60), 3.53–3.48 (m, 3H, H-4, H-5,
0
H-2), 3.01 (sl, 1H, OH-3), 0.89 (s, 9H, (CH3)3CSi), 0.13 (s, 3H, CH3Si),
0.11 (s, 3H, CH3Si); 13C NMR (75 MHz, CDCl3): d 162.2 (COCCl3),
137.1 (C aromatic), 129.5–126.4 (CH aromatic), 102.0 (CHPh), 95.3
(C-1), 92.6 (CCl3), 81.7 (C-4), 69.7 (C-3), 68.6 (C-6), 66.3 (C-5), 61.6
(C-2), 25.7 ((CH3)3CSi), 17.9 ((CH3)3CSi), ꢃ4.0 (CH3Si), ꢃ5.0 (CH3Si);
powder (11.6 g, 63% two steps); mp 155–156 °C; ½a D20
ꢃ6 (c 1.12,
ꢂ
CHCl3); 1H NMR (300 MHz, CDCl3): d 6.74 (d, 1H, J2,NH 9.4, NH),

1690
N. Barroca-Aubry et al. / Carbohydrate Research 345 (2010) 1685–1697
ESIMS: m/z 548 [M+Na]+; Anal. Calcd for C21H30Cl3NO6Si: C, 47.87; H,
5.74; N, 2.66. Found: C, 47.51; H, 5.53; N, 2.47.
CH3CO), 0.89 (s, 9H, (CH3)3CSi), 0.14 (s, 3H, CH3Si), 0.11 (s, 3H,
CH3Si); 13C NMR (75 MHz, CDCl3): d 169.9 (CO, Ac), 161.9 (COCCl3),
138.0, 137.7 (C aromatic), 128.6–127.8 (CH aromatic), 94.1 (C-1),
92.5 (CCl3), 77.1 (C-3), 74.1, 73.7 (CH2Ph), 73.4 (C-5), 71.7 (C-4),
69.8 (C-6), 60.9 (C-2), 25.7 ((CH3)3CSi), 21.0 (CH3CO), 17.9
((CH3)3CSi), ꢃ4.0 (CH3Si), ꢃ5.1 (CH3Si); ESIMS: m/z 682 [M+Na]+;
Anal. Calcd for C30H40Cl3NO7Si: C, 54.50; H, 6.10; N, 2.12. Found:
C, 54.09; H, 6.08; N, 2.16.
4.4. tert-Butyldimethylsilyl 3-O-benzyl-4,6-O-benzylidene-2-
deoxy-2-trichloroacetamido-b-D-glucopyranoside (3)
Sodium hydride (60% in mineral oil, 1.2 g, 29.3 mmol) was
added portionwise at 0 °C to a solution of 2 (7.4 g, 14.1 mmol) in
dry DMF (55 mL). The mixture was stirred for 30 min at 0 °C. Ben-
zyl bromide (2.2 mL, 18.4 mmol) was then added, and the mixture
was stirred for 30 min at 0 °C and for 90 min at rt. MeOH (5 mL)
was cautiously added, and the mixture was diluted with EtOAc
(400 mL), washed twice with water, dried (MgSO4) and concen-
trated. The residue was chromatographed on a column of silica
gel with 5:1 heptane–EtOAc and crystallized from EtOAc–heptane
4.7. 4-O-Acetyl-3,6-di-O-benzyl-2-deoxy-2-trichloroacetamido-
1-O-trichloroacetimidoyl-a-D-glucopyranose (6)
A mixture of 5 (1.37 g, 2.1 mmol), AcOH (145
lL, 2.5 mmol)
and Bu4NFꢀ3H2O (785 mg, 2.5 mmol) in dry THF (18 mL) was stir-
red at 0 °C for 14 h. The mixture was concentrated and diluted
with EtOAc (60 mL), washed with water, satd aq NH4Cl and
water, dried (MgSO4) and concentrated. A mixture of the ob-
to afford 3 as a white powder (6.4 g, 73%); ½a D20
ꢃ16 (c 1,1, CHCl3);
ꢂ
1H NMR (300 MHz, CDCl3): d 7.53–7.27 (m, 10H, Ph), 6.86 (d, 1H,
J2,NH 7.9, NH), 5.59 (s, 1H, PhCH), 5.18 (d, 1H, J1,2 7.9, H-1), 4.79
tained hemiacetal, CCl3CN (2 mL, 20 mmol) and DBU (77 lL,
0
(ABq, 2H, CH2Ph), 4.32 (dd, 1H, J5,6 4.9, J6,6 10.6, H-6), 4.23 (m,
0.5 mmol) in anhyd CH2Cl2 (10 mL) was stirred for 1 h at 0 °C
and concentrated. The residue was chromatographed on a col-
umn of silica gel with 5:2 heptane–EtOAc (0.2% (v/v) Et3N) to
1H, J2,3 10.3, J3,4 8.9, H-3), 3.81 (dd, 1H, J5,6 10.2, H-60), 3.90 (dd,
0
1H, J4,5 9.6, H-4), 3.58–3.45 (m, 2H, H-2, H-5), 0.91 (s, 9H,
(CH3)3CSi), 0.11 (s, 3H, CH3Si), 0.09 (s, 3H, CH3Si); 13C NMR
(75 MHz, CDCl3): d 161.8 (COCCl3), 137.9, 137.3 (C aromatic),
129.2–126.1 (CH aromatic), 101.3 (CHPh), 95.1 (C-1), 92.5 (CCl3),
82.8 (C-4), 75.8 (C-3), 74.7 (CH2Ph), 68.8 (C-6), 66.2 (C-5), 60.9
(C-2), 25.7 ((CH3)3CSi), 17.9 ((CH3)3CSi), ꢃ4.0 (CH3Si), ꢃ5.0 (CH3Si);
ESIMS: m/z 638 [M+Na]+; Anal. Calcd for C28H36Cl3NO6Si: C, 54.50;
H, 5.88; N, 2.27. Found: C, 54.46; H, 5.97; N, 2.38.
give 6 as a colourless oil (1.34 g, 94% from 5); ½a D20
ꢂ
+70 (c 0.72,
CHCl3); 1H NMR (300 MHz, CDCl3): d 8.77 (s, 1H, NH imidate),
7.35–7.27 (m, 10H, Ph), 6.60 (d, 1H, J2,NH 8.5, NH), 6.47 (d, 1H,
J1,2 3.4, H-1), 5.38 (dd, 1H, J3,4 9.6, J4,5 9.8, H-4), 4.65 (ABq, 2H,
CH2Ph), 4.51 (ABq, 2H, CH2Ph), 4.46 (m, 1H, J2,3 10.7, H-2), 4.06
0
(m, 1H, H-5), 4.03 (dd, 1H, H-3), 3.60 (dd, 1H, J5,6 3.3, J6,6 10.8,
H-6), 3.56 (dd, 1H, J5,6 4.2, H-60), 1.96 (s, 3H, CH3CO); 13C NMR
0
(75 MHz, CDCl3): d 169.4 (CO, Ac), 161.9 (COCCl3), 160.0 (C@NH),
137.6, 137.1 (C aromatic), 128.8–127.9 (CH aromatic), 94.4 (C-1),
92.1 (CCl3 trichloroacetamido), 90.8 (CCl3 imidate), 76.1 (C-3),
73.7, 73.0 (CH2Ph), 72.2 (C-5), 70.0 (C-4), 68.5 (C-6), 53.5 (C-2),
20.9 (CH3CO); ESIMS: m/z 530 [MꢃCCl3CONH]+; Anal. Calcd for
4.5. tert-Butyldimethylsilyl 3,6-di-O-benzyl-2-deoxy-2-
trichloroacetamido-b-D-glucopyranoside (4)
A mixture of 3 (17.4 g, 28.2 mmol), 3 Å molecular sieves and Et3-
SiH (45 mL, 282 mmol) in anhyd CH2Cl2 (250 mL) was cooled to
0 °C. CF3CO2H (22 mL, 285 mmol) was added and the mixture
was stirred for 1 h at 0 °C. Et3N (3.3 mL) was added, and the mix-
ture was diluted with CH2Cl2 (150 mL), washed with water, satd
aq NaHCO3 and water, dried (MgSO4) and concentrated. The resi-
due was chromatographed on a column of silica gel with 5:2 hep-
tane–EtOAc to give 4 as a colourless oil, which crystallized slowly.
White solid was obtained by crystallization of the residue from
C26H26Cl6N2O7: C, 45.18; H, 3.79; N, 4.05. Found: C, 45.09; H,
3.84; N, 4.12.
4.8. tert-Butyldimethylsilyl 3,4,6-tri-O-acetyl-2-
(benzyloxycarbonyl)amino-2-deoxy-b-D-glucopyranoside (7)
Hydrazine acetate (9.8 g, 106 mmol) was added to a solution of
1,3,4,6-tetra-O-acetyl-2-(benzyloxycarbonyl)amino-2-deoxy-
D-
EtOAc–heptane (14.7 g, 84%); ½a D20
ꢂ
ꢃ13 (c 1,1, CHCl3); 1H NMR
glucopyranose20 (33.6 g, 70 mmol) in DMF (130 mL). The solution
was stirred for 30 min at rt, poured into cold water and extracted
with EtOAc (3 ꢁ 350 mL). The organic extracts were washed with
water, satd aq NAHCO3 and water, dried (MgSO4) and concentrated.
A mixture of the obtained hemiacetal with imidazole (14.3 g,
209 mmol) and tert-butyldimethylsilyl chloride (15.8 g, 105 mmol)
in dry DMF (120 mL) was stirred 5 h at rt, diluted with EtOAc
(3 ꢁ 300 mL), washed with water, 5% (v/v) aq HCl and water, dried
(MgSO4) and concentrated. The residue was chromatographed on a
column of silica gel with 2:1 heptane–EtOAc and crystallized from
EtOAc–heptane to give 7 as a white powder (26.7 g, 69% two steps);
(300 MHz, CDCl3): d 7.35–7.24 (m, 10H, Ph), 6.98 (d, 1H, J2,NH 8.1,
NH), 5.02 (d, 1H, J1,2 7.9, H-1), 4.75 (ABq, 2H, CH2Ph), 4.56 (ABq,
2H, CH2Ph), 3.92 (dd, 1H, J3,4 8.5, J2,3 10.5, H-3), 3.71–3.64 (m,
3H, H-4, H-6, H-60), 3.58–3.48 (m, 2H, H-2, H-5), 2.95 (sl, 1H, OH-
4), 0.88 (s, 9H, (CH3)3CSi), 0.12 (s, 3H, CH3Si), 0.09 (s, 3H, CH3Si);
13C NMR (75 MHz, CDCl3): d 161.8 (COCCl3), 138.2, 137.8 (C aro-
matic), 128.7–127.8 (CH aromatic), 94.7 (C-1), 92.7 (CCl3), 79.7
(C-3), 74.6, 73.9 (CH2Ph), 73.8 (C-5), 73.6 (C-4), 70.8 (C-6), 60.4
(C-2), 25.8 ((CH3)3CSi), 18.0 ((CH3)3CSi), ꢃ4.0 (CH3Si), ꢃ5.0 (CH3Si);
ESIMS: m/z 640 [M+Na]+; Anal. Calcd for C28H38Cl3NO6Si: C, 54.33;
H, 6.19; N, 2.26. Found: C, 54.53; H, 6.21; N, 2.16.
½
a 2D0 +9 (c 1.0, CHCl3); 1H NMR (300 MHz, CDCl3): d 7.39–7.29 (m,
5H, Ph), 5.21 (m, 1H, NH), 5.07–5.01 (m, 3H, H-1, H-3, H-4), 4.98
ꢂ
0
4.6. tert-Butyldimethylsilyl 4-O-acetyl-3,6-di-O-benzyl-2-deoxy-
(m, 2H, CH2O), 4.19 (dd, 1H, J5,6 5.8, J6,6 12.1, H-6), 4.11 (dd, 1H,
J5,6 2.6, H-60), 3.68 (m, 1H, H-2), 3.57 (m, 1H, H-5), 2.07 (s, 3H,
0
2-trichloroacetamido-b-
D-glucopyranoside (5)
CH3CO), 2.02 (s, 3H, CH3CO), 1.97 (s, 3H, CH3CO), 0.86 (s, 9H,
(CH3)3CSi), 0.09 (s, 3H, CH3Si), 0.06 (s, 3H, CH3Si); 13C NMR
(75 MHz, CDCl3): d 170.9 (CO, Ac), 170.8 (CO, Ac), 169.6 (CO, Ac),
155.8 (CONH), 136.3 (C aromatic), 128.6, 128.2 (CH aromatic),
96.3 (C-1), 72.2 (C-3), 71.8 (C-5), 69.2 (C-4), 66.9 (CH2O), 62.6
(C-6), 58.1 (C-2), 25.6 ((CH3)3CSi), 20.8 (CH3CO), 20.8 (CH3CO),
20.7 (CH3CO), 18.0 ((CH3)3CSi), ꢃ4.2 (CH3Si), ꢃ5.3 (CH3Si); ESIMS:
m/z 576 [M+Na]+; Anal. Calcd for C26H39NO10Si: C, 56.40; H, 7.10;
N, 2.53. Found: C, 56.03; H, 7.05; N, 2.89.
