Synthesis of O-methylated disaccharides related to excretory/secretory antigens of Toxocara larvae

Article abstract of DOI:10.1081/CAR-100108285

The disaccharides 2-O-Me-α-L-Fucp-(1→2)-β-D-Galp-(1→OAllyl) 12, α-L-Fucp-(1→2)-4-O-Me-β-D-Galp-(1→OAllyl) 15, and 2-O-Me-α-L-Fucp-(1→2)-4-O-Me-β-D-Galp-(1→OAllyl) 18 have been synthesized. Glycosylation reactions were performed using ethyl 1-thiofucopyran

Full text of DOI:10.1081/CAR-100108285

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SYNTHESIS OF O-METHYLATED DISACCHARIDES
RELATED TO EXCRETORY/ SECRETORY ANTIGENS OF
TOXOCARA LARVAE
Hassan Amer a , Andreas Hofinger a , Michael Puchberger a & Paul Kosma b
a Institut für Chemie, Universität für Bodenkultur , Muthgasse 18, Wien, A-1190, Austria
b Institut für Chemie, Universität für Bodenkultur , Muthgasse 18, Wien, A-1190, Austria
Published online: 16 Aug 2006.
To cite this article: Hassan Amer , Andreas Hofinger , Michael Puchberger & Paul Kosma (2001) SYNTHESIS OF O-
METHYLATED DISACCHARIDES RELATED TO EXCRETORY/ SECRETORY ANTIGENS OF TOXOCARA LARVAE , Journal of
Carbohydrate Chemistry, 20:7-8, 719-731
To link to this article: http://dx.doi.org/10.1081/CAR-100108285
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J. CARBOHYDRATE CHEMISTRY, 20(7&8), 719–731 (2001)
SYNTHESIS OF O-METHYLATED
DISACCHARIDES RELATED TO EXCRETORY/
SECRETORY ANTIGENS OF TOXOCARA LARVAE1
Hassan Amer, Andreas Hofinger, Michael Puchberger,
and Paul Kosma*
Institut für Chemie, Universität für Bodenkultur, Muthgasse 18,
A-1190 Wien, Austria
ABSTRACT
The disaccharides 2-O-Me-ꢀ-L-Fucp-(1→2)-ꢁ-D-Galp-(1→OAllyl) 12, ꢀ-L-
Fucp-(1→2)-4-O-Me-ꢁ-D-Galp-(1→OAllyl) 15, and 2-O-Me-ꢀ-L-Fucp-
(1→2)-4-O-Me-ꢁ-D-Galp-(1→OAllyl) 18 have been synthesized. Glycosyla-
tion reactions were performed using ethyl 1-thiofucopyranosides as glycosyl
donors and N-iodosuccinimide-triflic acid as the activating agent. The O-
methylated disaccharides correspond to highly immunogenic O-glycan anti-
gens occurring at the surface of Toxocara canis and Toxocara cati larvae.
INTRODUCTION
Toxocara canis and Toxocara cati are parasitic roundworms usually occur-
ring in dogs and cats, which may cause severe infections in a human host affecting
eyes, liver and the central nervous system.2 The surface coat of the parasitic ne-
matode larvae represents the major immunological challenge to the host immune
system.3 In particular, glycoproteins being present in multiple copies at the outer
layer elicit a strong immune response, are subsequently released from the surface
and divert the immune attack from the mobile nematode. The structure of the ex-
creted and secreted glycoproteins (TES antigens) from Toxocara canis investi-
gated by MS analysis of alditol acetates revealed the presence of the trisaccharide
backbone ꢀ-L-Fucp-(1→2)-ꢁ-D-Galp-(1→3)-D-GalpNAc.4 The fucose part has
been found to be O-methylated at the 2-position. In addition, ꢀ50% of the glycans
719
Copyright © 2001 by Marcel Dekker, Inc.
www.dekker.com

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720
AMER ET AL.
contained a 4-O-methyl group at the galactopyranosyl unit, which is also the
prominent structure found in T. cati glycans. The anomeric configuration of the
GalpNAc residue has yet to be elucidated. Monoclonal anti-carbohydrate antibod-
ies which have been raised against the TES antigens bind to different sites within
the larval parasite.5 For a detailed immunochemical characterization of those mon-
oclonal antibodies, we have synthesized three potential carbohydrate ligands
which are O-methylated either at position 2 of the fucopyranosyl moiety or at po-
sition 4 of the galactopyranosyl unit or at both positions. Herein we report on the
synthesis of the corresponding disaccharide allyl glycosides, which may be con-
verted into spacer-elongated derivatives to be coupled to proteins.6
RESULTS AND DISCUSSION
For the synthesis of the allyl galactopyranoside acceptor derivatives, the
known7 allyl ꢁ-D-galactopyranoside 1 was reacted with anisaldehyde dimethyl ac-
etal in the presence of p-toluenesulphonic acid in MeCN to give the crystalline 4,6-
O-p-methoxybenzylidene derivative 2 in 81% yield.8 Regioselective protection of
the 3-OH group was achieved in 77% yield by reaction of the 2,3-O-dibutylstan-
nylene intermediate with p-methoxybenzyl chloride / tetra-n-butylammonium io-
dide9 to furnish the acceptor 3.
For the subsequent introduction of the 4-O-methyl group, compound 3 was
O-acetylated with acetic anhydride / pyridine to afford compound 4 in 92% yield.
1
The H NMR spectrum of 4 displayed a downfield shift for H-2 to 5.36 ppm,
thereby confirming the structural assignment of the 3-O-p-methoxybenzyl sub-
stituent. Reductive ring opening of the benzylidene acetal10 using NaCNBH3 / tri-
fluoroacetic acid in DMF furnished the 6-O-p-methoxybenzyl ether derivative 5 in
70% yield and the 4-O-p-methoxybenzyl isomer in 20% yield. Methylation of 5
was performed with MeI / NaH in DMF to give compound 6 in 87% yield. Re-
moval of the 2-O-acetyl group was accomplished by treatment of 6 with Bu4NOH
in aq 1,4-dioxane, which gave the 4-O-methyl-galactopyranoside acceptor 7 in
82% yield (Scheme 1).
For the synthesis of the ꢀ-L-Fucp-(1→2)-ꢁ-D-Galp-(1→OAllyl) disaccha-
ride11 derivatives, S-ethyl ꢁ-L-fucopyranosides were used as glycosyl donors.
They were synthesized by O-acetylation (of known precursors12) to give the 3,4-
di-O-acetyl derivatives 8 and 9, respectively. Coupling of the glycosyl donors with
the galactopyranoside acceptor derivatives was carried out under iodonium ion ac-
tivation of the thioglycoside using N-iodosuccinimide and trifluoromethanesul-
phonic acid at ꢂ20°C in dichloromethane-diethyl ether.13 Coupling of donor 9
with acceptor 3 gave the ꢀ-(1→2)- linked disaccharide derivative 10 in 58% yield
1
together with the ꢁ-(1→2)-linked isomer (18%). The H NMR spectrum of 10
showed a doublet for H-1ꢃ at 5.53 ppm with a coupling constant of 3.7 Hz. Similar
reactions with the 4-O-methylated acceptor 7 and the thiofucopyranoside donors 8
and 9 proceeded with better anomeric selectivity to furnish disaccharide 13 in 83%
yield (and 6% of the ꢁ-isomer) and the dimethylated disaccharide 16 in 88% yield

