Synthesis of Aminoethyl Glycosides of the Carbohydrate Chains of Glycolipids Gb3, Gb4, and Gb5

Article abstract of DOI:10.1023/A:1024905419008

4-O-Glycosylation of 2-azidoethyl 2,3,6-tri-O-benzoyl-4-O-(2,3,6-tri-O- benzoyl-β-D-galactopyranosyl)-β-D-glucopyranoside with ethyl 2,3,4,6-tetra-O-benzyl- and ethyl 3-O-acetyl-2,4,6-tri-O-benzyl-1-thio-α- D-galactopyranoside in the presence of methyl trifluoromethanesulfonate led to trisaccharide 2-azido-ethyl (2,3,4,6-tetra-O-benzyl-α-D-galactopyranosyl)- (1→4)-(2,3,6-tri-O-benzoyl-β-D-galactopyranosyl)-(1→4)-2,3, 6-tri-O-benzoyl-β-D-glucopyranoside and its 3″-O-acetylated analogue, 2-azidoethyl (3-O-acetyl-2,4,6-tri-O-benzyl-α-D-galactopyranosyl)- (1→4)-(2,3,6-tri-O-benzoyl-β-D-galactopyranosyl)-(1→4)-2,3, 6-tri-O-benzoyl-β-D-glucopyranoside in yields of 85 and 83%, respectively. Deacetylation of the latter compound and subsequent glycosylation with 4-trichloroacetamidophenyl 3,4,6-tri-O-acetyl-2-deoxy-1-thio-2-trichloro- acetamido-β-D-galactopyranoside and 4-trichloroacetamidophenyl 4,6-di-O-acetyl-2-deoxy-3-O-(2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl) -1-thio-2-trichloroacetamido-β-D-galactopyranoside in dichloromethane in the presence of N-iodosuccinimide and trifluoromethanesulfonic acid resulted in the corresponding selectively protected derivatives of the tetrasaccharide GalNAc(β1→3)Gal(α1→4)Gal(β1→4)Glcβ-OCH ₂CH₂N₃ and the pentasaccharide Gal(β1→3)GalNAc(β1→3)Gal(α→4)Gal(β1→4) Glcβ-OCH₂CH₂N₃ in 88 and 73% yields, respectively. Removal of O-protecting groups, substitution of acetyl group for the N-trichloroacetyl group, and reduction of the aglycone azide group resulted in the target 2-aminoethyl globo-tri-, -tetra-, and -pentasaccharide, respectively.

Full text of DOI:10.1023/A:1024905419008

Russian Journal of Bioorganic Chemistry, Vol. 29, No. 4, 2003, pp. 372–381. Translated from Bioorganicheskaya Khimiya, Vol. 29, No. 4, 2003, pp. 408–418.
Original Russian Text Copyright © 2003 by Cheshev, Khatuntseva, Gerbst, Tsvetkov, Shashkov, Nifantiev.
Synthesis of Aminoethyl Glycosides of the Carbohydrate Chains
of Glycolipids Gb3, Gb4, and Gb5
P. E. Cheshev, E. A. Khatuntseva, A. G. Gerbst, Yu. E. Tsvetkov,
1
A. S. Shashkov, and N. E. Nifantiev
Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninskii pr. 47, Moscow, 119991 Russia
Received June 20, 2002; in final form, August 22, 2002
Abstract—4-O-Glycosylation of 2-azidoethyl 2,3,6-tri-O-benzoyl-4-O-(2,3,6-tri-O-benzoyl-β-D-galactopyr-
anosyl)-β-D-glucopyranoside with ethyl 2,3,4,6-tetra-O-benzyl- and ethyl 3-O-acetyl-2,4,6-tri-O-benzyl-
1-thio-α-D-galactopyranoside in the presence of methyl trifluoromethanesulfonate led to trisaccharide 2-azido-
ethyl
(2,3,4,6-tetra-O-benzyl-α-D-galactopyranosyl)-(1 4)-(2,3,6-tri-O-benzoyl-β-D-galactopyranosyl)-
(1 4)-2,3,6-tri-O-benzoyl-β-D-glucopyranoside and its 3"-O-acetylated analogue, 2-azidoethyl (3-O-acetyl-
2,4,6-tri-O-benzyl-α-D-galactopyranosyl)-(1 4)-(2,3,6-tri-O-benzoyl-β-D-galactopyranosyl)-(1 4)-2,3,6-
tri-O-benzoyl-β-D-glucopyranoside in yields of 85 and 83%, respectively. Deacetylation of the latter compound
and subsequent glycosylation with 4-trichloroacetamidophenyl 3,4,6-tri-O-acetyl-2-deoxy-1-thio-2-trichloro-
acetamido-β-D-galactopyranoside and 4-trichloroacetamidophenyl 4,6-di-O-acetyl-2-deoxy-3-O-(2,3,4,6-
tetra-O-acetyl-β-D-galactopyranosyl)-1-thio-2-trichloroacetamido-β-D-galactopyranoside in dichloromethane
in the presence of N-iodosuccinimide and trifluoromethanesulfonic acid resulted in the corresponding selec-
tively protected derivatives of the tetrasaccharide GalNAc(β1 3)G‡l(α1 4)Gal(β1 4)Glcβ-
OëH2CH2N3 and the pentasaccharide Gal(β1 3)GalNAc(β1 3)G‡l(α1 4)Gal(β1 4)Glcβ-
OëH2CH2N3 in 88 and 73% yields, respectively. Removal of O-protecting groups, substitution of acetyl group
for the N-trichloroacetyl group, and reduction of the aglycone azide group resulted in the target 2-aminoethyl
globo-tri-, -tetra-, and -pentasaccharide, respectively.
Key words: aminoethyl glycosides, glycosylation; glycolipids Gb3, Gb4, and Gb5; globosides
1
INTRODUCTION
tose, D-galactosamine, and disaccharide β-D-Gal-
(1 3)-D-GalNAc. The target oligosaccharides have
been obtained in the spacered form for their subsequent
conjugation with carriers and labels.
Glycolipids of the globo series (Gb) refer to mem-
brane-associated antigens and are characterized by the
presence of galabiose fragment α-D-Gal-(1 4)-β-D-
Gal in their carbohydrate backbones, which is respon-
sible for their specific role in the processes of biological
RESULTS AND DISCUSSION
2
recognition. For example, globo-oligosaccharide
The target oligosaccharide structures (I), (II), and
(III) (Scheme 1) contain common lactose and α-galac-
tose fragments, to which the β-D-GalNAc residue
[Gb4-chain, structure (II)] or a β-D-Gal-(1 3)-β-D-
GalNAc moiety [Gb5-chain, structure (III)] is
attached.