Conventional acetylation (Ac2O in pyridine) of 4 (3.1 g, 5 mmol),
followed by concentration of the mixture and crystallization of the
residue from EtOAc–heptane gave 5 (3.1 g, 95%); ½a D20
ꢂ
+4 (c 0.8,
CHCl3); 1H NMR (300 MHz, CDCl3): d 7.34–7.21 (m, 10H, Ph),
6.96 (d, 1H, J2,NH 7.5, NH), 5.16 (d, 1H, J1,2 7.7, H-1), 5.06 (dd, 1H,
J3,4 8.9, J4,5 9.8, H-4), 4.60 (ABq, 2H, CH2Ph), 4.52 (s, 2H, CH2Ph),
0
4.29 (dd, 1H, J2,3 10.5, H-3), 3.67 (m, 1H, J5,6 4.8, J5,6 4.8, H-5),
3.55 (d, 2H, J6,6 <0.5, H-6, H-60), 3.44 (m, 1H, H-2), 1.87 (s, 3H,
0

N. Barroca-Aubry et al. / Carbohydrate Research 345 (2010) 1685–1697
1691
0
4.9. tert-Butyldimethylsilyl 4,6-O-benzylidene-2-
(benzyloxycarbonyl)amino-2-deoxy-b- -glucopyranoside (8)
CH2Ph), 3.81 (m, 1H, H-3), 3.72 (d, 2H, J6,6 4.9, H-6, H-60), 3.66 (dd,
1H, J3,4 8.5, J4,5 9.9, H-4), 3.45 (m, 2H, H-5, H-2), 2.95 (m, 1H, OH-4),
0.86 (s, 9H, (CH3)3CSi), 0.08 (s, 3H, CH3Si), 0.05 (s, 3H, CH3Si); 13C
NMR (75 MHz, CDCl3): d 155.8 (CO2CH2PH), 138.5, 136.5 (C aro-
matic), 128.6–127.7 (CH aromatic), 95.6 (C-1), 80.5 (C-3), 74.1,
73.8 (CH2Ph), 73.7 (C-5), 73.0 (C-4), 70.8 (C-6), 66.8 (CH2O), 59.4
(C-2), 25.7 ((CH3)3CSi), 18.0 ((CH3)3CSi), ꢃ4.1 (CH3Si), ꢃ5.2 (CH3Si);
ESIMS: m/z 630.15 [M+Na]+, 608.17 [M+H]+; Anal. Calcd for
D
A suspension of 7 (23.2 g, 42 mmol) in MeOH (250 mL) was
treated for 1 h at rt with methanolic NaOMe (1 M, 5 mL). The solu-
tion was deionized with an Amberlite IR-120 (H+) resin, filtered
and concentrated to give the corresponding triol. Camphorsulfonic
acid (395 mg, 1.7 mmol) was added to a solution of the obtained
triol in CH3CN (260 mL) and 2,2-dimethoxybenzaldehyde (7.6 mL,
50.6 mmol). The solution was stirred 18 h at rt. Et3N was added
C
34H45NO7Si: C, 67.19; H, 7.46; N, 2.30. Found: C, 66.96; H, 7.57;
N, 2.35.
(240 lL), and the solvent was removed under vacuum. The residue
was crystallized from EtOAc–heptane to afford 8 as a white powder
4.12. tert-Butyldimethylsilyl 4-O-acetyl-3,6-di-O-benzyl-2-
(benzyloxycarbonyl)amino-2-deoxy-b-D-glucopyranoside (11)
(19.8 g, 91% from 7); ½a D20
ꢂ
ꢃ32 (c 1.0, CHCl3); 1H NMR (300 MHz,
CDCl3): d 7.51–7.32 (m, 10H, Ph), 5.50 (s, 1H, PhCH), 5.08 (m, 2H,
CH2O), 4.99 (d, 1H, J2,NH 7.5, NH), 4.83 (m, 1H, H-1), 4.27 (dd, 1H,
Conventional acetylation (Ac2O in pyridine) of 10 (1.51 g,
2.48 mmol), followed by concentration of the mixture and crystal-
lization of the residue from EtOAc–heptane, gave 11 (1.5 g, 91%);
0
0
J5,6 4.9, J6,6 10.4, H-6), 4.04 (m, 1H, H-3), 3.75 (dd, 1H, J5,6 10.2,
H-60), 3.54 (dd, 1H, J3,4 9.1, J4,5 9.2, H-4), 3.46 (m, 1H, H-5), 3.34
(m, 1H, H-2), 3.18 (sl, 1H, OH-3), 0.87 (s, 9H, (CH3)3CSi), 0.09 (s,
3H, CH3Si), 0.06 (s, 3H, CH3Si); 13C NMR (75 MHz, CDCl3): d 156.5
(CO2CH2PH), 137.2, 136.2 (C aromatic), 129.3–126.5 (CH aromatic),
100.7 (CHPh), 96.4 (C-1), 81.6 (C-4), 70.9 (C-3), 68.7 (C-6), 67.1
CH2O, 66.3 (C-5), 60.8 (C-2), 25.6 ((CH3)3CSi), 17.9 ((CH3)3CSi),
ꢃ4.1 (CH3Si), ꢃ5.2 (CH3Si); ESIMS: m/z 538 [M+Na]+; Anal. Calcd
for C27H37NO7Si: C, 62.89; H, 7.23; N, 2.72. Found: C, 62.56; H,
7.33; N, 2.71.
½
a 2D0 +6 (c 1.0, CHCl3); 1H NMR (300 MHz, CDCl3): d 7.37–7.16 (m,
15H, Ph), 5.06–4.97 (m, 5H, J3,4 9.3, J4,5 9.3, H-4, H-1, CH2O, NH),
ꢂ
4.55 (ABq, 2H, CH2Ph), 4.51 (s, 2H, CH2Ph), 4.05 (m, 1H, H-3),
0
0
3.60 (m, 1H, J5,6 4.5, J5,6 4.8, H-5), 3.53 (d, 2H, J6,6 <0.5, H-6,
H-60), 3.25 (m, 1H, H-2), 1.87 (s, 3H, CH3CO), 0.87 (s, 9H, (CH3)3CSi),
0.11 (s, 3H, CH3Si), 0.07 (s, 3H, CH3Si); 13C NMR (75 MHz, CDCl3): d
169.9 (CO, Ac), 155.7 (CO2CH2PH), 138.1, 136.5 (C aromatic),
128.6–127.7 (CH aromatic), 95.1 (C-1), 77.9 (C-3), 73.7, 73.6
(CH2Ph), 73.4 (C-5), 71.8 (C-4), 70.0 (C-6), 66.8 (CH2O), 59.9
(C-2), 25.7 ((CH3)3CSi), 21.0 (CH3CO), 18.0 ((CH3)3CSi), ꢃ4.1 (CH3Si),
ꢃ5.2 (CH3Si); ESIMS: m/z 672 [M+Na]+; Anal. Calcd for C36H47NO8-
Si: C, 66.54; H, 7.29; N, 2.16. Found: C, 66.65; H, 7.42; N, 2.21.
4.10. tert-Butyldimethylsilyl 3-O-benzyl-4,6-O-benzylidene-2-
(benzyloxycarbonyl)amino-2-deoxy-b-D-glucopyranoside (9)
A solution of 8 (7.33 g, 14.2 mmol) in dry DMF (100 mL) was
stirred for 7 h at rt in the presence of barium oxide (8.72 g,
56.9 mmol), barium hydroxide octahydrate (2.36 g, 7.5 mmol)
and benzyl bromide (2.2 mL, 18.5 mmol). Celite was added, and
the mixture was stirred for 30 min and filtered. The residue was
washed with EtOAc (3 ꢁ 100 mL). The organic extracts were
washed with water, satd aq NaHCO3 and water, dried (MgSO4)
and concentrated. The residue was chromatographed on a column
of silica gel with 3:1 heptane–EtOAc to obtain 9 which was crystal-
4.13. 4-O-Acetyl-3,6-di-O-benzyl-2-(benzyloxycarbonyl)amino-
2-deoxy-1-O-trichloroacetimidoyl-a-D-glucopyranose (12)
A solution of Bu4NFꢀ3H2O (1.1 g, 3.5 mmol) and AcOH (200
lL,
3.5 mmol) in THF (8 mL) was added to a solution of 11 (1.9 g,
2.9 mmol) in dry THF (30 mL) with stirring for 7 h at rt. The mix-
ture was concentrated and diluted with EtOAc (30 mL), washed
with satd aq NH4Cl and water, dried (MgSO4) and concentrated.
A mixture of the obtained hemiacetal, CCl3CN (2.9 mL, 28.9 mmol)
lized from Et2O–heptane (5.9 g, 69%); ½a D20
ꢂ
+2 (c 1.0, CHCl3); 1H
NMR (300 MHz, CDCl3): d 7.53–7.28 (m, 15H, Ph), 5.55 (s, 1H,
PhCH), 5.15–5.05 (m, 4H, H-1, CH2O, NH), 4.74 (ABq, 2H, CH2Ph),
and DBU (109 lL, 0.73 mmol) in anhyd CH2Cl2 (20 mL) was stirred
for 1 h at rt and concentrated. The residue was chromatographed
on a column of silica gel with 5:2 heptane–EtOAc containing 0.2%
(v/v) of Et3N to give 12 as a colourless oil (1.9 g, 95% from 11);
0
4.29 (dd, 1H, J5,6 4.9, J6,6 10.5, H-6), 4.08 (m, 1H, H-3), 3.79 (dd,
1H, J5,6 10.2, H-60), 3.71 (dd, 1H, J3,4 9.2, J4,5 9.4, H-4), 3.47 (m,
0
1H, H-5), 3.22 (m, 1H, H-2), 0.86 (s, 9H, (CH3)3CSi), 0.07 (s, 3H,
CH3Si), 0.04 (s, 3H, CH3Si); 13C NMR (75 MHz, CDCl3): d 155.7
(CO2CH2PH), 138.4, 136.5 (C aromatic), 129.1–126.2 (CH aromatic),
101.3 (CHPh), 95.9 (C-1), 82.7 (C-4), 76.6 (C-3), 74.4 (CH2Ph), 68.9
(C-6), 66.8 (CH2O), 66.1 (C-5), 60.3 (C-2), 25.7 ((CH3)3CSi), 18.0
((CH3)3CSi), ꢃ4.2 (CH3Si), ꢃ5.2 (CH3Si); ESIMS: m/z 628 [M+Na]+,
606 [M+H]+; Anal. Calcd for C34H43NO7Si: C, 67.41; H, 7.15; N,
2.31. Found: C, 67.19; H, 7.36; N, 2.26.
½
a 2D0 +64 (c 0.7, CHCl3); 1H NMR (300 MHz, CDCl3): d 8.69 (s, 1H,
ꢂ
NH imidate), 7.35–7.19 (m, 15H, Ph), 6.37 (d, 1H, J1,2 3.2, H-1),
5.31 (dd, 1H, J3,4 9.7, J4,5 9.7, H-4), 5.07 (m, 3H, CH2O, NH), 4.67–
4.45 (m, 4H, 2 ꢁ CH2Ph), 4.26 (m, 1H, J2,3 10.2, J2,NH 10.2, H-2),
0
4.02 (m, 1H, J5,6 6.8, J5,6 6.8, H-5), 3.83 (t, 1H, H-3), 3.55 (m, 2H,
H-6, H-60), 1.93 (s, 3H, CH3CO); 13C NMR (75 MHz, CDCl3): d
169.4 (CO, Ac), 160.2 (C@NH), 155.7 (CO2CH2PH), 138.1, 137.7,
137.5, 136.2 (C aromatic), 128.6–127.7 (CH aromatic), 95.7 (C-1),
91.0 (CCl3 imidate), 76.4 (C-3), 73.6, 73.0 (CH2Ph), 72.1 (C-5),
70.2 (C-4), 68.7 (C-6), 66.8 (CH2O), 53.5 (C-2), 20.9 (CH3CO); ESIMS:
m/z 519 [MꢃCCl3CONH]+; Anal. Calcd for C32H33Cl3N2O8: C, 56.52;
H, 4.89; N, 4.12. Found: C, 56.64; H, 4.92; N, 4.01.
