Synthesis of the trisaccharide repeat of the O-antigen of rhanella aquatilis 1-95

Article abstract of DOI:10.1080/07328300903428989

A branched trisaccharide containing D-fucose and D-galactofuranose moieties corresponding to the repeating unit of the O-antigen of Rahnella aquatilis 1-95 has been synthesized from the monosaccharide intermediates in a five-step synthesis in an overall 38% yield. All glycosylation steps and protecting group functionalization steps are high yielding.

Full text of DOI:10.1080/07328300903428989

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Synthesis of the Trisaccharide Repeat of
the O-Antigen of Rhanella Aquatilis 1-95
Goutam Guchhait a & Anup Kumar Misra a
a Division of Molecular Medicine , Bose Institute , A.J.C. Bose
Centenary Campus, P-1/12, C.I.T. Scheme VII-M, Kolkata, 700054,
India
Published online: 04 Jan 2010.
To cite this article: Goutam Guchhait & Anup Kumar Misra (2010) Synthesis of the Trisaccharide
Repeat of the O-Antigen of Rhanella Aquatilis 1-95, Journal of Carbohydrate Chemistry, 29:1, 1-9,
DOI: 10.1080/07328300903428989
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Journal of Carbohydrate Chemistry, 29:1–9, 2010
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Copyright Taylor & Francis Group, LLC
ISSN: 0732-8303 print / 1532-2327 online
DOI: 10.1080/07328300903428989
Synthesis of the Trisaccharide
Repeat of the O-Antigen of
Rhanella Aquatilis 1-95
Goutam Guchhait and Anup Kumar Misra
Division of Molecular Medicine, Bose Institute, A.J.C. Bose Centenary Campus,
P-1/12, C.I.T. Scheme VII-M, Kolkata 700054, India
A branched trisaccharide containing D-fucose and D-galactofuranose moieties corre-
sponding to the repeating unit of the O-antigen of Rahnella aquatilis 1–95 has been
synthesized from the monosaccharide intermediates in a five-step synthesis in an over-
all 38% yield. All glycosylation steps and protecting group functionalization steps are
high yielding.
Keywords Trisaccharide; Rahnella aquatilis; Glycosylation; D-fucose; 2-Aminoethyl;
D-Galactofuranose.
INTRODUCTION
Rahnella aquatilis belongs to the family of Enterobacteriaceae, which are
found in soil and water.[1] Although formerly R. aquatilis was assigned to
the Enterobacter agglomerans biogroup, later it was recognized as a distinct
species.[2] R. aquatilis is an opportunistic pathogen responsible for a number of
pathogenic infections in the gastrointestinal and urinary tracts and in the res-
piratory and cardiovascular systems.[3] In the pathogenesis of diseases caused
by Gram-negative bacteria, endotoxin (lipopolysaccharide) plays a significant
role.[4] Recently, for the first time, the structure of the O-antigen of R. aquatilis
strain 1–95 was reported by Zdorovenko et al. (Fig. 1).[4] The trisaccharide re-
peating unit of the O-antigen is branched in nature and contains uncommon
monosaccharide units such as D-fucose and D-galactofuranose moieties.
Preparation of the glycoconjugate vaccines against infectious diseases
is considered an important area in medicinal research.[5] The prime re-
quirement for designing a glycoconjugate vaccine candidate is to have pure
Received August 12, 2009; accepted October 20, 2009.
Address correspondence to Anup Kumar Misra, Division of Molecular Medicine, Bose
Institute, A.J.C. Bose Centenary Campus, P-1/12, C.I.T. Scheme VII-M, Kolkata 700054,
India. E-mail: akmisra69@rediffmail.com
1

G. Guchhait & A.K. Misra
2
α-D-Galp
1
↓
2
→3)-β-D-Galf-(1→3)-α-D-Fucp-(1→
Figure 1: Structure of the repeating unit of the O-antigen of Rahnella aquatilis 1–95.
oligosaccharides or polysaccharides at hand. The limited availability of pure
oligosaccharide fragments of a particular polysaccharide isolated from the nat-
ural sources cannot meet the requirement for their extensive biological stud-
ies. Concise chemical synthesis can provide access to larger quantities of pure
oligosaccharides and several analogs thereof. As part of our program directed
toward the synthesis of bacterial O-antigen fragments for use in glycoconju-
gate preparation,[6] we describe a concise chemical synthesis of a branched
trisaccharide repeating unit of the O-antigen of R. aquatilis 1–95 as its 2-
aminoethyl glycoside (1, Fig. 2). The 2-aminoethyl group serves as a linker
for the conjugation to a carrier protein.