The synthesis of the target globo-oligosaccharides
was performed using selectively protected lactose
derivative (XII) containing the azidoethyl prespacer
and free OH group at C4' for subsequent introduction of
α-galactosyl residue. For the synthesis of block (XII),
which was the precursor of (VIII), we had examined
two routes based on 3',4'- or 4',6'-isopropylidenation of
lactose (IV) (Scheme 2).
chains serve as oncomarkers [1, 2], are parts of P-
group-specific blood antigens [3], and are recognized
by various bacterial adhesins [4].
Natural glycolipids of the globo-series [5–8] and
also their other glycoside derivatives [6–12] have been
synthesized in several laboratories. A spacered deriva-
tive, 3-aminopropyl glycoside of galactosyl globoside
(Gb5-chain) [13], has also been synthesized. However,
the suggested synthetic scheme had a low stereoselec-
tivity and, therefore, resulted in unsatisfactory yield of
the target product.
We herein report the synthesis of aminoethyl glyco-
sides of globo-tri-, -tetra-, and -pentasaccharides from
selectively protected derivatives of lactose, D-galac-
3'4'-Acetonation according to the method [14] we
used led to (V) only in 43% yield and was accompanied
by the formation of other isopropylidene derivatives of
lactose, whose separation required column chromatog-
raphy. The directed 4',6'-O-isopropylidenation of lac-
1
Corresponding author; phone/fax: +7 (095) 135-8784; e-mail:
nen@ioc.ac.ru
2
Abbreviations: Bn, benzyl; Boc, tert-butyloxycarbonyl; Bz, ben-
zoyl; NIS, N-iodosuccinimide; and Tf, trifluoromethanesulfonyl.
1068-1620/03/2904-0372$25.00 © 2003 MAIK “Nauka /Interperiodica”

SYNTHESIS OF AMINOETHYL GLYCOSIDES
373
(I)
β-D-Gal-(1
3)-β-D-GalNAc-(1
3)-α-D-Gal-(1
4)-β-D-Gal-(1
(II)
4)-β-D-Glc-OCH CH NH
2 2 2
(III)
Scheme 1. Target aminoethyl glycosides of globo-tri-, -tetra-, and -pentasaccharide (I)–(III) containing oligosaccharide chains of
glycolipids Gb3, Gb4, and Gb5, respectively.
tose by the method [15] resulted, according to TLC, in lated thiogalactoside (XIII) [17] and its 3-O-acetylated
practically quantitative yield of acetonide (VI) and, analogue (XV) for α-galactosylation of the lactose
therefore, was used for the preparative synthesis of
(VIII). The preparation of (VIII) included exhaustive
benzoylation of hexaol (VI), removal of isopropylidene
protecting group, and regioselective 6'-O-benzoylation
of diol (VII). This reaction sequence led to (VIII) in
total yield of 70% from lactose. The presence of ben-
zoyl group at O6' in (VIII) was confirmed by a low-
field chemical shift of the signals of ç6‡ (3.53–
3.63 ppm) and ç6b (3.96 ppm) protons of the Gal unit
as compared to those in the starting diol (VII), where
they resonate at 3.02–3.19 ppm. The presence of free
OH group was confirmed by the up-field chemical shift
of the signal of H4 in Gal (4.02 ppm, see Table 1).
Compound (VIII) was then acetylated and con-
verted to lactosyl bromide (IX), which was used for
glycosylation of chloroethanol in dichloromethane in
the presence of silver triflate to yield chloroethyl glyco-
side (X). The chlorine atom in the aglycone moiety of
(X) was replaced with azide group to give (XI), which
was selectively de-O-acetylated by acidic methanolysis
[16] to monohydroxy derivative (XII) in 40% yield
from the starting (VIII).
The structure of compound (XII) was confirmed by
1H and 13C NMR spectroscopy. In particular, the char-
acteristic value of coupling constant J1, 2 = 7.7 Hz
pointed out to the β-configuration of the anomeric cen-
ter of glucose unit, and the presence of azide group at
C2 of the aglycone was confirmed by the low-field
position of the signal of the carbon atom of the methyl-
ene group of CH2N3 (51.0 ppm). The presence of free
OH group at C4 of Gal residue was corroborated by the
upfield value of the chemical shift of H4 signal in Gal
(4.19 ppm) in the 1H NMR spectrum (see Table 1). This
signal was additionally split due to spin–spin coupling
with the proton of OH group.
Previously, various types of glycosyl donors with
nonparticipating groups at C2 were used in the synthe-
ses of globoside carbohydrate chains for the creation of
1,2-cis-glycoside bond. The use of glycosyl bromides
[9, 10], fluorides [5], chlorides [7, 8], and trichloroacet-
imidates [6, 12] proceeded with low stereoselectivity
and did not give high yields of target compounds. The
block (XII) (Scheme 3); (XV) was obtained by acetyla-
tion of the corresponding monohydroxy derivative
(XIV) [18].
Galactosylation of lactose acceptor (XII) with
thioglycoside (XIII) in the presence of methyl trifluo-
romethanesulfonate in dichloromethane proceeded ste-
reoselectively and led to protected derivative (XVI) in
85% yield. The α-configuration of the terminal galac-
tose unit in (XVI) followed from the characteristic
value of the coupling constant J1,2 (3.8 Hz, Table 1) for
H1 of the Galα unit of trisaccharide (I), which was
obtained directly from trisaccharide (XVI). The pres-
ence of namely (1 4)-coupling was confirmed by the
low-field resonance of C4 of Galα (76.4 ppm) in its 13C
NMR spectrum (Table 2).
Trisaccharide (XVI) was deacetylated with sodium
methylate in methanol. The simultaneous hydrogenoly-
sis of benzyl groups and the reduction of azide group
over Pd/C in the presence of HCl gave, after gel chro-
matography, the target aminoethyl globotrioside (I) in
total yield of 88%. The structure of trisaccharide (I)
1
was established by H and 13C NMR spectroscopy. In
particular, the values of coupling constants of the sig-
nals of anomeric protons H1 of Glc (δ 4.53 ppm, J1,2
=
8.0 Hz), H1 of Galβ (δ 4.49 ppm, J1, 2 = 7.8 Hz), and H1
of Galα (δ 4.93 ppm, J1,2 = 3.8 Hz) (Table 1) confirmed
the α-configuration of the terminal galactose unit and
the β-configuration of the other two monosaccharide
residues. The chemical shift of the signal of the carbon
atom in –CH2N of the aglycone of (I) (38.4 ppm) as
compared to that of (XVI) (51.0 ppm, Table 2) indi-
cated the transformation of azide to amino group.