4.11. tert-Butyldimethylsilyl 3,6-di-O-benzyl-2-
(benzyloxycarbonyl)amino-2-deoxy-b-D-glucopyranoside (10)
A mixture of 9 (7.95 g, 13.1 mmol), 3 Å powdered molecular
sieves (5 g) and Et3SiH (21 mL, 132 mmol) in anhyd CH2Cl2
(150 mL) was cooled to 0 °C. Trifluoroacetic anhydride (TFAA,
10 mL, 130 mmol) was added, and the mixture was stirred for
1 h at 0 °C. Et3N (3 mL) was added, and the mixture was diluted
with CH2Cl2 (100 mL), washed with water, satd aq NaHCO3 and
water, dried (MgSO4) and concentrated. The residue was chro-
matographed on a column of silica gel with 5:2 heptane–EtOAc
4.14. tert-Butyldimethylsilyl 4-O-acetyl-3,6-di-O-benzyl-2-
deoxy-2-trichloroacetamido-b-D-glucopyranosyl-(1?4)-3,6-di-
O-benzyl-2-deoxy-2-trichloroacetamido-b-D-glucopyranoside
(13)
A mixture of the donor 6 (390 mg, 0.56 mmol), acceptor 4
(233 mg, 0.38 mmol) and 3 Å powdered molecular sieves (0.5 g)
in anhyd CH2Cl2 (5 mL) was stirred for 1 h at rt under dry argon.
to give 10 as a colourless oil (5.97 g, 75%); ½a D20
ꢂ
+12 (c 1.0, CHCl3);
1H NMR (300 MHz, CDCl3): d 7.41–7.25 (m, 15H, Ph), 5.08 (m, 2H,
NH, H-1), 4.88 (m, 2H, CH2O), 4.71 (ABq, 2H, CH2Ph), 4.57 (ABq, 2H,
TMSOTf (13
lL, 0.07 mmol) was added, and the mixture was stir-
red for 2 h. Et3N (30
lL) was added, and the mixture was filtered

1692
N. Barroca-Aubry et al. / Carbohydrate Research 345 (2010) 1685–1697
through a pad of Celite and concentrated under vacuum. Flash sil-
ica gel chromatography with 9:1 toluene–EtOAc containing 0.2%
(v/v) Et3N afforded the disaccharide 13 (410 mg, 90%), which was
recrystallized from EtOAc–heptane; 1H NMR (500 MHz, CDCl3): d
7.39–7.21 (m, 20H, Ph), 6.87 (d, 1H, J2,NH 7.9, NHa), 6.77 (d, 1H,
J2,NH 7.7, NHb), 5.05 (t, 1H, J3,4 9.3, J4,5 9.3, H-4b), 5.04 (d, 1H, J1,2
7.5, H-1a), 4.96 (d, 1H, J1,2 8.3, H-1b), 4.73 (ABq, 2H, CH2Ph), 4.62
(ABq, 2H, CH2Ph), 4.57 (ABq, 2H, CH2Ph), 4.34 (ABq, 2H, CH2Ph),
4.14 (t, 1H, J2,3 8.7, J3,4 8.7, H-3a), 4.05 (dd, 1H, J2,3 10.4, J3,4 8.9,
H-3b), 4.01 (dd, 1H, J3,4 9.8, J4,5 8.3, H-4a), 3.67 (m, 2H, H-6a, H-
6b), 3.57 (m, 1H, H-2b), 3.52–3.42 (m, 4H, H-2a, H-5a, H-5b, H-
1H, J2,3 6.0, J3,4 6.0, H-3a), 3.73 (t, 1H, J2,3 6.2, J3,4 6.2, H-3b),
3.72–3.54 (m, 7H, H-2a, H-2b, H-4a, H-4b, H-5a, H-6a, H-6b),
0
0
3.50 (dd, 1H, J5,6 5.9, J6,6 9.7, H-6a), 3.38 (dd, 1H, J5,6 8.5, J6,6
0
10.6, H-6b), 3.26 (dd, 1H, J4,5 9.4, J5,6 4.7, H-5b), 3.02 (sl, 1H, OH-
4), 1.91 (s, 3H, CH3CONH), 1.83 (s, 3H, CH3CONH), 0.86 (s, 9H,
(CH3)3CSi), 0.12 (s, 3H, CH3Si), 0.10 (s, 3H, CH3Si); 13C NMR
(125 MHz, CDCl3): d 170.2, 170.1 (CONH), 139.0, 138.9, 138.2,
137.5 (C aromatic), 128.7–127.3 (CH aromatic), 100.0 (C-1b), 95.0
(C-1a), 80.9 (C-5a), 77.8 (C-4a), 77.3 (C-3b), 75.2 (C-3a), 74.6 (C-
4b), 73.6, 73.4, 73.1, 72.8 (4CH2Ph), 72.6 (C-5b), 69.4 (C-6b), 68.7
(C-6a), 59.1 (C-2a), 56.9 (C-2b), 25.7 ((CH3)3CSi), 23.6, 23.3
(CH3CONH), 18.0 ((CH3)3CSi), ꢃ4.2 (CH3Si), ꢃ5.1 (CH3Si); ESIMS:
m/z 922 [M+Na]+; Anal. Calcd for C50H66N2O11Si: C, 66.79; H,
7.40; N, 3.12. Found: C, 67.44; H, 7.80; N, 3.01.
0
6a), 3.55 (dd, 1H, J5,6 5.3, J6,6 10.7, H-6a), 1.87 (s, 3H, CH3CO),
0.87 (s, 9H, (CH3)3CSi), 0.11 (s, 3H, CH3Si), 0.07 (s, 3H, CH3Si); 13C
NMR (125 MHz, CDCl3): d 170.1 (CO, Ac), 162.2, 162.0 (COCCl3),
138.7, 138.4, 138.4, 137.8 (C aromatic), 128.9–128.0 (CH aromatic),
98.5 (C-1b), 94.9 (C-1a), 92.9, 92.8 (CCl3), 77.9 (C-3b), 77.9 (C-4a),
76.0 (C-3a), 74.9 (C-5a), 74.7, 74.5, 74.0 (CH2Ph), 73.8 (C-5b), 73.7
(CH2Ph), 72.3 (C-4b), 70.0 (C-6b), 68.7 (C-6a), 60.2 (C-2a), 59.2 (C-
2b), 26.0 ((CH3)3CSi), 21.2 (CH3CO), 18.3 ((CH3)3CSi), ꢃ3.7, ꢃ4.7
(CH3Si); ESIMS: m/z 1170 [M+Na]+; Anal. Calcd for C52H62Cl6N2O12-
Si: C, 54.41; H, 5.44; N, 2.44. Found: C, 54.62; H, 5.38; N, 2.41.
4.17. 2-Acetamido-3,6-di-O-benzyl-2-deoxy-b-
D-
glucopyranosyl-(1?4)-2-acetamido-3,6-di-O-benzyl-2-deoxy-
D-glucopyranose (16)
A mixture of 15 (556 mg, 0.62 mmol), AcOH (92 lL, 1.5 mmol)
and Bu4NFꢀ3H2O (490 mg, 1.5 mmol) in dry THF (23 mL) was stirred
at rt for 16 h. The mixture was concentrated and diluted with EtOAc
(30 mL), washed with water, satd aq NH4Cl and water, dried
(MgSO4) and concentrated. The residue was chromatographed on
a column of silica gel with 9:1 CH2Cl2–MeOH to give 16 as a white
solid (434 mg, 89%); 1H NMR (500 MHz, MeOD): d 7.41–7.18 (m,
20H, Ph), 5.09 (d, 1H, J1,2 3.6, H-1a), 5.00 (ABq, 2H, CH2Ph), 4.76
(ABq, 2H, CH2Ph), 4.72 (d, 1H, J1,2 8.5, H-1b), 4.63 (ABq, 2H, CH2Ph),
4.40 (ABq, 2H, CH2Ph), 4.13 (dd, 1H, J2,3 10.4, H-2a), 4.05 (m, 2H,
H-3b, H-4a), 3.85–3.70 (m, 5H, H-2b, H-3a, H-6a, H-6b, H-6b),
4.15. tert-Butyldimethylsilyl 2-acetamido-4-O-acetyl-3,6-di-O-
benzyl-2-deoxy-b-
O-benzyl-2-deoxy-b-
D
-glucopyranosyl-(1?4)-2-acetamido-3,6-di-
-glucopyranoside (14)
D
A mixture of 13 (690 mg, 0.6 mmol), Bu3SnH (1.9 mL, 7.2 mmol)
and AIBN (30 mg) in dry benzene (17 mL) was stirred for 1 h at rt un-
der a stream of dry argon. The mixture was then heated for 2 h at
80 °C, cooled and concentrated. The residue was stirred with hep-
tane (40 mL), and the crystalline material was filtered off. The resi-
due was chromatographed on a column of silica gel with 1:1
toluene–EtOAc to afford 14 as a white powder that was recrystal-
lized from EtOAc–heptane (550 mg, 97%); 1H NMR (500 MHz,
CDCl3): d 7.35–7.19 (m, 20H, Ph), 5.98 (sl, NHa), 5.21 (d, 1H, J2,NH
7.9, NHb), 5.07 (t, 1H, J3,4 9.1, J4,5 9.1, H-4b), 4.92 (d, 1H, J1,2 6.3, H-
1a), 4.74 (d, 1H, J1,2 7.3, H-1b), 4.70 (ABq, 2H, CH2Ph), 4.61 (ABq,
2H, CH2Ph), 4.57 (ABq, 2H, CH2Ph), 4.41 (ABq, 2H, CH2Ph), 4.04 (t,
1H, J2,3 6.8, J3,4 6.8, H-3a), 3.95–3.90 (m, 2H, H-3b, H-4a), 3.78 (dd,
0
3.55 (m, 2H, H-4b, H-5b), 3.45 (dd, 1H, J5,6 6.1, J6,6 11.7, H-6a),
3.35 (m, 1H, H-5a), 1.92 (s, 3H, CH3CONH), 1.91 (s, 3H, CH3CONH);
13C NMR (125 MHz, MeOD): d 174.1, 174.0 (CONH), 141.8, 141.0,
140.6, 140.5 (C aromatic), 130.2–128.8 (CH aromatic), 102.3
(C-1b), 93.2 (C-1a), 84.6 (C-4a), 80.0 (C-3a), 79.6 (C-5a), 78.0
(C-3b), 76.5, 75.8, 75.3, 75.0 (CH2Ph), 73.2 (C-5b), 72.5 (C-4b),
71.4 (C-6b), 70.7 (C-6a), 58.1 (C-2a), 55.4 (C-2b), 24.0, 23.5
(CH3CONH); HRESIMS: Calcd for C44H52N2O11Na [M+Na]+ m/z
807.3469; found 807.3477.
0
1H, J5,6 4.7, J6,6 10.4, H-6b), 3.70–3.65 (m, 2H, H-2a,
4.18. 2-Acetamido-2-deoxy-b-
D-glucopyranosyl-(1?4)-2-
H-6b), 3.64–3.56 (m, 2H, H-2b, H-5b), 3.53–3.49 (m, 2H, H-5a,
H-6a), 3.44 (dd, 1H, J5,6 6.3, J6,6 11.7 Hz, H-6a), 1.88 (s, 3H,
acetamido-2-deoxy- -glucopyranose (17)
D
0
CH3CONH), 1.86 (s, 3H, CH3CONH), 1.75 (s, 3H, CH3CO), 0.83 (s, 9H,
(CH3)3CSi), 0.08 (s, 3H, CH3Si), 0.06 (s, 3H, CH3Si); 13C NMR
(125 MHz, CDCl3): d 170.6 (CO, Ac), 170.2, 169.9 (CONH), 138.9,
138.3, 138.0, 137.9 (C aromatic), 128.6–127.4 (CH aromatic), 99.5
(C-1b), 95.1 (C-1a), 78.3 (C-4a), 77.8 (C-3b), 77.3 (C-3a), 74.9
(C-5b), 74.5 (C-5a), 73.6, 73.4, 73.1, 72.8 (CH2Ph), 71.7 (C-4b), 69.7
(C-6b), 69.4 (C-6a), 56.5 (C-2b), 55.7 (C-2a), 25.7 ((CH3)3CSi), 23.6,
23.4 (CH3CONH), 21.0 (CH3CO), 18.0 ((CH3)3CSi), ꢃ4.2, ꢃ5.1 (CH3Si);
ESIMS: m/z 964 [M+Na]+, 942 [M+H]+; Anal. Calcd for C52H68N2O12Si:
C, 66.36; H, 7.28; N, 2.98. Found: C, 66.52; H, 7.06; N, 2.90.
A solution of 16 (193 mg, 0.25 mmol) in 2:1 MeOH–water
(10 mL) was hydrogenated in the presence of 10% Pd–C (100 mg)
for 48 h at rt. The mixture was filtered through a pad of Celite, con-
centrated and freeze-dried. The residue was chromatographed on a
column of silica gel with 1:2 EtOAc–MeOH containing 0.2% (v/v)
Et3N to give 17 as
a
a
white powder (78 mg, 75%, isomer
:b = 3:2); 1H NMR (500 MHz, D2O): d 5.19 (d, 1H, J1,2 2.4,
H-1a
a
), 4.69 (d, 1H, J1,2 8.2, H-1ab), 4.59 (d, 1H, J1,2 8.3, H-1b),
, H-3a, H-5a, H-6b), 3.85–3.74 (m, 3H,
3.95–3.87 (m, 4H, H-2a
a
H-2b, H-6a, H-6b), 3.73–3.60 (m, 3H, H-2ab, H-4a, H-6a), 3.57
(m, 1H, H-3b), 3.56–3.45 (m, 2H, H-4b, H-5b), 2.05 (s, 3H,
CH3CONH), 2.02 (s, 3H, CH3CONH); 13C NMR (125 MHz, D2O): d
174.9, 174.8 (CONH), 101.8 (C-1b), 95.1 (C-1ab), 90.7 (C-1aa),
80.2 (C-4a), 76.2 (C-5b), 73.8 (C-3b), 70.3 (C-3a), 70.0 (C-4b),
4.16. tert-Butyldimethylsilyl 2-acetamido-3,6-di-O-benzyl-2-
deoxy-b-
2-deoxy-b-
D
-glucopyranosyl-(1?4)-2-acetamido-3,6-di-O-benzyl-
-glucopyranoside (15)
D
69.6 (C-5a), 60.8 (C-6b), 60.4 (C-6a), 56.4 (C-2ab), 55.9 (C-2b),
A suspension of 14 (738 mg, 0.78 mmol) in MeOH (20 mL) was
treated for 4 h from 0 °C to rt with methanolic NaOMe (1 M, 1 mL).