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TOXOCARA LARVAE
721
Scheme 1.
(and 11% of the ꢁ-isomer, respectively). Acid hydrolysis of the p-methoxybenzyl
or p-methoxybenzylidene group of derivatives 10 and 13 with 90% aq TFA fol-
lowed by O-acetylation afforded the penta-O-acetyl disaccharides 11 and 14 in
84% and 65% yield, respectively. The p-methoxybenzyl ether groups of compound
16 were cleaved by the action of ceric ammonium nitrate. Subsequent O-acetyla-
tion gave the dimethylated disaccharide 17 in 76% overall yield. Zemplén de-O-
acetylation of the acetylated disaccharides and final purification furnished the dis-
accharides 2-O-Me-ꢀ-L-Fucp-(1→2)-ꢁ-D-Galp-(1→OAllyl) 12, ꢀ-L-Fucp-(1→2)-
4-O-Me-ꢁ-D-Galp-(1→OAllyl) 15 and 2-O-Me-ꢀ-L-Fucp-(1→2)-4-O-Me-ꢁ-D-
Galp-(1→OAllyl) 18 in 92%, 96% and 97% yield, respectively (Scheme 2).
Structural assignments were confirmed by the 13C NMR data (based on
HMQC and HMBC spectra, Table 1) and compare favorably with data of related
O-methylated oligosaccharides.14
The synthesis of the trisaccharides and immunochemical data derived from
neoglycoconjugates will be published elsewhere.
EXPERIMENTAL
General methods. Melting points were determined with a Kofler hot stage
and are uncorrected. Optical rotations were measured with a Perkin-Elmer 243 B
1
polarimeter. H NMR spectra were recorded with a Bruker DPX 300 instrument
and tetramethylsilane or DSS as internal standards; coupling constants are first or-
der. Homo- and heteronuclear 2D NMR spectroscopy was performed with Bruker
standard software. Thin-layer chromatography was performed on Merck precoated
plates (5 x 10 cm, layer thickness 0.25 mm, Silica Gel 60F254); spots were detected
by spraying with anisaldehyde-H2SO4 reagent. Column chromatography was per-

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Scheme 2.
Table 1. 13C NMR Chemical Shiftsa (ppm) for Disaccharides 12, 15 and 18.
Unit
Carbon
12
15
18
ꢀ-L-Fucp
C-1
C-2
C-3
C-4
C-5
C-6
C-1
C-2
C-3
C-4
C-5
C-6
C-1
C-2
C-3
96.85
77.77
68.98
72.17
66.89
15.75
100.99
76.24
74.18
69.47
75.31
61.34
133.72
119.55
71.40
57.84
100.69
69.37
70.58
72.91
67.84
16.42
101.54
78.36
75.02
80.32
76.16
61.51
134.41
120.13
71.97
62.45
97.29
78.16
69.37
72.57
67.29
16.17
101.30
76.89
74.89
80.33
ꢁ-D-Galp
75.83
61.29
OAll
OMe
134.15
119.94
71.77
62.34 (O-4)
58.20 (O-2ꢃ)
a Spectra were recorded in D2O at 295 K.