As in the case of galactosylation of acceptor (XII)
with thioglycoside (XIII), the coupling of (XII) and
(XV) in the presence of methyl trifluoromethane-
sulfonate in dichloromethane proceeded stereoselec-
tively and resulted in selectively 3''-O-acetylated deriv-
ative (XVII) in 83% yield. The presence of α-(1 4)-
bond in this compound was proved by the characteristic
value of coupling constant J1, 2 (2.9 Hz) (Table 1) and
use of thioglycosides [7, 11, 13] appeared to be the the low-field position of the signal of C4 (75.4 ppm) in
most effective; therefore, we selected totally benzy- the Galα unit.
RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY Vol. 29 No. 4 2003

374
CHESHEV et al.
HO
HO
OH
OH
O
O
O
OH
HO
HO
HO
b
a
(IV)
Me
O
Me
O
O
Me
Me
OH
OH
OH
O
O
O
O
O
HO
O
OH
HO
OH
O
HO
HO
HO
HO
HO
(VI)
(V)
c, d
HO
BzO
OH
OBz
O
O
O
BzO
OBz
c, d, k, l
BzO
BzO
(VII)
e
HO
BzO
OBz
OBz
O
O
O
BzO
OBz
BzO
BzO
(VIII)
f, g
AcO
BzO
OBz
OBz
O
O
O
BzO
BzO
BzO
Br
(IX)
i, h, j
OBz
R2O
OBz
O
O
O
BzO
O
R1
BzO
BzO
BzO
(X) R1 = Cl, R2 = Ac
(XI) R1 = N3, R2 = Ac
(XII) R1 = N3, R2 = H
Scheme 2. Reagents: a, Me C(OMe) , TosOH; b, Me C(OMe) , TosOH, DMF; c, BzCl, Py; d, CF COOH, CH Cl ; e, BzCl,
2
2
2
2
3
2
2
CH Cl /Py; f, Ac O, Py; g, HBr/AcOH; h, ClCH CH OH, AgOTf, CH Cl ; i, NaN , DMF, 18-crown-6; j, HCl/MeOH;
2
2
2
2
2
2
2
3
k, Bu SnO/toluene; and l, BzCl/Py.
2
RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY Vol. 29 No. 4 2003

SYNTHESIS OF AMINOETHYL GLYCOSIDES
375
Table 1. Spectra 1H NMR for (I)–(III) (D2O) and (VII), (VIII), (X)–(XII), (XV)–(XVIII), (XX), and (XXII) (CDCl3)
Chemical shifts (δ), ppm
H3 H4 H5
3.62 3.82 3.98 8.0
4.49 3.56 3.74 4.03 3.77 3.82 3.92 7.8
4.93 3.83 3.88 4.01 4.33 3.69 3.8
4.54 3.37 3.66 3.62 3.84 3.85 4.00 8.0
Coupling constants (J), Hz
Com-
pound
Residue
H1
H2
H6a H6b J1, 2 J2, 3 J3, 4 J4, 5 J5, 6a J5, 6b J6a, 6b
(I)
Glcβ
Galβ
Galα
Glcβ
Galβ
Galα
GalN
Glcβ
Galβ
Galα
GalN
4.53 3.36
3.66
ND* ND
ND
3.0 <1
3.1 <1
6.3
ND
ND
ND
ND
ND
ND
4.6
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
<1
12.3
8.0 11.6
10.1
ND
ND
ND
ND
ND
ND
ND
ND
(II)
ND
ND
ND
ND
ND
ND
ND
4.51 3.58 3.75 4.92
4.91 3.85 3.96 4.24 4.37
3.70 3.91 7.8
3.73–3.82 3.8
10.2 ND
ND
ND
2.4
3.0
6.4
4.64 3.93 3.73 4.04 3.95 3.86 3.90 8.4
4.48 3.31 3.59 3.57 3.77 3.93 8.0
ND
ND
1.9 11.2
(III)
8.4 ND
10.1 3.3
4.44 3.52 3.68 3.97 3.83 ND
4.85 3.83 3.90 4.18 4.32
ND 7.8
3.9
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
12.0
ND
3.62
ND
8.6
9.9
2.6 <1
3.0
3.4
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
<1
4.63 3.99 3.84 4.12 3.75 ND
ND 8.5
ND 7.7
ND
Galβ** 4.38 3.46 3.55 3.84 ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
(VIIα) Glcα
Galβ
(VIIβ) Glcβ
Galβ
(VIIIα) Glcα
Galβ
(VIIIβ) Glcα
Galβ
6.58 5.48 6.04 4.25 3.99
4.77 5.70 5.01 4.09 3.27
6.07 5.62 5.78 4.24 4.22
4.71 5.68 5.01 4.07 3.27
6.62 5.48 6.04 4.24 4.00
4.34–4.49
3.02–3.19
4.34–4.49
3.02–3.19
4.37–4.46
3.75
7.9
7.8
7.9
3.4
9.3
10.4
8.8
10.4
10.2
9.3
9.2
9.3
9.5
3.2
8.8
3.2
4.75 5.73 5.03 4.02
6.03 5.65 5.81 4.22
4.69 5.71 5.03 4.02
3.53–3.63
4.40–4.45
3.53–3.63
3.96 7.9
9.2
3.96 7.9
3.1
9.2
3.1
9.5
(X)
Glcβ
Galβ
4.77 5.44 5.78 4.24 3.86 4.44 4.63 7.8
9.5 4.2
ND
4.83 5.62 5.27 5.45
3.73–3.80
3.3–4.0
7.8
10.3
3.3 <1
ND
(XI)
Glcβ
Galβ
4.77 5.47 5.80 4.26 3.85 4.45 4.63 7.7
9.4
10.4
9.4
3.5 <1
9.4 4.3
ND
1.1 12.3
4.83 5.63 5.27 5.49
3.65–3.80
3.3–4.0
7.9
ND
ND
(XII)
(XV)
(XVI) Glcβ
Galβ
Glcβ
Galβ
Galβ
4.79 5.47 5.80 4.24 3.89 4.50 4.62 8.0
4.82 5.79 5.19 4.19 3.67 3.36 4.15 8.0
4.60 3.84 4.97 4.05 3.63 3.73 3.74 9.3
4.66 5.30 5.72 4.18 3.81 4.66 4.41 7.8
4.82 5.66 4.98 4.23 3.63 4.48 4.10 7.8
8.0
10.5
9.3
8.1
3.0 <1
2.4 <1
9.2
2.7 <1
ND <1
9.0
2.8 <1
2.7 <1
8.0
2.5 <1
2.9 <1
8.1 4.4
<1
ND
ND
ND 12.0
ND
ND
11.6
ND
ND
ND
ND
4.4
ND
4.9
9.2
ND
10.8
ND
9.0
10.5
10.7
8.0
10.7
7.0
9.3
10.5 ND
10.4
8.0
9.1 ND
10.6 ND
ND
ND
ND
8.4
12.3
Galα
4.64
3.85
3.99 4.15 3.30 2.94 ND
(XVII) Glcβ
Galβ
4.75 5.41 5.83 4.26 3.93 4.48 4.70 7.5
