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4.15. 1,6-Di-O-acetyl-2-azido-3-O-benzyl-2-deoxy-4-O-
(methyl 2,3,4-tri-O-acetyl-b-D-glucopyranosyluronate)-D-
glucopyranose
for C28H35N3O13: C, 51.45; H, 5.40; N, 6.43. Found:
C, 51.27; H, 5.34; N, 6.22.
4.17. [6-O-Acetyl-2-azido-3-O-benzyl-2-deoxy-4-O-
(methyl 2,3,4-tri-O-acetyl-b-D-glucopyranosyluronate)-b-
D-glucopyranosyl] trichloroacetimidate (19)
A soln of 18 (1.67g, 2.8mmol) in Ac2O (4.5mL) and tri-
fluoroacetic acid (0.5mL) was stirred for 12h at rt, the
solvent removed under diminished pressure and the
resulting residue purified by flash chromatography to
yield the title compound as a white solid (1.96g, quanti-
tative); mp 40–45ꢁC ; a[ ]D +24.0 (c 0.28, CHCl3); Rf 0.50
(4:1 toluene–acetone); IR (KBr) cmꢁ1 3462, 2930, 2393,
2114, 1758, 1457, 1373, 1218, 1030, 775; 1H NMR
(300MHz, CDCl3, 5:2 mixture of a:b anomers): d
7.39–7.26 (m, 5H, Ar–H), 6.18 (d, 1H, J 4.0), 5.45 (m,
1H), 5.22–5.20 (m, 2H), 5.12 (d, 1H, J 11.4), 5.04–5.00
(m, 1H), 4.80–4.71 (m, 2H), 4.42 (d, 1H, J 12.0), 4.12
(d, 1H, J 12.0), 3.89–3.84 (m, 3H), 3.55 (overlapping sig-
nals, 5H), 2.16, 2.10, 2.07, 2.01, 1.99 (each s, each 3H);
13C NMR (75MHz, CDCl3): d 169.3, 169.0, 167.7,
165.6, 137.1 (each s), 127.3, 126.5, 126.3, 99.9, 99.7,
89.1, 77.3, 77.2 (each d), 74.2 (t), 72.4, 71.7, 71.1, 70.7,
70.6, 69.7, 68.2, 63.7, 61.4 (each d), 60.6 (t), 51.7 (q),
19.9, 19.8, 19.6, 19.5, 19.4 (each q); FABMS m/z
[M+Na]+ calcd 718.2072, found 718.2067.
A soln of 6-O-acetyl-2-azido-3-O-benzyl-2-deoxy-4-O-
(methyl 2,3,4-tri-O-b-D-glucopyranosyluronate)-b-D-
glucopyranose (0.9g, 1.37mmol) in dry CH2Cl2 (4mL)
˚
was stirred at rt for 5min in the presence of 4A mole-
cular sieves. Dry potassium carbonate (0.57g, 4.1mmol,
3equiv) and trichloroacetonitrile (1.24mL, 12.4mmol,
9equiv) were added and the reaction was allowed to stir
for 12h. The mixture was concentrated and the residue
purified by chromatography to give 19 as an off-white
solid (0.74g, 81%); [a]D +1.0 (c 0.21, CHCl3); Rf 0.62
(1:1 EtOAc–petroleum ether); IR (KBr) cmꢁ1 3439,
2936, 2392, 2116, 1758, 1663, 1369, 1244, 1053, 616;
13C NMR(75MHz, CDCl3): d 169.3, 169.0, 168.3,
168.2, 165.6, 159.8, 137.1 (each s), 127.3, 126.6, 126.4,
99.7, 95.4, 79.9, 76.9 (each d), 74.1 (t), 72.3, 71.6, 71.1,
70.6, 68.2, 64.3 (each d), 60.8 (t), 51.8, 19.8, 19.5, 19.4
(each q); ESMS m/z [M+Na]+ calcd 819.1, found 819.0.