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TOXOCARA LARVAE
723
formed on Merck Lichroprep columns (size A, 24 ꢄ 1; B, 31 ꢄ 2.5 and C, 44
ꢄ 3.7 cm; silica gel 40–63 ꢅm) under pressure (0.2 MPa). Elemental analyses were
performed by Dr. J. Theiner, Mikroanalytisches Laboratorium am Institut für
Physikalische Chemie, Universität Wien.
Allyl 4,6-O-p-Methoxybenzylidene-ꢁ-D-galactopyranoside (2). A mix-
ture of 1 (800 mg, 3.63 mmol), anisaldehyde dimethyl acetal (800 ꢅL, 4.40 mmol)
and p-toluenesulphonic acid monohydrate (100 mg) in dry acetonitrile (20 mL)
was stirred for 4 h at rt. Neutralization with triethylamine (0.5 mL) and evapora-
tion of the solvent gave a residue which was purified on silica gel (C, 50:1
CHCl3/EtOH) to furnish 2 as colorless crystals. Yield: 1.0 g (81%); mp 179°C
(hexane/EtOAc). [ꢀ]D20 ꢆ44° (c 0.5, CHCl3). 1H NMR (CDCl3) ꢇ 7.45 - 6.80 (m,
4H, arom H), 5.97 (m, 1H, -CHꢈ), 5.51 (s, 1H, MeOPhCH), 5.33 (dq, 1H,
ꢈCH2trans), 5.23 (dq, 1H, ꢈCH2cis ), 4.45 (ddt, 1H, OCH2), 4.35 (d, 1H, J1,2 ꢈ 7.6
Hz, H-1), 4.33 (dd, 1 H, J5,6a ꢈ 1.4, J6a,6b ꢈ 12.5 Hz, H-6a), 4.20 (d, 1H, J3,4 ꢈ 3.9
Hz, H-4), 4.14 (ddt, 1H, OCH2), 4.07 (dd, 1H, J5,6b ꢈ 2.0 Hz, H-6b), 3.81 (s, 3H,
OMe), 3.77 (ddd, 1H, J2,3 ꢈ 9.4, J2,OH ꢈ 1.8 Hz, H-2), 3.68 (ddd, 1H, J3,OH ꢈ 9.3
Hz, H-3), 3.47 (m, 1H, H-5) and 2.45–2.40 (m, 2H, OH).
Anal. Calcd for C17H22O7 (338.36): C, 60.35; H, 6.55. Found: C, 59.83;
H, 6.41.
Allyl 3-O-p-Methoxybenzyl-4,6-O-p-methoxybenzylidene-ꢁ-D-galac-
topyranoside (3). A mixture of 2 (1.1 g, 2.4 mmol) and dibutyltin oxide (800
mg, 3.21 mmol) in toluene (100 mL) was refluxed for 4 h with azeotropic removal
of water. The solution was concentrated and the residue was dissolved in CH3CN
(20 mL). Tetrabutylammonium iodide (1.2 g, 3.24 mmol) and p-methoxybenzyl
chloride (1.2 mL, 8.85 mmol) were added, and the mixture was refluxed overnight.
Evaporation of the solvents gave a residue which was purified on silica gel (C, 1:1
hexane/EtOAc) to give 3 as colorless crystals, mp 182°C (hexane/EtOAc). Yield :
1.15 g (77%); [ꢀ]D20 ꢆ43° (c 0.8, CHCl3). 1H NMR (CDCl3) ꢇ 7.50 - 6.80 (m, 8H,
arom H), 5.98 (m, 1H, -CHꢈ), 5.43 (s, 1H, MeOPhCH), 5.34 (dq, 1H, ꢈCH2trans),
5.23 (dq, 1H, ꢈCH2cis ), 4.73 and 4.67 (AB, 2 H, JA,B ꢈ 11.9 Hz, OCH2Ph), 4.44
(ddt, 1H, OCH2), 4.37 (d, 1H, J1,2 ꢈ 7.8 Hz, H-1), 4.31 (dd, 1H, J5,6a ꢈ 1.4, J6a,6b
ꢈ 12.3 Hz, H-6a), 4.15 (ddt, 1H, OCH2), 4.11 (d, 1H, J3,4 ꢈ 3.6 Hz, H-4), 4.07-
3.97 (m, 2H, H-2, H-6b), 3.81 (s, 6H, 2 OMe), 3.48 (dd, 1H, J2,3 ꢈ 9.7 Hz, H-3),
3.35 (m, 1H, H-5) and 2.47 (d, 1H, J2,OH ꢈ 1.9 Hz, OH).
Anal. Calcd for C25H30O8 (458.51): C, 65.49; H, 6.59. Found: C, 64.84;
H, 6.54.
Allyl 2-O-Acetyl-3-O-p-methoxybenzyl-4,6-O-p-methoxybenzylidene-ꢁ-
D-galactopyranoside (4). A solution of 3 (800 mg, 1.74 mmol) and a catalytic
amount of 4-N,N-dimethylaminopyridine in dry pyridine (10 mL) was stirred with
acetic anhydride (1 mL) overnight at rt. MeOH (2 mL) was added, and the solution
was coevaporated three times with addition of toluene and concentrated. Purifica-
tion of the residue on silica gel (C, 2:1 hexane/EtOAc) furnished 4 as colorless

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724
AMER ET AL.
crystals, mp 141°C (hexane/EtOAc). Yield: 800 mg (92%); [ꢀ]D20 ꢆ46° (c 0.8,
1
CHCl3). H NMR (CDCl3) ꢇ 7.50–6.80 (m, 8H, arom H), 5.85 (m, 1H, -CHꢈ),
5.43 (s, 1H, MeOPhCH), 5.36 (dd, 1H, J1,2 ꢈ 8.0, J2,3 ꢈ 10.1 Hz, H-2), 5.26 (dq,
1H, ꢈCH2trans), 5.15 (dq, 1H, ꢈCH2cis ), 4.62 and 4.55 (AB, 2H, JA,B ꢈ 12.3 Hz,
OCH2Ph), 4.45 (d, 1H, H-1), 4.35 (ddt, 1H, OCH2), 4.29 (dd, 1H, J5,6a ꢈ 1.6, J6a,6b
ꢈ 12.4 Hz, H-6a), 4.12 (d, 1H, J3,4 ꢈ 3.5 Hz, H-4), 4.10 (ddt, 1H, OCH2), 4.01 (dd,
1H, J5,6b ꢈ 1.8 Hz, H-6b), 3.80 (s, 6H, 2 OMe), 3.56 (dd, 1H, H-3), 3.32 (m, 1H,
H-5), and 2.06 (s, 3H, Ac).
Anal. Calcd for C27H32O9 (500.54): C, 64.79; H, 6.44. Found: C, 64.39;
H, 6.28.
Allyl 2-O-Acetyl-3,6-di-O-p-methoxybenzyl-ꢁ-D-galactopyranoside (5).
A suspension of 4 (200 mg, 0.4 mmol), 4 Å molecular sieves (0.4 g) in DMF (5
mL) and NaCNBH3 (450 mg, 7.16 mmol) was stirred under Ar at rt. After 15 min,
trifluoroacetic acid (400 ꢅL, 5.19 mmol) in DMF (2 mL) was added dropwise at
0°C. The suspension was stirred overnight at room temperature. Triethylamine (0.5
mL) was added, and the mixture was filtered over a pad of Celite. The filtrate was
concentrated and the residue was purified on a column of silica gel (C, 3:2 hex-
ane/EtOAc) to give 5 as a syrup. Yield: 140 mg (70%); [ꢀ]2D0 ꢆ8° (c 0.8,
CHCl3).1H NMR (CDCl3) ꢇ 7.35 - 6.85 (m, 8H, arom H), 5.85 (m, 1H, -CHꢈ),
5.26 (dq, 1H, ꢈCH2trans), 5.20 (dd, 1H, J1,2 ꢈ 8.1, J2,3 ꢈ 9.8 Hz, H-2), 5.16 (dq,
1H, ꢈCH2cis ), 4.63 and 4.48 (AB, 2H, JA,B ꢈ 11.9 Hz, OCH2Ph), 4.53 (s, 2H,
OCH2Ph), 4.38 (d, 1H, H-1), 4.33 (ddt, 1H, OCH2), 4.15–4.00 (m, 2H, H-4,
OCH2), 3.82 (s, 6H, 2 OMe), 3.81 (dd, 1H, J5,6a ꢈ 6.2, J6a,6b ꢈ 9.9 Hz, H-6a), 3.72
(dd, 1H, J5,6b ꢈ 5.8 Hz, H-6b), 3.70 (dd, 1H, H-5), 3.47 (dd, 1H, J3,4 ꢈ 3.4 Hz, H-
3), 2.56 (bs, 1H, OH), and 2.05 (s, 3H, Ac).
Anal. Calcd for C27H34O9 (502.57): C, 64.53; H, 6.82. Found: C, 64.10;
H, 6.83. Further elution afforded the 4-O-isomer as a syrup. Yield: 40 mg (20%).
Allyl 2-O-Acetyl-3,6-di-O-p-methoxybenzyl-4-O-methyl-ꢁ-D-galactopy-
ranoside (6). A suspension of 5 (95 mg, 0.19 mmol) in dry DMF (3 mL) and
NaH (12 mg, 80% in oil, 0.4 mmol) was stirred at rt. After stirring for 15 min, MeI
(60 ꢅL, 0.96 mmol) was added at ꢂ20°C and stirring was continued for 2 h. The
mixture was diluted with CH2Cl2, filtered over a pad of Celite, washed with 10%
aq Na2S2O3, satd aq NaHCO3 and dried (Na2SO4). Concentration of the solution
and purification of the residue on a column of silica gel (C, 3:2 hexane/EtOAc) af-
forded 6 as a syrup. Yield: 85 mg (87%); [ꢀ]D20 ꢆ8° (c 1.2, CHCl3).1H NMR
(CDCl3) ꢇ 7.27–6.75 (m, 8H, arom H), 5.81 (m, 1H, -CHꢈ), 5.25 (dd, 1H, J1,2
ꢈ 8.0, J2,3 ꢈ 9.8, H-2), 5.22 (dq, 1H, ꢈCH2trans), 5.12 (dq, 1H, ꢈCH2cis ), 4.64,
4.51 and 4.46 (AB, 4H, JA,B 11.5 Hz, 2 OCH2Ph), 4.35 (d, 1H, H-1), 4.28 (ddt, 1H,
OCH2), 4.03 (ddt, 1H, OCH2), 3.81, 3.80 (2 s, 6H, 2 MeOPh), 3.71 (dd, 1H, J5,6a
ꢈ 7.5, J6a,6b ꢈ 9.0 Hz, H-6a), 3.66 (d, 1H, J3,4 ꢈ 3.0 Hz, H-4), 3.60 (dd, 1H, J5,6b
ꢈ 5.4 Hz, H-6b), 3.54 (s, 3H, OMe), 3.51 (dd, 1H, H-5), 3.43 (dd, 1H, H-3), and
2.02 (s, 3H, Ac).