4.89 5.74 5.09 4.30 3.62 4.03 4.48 7.7
4.78 3.91 5.21 4.18 3.36 3.13 4.37 2.9
4.76 5.44 5.81 4.29 3.88 4.48 4.68 8.0
4.88 5.68 5.07 4.24 3.73 4.10 4.45 7.8
4.74 3.63 3.84 3.98 3.47 3.24 4.27 3.2
4.72 5.40 5.88 4.27 4.07 4.63 4.74 7.5
5.06 5.77 5.17 4.12 3.89 4.46 4.58 7.9
4.61 3.95 4.33 4.20 4.26 2.94 3.35 2.9
5.17 4.55 5.38 5.49 4.23 4.24 4.33 8.5
9.0 ND <1
5.6
5.2
8.0 ND
ND 11.0
ND
ND
ND 11.1
ND
ND
Galα
8.8
ND
(XVIII) Glcβ
Galβ
6.5
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
Galα
ND
ND
(XX)
Glcβ
Galβ
Galα
GalN
9.3
ND
ND
3.4 <1
2.9 <1
ND 11.2
ND
ND
ND
ND
ND
ND
ND
8.3
ND
ND
ND
ND
ND
ND
(XXII) Glcβ
Galβ
4.79 5.22 5.72 4.18 ND
4.88 5.60 4.96 4.17 ND
ND
ND
ND
ND
ND
ND 7.9
ND 7.8
ND 3.3
ND
ND
ND
ND
ND
Galα
GalN
4.74 3.91 4.63 ND
5.20 3.78 ND ND
ND
ND
ND
ND
3.5
ND
ND
Galβ** 4.05 5.10 4.90 5.27 ND
ND 8.0
10.4
*ND, not determined.
**Terminal Galβ unit.
Other signals: CH COO, 1.9–2.1 ppm; C H COO, 7.7–8.0 ppm; CH -Ph, 4.56 ppm; C H CH , 6.8–7.5 ppm; OCH CH Cl, 3.15–3.40
3
6
2
5
2
6
5
2
2
2
ppm; OCH CH Cl, 3.50–4.00 ppm; OCH CH N , 3.13–3.52 ppm; OCH CH N , 3.50–3.82 ppm; SCH CH , 3.67 ppm; SCH CH , 1.28
2
2
2
3
2
2
3
2
3
2
3
ppm; NHC(O)CCl , 6.8 ppm (J
10 Hz); OCH CH NH , 3.26 ppm; OCH CH NH , 3.94 and 4.12 ppm.
3
NH, 2
2 2 2 2 2 2
RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY Vol. 29 No. 4 2003

376
CHESHEV et al.
Table 2. Spectra 13C NMR for (I)–(III) (D2O) and (XVI), (XVII), (XX), and (XXII) (CDCl3)
Chemical shifts (δ), ppm
Compound
Residue
C1
C2
C3
C4
C5
C6
(I)
Glcβ
Galβ
Galα
Glcβ
Galβ
Galα
GalN
Glcβ
Galβ
Galα
GalN
Galβ**
Glcβ
Galβ
Galα
Glcβ
Galβ
Galα
Glcβ
Galβ
Galα
GalN
Glcβ
Galβ
Galα
GalN
Galβ**
100.9
102.3
99.3
71.8
69.9
67.5
74.0
72.1
67.0
53.8
73.2
71.2
67.9
51.8
70.9
72.2
69.9
73.3
71.2
68.1
75.5
72.0
79.9
73.4
74.6
72.5
79.0
79.9
72.8
73.0
74.4
77.6
76.4
68.0
79.9
79.9
70.1
78.5
79.0
77.6
69.3
68.3
68.9
76.3
75.8
74.9
75.9
75.4
75.1
76.1
ND
73.8
74.4
69.9
76.1
76.6
71.5
69.0
75.1
75.8
70.6
74.9
75.3
73.3
73.4
69.8
ND
58.9
59.5
59.4
61.1
61.6
62.2
61.6
60.2
60.7
60.7
61.3
61.3
62.5
62.4
67.5
62.3
62.1
67.2
62.7
62.4
67.4
61.4
62.2
61.2
66.7
60.7
60.0
(II)
103.1
104.5
101.6
104.4
102.2
103.6
100.7
103.2
105.1
100.8
101.1
101.2
100.4
100.8
101.2
100.9
100.0
100.4
103.0
100.4
101.0
100.4
101.0
101.2
(III)
(XVI)
(XVII)
(XX)
75.6
ND*
ND
ND
ND
64.9
ND
52.8
ND
ND
ND
53.0
ND
ND
ND
ND
ND
ND
80.8
71.2
ND
ND
79.9
ND
ND
ND
ND
ND
ND
70.9
66.8
ND
70.1
77.3
ND
(XXII)
ND
ND
ND
ND
ND
ND
ND
ND
*ND, not determined.
**Terminal Galβ unit.
Other signals: OCH CH NH , 64.8 ppm; OCH CH NH , 38.4 ppm; CH CONH, 22.6 ppm; CH CONH, 175.5 ppm; CH N , 51.0 ppm;
2
2
2
2
2
2
3
3
2 3
OCH CH N , 68.1–68.2 ppm; COCCl , 159.5–161.6 ppm.
2
2
3
3
corresponding coupling constant J1,2 (8.5 Hz) in the 1H
NMR spectrum (Table 1), and the presence of the
GalN-(1 3)-Gal bond, by the low-field shift of the C3
signal in GalN (80.8 ppm) in the 13C NMR spectrum
(Table 2).
Acetate (XVII) was converted into monohydroxy
derivative (XVIII) under the conditions of acidic meth-
anolysis [16] in 81% yield (Scheme 3). The position of
free OH group at C3 of the terminal galactose unit in
(XVIII) followed from the upfield shift of the signal of
H3 of Galα by 1.374 ppm (δ 5.21 3.84 ppm) in the
1H NMR spectrum of (XVIII) as compared to that of
(XVII) (Table 1).
In order to transform (XX) to the target tetrasaccha-
ride (II), all acyl groups were removed by the treatment
with 0.5 M NaOH in aqueous methanol. Then the
Trisaccharide (XVIII) was glycosylated with resulting free amino group in the galactosamine residue
was N-acetylated with acetic anhydride. The hydro-
genolysis of benzyl ethers and the reduction of azide
group were performed in 10% aqueous ethanol upon
the catalysis by Pd/C in the presence of Boc2O to fix the
thioglycoside (XIX) [19] in dichloromethane in the
presence of NIS and trifluoromethanesulfonic acid to
give tetrasaccharide (XX) in 88% yield (Scheme 3).
