Abstract
The title compounds were synthesized starting from 1, 6-anhydro-β-maltose, via 1, 6-anhydro-4', 6'-O-benzylidene-β-maltose with several steps. Heating of 2, 2', 3, 3'-tetra-O-acetyl-1, 6-anhydro-4', 6'-di-O-mesyl-β-maltose (9) with sodium benzoate in hexamethylphosphosphoric triamide afforded 2, 3-di-O-acetyl-1, 6-anhydro-4-O-(2, 3-di-O-acetyl-4, 6-di-O-benzoyl-α-D-galactopyranosyl)-β-D-glucopyranose (15) as an amorphous powder. Deacylation of 15 and sequential reacetylation gave crystalline hexaacetate (16). The former of the title compound (19), mp 227-229, [α]26D+159.6°, was obtained after acetolysis of 16 followed by deacetylation. Treatment of 9 with NaI in acetonitrile effected substitution of the mesyloxy at C6' to give the corresponding 6'-deoxy-6'-iodo-4'-O-mesyl derivative (11), from which 6'-deoxy compound (13) was prepared by catalytic hydrogenation. Benzoyloxy substitution with inversion at C4'-mesyloxy in 13 gave 2, 3-di-O-acetyl-1, 6-anhydro-4-O-(2, 3-di-O-acetyl-4-O-benzoyl-6-deoxy-α-D-galactopyranosyl)-β-D-glucopyranose (20), from which the latter of the title compound (24), hydroscopic, amorphous powder, [α]27D+128.3°, was obtained via the same pathway as for 19 from 15. Synthesis and characterization of the key intermediate (9) were described in full detail.
