ChemInform Abstract: Synthesis of 3‐ and 2′‐Fucosyl‐lactose and 3,2′‐Difucosyl‐lactose from Partially Benzylated Lactose Derivatives.

Abstract

Abstract O -β- d -Galactopyranosyl-(1→4)- O -[α- l -fucopyranosyl-(1→3)]- d -glucose has been synthesised by reaction of benzyl 2,6-di- O -benzyl-4- O -(2,3,4,6-tetra- O -benzyl-β- d -galactopyranosyl)-β- d -glucopyranoside with 2,3,4-tri- O -benzyl-α- l -fucopyranosyl bromide in the presence of mercuric bromide, followed by hydrogenolysis. Benzylation of benzyl 3′,4′- O -isopropylidene-β-lactoside, via tributylstannylation, in the presence of tetrabutylammonium bromide or N -methylimidazole, gave benzyl 2,6-di- O -benzyl-4- O -(6- O -benzyl-3,4- O -isopropylidene-β- d -galactopyranosyl)-β- d -glucopyranoside ( 6 ). α-Fucosylation of 6 in the presence of tetraethylammonium bromide provided either benzyl 2,6-di- O -benzyl-4- O -[6- O -benzyl-3,4- O -isopropylidene-2- O -(2,3,4-tri- O -benzyl-α- l -fucopyransoyl)-β- d - galactopyranosyl]-β- d -glucopyranoside ( 13 , 73%) or a mixture of 13 (42%) and benzyl 2,6-di- O -benzyl-4- O -[6- O -benzyl-3,4,- O -isopropylidene-2- O -(2,3,4-tri- O -benzyl-α- l -fucopyranosyl)-β- d - galactopyranosyl-3- O -(2,3,4-tri- O -benzyl-α- l -fucopyranosyl)-β- d -glucopyranoside ( 16 , 34%). α-Fucosylation of 13 in the presence of mercuric bromide and 2,6-di- tert -butyl-4-methylpyridine gave 16 (73%). Hydrogenolysis and acid hydrolysis of 13 and 16 afforded O -α- l -fucopyranosyl-(1→2)- O -β- d -galactopyranosyl-(1→4)- d -glucose and O -α- l -fucopyranosyl-(1→2)- O -β- d -galactopyranosyl-(1→4)- O -[α- l -fucopyranosyl-(1→3)]- d -glucose, respectively.