RESULTS AND DISCUSSION
In order to synthesize the target trisaccharide 1 having a branched D-
fucopyranosyl moiety, three suitably protected monosaccharide intermedi-
ates (2, 3, and 4, Fig. 2) have been prepared. Starting from 1,2:3,4-di-O-
isopropylidene-α-D-galactopyranose (5),[7] D-fucose derivative 6[8] was pre-
pared in 90% yield following Lerner’s procedure.[8] Compound 6 was con-
verted to 2-azidoethyl 3,4-O-isopropylidene-α-D-fucopyranoside (2) following a
set of reactions involving hydrolytic removal of isopropylidene acetal, Fischer
O
CH3
BnO OBn
O
O
HO
CH3
A
O
O
BnO
SEt
N3
HO
2
O
O
OBn
O
NH2
O
O
3
HO
O
OHC
HO
O
B
OAc
HO
OH
OH
SEt
OAc
AcO
AcO
HO
OH
4
1
Figure 2: Structure of the target trisaccharide 1 and of the monosaccharide building blocks
2, 3, and 4.

Synthesis of Rhanella aquatilis 1–95
3
[9]
glycosylation with 2-azido ethanol in the presence of HClO4-SiO2,
and
isopropylidenation in 80% overall yield. Compound 3[10] was synthesized
following literature-reported reaction conditions. Ethyl 2,3,5,6-tetra-O-acetyl-
1-thio-α-D-galactofuranoside (4)[11] was prepared from D-galactose diethyl-
dithioacetal (7) following the report of Wolfrom et al.[11] Stereoselective
glycosylation of compound 2 with thioethyl glycoside 3 in the presence of a
combination of copper(II) bromide-tetrabutylammonium bromide (TBAB)[12] in
a mixed solvent (1,2-dichloroethane-DMF; 5:1, v/v) at room temperature fur-
nished disaccharide derivative 8 in 76% yield. Appearance of a signature peak
1
at δ 5.02 (br s, H-1B) in the H NMR spectrum confirmed the stereoselective
formation of compound 8. Removal of the isopropylidene acetal followed by se-
lective acetylation of the axial hydroxyl group through orthoester formation[13]
gave disaccharide acceptor 9 in 88% yield. Iodonium ion promoted stereoselec-
tive glycosylation of compound 9 with D-galactofuranose thioglycoside donor
4 in the presence of N-iodosuccinimide, and trimethylsilyl trifluoromethane-
sulfonate (TMSOTf)[14,15] combination furnished trisaccharide derivative 10 in
82% yield. Appearance of signals at δ 5.34 (br s, H-1C), 5.07 (d, J = 3.2 Hz,
1
H-1B), and 5.00 (d, J = 3.2 Hz, H-1A) in the H NMR spectrum and δ 107.3
(C-1C), 96.9 (C-1A), and 95.3 (C-1B) in the 13C NMR spectrum supported the
formation of compound 10. As the value of 1,2-coupling constant of the β-D-
galactofuranosyl linkage is very low,[16] sometimes it appears as a broad sin-
glet. The formation of β-D-galactofuranosyl linkage can be explained by con-
sidering the neighboring participating O-acetyl group at the C-2 position of
thioglycoside donor 4. Saponification of compound 10 followed by hydrogenol-
ysis[17] furnished target trisaccharide 1 as its 2-aminoethyl glycoside in 70%
yield (Sch. 1). Appearance of anomeric signals at δ 5.16 (br s, 1 H, H-1C), 5.01
1
(br s, 1 H, H-1B), and 5.00 (br s, 1 H, H-1A) in the H NMR and at δ 107.8
(C-1C), 94.5 (C-1A), and 94.0 (C-1B) in the 13C NMR confirmed the formation of
trisaccharide 1. Anomeric signals of 1 were compared with those of the native
polysaccharide [δ 5.25 (br s, α-D-Fucp), 5.11 (br s, α-D-Galp), and 5.23 (br s,
1
β-D-Galf) in H NMR and δ 110.3, 97.4, and 96.8 in 13C NMR spectra].[4] The
signals of the native polysaccharide have been shifted from compound 1 and
may be due to the polysaccharide structure.