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TOXOCARA LARVAE
725
Anal. Calcd for C28H36O9 (516.59): C, 65.10; H, 7.02. Found: C, 64.90;
H, 6.92.
Allyl 3,6-Di-O-p-methoxybenzyl-4-O-methyl-ꢁ-D-galactopyranoside (7).
Compound 6 (65 mg, 0.13 mmol) was dissolved in 90% aq dioxane (5 mL), and
40% aq tetra-n-butylammonium hydroxide (100 ꢅL, 0.22 mmol) was added. After
stirring for 4 h at rt, the solution was neutralized by addition of Dowex 50 (Hꢆ)
resin, the resin was filtered off, and the filtrate was concentrated. The residue was
purified on a column of silica gel (C, 3:2 hexane/EtOAc) to give 7 as a syrup.
Yield: 48 mg (82%); [ꢀ]D20 ꢂ5° (c 1.2, CHCl3).1H NMR (CDCl3) ꢇ 7.35–6.85
(m, 8H, arom H), 5.92 (m, 1H, ꢈCH-), 5.28 (dq, 1H, ꢈCH2trans), 5.17 (dq, 1H,
ꢈCH2cis ), 4.71, 4.60, 4.51 and 4.46 (AB, 4H, JA,B ꢈ 11.5 Hz, OCH2Ph), 4.35 (ddt,
1H, OCH2), 4.27 (d, 1H, J1,2 ꢈ 7.7 Hz, H-1), 4.08 (ddt, 1H, OCH2), 4.00–3.79 (m,
7H, H-2, 2 MeOPh), 3.70 (dd, 1H, J5,6a ꢈ 7.6, J6a,6b ꢈ 8.9 Hz, H-6a), 3.64 (d, 1H,
J3,4 ꢈ 3.7 Hz, H-4), 3.59 (dd, 1H, J5,6b ꢈ 5.3 Hz, H-6b), 3.56 - 3.50 (m, 4H, H-5,
OMe), 3.36 (dd, 1H, J2,3 ꢈ 9.9 Hz, H-3), and 2.31 (bs, 1H, OH).
Anal. Calcd for C26H34O8 (474.55): C, 65.81; H, 7.22. Found: C, 65.76;
H, 7.27.
S-Ethyl 3,4-Di-O-acetyl-2-O-p-methoxybenzyl-1-thio-ꢁ-L-fucopyra-
noside (8). A solution of S-ethyl 3,4-O-isopropylidene-2-O-p-methoxybenzyl-1-
thio-ꢁ-L-fucopyrano-side (150 mg, 0.41 mmol) in CH2Cl2 (10 mL) was treated
with 90% aq trifluoroacetic acid (150 ꢅL ) at ꢂ35°C for 2 h. Triethylamine (0.5
mL) was added, and the solvent was evaporated. The residue was dissolved in pyri-
dine (3 mL) and stirred with a catalytic amount of 4-N,N-dimethylaminopyridine
and acetic anhydride (1 mL) for 48 h at rt. Methanol (2 mL) was added, and the so-
lution was concentrated. Purification of the residue on silica gel (C, 3:1
hexane/EtOAc) afforded 8 as a syrup; Yield: 65 mg (39%).[ ꢀ]D20 ꢂ9° (c 0.7,
CHCl3). 1H NMR (CDCl3) ꢇ 7.30–6.80 (m, 4H, arom. H), 5.25 (dd, 1H, J3,4 ꢈ 3.4
Hz, H-4), 4.99 (dd, 1H, J2,3 ꢈ 9.7 Hz, H-3), 4.78 and 4.54 (d, 2H, JA,B ꢈ 10.5 Hz,
OCH2Ph), 4.54 (d, 1H, J1,2 ꢈ 9.7 Hz, H-1), 3.79 (s, 1H, OMe), 3.76 (dd, 1H, J5,6
ꢈ 6.4 Hz, H-5), 3.62 (dd, 1H, H-2), 2.77 (m, 2H, SCH2), 2.15 and 1.97 (2 s, 6H,
2 Ac), 1.33 (t, 3H, CH2CH3), and 1.20 (d, 3H, H-6).
Anal. Calcd for C20H28O7S (412.51): C, 58.24; H, 6.84. Found: C, 57.95;
H, 6.78.
S-Ethyl 3,4-Di-O-acetyl-2-O-methyl-1-thio-ꢁ-L-fucopyranoside (9).
A
solution of S-ethyl 3,4-O-isopropylidene-2-O-methyl-1-thio-ꢁ-D-fucopyranoside
(500 mg, 1.91 mmol) in CH2Cl2 (40 mL) was treated with 90% aq trifluoroacetic
acid (1 mL ) at rt for 2 h. Triethylamine (0.5 mL) was added, and the solvent was
evaporated. The residue was dissolved in pyridine (20 mL) and stirred with a cat-
alytic amount of 4-N,N-dimethylaminopyridine and acetic anhydride (3 mL) for 48
h at rt. Methanol (6 mL) was added, and the solution was concentrated. Purifica-
tion of the residue on silica gel (C, 3:1 hexane/EtOAc) afforded 9 as a syrup.Yield:

