Chemical Modification of Lactose. XV. Syntheses of O-α- and O-β-L-Fucopyranosyl-(1→3)-O-β-D-galactopyranosyl-(1→4)-D-glucopyranoses (3'-O-α- and 3'-O-β-L-Fucopyranosyllactoses)

Abstract

1, 6-Anhydro-4', 6'-O-benzylidene-3'-O-tosyl-β-lactose was converted into 1, 6-anhydro-2, 2', 3-tri-O-benzyl-4', 6'-O-benzylidene-β-lactose (3) in 74.1% yield by benzylation followed by detosylation. Condensation of 3 with 2, 3, 4-tri-O-acetyl-α-L-fucopyranosyl bromide in benzene-nitromethane in the presence of mercuric cyanide and molecular sieves gave the corresponding trisaccharide derivatives (6 and 11) bearing α- and β-L-fucopyranosyl linkages in 37.1 and 43.1% yields, respectively. Compounds 6 and 11 were isolated by column chromatography on silica gel. The title sugars (10 and 15) were prepared in 4 steps from 6 and 11, respectively ; hydrogenolytic removal of the benzylidene and benzyl groups, acetylation, cleavage of the 1, 6-anhydro-β-ring to β-acetate, and deacetylation. ¹H-NMR and ¹³C-NMR spectral data of 10, 15, and the intermediates are also described.