The solution was deionized with an Amberlite IR-120 (H+) resin, fil-
tered and concentrated. The residue was chromatographed on a
column of silica gel with 1:2 heptane–EtOAc to afford 15 as a white
powder (585 mg, 83%); 1H NMR (500 MHz, CDCl3): d 7.40–7.19 (m,
20H, Ph), 5.95 (d, J2,NH 8.7, NHa), 4.84 (d, 1H, J2,NH 8.7, NHb), 4.79 (d,
1H, J1,2 5.7, H-1a), 4.65 (ABq, 2H, CH2Ph), 4.62 (ABq, 2H, CH2Ph),
4.56 (d, 1H, J1,2 8.8, H-1b), 4.45–4.35 (m, 4H, 2 ꢁ CH2Ph), 3.88 (t,
53.9 (C-2a
C
a), 22.5, 22.4 (CH3CONH). HRESIMS: Calcd for
16H28N2O11Na [M+Na]+ m/z 447.1591; found 447.1576.
4.19. tert-Butyldimethylsilyl 3,6-di-O-benzyl-2-deoxy-2-
trichloroacetamido-b- -glucopyranosyl-(1?4)-3,6-di-O-benzyl-
2-deoxy-2-trichloroacetamido-b- -glucopyranoside (18)
D
D
A suspension of 13 (680 mg, 0.59 mmol) in MeOH (20 mL) was
treated overnight from 0 °C to rt with methanolic NaOMe (1 M,

N. Barroca-Aubry et al. / Carbohydrate Research 345 (2010) 1685–1697
1693
0.5 mL). The solution was deionized with an Amberlite IR-120 (H+)
resin, filtered and concentrated. The residue was chromatographed
on a column of silica gel with 2:1 heptane–EtOAc to afford 18 as a
white powder (485 mg, 74%); 1H NMR (500 MHz, CDCl3): d 7.31–
7.11 (m, 20H, Ph), 6.85 (d, 1H, J2,NH 8.1, NHa), 6.62 (d, 1H, J2,NH
7.5, NHb), 4.89 (d, 1H, J1,2 7.4, H-1b), 4.80–4.60 (m, 6H, 3 ꢁ CH2Ph),
4.44 (d, 1H, J1,2 7.7, H-1a), 4.33 (ABq, 2H, CH2Ph), 4.00 (t, 1H, J3,4 8.6,
J4,5 8.6, H-4a), 3.84 (dd, 1H, J2,3 8.3, J3,4 9.5, H-3b), 3.65–3.45 (m, 6H,
H-2a, H-2b, H-3a, H-4b, H-6a, H-6b), 3.42–3.34 (m, 2H, H-6a, H-
6b), 3.32–3.29 (m, 2H, H-5a, H-5b), 3.27 (sl, 1H, OH4), 0.78 (s, 9H,
(CH3)3CSi), 0.06 (s, 3H, CH3Si), 0.01 (s, 3H, CH3Si); 13C NMR
(125 MHz, CDCl3): d 161.7, 161.6 (COCCl3), 138.4, 138.0, 137.8,
137.4 (C aromatic), 128.5–127.4 (CH aromatic), 98.9 (C-1b), 94.9
(C-1a), 92.5, 92.5 (CCl3), 79.9 (C-3b), 77.8 (C-4a), 75.7 (C-3a), 74.6
(C-5a), 74.4 (C-5b), 74.3, 74.0, 73.6, 73.4 (CH2Ph), 73.1 (C-4b),
70.9 (C-6b), 68.3 (C-6a), 59.2 (C-2a), 57.6 (C-2b), 25.6 ((CH3)3CSi),
17.8 ((CH3)3CSi), ꢃ4.1, ꢃ5.0 (CH3Si); ESIMS: m/z 1128 [M+Na]+;
Anal. Calcd for C50H60Cl6N2O11Si: C, 54.31; H, 5.47; N, 2.53. Found:
C, 54.53; H, 5.67; N, 2.51.
(d, 1H, J2,NH 7.7, NHb), 5.05 (t, 1H, J3,4 9.7, J4,5 9.7, H-4b), 4.95 (s,
2H, CH2O), 4.87 (d, 1H, J1,2 8.4, H-1b), 4.76 (d, 1H, J2,NH 8.3, NHa),
4.72 (d, 1H, J1,2 8.4, H-1a), 4.65–4.43 (m, 6H, 3 ꢁ CH2Ph), 4.28
(ABq, 2H, CH2Ph), 4.03 (t, 1H, J2,3 8.9, J3,4 8.9, H-3a), 3.95 (dd, 1H,
J2,3 10.4, H-3b), 3.63–3.50 (m, 4H, H-4a, H-5b, H-6a, H-6b), 3.45–
3.26 (m, 5H, H-2a, H-2b H-5a, H-6a, H-6b), 1.76 (s, 3H, CH3CO),
0.78 (s, 9H, (CH3)3CSi), ꢃ0.02 (s, 3H, CH3Si), ꢃ0.08 (s, 3H, CH3Si);
13C NMR (125 MHz, CDCl3): d 169.8 (CO, Ac), 168.7 (CO2CH2Ph),
162.0 (COCCl3), 138.8, 138.1, 138.0, 137.5 (C aromatic), 128.5–
127.4 (CH aromatic), 100.0 (C-1a), 98.1 (C-1b), 92.5 (CCl3), 77.7
(C-4a), 76.1 (C-3b), 74.4 (C-3a), 73.9, 73.6 (CH2Ph), 73.3 (C-5a),
73.3, 72.3 (CH2Ph), 71.8 (C-5b), 70.2 (C-4b), 69.6 (C-6a), 68.4 (C-
6b), 66.6 (CH2O), 58.6 (C-2a), 49.5 (C-2b), 25.6 ((CH3)3CSi), 20.9
(CH3CO), 17.9 ((CH3)3CSi), ꢃ4.1, ꢃ5.2 (CH3Si); ESIMS: m/z 1159
[M+Na]+, 1137 [M+H]+; Anal. Calcd for C58H69Cl3N2O13Si: C,
61.29; H, 6.12; N, 2.46. Found: C, 61.35; H, 6.39; N, 2.41.
4.22. tert-Butyldimethylsilyl 2-acetamido-4-O-acetyl-3,6-di-O-
benzyl-2-deoxy-b-
D-glucopyranosyl-(1?4)-3,6-di-O-benzyl-2-
(benzyloxycarbonyl)amino-2-deoxy-b-
D
-glucopyranoside (21)
4.20. 4-O-Acetyl-3,6-di-O-benzyl-2-deoxy-2-
trichloroacetamido-b-
2-deoxy-2-trichloroacetamido-1-O-trichloroacetimidoyl-a-D-
glucopyranose (19)
D
-glucopyranosyl-(1?4)-3,6-di-O-benzyl-
A mixture of 20 (792 mg, 0.7 mmol), Bu3SnH (1.1 mL, 4.1 mmol)
and AIBN (30 mg) in dry benzene (15 mL) was stirred for 1 h at rt
under a stream of dry argon, heated for 2 h at 80 °C, cooled and
concentrated. The residue was stirred with heptane (40 mL), and
the crystalline material was filtered off. The residue was chromato-
graphed on a column of silica gel with 1:1 heptane–EtOAc to afford
21 as a colourless powder (592 mg, 82%); 1H NMR (500 MHz,
CDCl3): d 7.35–7.05 (m, 25H, Ph), 5.15 (d, 1H, J2,NH 7.5, NHb),
4.96 (s, 2H, CH2O), 4.94 (t, 1H, J3,4 9.6, J4,5 9.6, H-4b), 4.81 (d, 1H,
J1,2 8.3, H-1b), 4.80–4.40 (m, 8H, 3 ꢁ CH2Ph, H-1a, NHa), 4.25
(ABq, 2H, CH2Ph), 3.91 (m, 2H, H-3a, H-3b), 3.57 (m, 2H, H-4a,
H-5b), 3.42–3.26 (m, 7H, H-2a, H-2b, H-5b, H-6a, H-6a, H-6b,
H-6b), 1.78 (s, 3H, CH3CONH), 1.66 (s, 3H, CH3CO), 0.77 (s, 9H,
(CH3)3CSi), 0.12 (s, 3H, CH3Si), 0.07 (s, 3H, CH3Si); 13C NMR
A solution of Bu4NFꢀ3H2O (132 mg, 0.42 mmol) and AcOH
(24 L, 0.42 mmol) in THF (1 mL) was added to a solution of 13
l
(400 mg, 0.35 mmol) in dry THF (4 mL), and the mixture was stir-
red 14 h at rt. The mixture was concentrated and diluted with
EtOAc (30 mL), washed with satd aq NH4Cl and water, dried
(MgSO4) and concentrated. A mixture of the obtained hemiacetal,
CCl3CN (350 lL, 3.5 mmol) and DBU (13 lL, 0.09 mmol) in anhyd
CH2Cl2 (5 mL) was stirred for 1 h at rt and concentrated. The resi-
due was chromatographed on a column of silica gel with 2:1 hep-
tane–EtOAc containing 0.2% (v/v) of Et3N to give 19 as a white
powder (365 mg, 89% from 13); 1H NMR (500 MHz, CDCl3): d
8.67 (s, 1H, NH imidate), 7.43–7.19 (m, 20H, Ph), 6.73 (d, 1H,
J2,NH 7.7, NHa), 6.47 (d, 1H, J2,NH 7.7, NHb), 6.43 (d, 1H, J1,2 3.4,
H-1a), 5.07 (t, 1H, J3,4 9.1, J4,5 9.1, H-4b), 4.82 (ABq, 2H, CH2Ph),
4.72 (d, 1H, J1,2 7.7, H-1b), 4.61 (ABq, 2H, CH2Ph), 4.56 (ABq, 2H,
CH2Ph), 4.40 (ABq, 2H, CH2Ph), 4.30 (dd, 1H, J2,3 9.5, J3,4 9.1,
H-3a), 4.22 (ddd, 1H, J2,3 10.9, H-2a), 3.90–3.72 (m, 4H, H-3a,
(125 MHz, CDCl3):
d 170.5 (CO, Ac), 169.9 (CONH), 155.7
(CO2CH2Ph), 138.9, 138.3, 138.1, 136.6 (C aromatic), 128.6–127.4
(CH aromatic), 99.2 (C-1b), 95.7 (C-1a), 78.5 (C-3a), 78.4 (C-3b),
74.5 (C-4a), 74.4 (C-5a), 73.6 (C-5b), 73.5, 73.5, 73.3 (CH2Ph),
73.1 (C-4b), 71.9 (CH2Ph), 69.8 (C-6b), 68.6 (C-6a), 66.6 (CH2O),
58.8 (C-2a), 57.3 (C-2b), 25.6 ((CH3)3CSi), 23.5 (CH3CONH), 20.9
(CH3CO), 18.0 ((CH3)3CSi), ꢃ4.1, ꢃ5.2 (CH3Si); ESIMS: m/z 1055
[M+Na]+, 1033 [M+H]+; Anal. Calcd for C58H72N2O13Si: C, 67.42;
H, 7.02; N, 2.71. Found: C, 67.82; H, 7.35; N, 2.59.
0
H-4a H-6a, H-6b), 3.63 (dd, 1H, J5,6 2.1, J5,6 11.3, H-6b), 3.52–
3.35 (m, 4H, H-2b, H-5a, H-5b, H-6a), 1.92 (s, 3H, CH3CO); 13C
NMR (125 MHz, CDCl3): d 169.7 (CO, Ac), 161.9, 161.8 (COCCl3),
160.0 (C@NH), 137.9, 137.7, 137.6, 137.3 (C aromatic), 128.7–
127.6 (CH aromatic), 98.6 (C-1b), 94.1 (C-1a), 92.4, 92.0 (CCl3 tri-
chloroacetamido), 90.8 (CCl3 imidate), 77.9 (C-4a), 75.2 (C-3b),
74.9 (C-3a), 74.3 (C-5a), 73.8 (C-5b), 73.6, 73.5, 73.5, 73.1 (CH2Ph),
71.4 (C-4b), 69.3 (C-6b), 67.3 (C-6a), 57.9 (C-2a), 53.9 (C-2b), 20.9
(CH3CO); HRESIMS: m/z calcd for C48H48Cl9N3O12Na [M+Na]+
1196.0332; found 1196.0337.
