Convenient syntheses of 5-O- 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 degrees, gave the 2,6-dibenzoate (2, 62%). Tin(IV) chloride-catalyzed glycosylation of 2 with 1,2,3,5,6-penta-O-benzoyl-alpha,beta-D-galactofuranose (1) afforded 2,6-di-O-benzoyl-5-O-(2,3,5,6-tetra-O-benzoyl-beta-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 beta-D-Galf-(1----5)-D-Gal-ol (8). Reduction of the lactone function of 5 with di-isoamylborane followed by debenzoylation gave beta-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-beta-D-galactofuranos yl)-D- galactono-1,4-lactone (9), which was converted, as for 5, into beta-D-Galf-(1----3)[beta-D-Galf-(1----5)]-D-Galf (13).