In summary, a concise synthesis of a branched trisaccharide repeating unit
of the O-antigen of R. aquatilis 1–95 as its 2-aminoethyl glycoside was achieved
in 38% yield starting from the three monosaccharide building blocks 2, 3, and
4. The key features of the synthesis are the preparation of the D-fucose precur-
sor from D-galactose and its subsequent glycosylation with 2-azido ethanol, as
well as glycosylation of the D-galactofuranose residue. It is noteworthy that D-
fucose and D-galactose moieties are linked through 1,2-cis linkages. The trisac-
charide 1 can be conjugated to a carrier protein using the amino function of its
2-aminoethyl aglycon.

G. Guchhait & A.K. Misra
4
OH
O
O CH3
O CH3
O
O
O
Ref. 8
a, b, c
O
O
O
N3
O
HO
O
O
O
O
5
6
2
AcO
HO
CH3
O CH3
O
O
A
A
d
e, f
O
N3
O
2 + 3
O
N3
O
BnO
O
BnO
B
BnO
BnO
B
BnO
BnO
O
O
OBn
8
OBn
9
AcO
CH3
A
O
O
h
4
g
O
1
N3
O
O
OAc
BnO
C
BnO
B
AcO
O
OBn
OAc
OAc
BnO
10
Scheme 1: Reagents: (a) 80% aq. AcOH, 80◦C, 6 h; (b) 2-azidoethanol, HClO4-SiO2, 80◦C, 50
h; (c) 2,2-dimethoxypropane, acetone, rt, 2 h, 80%; (d) Cu(II)Br2, TBAB, MS 4Å,
1,2-(CH2Cl)2-DMF, rt, 48 h, 76%; (e) 80% aq. AcOH, 80◦C, 2 h; (f) CH3C(OC2H5)3, p-TsOH, DMF,
rt, 2 h; 80% aq. AcOH, rt, 30 min, 88%; (g) N-iodosuccinimide, TMSOTf, CH2Cl2, MS 4Å, −40◦C,
1 h, 82%; (h) (i) CH3ONa, CH3OH, rt, 5 h; (ii) 20% Pd(OH)2-C, CH3OH-AcOH-H2O, rt, 12 h, 70%.
EXPERIMENTAL
General Procedure
All reactions were monitored by thin layer chromatography over silica gel-
coated TLC plates. The spots on TLC were visualized by warming ceric sul-
phate (2% Ce(SO4)2 in 2N H2SO4) sprayed plates on a hot plate. Silica gel
1
230–400 mesh was used for column chromatography. H and 13C NMR, 2D
COSY, and HMQC spectra were recorded on Bruker Avance DRX 500 MHz us-
ing CDCl3 and D2O as solvents and TMS as internal reference unless stated
otherwise. Chemical shift value is expressed in δ ppm. ESI-MS were recorded
on a Micromass Quattro II triple quadrupole mass spectrometer. Elementary
analysis was carried out on Carlo ERBA-1108 analyzer. Optical rotations were
measured at 25◦C on a Perkin Elmer 341 polarimeter. Commercially available
grades of organic solvents of adequate purity are used in many reactions.
2-Azidoethyl 3,4-O-isopropylidene-α-D-fucopyranoside (2)
A solution of compound 6 (4 g, 16.4 mmol) in 80% aq. AcOH (100 mL) was
allowed to stir at 80◦C for 6 h and evaporated and coevaporated with toluene

Synthesis of Rhanella aquatilis 1–95
5
(3 × 50 mL) under reduced pressure. To a solution of the crude product in
2-azidoethanol (15 mL) was added HClO4-SiO2 (500 mg) and the reaction mix-
ture was allowed to stir at 80◦C for 50 h. The reaction mixture was cooled
to rt and the solvents were removed under reduced pressure. To a solution
of the crude reaction mixture in anhydrous acetone (30 mL) was added 2,2-
dimethoxypropane (5 mL, 40.6 mmol) and it was allowed to stir at rt for 2 h.
