Chemical modification of lactose. XVII. Syntheses of O-.ALPHA.- and O-.BETA.-L-fucopyranosyl-(1.RAR.4)- or -(1.RAR.6)-O-.BETA.-D-galactopyranosyl-(1.RAR.4)-D-glucopyranoses (4'- or 6'-O-.ALPHA.- and -O-.BETA.-L-fucopyranosyllactoses).

1, 6-Anhydro-2, 2', 3, 3', 6'- and -2, 2', 3, 3', 4'-penta-O-benzyl-β-lactoses (4 and 7) were synthesized from 1, 6-anhydro-2, 2', 3, 3'-tetra-O-benzyl-4', 6'-O-benzylidene-β-lactose (1). Condensation of 4 with 2, 3, 4-tri-O-acetyl-α-L-fucopyranosyl bromide (acetobromofucose) in the conventional Koenigs-Knorr reaction, followed by deacetylation, gave 4'-O-linked trisaccharide derivatives bearing α- and β-L-fucopyranosyl linkages (10 and 15) in 13.4 and 25.6% yields, respectively. Analogous condensation of 7 with acetobromofucose gave a 6'-O-linked, fully protected trisaccharide bearing a β-L-fucopyranosyl linkage (20) in 64% yield. Halide ion-catalyzed condensation of 7 with 2, 3, 4-tri-O-benzyl-α-L-fucopyranosyl bromide gave a trisaccharide derivative bearing an α-L-fucopyranosyl linkage (26) in 51.8% yield. Removal of the protecting groups of 10, 15, 20, and 26 provided the title trisaccharides (14, 19, 25, and 30). 1H- and 13C-NMR spectral data of 14, 19, 25, 30, and synthetic intermediates are also presented.