The β-configuration of the galactosamine residue in
(XX) was confirmed by the characteristic value of the amine generated in the reaction. Upon the hydrogenol-
RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY Vol. 29 No. 4 2003

SYNTHESIS OF AMINOETHYL GLYCOSIDES
377
BnO
RO
OH
OBn
O
OBz
OBz
O
O
O
BzO
O
SEt
BzO
N3
BnO
BzO
BzO
BnO
HO
OBn
O
(XII)
(XIII) R = Bn
(XV) R = Ac
‡
SEt
BnO
(XIV)
b
BnO
RO
OBn
O
(I)
BnO
O
c, d
OBz
OBz
O
O
O
O
BzO
BzO
N3
BzO
BzO
(XVI) R = Bn
(XVII) R = Ac
(XVIII) R = H
c
OAc
OAc
OAc
OAc
OAc
OAc
O
O
O
O
S
NHC(O)CCl3
AcO
S
NHC(O)CCl3
AcO
AcO
NHC(O)CCl3
(XXI)
NHC(O)CCl3
(XIX)
d
OAc
BnO
OAc
OBn
O
O
O
AcO
BnO
d
O
NHCOCCl3
OBz
OBz
O
O
O
BzO
O
BzO
N3
BzO
BzO
(XX)
g, h, i, j
(II)
OAc
OAc
BnO
OAc
OAc
OBn
O
O
O
O
O
AcO
AcO
BnO
O
NHC(O)CCl3
OBz
OBz
O
O
O
BzO
O
BzO
(XXII)
N3
BzO
BzO
g, h, i, j
(III)
Scheme 3. a, Ac O, Py; b, MeOTf, CH Cl , MS-4 Å; c, HCl/MeOH; d, NIS/TfOH, CH Cl ; e, MeONa, MeOH; f, H , Pd/C, HCl;
2
2
2
2
2
2
g, NaOH, MeOH/H O; h, Ac O, NaOH; i, H , Pd/C, Boc O; and j, CF COOH, H O/MeOH.
2
2
2
2
3
2
RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY Vol. 29 No. 4 2003

378
CHESHEV et al.
ysis in the presence of HCl (without addition of
Boc2O), i.e., under the conditions used in the synthesis
of trisaccharide (I), we failed to completely remove
benzyl groups, which was likely due to a partial poison-
ing of the catalyst with the generated amine. After the
removal of Boc protecting group by the treatment with
trifluoroacetic acid in aqueous methanol, aminoethyl
globotetraoside (II) was obtained in 54% yield from the
starting (XX). The structure of (II), in particular, the
configurations of its anomeric centers, directions of
interunit bonds, and the presence of the aminoethyl
EXPERIMENTAL
The procedures for purification of solvents and
reagents and the conditions for registration of NMR
spectra and for determination of physicochemical con-
1
stants are the same as in [20]. H NMR spectra were
registered on Bruker DRX-500 and Bruker AM-300
spectrometers at 25°ë. Optical rotation values were
measured on a Jasco DIP-360 digital polarimeter at 18–
25°ë. TLC was performed on Silica gel 60 (Merck)
precoated plates. The spots were visualized by the treat-
ment with 10 vol % solution of orthophosphoric acid in
ethanol or with ninhydrin solution (3 g/l in 30 : 1
butanol–acetic acid for amines) and subsequent heating
at ~150°ë. Column chromatography was carried out on
0.063–0.2 mm Silica gel 60 (Fluka); MPLC on Silasorb
600 (200 µm, Chemapol) columns, and gel chromatog-
raphy on Sephadex LH-20 (2 × 40 cm) columns (elu-
tion with methanol, 1 ml/min), Sephadex G-10 (1.5 ×
20 cm) columns (elution with water, 2 ml/min), and
TSK-HW40s (1.5 × 90 cm) columns (elution with
0.1 M aqueous acetic acid, 1 ml/min). Hydrogenolysis
was performed over 10% Pd/C (Merck) at atmospheric
pressure. TLC of the deprotected aminoethyl glyco-
sides was performed in (BPH) 1 : 2 : 1 butanol–pro-
panol—0.1 M hydrochloric acid and (AMW) 1 : 1 : 1
acetonitrile–methanol–water developing systems.
1
aglycone (δCH2Nç2 38.4 ppm) were proven by H
(Table 1) and 13C (Table 2) NMR spectra.
To obtain the target pentasaccharide (III), we glyc-
osylated trisaccharide (XXI) with disaccharide thiogly-
coside (XVIII) [19] under the conditions used for the
synthesis of tetrasaccharide (XX) to give pentasaccha-
ride (XXII) in 73% yield (Scheme 3). The β-configura-
tion of the galactosamine residue in (XXII) was proved
by the characteristic value of coupling constant J1,2
(8.5 Hz), and the presence of the Gal-(1 3)Gal bond,
by the low-field shift of the signal of C3 in Galα at
79.9 ppm in the 13C NMR spectrum.
Note that trichloroacetimidate glycosyl donors
based on N-phthaloylated disaccharide β-D-Gal-
(1 3)-D-GalN [8, 13] were previously used in the
syntheses of pentasaccharide Gb5. However, the glyco-
4-O-(3,4-O-Isopropylidene-b-D-galactopyranosyl)-
sylation of the derivatives of trisaccharide Gb3 with a,b-D-glucopyranose (V). A suspension of lactose
these glycosyl donors proceeded much less effectively, (18 g, 52.7 mmol) and TsOH · H2O (180 mg,
than in the case of the synthesis of pentasaccharide
(XXII). This was connected with a low stereoselectiv-
ity of the reaction [13] and the side rearrangement of
glycosylimidate to the corresponding glycosyl amide
[8]. We have recently demonstrated a high effectiveness
of glycosyl donor (XXI) by the example of successful
synthesis of the derivative of tetrasaccharide asialo-
GM1 [19].
0.915 mmol) in 2,2-dimethoxypropane (10 ml) and
DMF (50 ml) was stirred for 1 h at 70°ë. Triethylamine
(3 ml) was added, and the mixture was concentrated in
a vacuum. Acetonide (V) was isolated by column chro-
matography (elution with 1 : 2 methanol–chloroform);
yield 9.6 g (43%); Rf 0.25 (1 : 2 methanol–chloroform).
