4-O-beta-D-Galactopyranosyl-3-O-methyl-D-glucose: a new synthesis and application to the evaluation of intestinal lactase

Abstract

4-O-beta-D-Galactopyranosyl-3-O-methyl-D-glucose (1, 3-O-methyl-lactose) has been prepared from benzyl 2,6-di-O-benzyl-4-O-(2,6-di-O-benzyl-3, 4-O-isopropylidene-beta-D-galactopyranosyl)-beta-D-glucopyranoside (5) and from benzyl 2,6-di-O-benzyl-4-O-(2,3,4,6-tetra-O-benzyl-beta-D-galactopyranosyl)-bet a-D-glucopyranoside (15). Partial benzylation of benzyl 3',4'-O-isopropylidene-beta-lactoside (4) gave 5 and partial benzylation of either benzyl beta-lactoside (13) or benzyl hepta-O-acetyl-beta-lactoside (24) gave 15. All other products from the partial benzylation of 4, 13, and 24 were also isolated and characterised. The hydrolysis of 1 in vitro by intestinal lactase was linear during 20 h; the Vmax was 5% of that with lactose and the Km was 120mM (cf. 30mM for lactose). Oral administration of 1 to suckling rats led to urinary excretion of 3-O-methyl-D-glucose.