4.18. Methyl 6-O-acetyl-2-azido-3-O-benzyl-2-deoxy-4-
O-(methyl 2,3,4-tri-O-acetyl-b-D-glucopyranosyluronate)-
a-D-glucopyranoside (20a)
4.16. 6-O-Acetyl-2-azido-3-O-benzyl-2-deoxy-4-O-
(methyl 2,3,4-tri-O-acetyl-b-D-glucopyranosyluronate)-D-
glucopyranose
A soln of MeOH (0.3mL, 0.92mmol, 10equiv) and bor-
on trifluoride-diethyl ether (0.017mL, 0.09mmol,
˚
0.1equiv) in anhyd CH2Cl2 (4.0mL) over 4A molecular
Benzylamine (11.2mL, 2.6mmol, 39equiv) was added to
a soln of 1,6-di-O-acetyl-2-azido-3-O-benzyl-2-deoxy-4-
O-(methyl 2,3,4-tri-O-b-D-glucopyranosyluronate)-b-D-
glucopyranose in anhyd diethyl ether at 0ꢁC. After 1h,
the solvent was removed, and CH2Cl2 (150mL) was
added. The soln was washed with 1M HCl, dried over
anhyd MgSO4 and the solvent evaporated to give the
title compound as a white foam (1.1g, 65%); [a]D +30
(c 0.3, CHCl3); Rf 0.27 (1:1 EtOAc–petroleum ether);
IR (KBr) cmꢁ1 3424, 2939, 2115, 1751, 1648, 1383,
1229, 1074, 869, 688; 1H NMR (300MHz, CDCl3,
1.5:1 mixture of a and b anomers): d 7.39–7.26 (m,
5H), 5.25 (d, 1H, J 4.0), 5.22–4.95 (overlapping signals,
5H), 4.82 (d, 1H, J 11.0), 4.74 (d, 1H, J 8.0), 4.58 (d, 1H,
J 8.0), 4.50–4.45 (overlapping signals), 4.13–4.06 (over-
lapping signals), 3.96 (d, 1H, J 10.0), 3.87–3.71 (overlap-
ping signals), 3.51 (s, 3H), 3.50 (s, 3H, OCH3), 3.37–3.31
(overlapping signals), 2.10, 2.05, 2.00, 1.98 (each s, each
3H), 1.89 (s, 1H, OH); 13C NMR (75MHz, CDCl3):
d 170.8, 170.3, 169.6, 169.6, 169.5, 167.0, 167.0,
138.6, 138.3 (each s), 129.0, 128.6, 128.1, 127.9,
127.7, 127.4, 101.0, 96.3, 92.1, 81.2, 79.0, 78.6, 78.1
(each d), 75.3, 75.1 (each t), 72.9, 72.9, 72.8, 72.4,
72.0, 69.5, 68.7, 67.5, 63.9 (each d), 62.6, 62.3 (each t),
53.0, 21.1, 21.1, 20.8, 20.7 (each q); FABMS m/z
[M+Na]+ calcd 676.1966, found 676.1965. Anal. Calcd
sieves was stirred under a nitrogen atmosphere for
10min at 0ꢁC. A soln of 19 [736mg, 0.92mmol, 1equiv,
0.6M in anhyd CH2Cl2] was added dropwise to the reac-
tion over 10min. The reaction was allowed to stir at rt
for 12h, filtered through a pad of Celite, diluted with
CH2Cl2 (50mL) and washed with satd NaHCO3. The
organic layer was dried over anhyd MgSO4, concen-
trated and the resulting residue purified by flash
chromatography to give the title compound 20a as an
off-white solid (331mg, 54%) as well as the b-anomer
20b (136mg, 22%). Analytical data for 20a: [a]D +58 (c
0.25, CHCl3); Rf 0.14 (1:2 EtOAc–petroleum ether); IR
(KBr) cmꢁ1 3445, 2956, 2363, 2110, 1455, 1362, 1250,
1102, 892; 13C NMR (75MHz, CDCl3): d 169.4, 169.1,
168.2, 165.6, 137.3 (each s), 127.3, 126.4, 99.8, 97.5,
77.8, 77.1 (each d), 74.0 (t), 71.7, 71.7, 71.2, 70.7, 68.2,
67.4, 62.2 (each d), 61.0 (t), 54.4, 51.7, 19.8, 19.6, 19.5,
19.4 (each q); FABMS m/z [M+Na]+ calcd 690.2122,
found 690.2120. Analytical data for 20b: Rf 0.16 (1:2
EtOAc–petroleum ether); [a]D ꢁ7.0 (c 0.26, CHCl3);
IR (KBr) cmꢁ1 3470, 2962, 2114, 1375, 1261, 1098,
801; 13C NMR (75MHz, CDCl3): d 169.4, 169.0,
168.3, 168.3, 165.6 (each s), 137.4 (q), 101.8, 99.8,
80.0, 77.5 (each d), 73.8 (t), 71.5, 71.5, 71.1, 70.7, 68.2,