1,2,3,6-Tetra-O-benzoyl-4-O-(2,3-di-O-benzoyl-b-
D-galactopyranosyl)-a,b-D-glucopyranose (VII). A
suspension of lactose (3.2 g, 9.36 mmol) and TsOH ·
H2O (210 mg, 1.1 mmol) in 2,2-dimethoxypropane
(3 ml) was stirred for 2 h at 20°ë until is was com-
pletely dissolved and form acetonide (VI). Triethyl-
amine (3 ml) was then added, and the reaction mixture
was evaporated in a vacuum. The residue was sus-
pended in anhydrous pyridine (30 ml, 370 mmol), and
benzoyl chloride (20 ml, 172 mmol) was added at
intensive stirring and cooling to 0°ë. The reaction mix-
ture was stirred for 3 h at 20°ë, poured on ice, and
diluted with dichloromethane (500 ml). The organic
layer was separated; washed with 1 M H2SO4 (400 ml),
water (2 × 400 ml), and saturated NaHCO3 solution
The saponification of ester groups in pentasaccha-
ride (XXII) was performed in 1 M NaOH solution in
aqueous methanol (10% of water). N-Acetylation,
hydrogenolysis, and isolation by gel filtration were car-
ried out under the conditions similar to those used for
the transformation of protected tetrasaccharide (ïX) to
the target (II). The deprotected aminoethyl pentaoside
(III) resulted in total yield of 86% from (XXII). The
structure of (III) was proved by 1H and 13C NMR spec-
troscopy (Tables 1 and 2) as described above for (I) and
(II).
Thus, oligosaccharide chains of glycolipids Gb3,
Gb4, and Gb5 were synthesized in the form of amino-
ethyl glycosides. The effectiveness of the synthetic (200 ml); filtered through a layer of cotton; and evapo-
scheme using the division of the target structures into β- rated in a vacuum. The residue was dissolved in a mix-
D-Gal-(1 4)-D-Glc, α-D-Gal, β-D-GalNAc, and β- ture of dichloromethane (80 ml) and 90% trifluoroace-
D-Gal-(1 3)-D-GalNAc blocks and also the effec- tic acid (10 ml), kept for 30 min at 20°ë, concentrated,
tiveness of the use of thioglycoside glycosyl donors like and coevaporated with toluene (5 × 50 ml). The residue
(XIX) and (XXI) for the obtaining of the globoside oli- was chromatographed on a column eluted with 3 : 1 tol-
gosaccharide chains was demonstrated.
uene–ethyl acetate to isolate 5.67 g (63%) of diol (VII),
RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY Vol. 29 No. 4 2003

SYNTHESIS OF AMINOETHYL GLYCOSIDES
379
Rf 0.21 (3 : 1 toluene–ethyl acetate). For 1H NMR spec-
trum, see Table 1.
glucopyranoside (XI). A suspension of NaN3 (297 mg,
4.57 mmol) in a solution of chloroethyl glycoside (X)
(490 mg, 0.457 mmol) and 18-crown-6 (120 mg,
0.45 mmol) in DMF (2.5 ml) was stirred for 22 h at
65°C. The mixture was diluted with ethyl acetate
(150 ml), washed with water (4 × 50 ml), filtered
through a layer of cotton, and evaporated. The residue
was chromatographed on a column eluted with 15 : 1
toluene–ethyl acetate to isolate 427 mg (86%) of azide
(XI) as a white foam; Rf 0.27 (8 : 1 toluene–ethyl ace-
tate); [α]D +34° (c 1, ethyl acetate). Found, %: C 64.63,
H 4.77, N 3.90. C58H51O18N3. Calculated, %: C 64.62,
1,2,3,6-Tetra-O-benzoyl-4-O-(2,3,6-tri-O-benzoyl-
b-D-galactopyranosyl)-a,b-D-glucopyranose (VIII).
Benzoyl chloride (750 µl, 6.5 mmol) was added for
10 min to intensively stirred and cooled to 0°ë solution
of diol (VII) (5.67 g, 5.9 mmol) in a mixture of anhy-
drous dichloromethane (66 ml) and anhydrous pyridine
(1.4 ml, 17.3 mmol). The reaction mixture was stirred
for 2 h at 0°ë and diluted with dichloromethane
(500 ml) and water (10 ml). Then the reaction mixture
was treated as described for (VII). Product (VIII)
(4.24 g, 70%) was isolated by column chromatography
(elution with 10 : 1 toluene–ethyl acetate), Rf 0.31 (10 :
1 toluene–ethyl acetate). Found, %: C 68.54, H 4.68.
H 4.77, N 3.90. For 1H NMR spectrum, see Table 1.
2-Azidoethyl 4-O-(2,3,6-tri-O-benzoyl-b-D-galac-
topyranosyl)-2,3,6-tri-O-benzoyl-b-D-glucopyrano-
side (XII). Acetyl chloride (165 µl, 2.3 mmol) was
added to absolute methanol (4.14 ml) at 0°ë and kept
for 10 min. A solution of acetate (XI) (402 mg,
0.373 mmol) in anhydrous dichloromethane (2.4 ml)
was added to the resulting solution. The mixture was
kept for 60 h at 20°ë, poured on ice, and diluted with
dichloromethane (150 ml). The organic layer was sepa-
rated, washed with saturated NaHCO3 solution (50 ml)
and water (50 ml), and evaporated. The residue was
separated by column chromatography in 20 : 1 toluene–
acetone to get 197 mg (51%) of alcohol (XII) as a white
foam, Rf 0.15 (8 : 1 toluene–ethyl acetate), [α]D +58° (c
1, ethyl acetate). Found, %: C 64.86, H 4.68, N 4.05.
C56H48O17N3. Calculated, %: C 64.98, H 4.67, N 4.06.
1
C61H50O18. Calculated, %: C 68.41, H 4.67. For H
NMR spectrum, see Table 1.
4-O-(4-O-Acetyl-2,3,6-tri-O-benzoyl-b-D-galacto-
pyranosyl)-2,3,6-tri-O-benzoyl-a-D-glucopyranosyl
bromide (IX). Compound (VIII) (4.24 g, 4.13 mmol)
was acetylated with acetic anhydride (6 ml, 64 mmol)
in anhydrous pyridine (9 ml, 110 mmol) for 18 h at
20°ë, evaporated, coevaporated with toluene (3 ×
50 ml), and dissolved in anhydrous dichloromethane
(9.5 ml). A 40% solution of HBr in AcOH (18.5 ml)
was added at –10°ë and intensive stirring. The reaction
mixture was kept without stirring for 40 min at –10°ë,
poured on ice, and diluted with dichloromethane
(400 ml). The organic layer was separated; washed
with ice-cold water (300 ml), cold saturated NaHCO3
solution (2 × 150 ml), and ice-cold water (150 ml); fil-
tered through a layer of cotton; and evaporated. The
residue was dried in a vacuum of oil pump to give
4.21 g (99%) of bromide (IX) as a white foam, Rf 0.42
(10 : 1 toluene–ethyl acetate).