4.23. tert-Butyldimethylsilyl 2-acetamido-3,6-di-O-benzyl-2-
deoxy-b-
D
-glucopyranosyl-(1?4)-3,6-di-O-benzyl-2-
-glucopyranoside (22)
(benzyloxycarbonyl)amino-2-deoxy-b-
D
A suspension of 21 (681 mg, 0.66 mmol) in MeOH (20 mL) was
treated for 4 h at 0 °C to rt with methanolic NaOMe (1 M, 0.5 mL).
The solution was deionized with an Amberlite IR-120 (H+) resin, fil-
tered and concentrated. The residue was chromatographed on a
column of silica gel with 1:1 heptane–EtOAc to afford 22 as a white
powder that was recrystallized from EtOAc–heptane (614 mg,
87%); 1H NMR (500 MHz, CDCl3): d 7.39–7.21 (m, 25H, Ph), 5.05
(s, 2H, CH2O), 4.90 (d, 1H, J2,NH 7.9, NHb), 4.85 (m, 1H, NHa), 4.82
(d, 1H, J1,2 8.8, H-1b), 4.72 (ABq, 2H, CH2Ph), 4.70 (ABq, 2H, CH2Ph),
4.63 (d, 1H, J1,2 7.9, H-1a), 4.60 (ABq, 2H, CH2Ph), 4.43 (s, 2H,
CH2Ph), 3.94 (t, 1H, J2,3 8.7, J3,4 8.7, H-3a), 3.82 (m, 1H, H-3b),
4.21. tert-Butyldimethylsilyl 4-O-acetyl-3,6-di-O-benzyl-2-
deoxy-2-trichloroacetamido-b-D-glucopyranosyl-(1?4)-3,6-di-
O-benzyl-2-(benzyloxycarbonyl)amino-2-deoxy-b-D-
glucopyranoside (20)
A mixture of the donor 6 (1.2 g, 1.74 mmol) and the acceptor 10
(705 mg, 1.16 mmol) in anhyd CH2Cl2 (30 mL) was stirred for 1 h at
0
rt under dry argon. BF3ꢀEt2O (35
l
L, 0.28 mmol) was added, and the
3.69 (t, 1H, J3,4 8.8, J4,5 8.8, H-4b), 3.65 (dd, 1H, J5,6 2.8, J6,6 8.2,
mixture was stirred for 3 h. Et3N (120
l
L) was added, and the mix-
H-6a), 3.60–3.49 (m, 4H, H-2b, H-4a, H-6a, H-6b), 3.47 (dd, 1H,
J5,6 6.4, J6,6 9.6, H-6b), 3.44 (m, 1H, H-5a), 3.33 (m, 1H, J4,5 10.1,
J5,6 4.0, H-5b), 3.29 (m, 1H, H-2a), 3.12 (sl, 1H, OH-4), 1.75 (s, 3H,
CH3CONH), 0.86 (s, 9H, (CH3)3CSi), 0.11 (s, 3H, CH3Si), ꢃ0.03 (s,
3H, CH3Si); 13C NMR (125 MHz, CDCl3): d 170.1 (CONH), 155.7
0
ture was concentrated under reduced pressure. Flash silica gel
chromatography with 9:1 toluene–EtOAc containing 0.2% (v/v)
Et3N afforded the disaccharide 20 as a white powder (958 mg,
73%); 1H NMR (500 MHz, CDCl3): d 7.33–7.11 (m, 25H, Ph), 6.80

1694
N. Barroca-Aubry et al. / Carbohydrate Research 345 (2010) 1685–1697
(CO2CH2Ph), 139.0, 138.7, 138.2, 137.5, 136.6 (C aromatic), 128.7–
127.3 (CH aromatic), 100.0 (C-1b), 96.5 (C-1a), 81.1 (C-4a), 77.3 (C-
3b), 76.7 (C-3a), 74.6 (C-4b), 74.5, 74.0 (CH2Ph), 73.9 (C-5a), 73.8,
73.6 (CH2Ph), 72.7 (C-5b), 71.4 (C-6b), 68.7 (C-6a), 66.7 (CH2O),
59.1 (C-2a), 56.0 (C-2b), 25.7 ((CH3)3CSi), 23.6 (CH3CONH), 18.0
((CH3)3CSi), ꢃ4.1, ꢃ5.2 (CH3Si); ESIMS: m/z 1013 [M+Na]+, 991
[M+H]+; Anal. Calcd for C56H70N2O12Si: C, 67.85; H, 7.12; N, 2.83.
Found: C, 67.70; H, 7.27; N, 2.73.
62%). From 24: A mixture of 24 (106 mg, 0.21 mmol), AcOH
(30
THF (20 mL) was stirred at rt for 16 h. The mixture was concen-
trated and diluted with EtOAc (30 mL), washed with water, satd
aq NH4Cl and water, dried (MgSO4) and concentrated. The residue
was chromatographed on a column of silica gel with 1:2 EtOAc–
l
L, 0.52 mmol) and Bu4NFꢀ3H2O (168 mg, 0.53 mmol) in dry
MeOH to give 25 as a white solid (74 mg, 92%, isomer
a
:b = 3:2);
1H NMR (500 MHz, D2O): d 5.55 (d, 1H, J1,2 3.5, H-1a
a
), 5.08 (d,
1H, J1,2 8.6, H-1ab), 4.58 (d, 1H, J1,2 8.5, H-1b), 4.05 (m, 1H, H-3a),
3.99–3.92 (m, 2H, H-5a, H-6b), 3.90–3.76 (m, 3H, H-2b, H-6a, H-
6b), 3.73–3.62 (m, 2H, H-4a, H-6a), 3.60 (m, 1H, H-3b), 3.58–3.43
4.24. 2-Acetamido-3,6-di-O-benzyl-2-deoxy-b-
glucopyranosyl-(1?4)-3,6-di-O-benzyl-2-
D-
(benzyloxycarbonyl)amino-2-deoxy-
D
-glucopyranose (23)
L, 1.2 mmol)
(m, 2H, H-4b, H-5b), 3.29 (m, 1H, H-2a
2.05 (s, 3H, CH3CONH); 13C NMR (125 MHz, D2O): d 175.1 (CONH),
101.8 (C-1b), 91.5 (C-1ab), 87.6 (C-1a ), 79.0 (C-4a), 76.3 (C-5b),
73.8 (C-3b), 70.2 (C-4b), 70.2 (C-5a), 68.7 (C-3a), 62.5 (C-2ab),
a), 3.02 (m, 1H, H-2ab),
A mixture of 22 (480 mg, 0.48 mmol), AcOH (69
l
a
and Bu4NFꢀ3H2O (382 mg, 1.2 mmol) in dry THF (20 mL) was stir-
red at rt for 16 h. The mixture was concentrated and diluted with
EtOAc (30 mL), washed with water, satd aq NH4Cl and water, dried
(MgSO4) and concentrated. The residue was chromatographed on a
column of silica gel with 9:1 CH2Cl2–MeOH to give 23 as a white
solid (369 mg, 87%); 1H NMR (500 MHz, MeOD): d 7.42–7.21 (m,
25H, Ph), 5.17 (d, 1H, J1,2 3.5, H-1a), 5.14 (ABq, 2H, CH2O), 4.90
(ABq, 2H, CH2Ph), 4.83 (ABq, 2H, CH2Ph), 4.80 (d, 1H, J1,2 8.2, H-
1b), 4.68 (ABq, 2H, CH2Ph), 4.47 (ABq, 2H, CH2Ph), 4.11 (dd, 1H,
J2,3 7.9, J3,4 9.9, H-3b), 4.07 (dd, 1H, J2,3 8.2, J3,4 10.1, H-3a), 3.91
(m, 6H, H-2a, H-2b, H-4b, H-6a, H-6a, H-6b), 3.60 (m, 2H, H-4b,
61.3 (C-2aa), 61.0 (C-6b), 60.1 (C-6a), 56.0 (C-2b), 22.5
(CH3CONH); HRESIMS: m/z calcd for C14H27 N2O10 [M+H]+
383.1666; found 383.1671.
4.27. tert-Butyldimethylsilyl 3,6-di-O-benzyl-2-deoxy-2-
trichloroacetamido-b-
D-glucopyranosyl-(1?4)-3,6-di-O-benzyl-
2-(benzyloxycarbonyl)amino-2-deoxy-b-
D-glucopyranoside (26)
A suspension of 20 (1.11 g, 0.98 mmol) in MeOH (20 mL) was
treated overnight from 0 °C to rt with methanolic NaOMe (1 M,
1 mL). The solution was deionized with an Amberlite IR-120 (H+)
resin, filtered and concentrated. The residue was chromatographed
on a column of silica gel with 2:1 heptane–EtOAc to afford 26 as a
white powder (750 mg, 70%); 1H NMR (500 MHz, CDCl3): d 7.31–
7.08 (m, 25H, Ph), 6.54 (d, 1H, J2,NH 7.4, NHb), 5.00 (d, 1H, J2,NH
9.0, NHa), 4.97 (s, 2H, CH2O), 4.77 (d, 1H, J1,2 8.2, H-1a), 4.72 (d,
1H, J1,2 8.4, H-1b), 4.72–4.36 (m, 8H, 4 ꢁ CH2Ph), 3.98 (t, 1H, J2,3
8.8, J3,4 8.8, H-3a), 3.68–3.50 (m, 4H, H-2b, H-3b, H-4a, H-4b, H-
0
H-5a), 3.49 (dd, 1H, J5,6 6.0, J6,6 11.0, H-6b), 3.39 (m, 1H, H-5a),
1.98 (s, 3H, CH3CONH); 13C NMR (125 MHz, MeOD): d 174.1
(CONH), 159.4 (CO2CH2Ph), 141.6, 141.0, 140.7, 140.5, 139.1 (C aro-
matic), 130.2–128.8 (CH aromatic), 102.2 (C-1b), 93.7 (C-1a), 84.6
(C-4b), 80.5 (C-4a), 78.2 (C-3b), 78.1 (C-5b), 76.5, 76.1, 75.3, 75.0
(CH2Ph), 73.3 (C-3a), 72.4 (C-5a), 71.4 (C-6a), 70.8 (C-6a), 68.3
(CH2O), 58.2 (C-2b), 57.5 (C-2a), 23.9 (CH3CONH); HRESIMS: m/z
calcd for C50H56N2O12Na [M+Na]+ 899.3731; found 899.3737.
0
6a, H-6a, H-6b), 3.42 (dd, 1H, J5,6 6.1, J6,6 9.9, H-6b), 3.33–3.20
4.25. tert-Butyldimethylsilyl 2-acetamido-2-deoxy-b-
glucopyranosyl-(1?4)-2-amino-2-deoxy-b-D-glucopyranoside
(24)
D
-
(m, 3H, H-2a, H-5a, H-5b), 3.09 (sl, 1H, OH-4), 0.82 (s, 9H,
(CH3)3CSi), 0.03 (s, 3H, CH3Si), ꢃ0.04 (s, 3H, CH3Si); 13C NMR
(125 MHz, CDCl3): d 161.7 (COCCl3), 155.7 (CO2CH2Ph), 138.9,
138.1, 138.0, 137.5, 136.5 (C aromatic), 128.6–127.3 (CH aromatic),
98.6 (C-1b), 95.6 (C-1a), 92.6 (CCl3), 79.9 (C-4a), 78.3 (C-3a), 75.7
(C-3b), 74.6 (C-4b), 74.4 (C-5a), 74.3, 73.8, 73.7, 73.4 (CH2Ph),
72.9 (C-5b), 71.1 (C-6a), 68.4 (C-6b), 66.6 (CH2O), 59.1 (C-2a),
57.9 (C-2b), 25.6 ((CH3)3CSi), 17.9 ((CH3)3CSi), ꢃ4.1, ꢃ5.1 (CH3Si);
ESIMS: m/z 1117 [M+Na]+, 1095 [M+H]+; Anal. Calcd for
A solution of 22 (280 mg, 0.28 mmol) in 5:10:4 EtOAc–MeOH–
water (25 mL) was hydrogenated in the presence of 10% Pd–C
(100 mg) for 48 h at rt. The mixture was filtered through a pad of
Celite, concentrated and freeze-dried. The residue was chromato-
graphed on a column of silica gel with 1:2 EtOAc–MeOH containing
0.2% (v/v) Et3N to give 24 as a white powder (105 mg, 75%); 1H
NMR (500 MHz, MeOD): d 4.94 (d, 1H, J1,2 8.1, H-1a), 4.49 (d, 1H,
C56H67Cl3N2O12Si: C, 61.45; H, 6.17; N, 2.56. Found: C, 61.23; H,
6.10; N, 2.56.
