Synthesis and characterization of 6-O-beta-lactosyl-alpha,beta-lactoses, 1-O-(6-O-beta-lactosyl-beta-lactosyl)-(R,S)-glycerols, and 4,6-di-O-beta-D-galactopyranosyl-alpha,beta-D-glucoses.

1,2,3,2',3',4',6'-Hepta-O-acetyl-beta-lactose (4) was coupled with 2,3,6,2',3',4',6'-hepta-O-acetyl-alpha-lactosyl bromide (7) in the presence of Hg(CN)2 to afford 1,2,3,2',3',4',6'-hepta-O-acetyl-6-O-(2,3,6,2',3',4',6'-hepta-O-acetyl-b eta- lactosyl)-beta-lactose (11) which, upon O-deacetylation, gave 6-O-beta-lactosyl-alpha,beta-lactoses (64% from 4). In contrast, the reaction of 7 with benzyl 2,3,2',3',4',6'-hexa-O-acetyl-beta-lactoside in the presence of Hg(CN)2 produced 3,6,2',3',4',6'-hexa-O-acetyl-1,2-O- (2,3,2',3',4',6'-hexa-O-acetyl-1-O-benzyl-beta-lactos-6-yl orthoacetyl)-alpha-lactose (63%) and 3,6,2',3',4',6'-hexa-O-acetyl-1,2-O-(1- cyanoethylidene)-alpha-lactose (27%). The glycosidation of 4 using 2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl bromide in the presence of Hg(CN)2 afforded, after deprotection, 4,6-di-O-beta-D-galactopyranosyl-alpha,beta-D-glucoses (66%). The reaction of 11 with 1,2-di-O-benzyl-(R,S)-glycerols and trimethylsilyl trifluoromethanesulfonate yielded, after deprotection, 1-O-(6-O-beta-lactosyl-beta-lactosyl)-(R,S)-glycerols (18%). Under the same coupling conditions 11 reacted with 2-O-benzylglycerol to form 3-O-acetyl-2-O-benzyl-1-O-[2',3',4',6'-hexa-O-acetyl-6-O-(2,3,6,2',3',4' ,6'- hepta-O-acetyl-beta-lactosyl)-beta-lactosyl]-(R,S)-glycerols (16%).