The reaction mixture was neutralized with Et3N (1 mL), filtered, and concen-
trated under reduced pressure. The crude product was purified over SiO2 using
hexane-EtOAc (4:1) as eluant to give pure compound 2 (3.6 g, 80%). Yellow oil;
25
[α]D +5 (c 1.6, CHCl3); IR (neat): 3450, 2989, 2933, 2877, 2107, 1738, 1635,
1456, 1381, 1345, 1292, 1245, 1218, 1180, 1155, 1130, 1072, 992, 921, 800, 756,
687 cm−1; 1H NMR (500 MHz, CDCl3): δ 4.86 (d, J = 3.8 Hz, 1 H, H-1), 4.24 (t,
J = 6.3 Hz, 1 H, H-2), 4.19–4.17 (m, 1 H, H-5), 4.08 (dd, J = 2.3, 6.1 Hz, 1 H,
H-3), 4.00–3.96 (m, 2 H, OCH2), 3.83 (dd, J = 3.9, 6.1 Hz, 1 H, H-4), 3.72–3.68
(m, 2 H, OCH2), 3.50–3.39 (m, 2 H, N-CH2), 1.51 (s, 3 H, CH3), 1.35 (s, 3 H,
CCH3), 1.31 (d, J = 6.0 Hz, 3 H, CCH3); 13C NMR (125 MHz, CDCl3): δ 109.7
(C(CH3)2), 98.1 (C-1), 76.2 (C-5), 75.9 (C-3), 69.5 (C-4), 67.6 (C-2), 64.8 (OCH2),
51.1 (NCH2), 28.1 (CH3), 26.2 (CH3), 16.7 (CCH3); ESI-MS: 296.1 [M+Na]+;
Anal. Calcd. for C11H19N3O5 (273.13): C, 48.34; H, 7.01; Found: C, 48.15; H,
7.25.
2-Azidoethyl (2,3,4,6-tetra-O-benzyl-α-D-galactopyranosyl)-(1→
2)-3,4-O-isopropylidene-α-D-fucopyranoside (8)
To a solution of compound 2 (2.5 g, 9.15 mmol) and compound 3 (6.4 g,
10.94 mmol) in anhydrous 1,2-(CH2Cl)2-DMF (30 mL, 5:1 v/v) were added MS
˚
4A (5 g), CuBr2 (3.6 g, 16.12 mmol), and TBAB (700 mg, 2.17 mmol) and the
reaction mixture was allowed to stir at rt under argon for 48 h. The reac-
tion mixture was filtered through a Celite bed and washed with CH2Cl2 (150
mL). The organic layer was successively washed with satd. NaHCO3 and H2O,
dried (Na2SO4), and concentrated under reduced pressure. The crude prod-
uct was purified over SiO2 using hexane-EtOAc (5:1) as eluant to give pure
25
compound 8 (5.5 g, 76%). Yellow oil; [α]D +2.28 (c 1.6, CHCl3); IR (neat):
3062, 3030, 2979, 2927, 2873, 2144, 2105, 1606, 1480, 1454, 1355, 1339, 1299,
1209, 1158, 1109, 1089, 1068, 1049, 989, 967, 863, 751, 727, 702, 632 cm−1
;
1H NMR (500 MHz, CDCl3): δ 7.36–7.22 (m, 20 H, Ar-H), 5.02 (br s, 1 H, H-
1B), 4.94 (d, J = 11.3 Hz, 1 H, PhCH2), 4.82–4.78 (m, 3 H, PhCH2, H-1A), 4.74
(d, J = 11.7 Hz, 1 H, PhCH2), 4.64 (d, J = 11.7 Hz, 1 H, PhCH2), 4.57 (d,
J = 11.3 Hz, 1 H, PhCH2), 4.43 (d, J = 11.9 Hz, 1 H, PhCH2), 4.40 (d, J =
11.9 Hz, 1 H, PhCH2), 4.30 (dd, J = 5.6, 7.7 Hz, 1 H, H-5B), 4.26–4.23 (m,
1 H, H-3A), 4.19–4.18 (m, 1 H, H-5A), 4.09–4.07 (m, 3 H, H-2B, H-3B, H-4B),
4.03 (dd, J = 2.4, 5.4 Hz, 1 H, H-4A), 3.77–3.71 (m, 2 H, H-2A, OCH2a), 3.6

G. Guchhait & A.K. Misra
6
(t, J = 8.6 Hz, 1 H, OCH2b), 3.48–3.43 (m, 2 H, H-6abB), 3.31–3.26 (m, 1 H,
NCH2a), 3.05–3.00 (m, 1 H, NCH2b), 1.39 (s, 3 H, CH3), 1.32 (d, J = 6.6 Hz, 3