For 1H NMR spectrum, see Table 1.
Ethyl 3-O-acetyl-2,4,6-tri-O-benzyl-1-thio-b-D-
galactopyranoside (XV). Acetic anhydride (3 ml,
31 mmol) was added to a solution of (XIV) [18] (0.5 g,
1.01 mmol) in anhydrous pyridine (5 ml), the mixture
was kept for 12 h at 20°ë, and the excess of ÄÒ2é was
quenched with methanol (10 ml). The mixture was
evaporated and coevaporated with toluene (3 × 20 ml).
The residue was filtered through a silica gel layer in
12 : 1 toluene–ethyl acetate, evaporated, and dried in a
vacuum of oil pump to isolate 0.5 g (92%) of acetate
(XV) as a white foam, Rf 0.3 (12 : 1 toluene–ethyl ace-
tate), [α]D +25.7° (c 0.63, CHCl3).
2-Chloroethyl 4-O-(4-O-acetyl-2,3,6-tri-O-ben-
zoyl-b-D-galactopyranosyl)-(2,3,6-tri-O-benzoyl-b-
D-glucopyranoside (X). A solution of lactosyl bro-
mide (IX) (6.53 g, 6.1 mmol) in a mixture of anhydrous
2-chloroethanol (6.4 ml, 95 mmol) and anhydrous
dichloromethane (64 ml) was stirred under argon for
30 min at 20°ë with the preliminarily heated molecular
sieves MS-4 Å (200 mg); silver triflate (1.87 g,
7.3 mmol) was added; and the mixture was stirred for
1 h at 20°ë. Triethylamine (3 ml) was added; the mix-
ture was diluted with dichloromethane (350 ml); the
organic layer was washed with 1 M Na2S2O3 solution
(2 × 50 ml), saturated NaHCO3 solution (2 × 150 ml),
and water (200 ml), and evaporated. The residue was
chromatographed on a silica gel column in 30 : 1 tolu-
ene–acetone to give 6.35 g (91%) of glycoside (X) as a
white foam, Rf 0.4 (8 : 1 toluene–ethyl acetate), [α]D
+36.5° (c 1, ethyl acetate). Found, %: 64.85, H 4.79.
2-Azidoethyl 4-O-[4-O-(2,3,4,6-tetra-O-benzyl-
a-D-galactopyranosyl)-2,3,6-tri-O-benzoyl-b-D-galac-
topyranosyl]-2,3,6-tri-O-benzoyl-b-D-glucopyrano-
side (XVI). A solution of glycosyl acceptor (XII)
(405 mg, 0.388 mmol) and thiogalactoside (XIII)
(575.7 mg, 0.985 mmol) in anhydrous dichloromethane
(35 ml) was stirred with heated molecular sieves MS-
4 Å (6.6 g) under argon for 30 min at 20°ë, methyl tri-
flate (540 µl, 4.78 mmol) was added, and the mixture
was stirred for addional 30 min. Triethylamine (2 ml)
was added; the reaction mixture was filtered, the filtrate
was diluted with dichloromethane (150 ml) and washed
with saturated NaHCO3 solution (2 × 50 ml) and water
1
C58H50O18Cl. Calculated, %: C 65.02, H 4.77. For H
NMR spectrum, see Table 1.
2-Azidoethyl
4-O-(4-O-acetyl-2,3,6-tri-O-ben- (100 ml). The organic layer was separated and evapo-
zoyl-b-D-galactopyranosyl)-2,3,6-tri-O-benzoyl-b-D- rated. The residue was chromatographed on a column
RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY Vol. 29 No. 4 2003

380
CHESHEV et al.
eluted with 12 : 1 toluene–ethyl acetate to isolate charide (XX) as a white foam, Rf 0.5 (5 : 1 toluene–
ethyl acetate). For 1H NMR spectrum, see Table 1.
517 mg (85%) of trisaccharide (XVI) as a white foam,
Rf 0.48 (8 : 1 toluene–ethyl acetate), [α]D +55.5° (c 1,
ethyl acetate). Found, %: C 69.51, H 5.36, N 2.69.
C90H83O22N3. Calculated, %: C 69.35, H 5.36, N 2.69.
2-Azidoethyl (2,3,4,6-tetra-O-acetyl-b-D-galac-
topyranosyl)-(1 3)-(4,6-di-O-acetyl-2-deoxy-2-tri-
chloroacetamido-b-D-galactopyranosyl)-(1 3)-
(2,4,6-tri-O-benzyl-a-D-galactopyranosyl)-(1 4)-
(2,3,6-tri-O-benzoyl-b-D-galactopyranosyl)-(1 4)-
2,3,6-tri-O-benzoyl-b-D-glucopyranoside (XXII). A
solution of trisaccharide (XVIII) (60 mg, 0.041 mmol)
and glycosyl donor (XXI) (44 mg, 0.044 mmol) in
anhydrous dichloromethane (3 ml) was stirred under
dry argon for 2 h at 20°ë with preliminarily heated
molecular sieves MS-4 Å (200 mg). Then NIS (13 mg,
0.058 mmol) was added; the mixture was stirred for
additional 20 min at 20°ë, cooled to –30°ë; and treated
dropwise at the same temperature with 5% TfOH in
CH2Cl2 (200 µl). The reaction mixture was stirred for
2 h at –30 to –20°C. The product was isolated and puri-
fied as described for (XX) to give 65 mg (73%) of pen-
tasaccharide (XXII) as a white foam, Rf 0.43 (5 : 1
dichloromethane–ethyl acetate), [α]D + 75.7° (c 0.5,
For 1H NMR spectrum, see Table 1.
2-Azidoethyl 4-O-[4-O-(4-O-acetyl-2,3,6-tri-O-
benzyl-a-D-galactopyranosyl)-2,3,6-tri-O-benzoyl-
b-D-galactopyranosyl]-2,3,6-tri-O-benzoyl-b-D-glu-
copyranoside (XVII). The reaction of glycosyl accep-
tor (XII) (360 mg, 0.347 mmol) and thioglycoside
(XV) (466 mg, 0.868 mmol) was carried out and treated
as described for (XVI). Glycoside (XVII) (580 mg,
83%) was isolated by column chromatography in 3 : 1
petroleum ether–ethyl acetate as a white foam, Rf 0.28
(2 : 1 petroleum ether–ethyl acetate). Found, %: C
67.58, H 5.32, N 2.78. C85H80O23N3. Calculated, %: C
1
67.60, H 5.33, N 2.78. For H NMR spectrum, see
Table 1.
