CONVENIENT SYNTHESES OF 5-O-(BETA-D-GALACTOFURANOSYL-D-GALACTOFURANOSE AND 3,5-DI-O-(BETA-D-GALACTOFURANOSYL)-D-GALACTOFURANOSE

Benzoylation of d-galactono-1,4-lactone with 2.2 mol of benzoyl chloride, at -23°, gave the 2,6-dibenzoate (2, 62%). Tin(IV) chloride-catalyzed glycosylation of 2 with 1,2,3,5,6-penta-O-benzoyl-α,β-d-galactofuranose (1) afforded 2,6-di-O-benzoyl-5-O-(2,3,5,6-tetra-O-benzoyl-β-d-galactofuranosyl)-d-galactono-1,4-lactone (4, 70%), HO-3 of which was benzoylated to give 5. The structure of 4 was confirmed by its conversion into crystalline β-d-Galf-(1→5)-d-Gal-ol (8). Reduction of the lactone function of 5 with di-isoamylborane followed by debenzoylation gave β-d-Galf-(1→5)-d-Galf (7). A by-product of the condensation of 1 with 2 was characterized as 2,6-di-O-benzoyl-3,5-di-O-(2,3,5,6-tetra-O-benzoyl-β-d-galactofuranosyl)-d-galactono-1,4-lactone (9), which was converted, as for 5, into β-d-Galf-(1→3)[β-d-Galf-(1→5)]-d-Galf (13). © 1990.