0
J1,2 8.5, H-1b), 3.88 (dd, 1H, J5,6 1.9, J6,6 11.8, H-6a), 3.80–3.71
(m, 2H, H-3a, H-6b), 3.68–3.50 (m, 3H, H-2b, H-6b, H-6a), 3.47–
3.41 (m, 1H, H-4a), 3.34–3.30 (m, 1H, H-3b), 3.28–3.12 (m, 3H,
H-4b, H-5a, H-5b), 2.65 (m, 1H, H-2a), 1.98 (s, 3H, CH3CONH),
0.92 (s, 9H, (CH3)3CSi), 0.17 (s, 3H, CH3Si), 0.15 (s, 3H, CH3Si); 13C
NMR (125 MHz, MeOD): d 172.8 (CONH), 102.2 (C-1b), 94.8 (C-
1a), 80.9 (C-4a), 77.1 (C-5b), 75.5 (C-5a), 74.7 (C-3b), 71.0 (C-4b),
70.1 (C-2a), 69.9 (C-3a), 61.5 (C-6a), 60.5 (C-6b), 56.3 (C-2b), 25.4
((CH3)3CSi), 22.1 (CH3CONH), 17.6 ((CH3)3CSi), 8.2 (CH3Si), 7.4
(CH3Si); HRESIMS: m/z calcd for C20H40N2O10SiNa [M+Na]+
519.2350; found 519.2353.
4.28. 4-O-Acetyl-3,6-di-O-benzyl-2-deoxy-2-trichloroacetam-
ido-b-D-glucopyranosyl-(1?4)-3,6-di-O-benzyl-2-(benzyloxy-
carbonyl)amino-2-deoxy-1-O-trichloroacetimidoyl-a-D-
glucopyranose (27)
A solution of Bu4NFꢀ3H2O (210 mg, 0.67 mmol) and AcOH
(37 L, 0.65 mmol) in THF (1 mL) was added to a solution of 20
l
(416 mg, 0.37 mmol) in dry THF (4 mL), and the mixture was stir-
red for 14 h at rt. The mixture was concentrated, diluted with
EtOAc (30 mL), washed with satd aq NH4Cl and water, dried
(MgSO4) and concentrated. A mixture of the obtained hemiacetal,
4.26. 2-Acetamido-2-deoxy-b-
D-glucopyranosyl-(1?4)-2-
CCl3CN (370 lL, 3.7 mmol) and DBU (20 lL, 0.13 mmol) in anhyd
amino-2-deoxy- -glucopyranose (25)
D
CH2Cl2 (5 mL) was stirred for 1 h at rt and concentrated. The resi-
due was chromatographed on a column of silica gel with 2:1 hep-
tane–EtOAc containing 0.2% (v/v) Et3N to give 27 as a white
powder (362 mg, 84% from 20); 1H NMR (500 MHz, CDCl3): d
8.62 (s, 1H, NH imidate), 7.37–7.18 (m, 25H, Ph), 6.83 (d, 1H,
J2,NHa 8.7, NHa), 6.61 (d, 1H, J2,NHb 8.1, NHb), 6.31 (d, 1H, J1,2 3.4,
H-1a), 5.14–4.99 (m, 3H, H-4b, CH2O), 4.74–4.35 (m, 11H, H-1b,
H-2a, H-3a, 4 ꢁ CH2Ph), 4.25 (t, 1H, J3,4 9.4, J2,3 9.4, H-3b), 4.09
From 23: A solution of 23 (190 mg, 0.22 mmol) in 2:1 MeOH–
water (10 mL) was hydrogenated in the presence of 10%
Pd–C (100 mg) for 48 h at rt. The mixture was filtered through a
pad of Celite, concentrated and freeze-dried. The residue was chro-
matographed on a column of silica gel with 1:2 EtOAc–MeOH
containing 0.2% (v/v) Et3N to give 25 as a white powder (52 mg,

N. Barroca-Aubry et al. / Carbohydrate Research 345 (2010) 1685–1697
1695
(m,1H, H-5a), 3.84–3.58 (m, 5H, H-2b, H-4a, H-5b, H-6a, H-6b),
3.50–3.36 (m, 2H, H-6a, H-6b), 1.92 (s, 3H, CH3CO); 13C NMR
(125 MHz, CDCl3): d 169.7 (CO, Ac), 168.7 (CO2CH2Ph), 161.9
(COCCl3), 159.9 (C@NH), 137.9, 137.7, 137.5, 137.3, 136.9 (C aro-
matic), 128.8–127.6 (CH aromatic), 99.0 (C-1a), 98.0 (C-1b), 92.0
(CCl3 trichloroacetamido), 90.7 (CCl3 imidate), 77.7 (C-4a), 76.0
(C-3b), 74.4 (C-3a), 73.9, 73.5 (CH2Ph), 73.4 (C-5a), 73.3, 72.2
(CH2Ph), 71.9 (C-5b), 71.4 (C-4b), 69.5 (C-6a), 68.9 (C-6b), 66.8
(CH2O), 58.1 (C-2a), 54.1 (C-2b), 20.9 (CH3CO); ESIMS: m/z 1005
[M-CCl3CONH]+; Anal. Calcd for C54H55Cl6N3O13: C, 55.59; H,
4.75; N, 3.60. Found: C, 55.22; H, 4.29; N, 3.72.
(C-2a), 55.9 (C-2b), 25.7 ((CH3)3CSi), 23.5 (CH3CONH), 21.0
(CH3CO), 18.0 ((CH3)3CSi), ꢃ4.1, ꢃ5.1 (CH3Si); ESIMS: m/z 1055
[M+Na]+, 1033 [M+H]+; Anal. Calcd for C58H72N2O13Si: C, 67.42;
H, 7.02; N, 2.71. Found: C, 67.94; H, 7.36; N, 2.68.
4.31. tert-Butyldimethylsilyl 3,6-di-O-benzyl-2-
(benzyloxycarbonyl)amino-2-deoxy-b-
2-acetamido-3,6-di-O-benzyl-2-deoxy-b-
D
-glucopyranosyl-(1?4)-
-glucopyranoside (30)
D
A suspension of 29 (507 mg, 0.49 mmol) in MeOH (20 mL) was
treated for 4 h at 0 °C to rt with methanolic NaOMe (1 M, 0.6 mL).
The solution was deionized with an Amberlite IR-120 (H+) resin, fil-
tered and concentrated. The residue was chromatographed on a
column of silica gel with 1:1 heptane–EtOAc to afford 30 as a white
powder (460 mg, 95%); 1H NMR (500 MHz, CDCl3): d 7.46–7.19 (m,
25H, Ph), 5.71 (sl, 1H, NHa), 5.07 (s, 2H, CH2O), 4.90 (d, 1H, J1,2 6.4,
H-1a), 4.70 (ABq, 2H, CH2Ph), 4.73–4.35 (m, 8H, H-1b, NHb,
3 ꢁ CH2Ph), 3.92 (t, 1H, J2,3 6.8, J3,4 6.8, H-3a), 3.84 (dd, 1H, J4,5
7.4, H-4a), 3.68 (t, 1H, J2,3 9.1, J3,4 9.1, H-3b), 3.65–3.40 (m, 8H,
H-2a, H-2b, H-4b, H-5a, H-6a, H-6a, H-6b, H-6b), 3.27 (m, 1H, J4,5
9.7, J5,6a 5.1, J5,6b 5.1, H-5b), 2.99 (sl, 1H, OH-4), 1.89 (s, 3H,
CH3CONH), 0.87 (s, 9H, (CH3)3CSi), 0.12 (s, 3H, CH3Si), 0.07 (s, 3H,
4.29. tert-Butyldimethylsilyl 4-O-acetyl-3,6-di-O-benzyl-2-
(benzyloxycarbonyl)amino-2-deoxy-b-D-glucopyranosyl-(1?4)-
3,6-di-O-benzyl-2-deoxy-2-trichloroacetamido-b-D-
glucopyranoside (28)
A mixture of the donor 12 (922 mg, 1.36 mmol) and the accep-
tor 4 (560 mg, 0.9 mmol) in anhyd CH2Cl2 (20 mL) was stirred for
1 h at rt under dry argon. BF3ꢀEt2O (26
l
L, 0.21 mmol) was added,
and the mixture was stirred for 3 h. Et3N (100
lL) was added, and
the mixture was concentrated under vacuum. Flash silica gel chro-
matography with 9:1 toluene–EtOAc containing 0.2% (v/v) Et3N
afforded the disaccharide 28 as a white powder (720 mg, 70%);
1H NMR (500 MHz, CDCl3): d 7.45–7.22 (m, 25H, Ph), 6.91 (d, 1H,
J2,NH 7.4, NHa), 5.09–4.85 (m, 5H, CH2O, H-1a, NHa, H-1b), 4.97 (t,
1H, J3,4 9.2 Hz, H-4b), 4.70–4.41 (m, 6H, 3 ꢁ CH2Ph), 4.26 (ABq,
2H, CH2Ph), 4.07–3.90 (m, 2H, H-3a, H-3b), 3.70–3.25 (m, 9H, H-
2a, H-2b, H-4a, H-5a, H-5b, H-6a, H-6a, H-6b, H-6b), 1.82 (s, 3H,
CH3CO), 0.88 (s, 9H, (CH3)3CSi), 0.14 (s, 3H, CH3Si), 0.08 (s, 3H,
CH3Si); 13C NMR (125 MHz, CDCl3): d 170.2 (CO, Ac), 169.9
(CO2CH2Ph), 162.1 (COCCl3), 138.9, 138.8, 138.4, 138.4, 138.3 (C
aromatic), 129.0–127.8 (CH aromatic), 100.0 (C-1b), 95.1 (C-1a),
93.0 (CCl3), 79.1 (C-3b), 78.2 (C-4a), 76.5 (C-3a), 75.5 (C-5b),
74.9, 74.7, 74.2, 73.9 (CH2Ph), 73.5 (C-5a), 72.2 (C-4b), 70.2 (C-
6b), 68.4 (C-6a), 67.2 (CH2O), 60.1 (C-2a), 58.3 (C-2b), 26.1
((CH3)3CSi), 21.3 (CH3CO), 18.3 ((CH3)3CSi), ꢃ3.7, ꢃ4.6 (CH3Si);
ESIMS: m/z 1159 [M+Na]+, 1137 [M+H]+; Anal. Calcd for
CH3Si); 13C NMR (125 MHz, CDCl3):
d 170.1 (CONH), 156.2
(CO2CH2Ph), 139.0, 138.9, 138.1, 137.6, 136.6 (C aromatic),
128.5–127.3 (CH aromatic), 100.4 (C-1b), 95.0 (C-1a), 80.9 (C-5a),
77.8 (C-4a), 75.2 (C-3a), 74.2 (C-3b), 73.7, 73.7 (CH2Ph), 73.6
(C-4b), 73.3 (CH2Ph), 73.1 (C-5b), 70.9 (CH2Ph), 69.4 (C-6b), 69.0
(C-6a), 66.8 (CH2O), 56.9 (C-2b), 55.6 (C-2a), 25.7 ((CH3)3CSi),
23.3 (CH3CONH), 17.9 ((CH3)3CSi), ꢃ4.2, ꢃ5.1 (CH3Si); ESIMS: m/z
1013 [M+Na]+, 991 [M+H]+; Anal. Calcd for C56H70N2O12Si: C,
67.85; H, 7.12; N, 2.83. Found: C, 67.62; H, 7.48; N, 2.70.
4.32. 3,6-Di-O-benzyl-2-(benzyloxycarbonyl)amino-2-deoxy-b-
D-glucopyranosyl-(1?4)-2-acetamido-3,6-di-O-benzyl-2-deoxy-
D-glucopyranose (31)
A mixture of 30 (469 mg, 0.47 mmol), AcOH (68 lL, 1.2 mmol)
and Bu4NFꢀ3H2O (383 mg, 1.2 mmol) in dry THF (20 mL) was stir-
red at rt for 16 h. The mixture was concentrated and diluted with
EtOAc (30 mL), washed with water, satd aq NH4Cl and water, dried
(MgSO4) and concentrated. The residue was chromatographed on a
column of silica gel with 9:1 CH2Cl2–MeOH to give 31 as a white
solid (370 mg, 89%); 1H NMR (500 MHz, MeOD): d 7.45–7.22 (m,
25H, Ph), 5.11 (m, 2H, CH2O), 5.10 (d, 1H, J1,2 3.4, H-1a), 4.80
(ABq, 2H, CH2Ph), 4.70–4.50 (m, 4H, 2 ꢁ CH2Ph), 4.61 (d, 1H, J1,2
8.2, H-1b), 4.37 (ABq, 2H, CH2Ph), 4.12 (dd, 1H, J2,3 10.4, H-2a),
4.04 (t, 1H, J4,5 8.8, J3,4 8.8, H-4a), 4.00 (m, 1H, H-3b), 3.81 (dd,
C58H69Cl3N2O13Si: C, 61.29; H, 6.12; N, 2.46. Found: C, 61.13; H,
6.45; N, 2.40.