2-Azidoethyl 4-O-[4-O-(2,3,6-tri-O-benzyl-a-D-
galactopyranosyl)-2,3,6-tri-O-benzoyl-b-D-galacto-
pyranosyl]-2,3,6-tri-O-benzoyl-b-D-glucopyranoside
(XVIII). A solution of acetate (XVII) (101 mg,
0.069 mmol) in anhydrous dichloromethane (0.5 ml)
was added to a solution of HCl in methanol obtained by
addition of acetyl chloride (40 µl, 0.56 mmol) to abso-
lute methanol (1.0 ml). Then the reaction mixture was
treated as described for (XII). Alcohol (XVIII) (82 mg,
81%) was isolated by column chromatography in 20 : 1
toluene–acetone as a white foam, Rf 0.33 (3 : 1 petro-
leum ether–ethyl acetate), [α]D +55° (c 1, ethyl ace-
tate). Found, %: C 67.92, H 5.29, N 2.86. C83H77O22N3.
CHCl3). For 1H NMR spectrum, see Table 1.
2-Aminoethyl a-D-galactopyranosyl-(1 4)-b-
D-galactopyranosyl-(1 4)-a-D-glucopyranoside (I).
Trisaccharide (XVI) (180.4 mg, 0.116 mmol) was dis-
solved in absolute methanol (3 ml) and treated with 1 M
sodium methylate in methanol (0.3 ml). After 20 min,
the solution was neutralized with cation exchange resin
KU-2 (ç+) and filtered. The resin was washed with
methanol (2 × 5 ml), the combined filtrate was evapo-
rated in a vacuum, and the residue was chromato-
graphed on a column eluted with ethyl acetate to isolate
88.5 g of hexaol, the product of é-debenzoylation of
trisaccharide (XV). The resulting hexaol was dissolved
in absolute methanol (2 ml), the solution of HCl in
methanol [obtained by addition of acetyl chloride
(0.12 ml, 1.7 mmol) to absolute methanol (3 ml) and
subsequent keeping at 20°C for 20 min] and Pd/C
(115 mg) were added, and the mixture was stirred for
1 h under hydrogen. Then triethylamine (2 ml) was
added, the reaction mixture was filtered through a layer
of Celite, the filtrate was evaporated, and the residue
was dissolved in water (5 ml) and treated with anion
exchange resin A-26 (OH–) (Serva). The resin was fil-
tered off and washed with water (1 ml), the combined
filtrate was evaporated in a vacuum, and the residue was
chromatographed on TSK-HW40s gel to isolate 58 mg
(87%) of trisaccharide (I), Rf 0.32 (3 : 2 BPH–AMW),
Calculated, %: C 67.89, H 5.28, N 2.86. For 1H NMR
spectrum, see Table 1.
2-Azidoethyl
(3,4,6-tri-O-acetyl-2-deoxy-2-
3)-
trichloroacetamido-b-D-galactopyranosyl)-(1
(2,4,6-tri-O-benzyl-a-D-galactopyranosyl)-(1 4)-
(2,3,6-tri-O-benzoyl-b-D-galactopyranosyl)-(1 4)-
(2,3,6-tri-O-benzoyl-b-D-glucopyranoside (XX). A
solution of trisaccharide (XVIII) (50 mg, 0.034 mmol)
and glycosyl donor (XIX) [19] (29 mg, 0.041 mmol) in
anhydrous dichloromethane (2.5 ml) was stirred with
preliminarily heated molecular sieves MS-4 Å
(200 mg) for 2 h at 20°ë. Then NIS (10 mg,
0.044 mmol) was added; the mixture was stirred for
additional 20 min at 20°ë, cooled to −30°ë; and drop-
wise treated with 5% TfOH in CH2Cl2 (100 µl) at the
same temperature. The mixture was stirred for 1.5 h at
a temperatures from –30 to 20°C, treated with saturated
NaHCO3 solution (1 ml) and 1 M Na2S2O3 solution
(1 ml), stirred for 10 min, and filtered through a layer of
Celite. The filtrate was diluted with dichloromethane
(75 ml), washed with saturated NaHCO3 solution
13
[α]D + 76° (c 2, water). For 1H and C NMR spectra,
see Tables 1, 2.
2-Aminoethyl (2-acetamido-2-deoxy-b-D-galac-
topyranosyl)-(1 3)-a-D-galactopyranosyl-(1 4)-
b-D-galactopyranosyl-(1 4)-b-D-glucopyranoside
(50 ml), and the organic layer was separated and evap- (II). Tetrasaccharide (XX) (53 mg, 0.028 mmol) was
orated. The residue was chromatographed on a column dissolved in 5% aqueous methanol (4 ml), NaOH
eluted with the dichloromethane–ethyl acetate (10 : (80 mg) was added, and the mixture was stirred until
1
5 : 1) gradient to isolate 57 mg (88%) of tetrasac- complete dissolution and kept for 17 h at 20°ë. Then
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SYNTHESIS OF AMINOETHYL GLYCOSIDES
381
ÄÒ2é was added dropwise to pH 6 upon cooling to 0°ë
REFERENCES
(monitoring by universal pH-indicator, Merck), the
reaction mixture was deionized with cation exchange
resin KU-2 (ç+), the resin was filtered off and washed
with methanol (2 × 3 ml), and the combined filtrate was
evaporated. The residue was chromatographed on a
Sephadex LH-20 column. The carbohydrate-containing
fractions were evaporated and dried in a vacuum of oil
pump. The dry residue was dissolved in 10% aqueous
ethanol (3 ml), Boc2O (60 mg) and the catalytic amount
of Pd/C were added, and the reaction mixture was
stirred for 14 h under hydrogen at 20°ë up to complete
removal of benzyl protective groups (TLC monitoring).
The reaction mixture was filtered through a layer of
Celite, the filtrate was washed with aqueous methanol
in the 100–0% methanol–water gradient (30 ml), and
90% aqueous CF3COOH (2 ml) was added. The reac-
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evaporated with water to remove the acid. The residue
was chromatographed on TSK-HW-40s gel column to
isolate 13 mg (54%) of aminoethyl glycoside (II) (in
the form of trifluoroacetate), Rf 0.21 (1 : 1 BPH–
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a-D-galactopyranosyl-(1 4)-b-D-galactopyranosyl-
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ACKNOWLEDGMENTS
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The work was supported by the Russian Foundation
for Basic Research (project nos. 00-03-32815a and 02-
03-06588-MAS), Russian Sciences Support Founda-
tion, and International Soros’ Program in the Field of
Exact Sciences.
RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY Vol. 29 No. 4 2003