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AMER ET AL.
520 mg (89%); [ꢀ]D20 ꢆ17° (c 0.6, CHCl3).1H NMR (CDCl3) ꢇ 5.24 (dd, 1H, J5,4
ꢈ 1.0, J3,4 ꢈ 3.4 Hz, H-4), 4.93 (dd, 1H, J2,3 ꢈ 9.7 Hz, H-3), 4.43 (d, 1H, J1,2
ꢈ 9.7 Hz, H-1), 3.76 (dd, 1H, J5,6 ꢈ 6.5 Hz, H-5), 3.52 (s, 3H, OMe), 3.35 (dd, 1H,
H-2), 2.77 (m, 2H, SCH2), 2.16, 2.04 (2 s, 6H, 2 Ac), 1.32 (t, 3H, CH2CH3), and
1.19 (d, 3H, J5,6 ꢈ 6.5 Hz, H-6).
Anal. Calcd for C13H22O6S (306.38): C, 50.96; H, 7.24. Found: C, 51.26;
H, 7.41.
Allyl (3,4-Di-O-acetyl-2-O-methyl-ꢀ-L-fucopyranosyl)-(1(2)-3-O-p-
methoxy-benzyl-4,6-O-p-methoxybenzylidene-ꢁ-D-galactopyranoside (10).
To a suspension of 3 (95 mg, 0.21 mmol), 9 (83 mg, 0.27 mmol), and powdered
molecular sieves 4 Å (0.2 g) in CH2Cl2/Et2O (1:1, v/v, 2 mL) was added a solution
of N-iodosuccinimide (16 mg) and trifluoromethanesulphonic acid (4 ꢅL) in
CH2Cl2/Et2O (1:1, v/v, 2 mL) at ꢂ20°C under Ar. The mixture was stirred at 0°C
for 1 h, diluted with CH2Cl2 (50 mL), and filtered over a pad of Celite. The filtrate
was washed with 10% aq Na2S2O3, aq satd NaHCO3, dried (Na2SO4) and concen-
trated. Purification of the residue on silica gel (C, 3:1:1 toluene/EtOAc/MeOH,
v/v/v) gave 10 as a syrup. Yield: 77 mg (53%); [ꢀ]D20 ꢂ47° (c 0.6, CHCl3). H
1
NMR (CDCl3) ꢇ 7.45–6.75 (m, 8H, arom H), 5.93 (m, 1H, -CHꢈ), 5.53 (d, 1H,
J1ꢃ,2ꢃ ꢈ 3.7 Hz, H-1ꢃ), 5.36 (s, 1H, PhCH), 5.34 - 5.15 (m, 4H, H-3ꢃ, H-4ꢃ,
ꢈCH2trans, ꢈCH2cis), 4.66 and 4.56 (AB, 2H, JA,B ꢈ 11.4 OCH2Ph), 4.62 (dd, 1H,
J5ꢃ,6ꢃ ꢈ 6.5 Hz, H-5ꢃ), 4.48 (d, 1H, J1,2 ꢈ 7.8, H-1), 4.40 (ddt, 1H, OCH2), 4.28 (dd,
1H, J6a,6b ꢈ 12.2 Hz, H-6a), 4.14–4.02 (m, 3H, H-2, H-4, OCH2), 3.98 (dd, 1H,
J
J
5,6a ꢈ 1.6 Hz, H-6b), 3.81 and 3.79 (2 s, 6H, 2 MeOPh), 3.72 (dd, 1H, J2,3 ꢈ 9.5,
3,4 ꢈ 3.7 Hz, H-3), 3.56 (dd, 1H, J2ꢃ,3ꢃ ꢈ 10.5 Hz, H-2ꢃ), 3.36 (s, 3H, OMe), 3.31
(m, 1H, H-5), 2.14 and 2.01 (2 s, 6H, 2 Ac), and 1.04 (d, 3H, H-6ꢃ).
Anal. Calcd for C36H46O14 (702.76): C, 61.53; H, 6.60. Found: C, 61.26; H,
1
6.51. Further elution furnished the ꢁ-isomer as a syrup. Yield: 25 mg (18%); H
NMR (CDCl3) for anomeric protons ꢇ 4.92 (d, 1H, J1ꢃ,2ꢃ ꢈ 7.8 Hz, H-1ꢃ), and 4.45
(d, 1H, J1,2 ꢈ 7.8 Hz, H-1).
Allyl (3,4-Di-O-acetyl-2-O-p-methoxybenzyl-ꢁ-L-fucopyranosyl)-(1→2)-
3,6-di-O-p-methoxybenzyl-4-O-methyl-ꢁ-D-galactopyranoside (13). Com-
pound 7 (45 mg, 0.10 mmol) was reacted with 8 (50 mg, 0.12 mmol) in the same
way as described for 10. Purification of the residue on silica gel (C, 3:2
hexane/EtOAc) afforded 13 as syrup. Yield: 65 mg (83%); [ꢀ]D20 ꢂ60° (c 0.7,
1
CHCl3). H NMR (CDCl3) ꢇ7.30–6.50 (m, 12H, arom H), 5.90 (m, 1H, -CHꢈ),
5.57 (d, 1H, J1ꢃ,2ꢃ ꢈ 3.8 Hz, H-1ꢃ), 5.35 - 5.10 (m, 4H, H-3ꢃ, H-4ꢃ, ꢈCH2trans
,
ꢈCH2cis), 4.71 and 4.28 (AB, 2H, JA,B ꢈ 11.9 Hz, OCH2Ph), 4.65 (dd, 1H, J5ꢃ,6ꢃ
ꢈ 6.5 Hz, H-5ꢃ), 4.52–4.40 (m, 5H, H-1, 2 OCH2Ph ), 4.35 (ddt, 1H, OCH2),
4.10–3.95 (m, 2H, H-2, OCH2), 3.80, 3.79 and 3.75 (3 s, 9H, 3 MeOPh), 3.75 (dd,
1H, J2ꢃ,3ꢃ ꢈ 10.7 Hz, H-2ꢃ), 3.72–3.49 (m, 5H, H-3, H-4, H-5, H-6a, H-6b), 3.48
(s, 3H, OMe), 2.06 and 1.95 (2 s, 6H, 2 Ac), and 1.02 (d, 3H, H-6ꢃ).
Anal. Calcd for C44H56O15 (824.93): C, 64.07; H, 6.84. Found: C, 63.56; H,
6.77. Further elution furnished the ꢁ-isomer as a syrup. Yield: 6 mg (7%). 1H NMR