H, CCH3), 1.27 (s, 3 H, CCH3); 13C NMR (125 MHz, CDCl3): δ 128.8–127.8
(Ar-C), 109.1 (C(CH3)2), 97.1 (C-1A), 96.5 (C-1B), 79.2 (C-3B), 76.6 (C-2B),
76.4 (C-4B), 75.3 (PhCH2), 75.2 (C-2A), 74.8 (C-3A), 74.5 (C-4A), 73.8 (PhCH2),
73.4 (PhCH2), 73.0 (PhCH2), 69.4 (C-5B), 68.5 (C-6B), 68.0 (OCH2), 64.2 (C-
5A), 50.8 (N-CH2), 28.5, 26.8 (2 CH3), 16.7 (CCH3); ESI-MS: 818.3 [M+Na]+;
Anal. Calcd. for C45H53N3O10 (795.37): C, 67.91; H, 6.71; Found: C, 67.73; H,
6.95.
2-Azidoethyl (2,3,4,6-tetra-O-benzyl-α-D-galactopyranosyl)-
(1→2)-4-O-acetyl-α-D-fucopyranoside (9)
A solution of compound 8 (5 g, 6.28 mmol) in 80% aq. AcOH (100 mL)
was allowed to stir at 80◦C for 2 h and the solvents were evaporated and
coevaporated under reduced pressure. To a solution of the crude product in
anhydrous DMF (10 mL) was added CH3C(OC2H5)3 (7 mL, 38.18 mmol) fol-
lowed by p-TsOH (200 mg) and the reaction mixture was allowed to stir at
rt for 2 h concentrated under reduced pressure. The crude product was dis-
solved in 80% aq. AcOH (50 mL) and the reaction mixture was allowed to stir
at rt for 30 min. The solvents were removed under reduced pressure and the
crude product was purified over SiO2 using hexane-EtOAc (5:1) as eluant to
25
give pure compound 9 (4.4 g, 88%). Yellow oil; [α]D +8.5 (c 1.6, CHCl3); IR
(neat): 3414, 3019, 2923, 2400, 2109, 1740, 1454, 1373, 1215, 1094, 1047, 928,
1
760, 699, 669, cm−1; H NMR (500 MHz, CDCl3): δ 7.33–7.25 (m, 20 H, Ar-H),
5.25 (d, J = 2.8 Hz, 1 H, H-4A), 4.99 (d, J = 3.7 Hz, 1 H, H-1B), 4.91 (d, J =
11.6 Hz, 1 H, PhCH2), 4.88 (d, J = 3.6 Hz, 1 H, H-1A), 4.83 (d, J = 11.7 Hz,
1 H, PhCH2), 4.79 (d, J = 11.9 Hz, 1 H, PhCH2), 4.74 (d, J = 11.9 Hz, 1 H,
PhCH2), 4.64 (d, J = 11.9 Hz, 1 H, PhCH2), 4.54 (d, J = 11.6 Hz, 1 H, PhCH2),
4.47 (d, J = 11.9 Hz, 1 H, PhCH2), 4.37 (d, J = 12.0 Hz, 1 H, PhCH2), 4.21
(dd, J = 6.5, 12.1 Hz, 1 H, H-5B), 4.11–4.05 (m, 3 H, H-3A, H-2B, H-5A), 3.99
(dd, J = 2.7, 10.1 Hz, 1 H, H-3B), 3.8 (d, J = 1.8 Hz, 1 H, H-4B), 3.77–3.73
(m, 2 H, H-2A, H-6aB), 3.55–3.51 (m, 3 H, H-6bB, OCH2a, OH), 3.36–3.30 (m,
1 H, OCH2b), 3.28–3.26 (m, 1 H, NCH2a), 3.19–3.17 (m, 1 H, NCH2b), 2.06 (s,
3 H, COCH3), 1.11 (d, J = 6.6 Hz, 3 H, CCH3); 13C NMR (125 MHz, CDCl3):
δ 171.2 (COCH3), 139.0–127.9 (Ar-C), 98.7 (2 C, C-1A, C-1B), 79.0 (C-2A), 78.8
(C-3A), 76.7 (C-5A), 75.2 (C-4B), 75.0 (PhCH2), 73.9 (PhCH2), 73.8 (PhCH2),
73.5 (C-4A), 73.2 (PhCH2), 70.7 (C-5B), 70.0 (C-6B), 68.2 (OCH2), 67.3 (C-3B),
65.8 (C-2B), 50.9 (NCH2), 21.2 (COCH3), 16.6 (CCH3); ESI-MS: 820.3 [M+Na]+;
Anal. Calcd. for C44H51N3O11 (797.35): C, 66.23; H, 6.44; Found: C, 66.05; H,
6.68.

