Regioselective Synthesis of Novel Mono-Substituted D-lactose Fatty Acid Ester Derivatives

Three regioisomers of lactose fatty acid monoesters at positions 3', 6' and 3 and other related compounds have been chemically synthesized. The 3'- and 6'-O-palmitoyl-D-lactose derivatives were prepared via the regioselective esterification at O-3' and O-6' of the dibutylstannylene derivatives obtained from benzyl 2,3,6-tri-O-benzyl-4-O-(2,6-di-Obenzyl-β-D-galactopyranosyl)-β-D-glucopyranoside (1) and benzyl 2,3,6-tri-O-benzyl-4-O-(2,3-di-O-benzyl-β-Dgalactopyranosyl)-β-D-glucopyranoside (5), respectively, with the acid chloride, followed by hydrogenolysis of the benzyl groups. The 3-O-acyl-D-lactose derivatives were prepared via the regioselective esterification at O-3 of benzyl 2,6-di-Obenzyl- 4-O-(2,6-di-O-benzyl-3,4-O-isopropylidene-β-D-galactopyranosyl)-β-D-glucopyranoside (9) using DCC coupling method with the free acids, followed by selective removal of the 3',4'-O-isopropylidene group, and then hydrogenolysis of the benzyl groups.