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727
(CDCl3) for anomeric protons ꢇ 4.96 (d, 1H, J1ꢃ,2ꢃ ꢈ 7.8 Hz, H-1ꢃ), and 4.37 (d, 1H,
J1,2 ꢈ 7.7 Hz, H-1).
Allyl (3,4-Di-O-acetyl-2-O-methyl-ꢀ-L-fucopyranosyl)-(1→2)-3,6-di-O-
p-methoxybenzyl-4-O-methyl-ꢁ-D-galactopyranoside (16). To a mixture of 7
(45 mg, 0.09 mmol), 9 (40 mg, 0.13 mmol) and powdered molecular sieves 4 Å
(0.2 g) in CH2Cl2/Et2O (1:1, v/v, 2 mL) was added a solution of N-iodosuccinimide
(16 mg) and trifluoromethanesulphonic acid (4 ꢅL) in CH2Cl2/Et2O (1:1, v/v, 2
mL) at ꢂ20°C under Ar. The suspension was stirred at 0°C for 1 h, diluted with
CH2Cl2 (50 mL) and filtered over Celite. The filtrate was washed with 10% aq
Na2S2O3, aq NaHCO3, dried over Na2SO4 and concentrated. Purification of the
residue on silica gel (B, 3:1 hexane/EtOAc) gave contaminated product 16, which
could not be further purified at this stage. Yield: 60 mg (88%). 1H NMR (CDCl3)
ꢇ 7.30–6.80 (m, 8H, arom H), 5.88 (m, 1H, -CHꢈ), 5.55 (d, 1H, J1ꢃ,2ꢃ ꢈ 3.7 Hz,
H-1ꢃ), 5.35–5.10 (m, 4H, H-3ꢃ, H-4ꢃ, ꢈCH2trans, ꢈCH2cis), 4.71 and 4.53 (AB, 2H,
JAB ꢈ 11.1 Hz, OCH2Ph), 4.62 (dd, 1H, J5ꢃ,6ꢃ ꢈ 6.5 Hz, H-5ꢃ), 4.48 and 4.47 (2 s,
2H, OCH2Ph ), 4.43 (d, 1H, J1,2 ꢈ 7.7 Hz, H-1), 4.35 (ddt, 1H, OCH2), 4.10–3.95
(m, 2H, H-2, OCH2), 3.81 and 3.79 (2 s, 6H, 2 MeOPh), 3.70–3.50 (m, 6H, H-3,
H-4, H-5, H-6a, H-6b, H-2ꢃ), 3.49 and 3.30 (2 s, 3H, 2 OMe), 2.13 and 1.99
(2s, 6H, 2 Ac), and 1.02 (d, 3H, H-6ꢃ).
1
Further elution furnished the ꢁ-isomer as a syrup. Yield: 8 mg (11%). H
NMR (CDCl3) for anomeric protons ꢇ 4.87 (d, 1H, J1ꢃ,2ꢃ ꢈ 7.7 Hz, H-1ꢃ), and 4.37
(d, 1H, J1,2 ꢈ 7.7 Hz, H-1)
Allyl (3,4-Di-O-acetyl-2-O-methyl-ꢀ-L-fucopyranosyl)-(1→2)-3,4,6-tri-
O-ace-tyl-ꢁ-D-galactopyranoside (11). A solution of 10 (28 mg, 0.04 mmol) in
CH2Cl2 (3 mL) was treated with aq 90% trifluoroacetic acid (100 ꢅL) at rt for 1 h.
The mixture was neutralized with triethylamine (0.5 mL), and the solvent was evap-
orated. The residue was dissolved in pyridine (2 mL) and stirred with a catalytic
amount of 4-N,N-dimethylaminopyridine and acetic anhydride (200 ꢅL) overnight
at rt. MeOH (1 mL) was added, and the solution was concentrated. Purification of
the residue on silica gel (B, 1:2 hexane/EtOAc) afforded 11 as a syrup. Yield: 15 mg
(65%); [ꢀ]D20 ꢂ46° (c 1.0, CHCl3). 1H NMR (CDCl3) ꢇ 5.93 (m, 1H, -CHꢈ), 5.37
(d, 1H, J3,4 ꢈ 3.4 Hz, H-4), 5.32 (dq, 1H, ꢈCH2trans), 5.28–5.15 (m, 4H, H-1ꢃ,
H-3ꢃ, H-4ꢃ, ꢈCH2cis), 5.10 (dd, 1H, J2,3 ꢈ 10.1 Hz, H-3), 4.55 (d, 1H, J1,2 ꢈ 7.8 Hz,
H-1), 4.51 (dd, 1H, J5ꢃ,6ꢃ ꢈ 6.5 Hz, H-5ꢃ), 4.40 (ddt, 1H, OCH2), 4.25–4.05 (m, 3H,
H-6a, H-6b, OCH2), 3.98 (dd, 1H, H-2), 3.87 (dd, 1H, J5,6a ꢈ J5,6b ꢈ 6.7 Hz, H-5),
3.61 (dd, 1H, J1ꢃ,2ꢃ ꢈ 3.7, J2ꢃ,3ꢃ ꢈ 10.1 Hz, H-2ꢃ), 3.39 (1 s, 3H, OMe), 2.15, 2.12,
2.05, 2.00 and 1.99 (5s, 15H, 5 Ac), and 1.08 (d, 3H, H-6ꢃ).
Anal. Calcd for C26H38O15 (590.58): C, 52.88; H, 6.49. Found: C, 53.20;
H, 6.44.
Allyl (2,3,4-Tri-O-acetyl-ꢀ-L-fucopyranosyl)-(1→2)-3,6-di-O-acetyl-4-O-
methyl-ꢁ-D-galactopyranoside (14). A solution of 13 (55 mg, 0.07 mmol) in
CH2Cl2 (8 mL) was treated with aq 90% trifluoroacetic acid (150 ꢅL) at rt for 1 h.