Synthesis of Rhanella aquatilis 1–95
7
2-Azidoethyl (2,3,5,6-tetra-O-acetyl-β-D-galactofuranosyl)-
(1→3)-[(2,3,4,6-tetra-O-benzyl-α-D-galactopyranosyl)-
(1→2)]-4-O-acetyl-α-D-fucopyranoside (10)
To a solution of compound 9 (2 g, 2.5 mmol) and compound 4 (1.2 g, 3 mmol)
˚
in anhydrous CH2Cl2 (15 mL) was added MS 4A (2 g) and the reaction mixture
was allowed to stir under argon at rt for 1 h and then cooled to −40◦C. To
the cold reaction mixture were added N-iodosuccinimide (800 mg, 3.55 mmol)
and TMSOTf (15 µL) and the reaction mixture was allowed to stir at the same
temperature for 1 h. The reaction mixture was filtered through a Celite bed
and washed with CH2Cl2 (100 mL). The organic layer was successively washed
with 5% aq. Na2S2O3, H2O, dried (Na2SO4), and evaporated to dryness. The
crude product was purified over SiO2 using hexane-EtOAc (4:1) as eluant to
25
give pure compound 10 (2.3 g, 82%). Yellow oil; [α]D +5.85 (c 1.6, CHCl3); IR
(neat): 3020, 2926, 2857, 2401, 2108, 1744, 1496, 1454, 1372, 1217, 1054, 980,
1
758, 698, 668 cm−1; H NMR (500 MHz, CDCl3): δ 7.33–7.25 (m, 20 H, Ar-H),
5.43 (m, 1 H, H-5C), 5.34 (br s, 1 H, H-1C), 5.18 (d, J = 2.3 Hz, 1 H, H-4A), 5.09
(d, J = 1.4 Hz, 1 H, H-2C), 5.07 (d, J = 3.2 Hz, 1 H, H-1B), 5.0 (d, J = 3.2 Hz,
1 H, H-1A), 4.92 (d, J = 11.4 Hz, 1 H, PhCH2), 4.91 (s, 1 H, H-3C), 4.80–4.78
(m, 3 H, 3 PhCH2), 4.68 (d, J = 11.7 Hz, 1 H, PhCH2), 4.53 (d, J = 11.4 Hz,
1 H, PhCH2), 4.50 (d, J = 12.1 Hz, 1 H, PhCH2), 4.45 (d, J = 12.1 Hz, 1 H,
PhCH2), 4.39–4.35 (m, 2 H, H-4B, OCH2a), 4.28–4.21 (m, 3 H, OCH2b, H-3B,
H-3A), 4.17–4.14 (m, 3 H, H-2A, H-5A, H-5B), 4.06–4.04 (m, 2 H, H-2B, H-4C),
3.74–3.72 (m, 1 H, H-6aC), 3.56–3.54 (m, 1 H, H-6abB), 3.49–3.47 (m, 1 H, H-
6bC), 3.29–3.28 (m, 1 H, NCH2a), 3.14–3.11 (m, 1 H, NCH2b), 2.11, 2.06, 2.01,
1.98, 1.96 (5 s, 15 H, 5 COCH3), 1.1 (d, J = 6.6 Hz, 3 H, CCH3); 13C NMR (125
MHz, CDCl3): δ 171.0, 170.8, 170.4 (2 C), 169.7 (5 COCH3), 139.4–127.6 (Ar-C),
107.3 (C-1C), 96.9 (C-1A), 95.3 (C-1B), 81.4 (C-2C), 81.2 (C-4B), 79.5 (C-2B), 77.5
(C-3C), 76.5 (C-4C), 75.7 (C-2A), 75.2 (PhCH2), 73.9 (C-5A), 73.5 (2 C, 2 PhCH2),
73.0 (PhCH2), 72.9 (C-4A), 71.3 (C-5B), 70.2 (C-3B), 69.8 (2 C, C-3A, C-5C), 67.5
(C-6B), 65.6 (C-6C), 62.8 (OCH2), 21.2, 21.1, 21.0 (2 C), 20.9 (5 COCH3), 16.3
(CCH3); ESI-MS: 1150.5 [M+Na]+; Anal. Calcd. for C58H69N3O20 (1127.45): C,
61.75; H, 6.16; Found: C, 61.57; H, 6.40.