4.30. tert-Butyldimethylsilyl 4-O-acetyl-3,6-di-O-benzyl-2-
(benzyloxycarbonyl)amino-2-deoxy-b-
D-glucopyranosyl-(1?4)-
2-acetamido-3,6-di-O-benzyl-2-deoxy-b-
D
-glucopyranoside (29)
A
mixture of 28 (837 mg, 0.74 mmol), Bu3SnH (1.2 mL,
4.5 mmol) and AIBN (30 mg) in dry benzene (16 mL) was stirred
for 1 h at rt under a stream of dry argon, heated for 2 h at 80 °C,
cooled and concentrated. The residue was stirred with heptane
(40 mL), and the crystalline material was filtered off. The residue
was chromatographed on a column of silica gel with 1:1 hep-
tane–EtOAc to afford 29 as a white powder which was recrystal-
lized from CH2Cl2–heptane (571 mg, 75%); 1H NMR (500 MHz,
CDCl3): d 7.39–7.16 (m, 25H, Ph), 5.74 (m, 1H, NHa), 5.07 (m, 3H,
CH2O, NHb), 5.03 (t, 1H, J3,4 9.1, J4,5 9.1, H-4b), 4.93 (d, 1H, J1,2
6.6, H-1a), 4.71 (ABq, 2H, CH2Ph), 4.59 (d, 1H, J1,2 8.8, H-1b), 4.52
(m, 2H, CH2Ph), 4.47–4.30 (m, 4H, 2 ꢁ CH2Ph), 3.99 (m, 1H,
H-4a), 3.91 (t, 1H, J2,3 7.8, J3,4 7.8, H-3a), 3.70 (m, 1H, H-3b), 3.56
(m, 2H, H-6a, H-6b), 3.53–3.37 (m, 6H, H-2a, H-2b, H-5a, H-5b,
H-6a, H-6b), 1.89 (s, 3H, CH3CONH), 1.87 (s, 3H, CH3CO), 0.86 (s,
9H, (CH3)3CSi), 0.09 (s, 3H, CH3Si), 0.07 (s, 3H, CH3Si); 13C NMR
0
1H, J3,4 8.5, H-3a), 3.76 (dd, 1H, J5,6 1.7, J6,6 11.2, H-6a), 3.72 (m,
1H, H-6b), 3.60–3.47 (m, 4H, H-2b, H-4b, H-5b, H-6b), 3.43 (dd,
1H, J5,6 6.1, H-6a), 3.32 (m, 1H, H-5a), 1.97 (s, 3H, CH3CONH); 13C
NMR (125 MHz, MeOD): d 173.9 (CONH), 159.3 (CO2CH2Ph),
141.8, 140.9, 140.6, 140.4, 139.2 (C aromatic), 130.3–128.8 (CH
aromatic), 102.8 (C-1b), 93.2 (C-1a), 84.6 (C-4a), 80.4 (C-3a), 78.4
(C-3b), 78.0 (C-5a), 76.7, 75.9, 75.3, 74.9 (CH2Ph), 73.2 (C-5b),
72.2 (C-4b), 71.5 (C-6b), 70.6 (C-6a), 68.2 (CH2O), 59.7 (C-2b),
55.3 (C-2a), 23.5 (CH3CONH); HRESIMS: m/z calcd for C50H56N2O12-
Na [M+Na]+ 899.3731; found 899.3737.
4.33. 2-Amino-2-deoxy-b-D-glucopyranosyl-(1?4)-2-
acetamido-2-deoxy- -glucopyranose (32)
D
(125 MHz, CDCl3):
d
170.1 (CO, Ac), 169.8 (CONH), 156.0
A solution of 31 (226 mg, 0.26 mmol) in 2:1 MeOH–water
(10 mL) was hydrogenated in the presence of 10% Pd–C (100 mg)
for 48 h at rt. The mixture was filtered through a pad of Celite, con-
centrated and freeze-dried. The residue was chromatographed on a
column of silica gel with 1:2 EtOAc–MeOH containing 0.2% (v/v)
(CO2CH2Ph), 139.1, 138.3, 138.0, 137.9, 136.5 (C aromatic),
128.6–127.4 (CH aromatic), 100.0 (C-1b), 95.0 (C-1a), 78.6 (C-3b),
77.9 (C-3a), 76.1 (C-4a), 74.3 (C-5a), 73.7, 73.7, 73.7, 73.3 (CH2Ph),
73.2 (C-5b), 71.5 (C-4b), 69.8 (C-6a), 68.8 (C-6b), 66.9 (CH2O), 57.5

1696
N. Barroca-Aubry et al. / Carbohydrate Research 345 (2010) 1685–1697
Et3N to give 32 as a white powder (74 mg, 75%, isomer
1H NMR (500 MHz, D2O): d 5.20 (d, 1H, J1,2 2.2, H-1a
), 4.74 (d, 1H,
J1,2 7.9, H-1ab), 4.52 (d, 1H, J1,2 7.9, H-1b), 3.99 (m, 1H, H-3a), 3.97–
3.82 (m, 3H, H-2a , H-6a, H-6a), 3.79–3.55 (m, 6H, H-2ab, H-4a, H-
a
:b = 3:2);
[M+Na]+ 1125 [M+H]+; Anal. Calcd for C64H76N2O14Si: C, 68.30;
H, 6.81; N, 2.49. Found: C, 68.37; H, 7.01; N, 2.44.
,
a
a
4.36. tert-Butyldimethylsilyl 3,6-di-O-benzyl-2-
5a, H-5b, H-6b, H-6b), 3.53–3.38 (m, 2H, H-3b, H-4b), 2.72 (m, 1H,
(benzyloxycarbonyl)amino-2-deoxy-b-D-glucopyranosyl-(1?4)-
3,6-di-O-benzyl-2-(benzyloxycarbonyl)amino-2-deoxy-b-D-
H-2b), 2.05 (s, 3H, CH3CONH); 13C NMR (125 MHz, D2O): d 175.1
(CONH), 102.8 (C-1b), 95.2 (C-1ab), 90.9 (C-1aa), 79.0 (C-4a),
glucopyranoside (35)
76.5 (C-4b), 75.8 (C-3b), 75.1 (C-5a), 72.7 (C-5b), 70.5 (C-3a),
61.0 (C-6b), 60.5 (C-6a), 57.0 (C-2b), 56.7 (C-2ab), 54.2 (C-2a
a
),
A suspension of 34 (1.42 g, 1.26 mmol) in MeOH (30 mL) was
treated for 4 h at 0 °C to rt with methanolic NaOMe (1 M,
1.3 mL). The solution was deionized with Amberlite IR-120 (H+) re-
sin, filtered and concentrated. The residue was chromatographed
on a column of silica gel with 2:1 heptane–EtOAc to afford 35 as
a white powder (1.08 g, 79%); 1H NMR (500 MHz, CDCl3): d 7.38–
7.16 (m, 30H, Ph), 5.10 (m, 2H, CH2O), 5.02 (s, 2H, CH2O), 4.83–
4.50 (m, 10H, NHa, NHb, H-1a, H-1b, 3 ꢁ CH2Ph), 4.39 (s, 2H,
CH2Ph), 3.90 (t, 1H, J2,3 8.9, J3,4 8.9, H-3b), 3.73 (m, 1H, H-4a),
22.5 (CH3CONH); HRESIMS: m/z calcd for C14H27N2O10 [M+H]+
383.1666; found 383.1647.
4.34. tert-Butyldimethylsilyl 3,6-di-O-benzyl-2-
(benzyloxycarbonyl)amino-2-deoxy-b-D-glucopyranosyl-(1?4)-
3,6-di-O-benzyl-2-deoxy-2-trichloroacetamido-b-D-
glucopyranoside (33)
0
A suspension of 28 (500 mg, 0.44 mmol) in MeOH (12 mL) was
treated overnight at 0 °C to rt with methanolic NaOMe (1 M,
0.4 mL). The solution was deionized with Amberlite IR-120 (H+) re-
sin, filtered and concentrated. The residue was chromatographed
on a column of silica gel with 3:2 heptane–EtOAc to afford 33 as
a white powder (433 mg, 90%); 1H NMR (500 MHz, CDCl3): d
7.39–7.18 (m, 25H, Ph), 6.62 (d, 1H, J2,NH 7.4, NHa), 5.08 (m, 3H,
CH2O, NHab), 4.97 (d, 1H, J1,2 7.5, H-1b), 4.77 (ABq, 2H, CH2Ph),
4.71 (ABq, 2H, CH2Ph), 4.69 (d, 1H, J1,2 7.7, H-1a), 4.60 (ABq, 2H,
CH2Ph), 4.36 (ABq, 2H, CH2Ph), 3.95 (t, 1H, J2,3 8.4, J3,4 8.4, H-3b),
3.91 (m, 1H, H-3a), 3.75 (t, 1H, J3,4 8.6, J4,5 7.5, H-4a), 3.65–3.55
3.63 (t, 1H, J2,3 8.7, J3,4 8.7, H-3a), 3.54 (dd, 1H, J5,6 4.8, J6,6 9.9,
0
H-6b), 3.44 (dd, 1H, J5,6 6.1, J6,6 9.9, H-6b), 3.42–3.30 (m, 3H, H-
2a, H-2b, H-4b), 3.25 (m, 1H, J4,5 9.7, H-5b), 3.22–3.13 (m, 2H, H-
6a, H-6b), 3.03 (m, 1H, H-5a), 2.66 (sl, 1H, OH-4), 0.86 (s, 9H,
(CH3)3CSi), 0.08 (s, 3H, CH3Si), 0.04 (s, 3H, CH3Si); 13C NMR
(125 MHz, CDCl3): d 156.0, 155.9 (CO2CH2Ph), 138.9, 138.4, 137.9,
137.6, 136.5, 136.5 (C aromatic), 128.4–127.0 (CH aromatic),
100.3 (C-1b), 95.6 (C-1a), 81.1 (C-5b), 78.8 (C-4b), 78.6 (C-4a),
76.3 (C-3a), 76.2 (C-3b), 74.3 (C-5a), 73.9, 73.4, 73.3, 73.2 (CH2Ph),
70.6 (C-6a), 68.1 (C-6b), 66.7, 66.5 (CH2O), 58.8 (C-2a), 57.1 (C-2b),
25.5 ((CH3)3CSi), 17.8 ((CH3)3CSi), ꢃ4.2 (CH3Si), ꢃ5.3 (CH3Si); HRE-
SIMS: m/z calcd for C62H74N2O13SiNa [M+Na]+ 1105.4858; found
1105.4850.
0
(m, 3H, H-2a, H-2b, H-4b), 3.50 (dd, 1H, J5,6 4.9, J6,6 9.8, H-6b),
0
3.40 (dd, 1H, J5,6 6.2, J6,6 9.8, H-6a), 3.30–3.20 (m, 4H, H-5a, H-
5b, H-6a, H-6b), 3.05 (sl, 1H, OH-4), 0.88 (s, 9H, (CH3)3CSi), 0.12
(s, 3H, CH3Si), 0.09 (s, 3H, CH3Si); 13C NMR (125 MHz, CDCl3): d
161.7 (COCCl3), 155.9 (CO2CH2Ph), 138.6, 138.4, 137.9, 137.5,
136.6 (C aromatic), 128.6–127.3 (CH aromatic), 100.4 (C-1b), 94.7
(C-1a), 92.6 (CCl3), 81.1 (C-3a), 77.8 (C-4a), 76.2 (C-5b), 74.5 (C-
3b), 74.2 (CH2Ph), 74.0 (C-5a), 73.9, 73.6, 73.3 (CH2Ph), 73.0 (C-
4b), 71.0 (C-6a), 68.0 (C-6b), 66.7 (CH2O), 59.5 (C-2a), 57.2 (C-
2b), 25.6 ((CH3)3CSi), 17.9 ((CH3)3CSi), ꢃ4.1, ꢃ5.0 (CH3Si); HRE-
SIMS: m/z calcd for C56H67Cl3N2O12SiNa [M+Na]+ 1115.3427; found
1115.3389.
4.37. 3,6-Di-O-benzyl-2-(benzyloxycarbonyl)amino-2-deoxy-b-
D-glucopyranosyl-(1?4)-3,6-di-O-benzyl-2-
(benzyloxycarbonyl)amino-2-deoxy- -glucopyranose (36)
D
A mixture of 35 (502 mg, 0.52 mmol), AcOH (67 lL, 1.16 mmol)
and Bu4NFꢀ3H2O (366 mg, 1.16 mmol) in dry THF (20 mL) was stir-
red at rt for 16 h. The mixture was concentrated and diluted with
EtOAc (30 mL), washed with water, satd aq NH4Cl and water, dried
(MgSO4) and concentrated. The residue was chromatographed on a
column of silica gel with 9:1 CH2Cl2–MeOH to give 36 as a white
solid (385 mg, 86%); 1H NMR (500 MHz, CDCl3): d 7.41–7.14 (m,
30H, Ph), 5.27 (m, 1H, H-1a), 5.20–4.30 (m, 10H, 4 ꢁ CH2Ph, NHa,
NHb), 4.28 (d, 1H, J1,2 11.9, H-1b), 4.02 (m, 1H, H-4a), 3.88 (m,
2H, H-2a, H-3a), 3.75–3.58 (m, 2H, H-3b, H-6b), 3.52 (m, 1H, H-
6a), 3.50–3.33 (m, 4H, H-2b, H-4b, H-6a, H-6b), 3.25 (m, 1H, H-
5a), 3.19 (m, 1H, H-5b); 13C NMR (125 MHz, CDCl3): d 156.4,
156.3 (CO2CH2Ph), 139.2, 138.6, 137.9, 137.5, 136.6, 136.5 (C aro-
matic), 129.1–127.1 (CH aromatic), 100.7 (C-1b), 92.8 (C-1a), 77.8
(C-5b), 77.1 (C-3a), 74.5 (C-3b), 74.3, 74.1, 73.8, 73.5 (CH2Ph),
72.8 (C-4b), 72.4 (C-5a), 71.5 (C-6a), 70.3 (C-4a), 67.7 (C-6b), 67.4
(CH2O), 66.9 (CH2O), 55.8 (C-2a), 54.8 (C-2b); HRESIMS: m/z calcd
for C56H60N2O13Na [M+Na]+ 991.3995; found 991.3990.