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AMER ET AL.
The mixture was neutralized with triethylamine (0.5 mL), and the solvent was
evaporated. The residue was dissolved in pyridine (3 mL) and stirred with a cat-
alytic amount of 4-N,N-dimethylaminopyridine and acetic anhydride (400 ꢅL)
overnight at rt. MeOH (1 mL) was added, and the solution was concentrated. Pu-
rification of the residue on silica gel (B, 1:1 hexane/EtOAc) afforded 14 as a syrup.
Yield: 33 mg (84%); [ꢀ]D20 ꢂ117° (c 0.6, CHCl3). 1H NMR (CDCl3) ꢇ5.90 (m, 1H,
ꢈCH-), 5.40 (d, 1H, J1ꢃ,2ꢃ ꢈ 3.9 Hz, H-1ꢃ), 5.40 (dd, 1H, J2ꢃ,3ꢃ ꢈ 10.9, J3ꢃ,4ꢃ ꢈ 3.4
Hz, H-3ꢃ), 5.29 (dq, 1H, ꢈCH2trans), 5.26–5.18 (m, 2H, H-4ꢃ, ꢈCH2cis), 5.02 (dd,
1H, H-2ꢃ), 4.94 (dd, 1H, J2,3 ꢈ 9.9, J3,4 ꢈ 3.0 Hz, H-3), 4.57 (dd, 1H, J5ꢃ,6ꢃ ꢈ 6.5
Hz, H-5ꢃ), 4.45 (d, 1H, J1,2 ꢈ 7.7 Hz, H-1), 4.38 (ddt, 1H, OCH2), 4.32 (dd, 1H,
J5,6a ꢈ 6.4, J6a,6b ꢈ 11.1 Hz, H-6a), 4.18 (dd, 1H, J5,6b ꢈ 6.6 Hz, H-6b), 4.08 (ddt,
1H, OCH2), 4.06 (dd, 1H, H-2), 3.67 (dd, 1H, H-5), 3.57 (d, 1H, H-4), 3.46 (1 s,
3H, OMe), 2.14, 2.11, 2.08, 2.02 and 1.98 (5 s, 15H, 5 Ac), and 1.06 (d, 3H, H-6ꢃ).
Anal. Calcd for C26H38O15 (590.58): C, 52.88; H, 6.49. Found: C, 53.58;
H, 6.43.
Allyl (3,4-Di-O-acetyl-2-O-methyl-ꢀ-L-fucopyranosyl)-(1→2)-3,6-di-O-
acetyl-4-O-methyl-ꢁ-D-galactopyranoside (17). To a solution of 16 (54 mg,
0.08 mmol) in 9:1 CH3CN/H2O (5 mL) was added ceric ammonium nitrate (300
mg, 0.55 mmol) and 2 drops of pyridine, and the mixture was stirred for 2 h at rt.
Additional ceric ammonium nitrate (100 mg) was added and stirring was contin-
ued for 1 h. The mixture was diluted with CH3CN (10 mL), filtered over a pad of
Celite, and the solvent was evaporated. The residue was dissolved in pyridine
(3 mL) and stirred with a catalytic amount of 4-N,N-dimethylaminopyridine and
acetic anhydride (0.5 mL) at rt for 12 h. MeOH (2 mL) was added, and the solution
was concentrated. Purification of the residue on silica gel (B, 2:1 hexane/EtOAc)
afforded 16 as a syrup. Yield: 32 mg (76%); [ꢀ]D20 ꢂ88° (c 0.7, CHCl3). 1H NMR
(CDCl3) ꢇ 5.89 (m, 1H, -CHꢈ), 5.35 - 5.10 (m, 5H, H-1ꢃ, 3ꢃ, 4ꢃ, ꢈCH2trans
,
ꢈCH2cis), 4.98 (dd, 1H, J2,3 ꢈ 10.3, J3,4 ꢈ 3.0 Hz, H-3), 4.56 (dd, 1H, J5ꢃ,6ꢃ ꢈ 6.5
Hz, H-5ꢃ), 4.45 (d, 1H, J1,2 ꢈ 7.7 Hz, H-1), 4.40–4.25 (m, 2H, H-6a, OCH2), 4.17
(dd, 1H, J5,6b ꢈ 6.5, J6a,6b ꢈ 11.1 Hz, H-6b), 4.13–4.00 (m, 2H, H-2, OCH2), 3.75
- 3.55 (m, 3H, H-4, 5, 2ꢃ), 3.46 and 3.41 (2 s, 6H, 2 OMe), 2.14, 2.11, 2.07 and 1.99
(4 s, 12H, 4 Ac), and 1.04 (d, 3H, H-6ꢃ).
Anal. Calcd for C25H38O14 (562.57): C, 53.38; H, 6.81. Found: C, 53.61;
H, 6.62.
Allyl 2-O-Methyl-ꢀ-L-fucopyranosyl-(1→2)-ꢁ-D-galactopyranoside (12).
A solution of 11 (19 mg, 0.032 mmol) in dry MeOH (3 mL) was stirred with 0.1 M
methanolic NaOMe (200 ꢅL) overnight at rt. The pH of the solution was adjusted
to 7.0 by addition of Dowex 50 (Hꢆ) resin, the resin was filtered off, and the filtrate
was concentrated. Purification of the residue on silica gel (A, 1:2 MeOH/EtOAc) af-
forded 12 as a syrup. Yield: 12 mg (96%); [ꢀ]D20 ꢂ134° (c 0.6, MeOH). 1H NMR
(D2O) ꢇ 5.97 (m, 1H, -CHꢈ), 5.44 (d, 1H, J1ꢃ,2ꢃ ꢈ 3.9 Hz, H-1ꢃ), 5.35 (dq, 1H,
ꢈCH2trans), 5.27 (dq, 1H, ꢈCH2cis), 4.52 (d, 1H, J1,2 ꢈ 7.9 Hz, H-1), 4.38 (ddt, 1H,
OCH2), 4.31 (dd, 1H, J5ꢃ,6ꢃ ꢈ 6.6 Hz, H-5ꢃ), 4.21 (ddt, 1H, OCH2), 3.90–3.63 (m,