2-Aminoethyl (β-D-galactofuranosyl)-(1→3)
-[(α-D-galactopyranosyl)-(1→2)]-α-D-fucopyranoside (1)
A solution of compound 10 (1.5 g, 1.33 mmol) in 0.1 M CH3ONa in CH3OH
(50 mL) was allowed to stir at rt for 5 h and neutralized with Dowex 50W X8
(H+) resin. The reaction mixture was filtered and concentrated under reduced
pressure. To a solution of the crude product in CH3OH-H2O-AcOH (20 mL,
10:1:0.1, v/v) was added 20% Pd(OH)2-C (100 mg) and the reaction mixture
was allowed to stir under a positive pressure of hydrogen at rt for 12 h. The

G. Guchhait & A.K. Misra
8
reaction mixture was filtered through a Celite bed and evaporated to dryness
to give compound 1, which was further purified over Sephadex LH-20 column
25
using CH3OH-H2O (5:1) as eluant (490 mg, 70%). White powder; [α]D +6.24
(c 1.6, CH3OH); IR (KBr): 3406, 2936, 2107, 1639, 1433, 1380, 1244, 1073,
1
1032, 977, cm−1; H NMR (500 MHz, CD3OD): δ 5.16 (br s, 1 H, H-1C), 5.01
(br s, 1 H, H-1B), 5.00 (br s, 1 H, H-1A), 4.12–4.04 (m, 4 H, H-2A, H-2C, H-3B,
H-3C), 4.01–3.97 (m, 3 H, H-2B, H-3A, H-2A), 3.94 (br s, 1 H, H-4C), 3.84 (d, J
= 2.6 Hz, 1 H, H-5B), 3.80–3.78 (m, 2 H, H-4B, H-5A), 3.77–3.70 (m, 4 H, H-5C,
H-6aC, OCH2), 3.64–3.60 (m, 2 H, H-6abB), 3.52–3.47 (m, 2 H, NCH2a, H-6bc),
3.33–3.28 (m, 1 H, NCH2b), 1.21 (d, J = 6.1 Hz, 3 H, CCH3); 13C NMR (125
MHz, CD3OD): δ 107.8 (C-1C), 94.5 (C-1A), 94.0 (C-1B), 81.9 (C-3C), 80.0 (C-2C),
76.1 (C-3A), 73.6 (C-4C), 70.3 (C-5B), 69.3 (2 C, C-2A, C-5A), 69.0 (C-3B), 68.3 (C-
4B), 67.7 (C-4A), 67.0 (C-5C), 64.4 (C-6C), 64.0 (C-2B), 61.1 (C-6B), 59.4 (OCH2),
45.3 (NCH2), 13.3 (CCH3); Anal. Calcd. for C20H37NO15 (531.22): C, 45.20; H,
7.02; found: C, 44.95; H, 7.33.
ACKNOWLEDGEMENTS
G.G. thanks CSIR, New Delhi, for providing a Junior Research Fellowship.
This work was supported by Ramanna Fellowship (AKM), Department of Sci-
ence and Technology, New Delhi (SR/S1/RFPC-06/2006).
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