4.35. tert-Butyldimethylsilyl 4-O-acetyl-3,6-di-O-benzyl-2-
(benzyloxycarbonyl)amino-2-deoxy-b-
3,6-di-O-benzyl-2-(benzyloxycarbonyl)amino-2-deoxy
-b- -glucopyranoside (34)
D-glucopyranosyl-(1?4)-
D
A mixture of the donor 12 (1.9 g, 2.8 mmol) and the acceptor 10
(1.13 g, 1.86 mmol) in anhyd CH2Cl2 (38 mL) was stirred for 1 h at
rt under dry argon. BF3ꢀEt2O (53 L, 0.42 mmol) was added and the
mixture was stirred for 3 h. Et3N (100 L) was added, and the mix-
l
l
ture was concentrated under vacuum. Flash silica gel chromatogra-
phy with 9:1 toluene–EtOAc containing 0.2% (v/v) Et3N afforded
the disaccharide 34 as a white powder (1.46 g, 70%); 1H NMR
(500 MHz, CDCl3): d 7.38–7.15 (m, 30H, Ph), 5.09–5.02 (m, 4H,
CH2O), 5.00 (t, 1H, J3,4 9.3, J4,5 9.3, H-4b), 4.85–4.40 (m, 10H,
H-1a, H-1b, NHa, NHb, 3 ꢁ CH2Ph), 4.32 (ABq, 2H, CH2Ph), 3.95 (t,
1H, J2,3 8.8, J3,4 8.8, H-3a), 3.74–3.63 (m, 2H, H-3b, H-4a), 3.52–
3.25 (m, 8H, H-2a, H-2b, H-5a, H-5b, H-6a, H-6a, H-6b, H-6b),
1.88 (s, 3H, CH3CO), 0.87 (s, 9H, (CH3)3CSi), 0.09 (s, 3H, CH3Si),
0.04 (s, 3H, CH3Si); 13C NMR (125 MHz, CDCl3): d 169.7 (CO, Ac),
157.4, 155.7 (CO2CH2Ph), 138.9, 138.1, 138.0, 138.0, 136.6 (C aro-
matic), 128.7–127.2 (CH aromatic), 99.8 (C-1b), 95.6 (C-1a), 78.7
(C-4a), 78.6 (C-3a), 76.5 (C-3b), 74.4 (C-5a), 73.8, 73.6, 73.5, 73.2
(CH2Ph), 73.1 (C-5b), 71.7 (C-4b), 69.8 (C-6a), 68.1 (C-6b), 66.7,
66.5 (CH2O), 59.1 (C-2a), 57.8 (C-2b), 25.6 ((CH3)3CSi), 20.8
(CH3CO), 17.9 ((CH3)3CSi), ꢃ4.2, ꢃ5.2 (CH3Si); ESIMS: m/z 1147
4.38. tert-Butyldimethylsilyl 2-amino-2-deoxy-b-D-
glucopyranosyl-(1?4)-2-amino-2-deoxy-b-D-glucopyranoside
(37)
A solution of 35 (260 mg, 0.24 mmol) in 5:10:4 EtOAc–MeOH–
water (25 mL) was hydrogenated in the presence of 10% Pd–C
(100 mg) for 48 h at rt. The mixture was filtered through a pad of
Celite, concentrated and freeze-dried. The residue was chromato-
graphed on a column of silica gel with 1:2 EtOAc–MeOH containing
0.2% (v/v) Et3N to give 37 as a white powder (81 mg, 74%); 1H NMR
(300 MHz, MeOD): d 4.90 (d, 1H, J1,2 8.0, H-1a), 4.52 (d, 1H, J1,2
8.4 Hz, H-1b), 3.86 (m, 1H, H-6a), 3.79–3.71 (m, 2H, H-3a, H-6b),

N. Barroca-Aubry et al. / Carbohydrate Research 345 (2010) 1685–1697
1697
3.66–3.52 (m, 3H, H-2b, H-6b, H-6a), 3.47–3.41 (m, 1H, H-4a),
3.34–3.29 (m, 1H, H-3b), 3.25–3.10 (m, 3H, H-4b, H-5a, H-5b),
2.65 (m, 1H, H-2a), 0.92 (s, 9H, (CH3)3CSi), 0.19 (s, 3H, CH3Si),
0.13 (s, 3H, CH3Si); 13C NMR (125 MHz, MeOD,): d 102.4 (C-1b),
95.1 (C-1a), 80.8 (C-4a), 77.1 (C-5b), 75.3 (C-5a), 75.0 (C-3b), 71.1
(C-4b), 70.1 (C-2a), 69.7 (C-3a), 61.5 (C-6a), 60.8 (C-6b), 56.0 (C-
2b), 25.4 ((CH3)3CSi), 17.6 ((CH3)3CSi), 8.2 (CH3Si), 7.6 (CH3Si);
HRESIMS: m/z calcd for C18H38N2O9SiNa [M+Na]+ 477.2244; found
477.2237.
(CH3)3CSi), 0.13 (s, 3H, CH3Si), 0.07 (s, 3H, CH3Si); 13C NMR
(125 MHz, CDCl3): d 170.2 (CO, Ac), 162.3, 162.2, 162.1 (COCCl3),
139.0, 138.7, 138.5, 138.4, 138.1, 137.9 (C aromatic), 129.3–127.9
(CH aromatic), 99.6 (C-1b), 99.0 (C-1c), 95.3 (C-1a), 93.1, 93.0,
92.9 (CCl3), 79.1 (C-3b), 78.5 (C-3c), 78.4 (C-3a), 76.5 (C-5b), 76.5
(C-5c), 75.2 (CH2Ph), 75.1 (C-5a), 75.0 (C-4c), 74.7, 74.3, 74.2,
74.0 (CH2Ph), 73.9 (C-4b), 73.8 (CH2Ph), 72.2 (C-4a), 70.2 (C-6b),
68.9 (C-6c), 68.8 (C-6a), 60.1 (C-2a), 58.5 (C-2c), 58.2 (C-2b), 26.1
((CH3)3CSi), 21.4 (CH3CO), 18.4 ((CH3)3CSi), ꢃ3.6 (CH3Si), ꢃ4.5
(CH3Si); HRESIMS: m/z calcd for C74H84Cl9N3O17SiNa [M+Na]+
1652.2798; found 1652.2792.
4.39. 2-Amino-2-deoxy-b-
D-glucopyranosyl-(1?4)-2-amino-2-
deoxy- -glucopyranose (38)
D
Acknowledgements
From 36: A solution of 36 (175 mg, 0.18 mmol) in 2:1 MeOH–
water (10 mL) was hydrogenated in the presence of 10% Pd–C
(100 mg) for 48 h at rt. The mixture was filtered through a pad of
Celite, concentrated and freeze-dried. The residue was chromato-
graphed on a column of silica gel with 1:2 EtOAc–MeOH containing
0.2% (v/v) Et3N to give 38 as a white powder (36 mg, 58%); From
This study is part of the CARAPAX and NANOBIOSACCHARIDES
projects funded by the European Community within the fifth and
sixth European framework Programs, respectively. Nadine Aubry-
Barroca and Astrid Pernet-Poil-Chevrier are grateful for the E.U.
Network Fellowship.
37: A mixture of 37 (71 mg, 0.16 mmol), AcOH (30 lL, 0.39 mmol)
and Bu4NFꢀ3H2O (124 mg, 0.40 mmol) in dry THF (15 mL) was stir-
red at rt for 16 h. The mixture was concentrated, diluted with
EtOAc (30 mL), washed with water, satd aq NH4Cl and water, dried
(MgSO4) and concentrated. The residue was chromatographed on a
column of silica gel with 1:2 EtOAc–MeOH to give 38 as a white so-
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260.
lid (49 mg, 90%, isomer
(d, 1H, J1,2 3.7, H-1a ), 4.97 (d, 1H, J1,2 8.4, H-1ab), 4.86 (d, 1H, J1,2
a
:b = 3:2); 1H NMR (500 MHz, D2O): d 5.46
a
8.3, H-1b), 4.06 (m, 1H, H-5a), 4.06 (dd, 1H, J2,3 10.6, J3,4 9.8, H-3a),
0
3.97 (dd, 1H, J5,6 2.1, J6,6 12.5, H-6b), 3.95–3.85 (m, 2H, H-4a, H-6a),
0
0
3.81 (dd, 1H, J5,6 5.1, J6,6 12.5, H-6b), 3.81 (m, 1H, H-6a), 3.73 (dd,
1H, J2,3 8.3, J3,4 10.7, H-3b), 3.60–3.48 (m, 2H, H-4b, H-5b), 3.38 (dd,
1H, J1,2 3.7, J2,3 10.6, H-2a
3.06 (m, 1H, H-2ab); 13C NMR (125 MHz, D2O): d 98.1 (C-1b),
93.0 (C-1ab), 89.3 (C-1a ), 77.0 (C-4a), 76.8 (C-5b), 72.2 (C-3b),
70.3 (C-5a), 70.0 (C-4b), 68.3 (C-3a), 60.7 (C-6b), 60.7 (C-6a), 57.0
(C-2ab), 56.3 (C-2b), 54.6 (C-2a ); HRESIMS: m/z calcd for
12H25N2O9 [M+H]+ 341.1560; found 341.1557.
a), 3.16 (dd, 1H, J1,2 8.4, J2,3 10.6, H-2b),
a
a
C
9. (a) Kuyama, H.; Nakahara, Y.; Nukada, T.; Ito, Y.; Nakahara, Y.; Ogawa, T.
Carbohydr. Res. 1993, 243, C1–C7; (b) Aly, M. R. E.; Ibrahim, E. S. I.; El Ashry, E. S.
H.; Schmidt, R. R. Carbohydr. Res. 2001, 331, 129–142.
10. Issaree, A. Ph.D. Thesis, University of Potsdam, 2008.; Vijayakrishnan, B. Ph.D.
Thesis, University of Potsdam, 2008.
4.40. tert-Butyldimethylsilyl 4-O-acetyl-3,6-di-O-benzyl-2-
deoxy-2-trichloroacetamido-b- -glucopyranosyl-(1?4)-3,6-di-
O-benzyl-2-deoxy-2-trichloroacetamido-b- -glucopyranosyl-
(1?4)-3,6-di-O-benzyl-2-deoxy-2-trichloroacetamido-
D
D
11. Kusomoto, S.; Yamamoto, K.; Imoto, M.; Inage, M.; Tsujimoto, M.; Kotani, S.;
Shiba, T. Bull. Chem. Soc. Jpn. 1986, 59, 1411–1417.
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(c) Wang, L.-X.; Li, C.; Wang, Q.-W.; Hui, Y.-Z. J. Chem. Soc., Perkin Trans. 1 1994,
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9, 1731–1738.
b-
D
-glucopyranoside (39)
A mixture of the donor 6 (219 mg, 0.32 mmol), the acceptor 18
(233 mg, 0.21 mmol) and 3 Å powdered molecular sieves (0.5 g) in
anhyd CH2Cl2 (7 mL) was stirred for 1 h at rt under dry argon.
BF3ꢀEt2O 1 M (48
lL, 0.05 mmol) was added, and the mixture was
stirred for 3 h. Et3N (30
l
L) was added and the mixture was filtered
through a pad of Celite and concentrated under vacuum. Flash sil-
ica gel chromatography with 9:1 toluene–EtOAc containing 0.2%
(v/v) Et3N afforded the trisaccharide 39 (262 mg, 76%), which
was recrystallized from Et2O–heptane; 1H NMR (500 MHz, CDCl3):
d 7.45–7.16 (m, 30H, Ph), 6.79 (d, 1H, J2,NH 8.2, NHa), 6.56 (d, 1H,
J2,NH 7.9, NHc), 6.50 (d, 1H, J2,NH 8.5, NHb), 5.07 (t, 1H, J3,4 9.1, J4,5
9.1, H-4c), 4.77 (d, 1H, J1,2 7.6, H-1a), 4.71 (d, 1H, J1,2 7.6, H-1c),
4.66 (d, 1H, J1,2 8.2, H-1b), 4.63–4.48 (m, 12H, CH2Ph), 4.12–4.08
(m, 3H, H-4a, H-4b, H-5b), 3.92 (dd, 1H, J2,3 8.5, J3,4 9.8, H-3a),
3.78–3.73 (m, 3H, H-2c, H-3c, H-6a), 3.69–3.55 (m, 5H, H-2a,
H-2b, H-3b, H-5a, H-6a), 3.47–3.40 (m, 3H, H-5c, H-6c, H-6b),
3.34–3.27 (m, 2H, H-6b, H-6c), 1.97 (s, 3H, CH3CO), 0.98 (s, 9H,
15. Banoub, J.; Boullanger, P.; Lafont, D. Chem. Rev. 1992, 92, 1167–1195.
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