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729
7H, H-3, H-4, 5, 6a, 6b, 3ꢃ, 4ꢃ), 3.60 (dd, 1H, J2,3 ꢈ 9.6 Hz, H-2), 3.49 (s, 3H, OMe),
3.47 (dd, 1H, J2ꢃ,3ꢃ ꢈ 10.5 Hz, H-2ꢃ), and 1.17 (d, 3H, H-6ꢃ).
Anal. Calcd for C16H28O10 (380.39): C, 50.52; H, 7.42. Found: C, 49.69;
H, 7.19.
Allyl ꢀ-L-Fucopyranosyl-(1→2)-4-O-methyl-ꢁ-D-galactopyranoside (15).
A solution of 14 (27 mg, 0.046 mmol) in dry MeOH (5 mL) was stirred with 0.1 M
methanolic NaOMe (100 ꢅL) for 48 h at rt. The pH of the solution was adjusted to
7.0 by addition of Dowex 50 (Hꢆ) resin, the resin was filtered off, and the residue
was concentrated. Purification of the residue on silica gel (A, 1:3 MeOH/EtOAc)
afforded 15 as a syrup. Yield: 16 mg (92%); [ꢀ]D20 ꢂ129° (c 0.9, MeOH). 1H NMR
(D2O) ꢇ 5.98 (m, 1H, -CHꢈ), 5.35 (dq, 1H, ꢈCH2trans), 5.28 (dq, 1H, ꢈCH2cis),
5.17 (d, 1H, J1ꢃ,2ꢃ ꢈ 3.7 Hz, H-1ꢃ), 4.50 (d, 1H, J1,2 ꢈ 7.8 Hz, H-1), 4.37 (ddt, 1H,
OCH2), 4.31 (dd, 1H, J5ꢃ,6ꢃ ꢈ 6.6 Hz, H-5ꢃ), 4.21 (ddt, 1H, OCH2), 3.95–3.73 (m,
6H, H-3, 6a, 6b, 2ꢃ, 3ꢃ, 4ꢃ), 3.68 (dd, 1H, J5,6a ꢈ 6.4 J5,6b ꢈ 6.2 Hz, H-5), 3.62 (d,
1H, J3,4 ꢈ 3.4 Hz, H-4), 3.60–3.45 (m, 4H, H-2, OMe), and 1.18 (d, 3H, H-6ꢃ).
Anal. Calcd for C16H28O10 (380.39): C, 50.52; H, 7.42. Found: C, 49.82;
H, 7.31.
Allyl 2-O-Methyl-ꢀ-L-fucopyranosyl-(1→2)-4-O-methyl-ꢁ-D-galactopy-
rano-side (18). A solution of 17 (22 mg, 0.039 mmol) in dry MeOH (3 mL) was
stirred with 0.1 M methanolic NaOMe (100 ꢅL) for 3 h at rt. The pH of the solu-
tion was adjusted to 7.0 by addition of Dowex 50 (Hꢆ) resin, the resin was filtered
off, and the residue was concentrated. Purification of the residue on silica gel (A,
1:3 MeOH/EtOAc) afforded 18 as a syrup. Yield: 15 mg (97%); [ꢀ]D20 ꢂ138°
1
(c 0.7, MeOH). H NMR (D2O) ꢇ 5.96 (m, 1H, -CHꢈ), 5.41 (d, 1H, J1ꢃ,2ꢃ ꢈ 3.8
Hz, H-1ꢃ), 5.33 (dq, 1H, ꢈCH2trans), 5.26 (dq, 1H, ꢈCH2cis), 4.49 (d, 1H, J1,2 ꢈ
7.8 Hz, H-1), 4.40–4.25 (m, 2H, H-5ꢃ, OCH2), 4.19 (ddt, 1H, OCH2), 4.00–3.70
(m, 5H, H-3, 6a, 6b, 3ꢃ, 4ꢃ), 3.67 (dd, 1H, J5,6a ꢈ 5.8, J5,6b ꢈ 6.8 Hz, H-5),
3.60–3.40 (m, 9H, H-2, 4, 2ꢃ, 2 OMe), 1.06 (d, 3H, J5ꢃ,6ꢃ ꢈ 6.5 Hz, H-6ꢃ).
Anal. Calcd for C17H30O10 (394.42): C, 51.77; H, 7.67. Found: C, 51.02;
H, 7.43
ACKNOWLEDGMENTS
Technical assistance by Maria Hobel is gratefully acknowledged. The authors
are grateful for a scholarship by ÖAD (Austrian Academic Exchange Office) and
the Cultural Office of the Republic of Egypt.
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Boom, J. H. Iodonium ion assisted synthesis of a common inner core trisaccharide
fragment corresponding to the cell-wall phenolic glycolipid of Mycobacterium
kansasii. Tetrahedron 1992, 48, 10133–10148.
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analogues of the acceptor ꢀ-L-Fucp-(1→2)-ꢁ-D-Galp-OR by the blood-group A and
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Received March 19, 2001
Accepted September 26, 2001

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