Synthesis and characterization of 2-O-beta-lactosylglycerol, 1,2-di-O-beta-lactosyl-(R,S)-glycerols, and 1,2,3,-tri-O-beta-lactosylglycerol.

The reaction of 2,3,6,2',3',4',6'-hepta-O-acetyl-alpha-lactosyl bromide (5) and 1,3-di-O-benzylglycerol in the presence of mercury(II) cyanide in benzene-nitromethane afforded 1,3-di-O-benzyl-2-O-(2,3,6,2',3',4',6'-hepta-O-acetyl-beta-lactosyl)glyc erol (70%), which was converted into 2-O-beta-lactosylglycerol. 1,2-Di-O-beta-lactosyl-(R,S)-glycerols were obtained by way of the coupling of 5 to either 1-O-benzyl-(R,S)-glycerol or 1-O-benzyl-2-O-(2,3,6,2',3',4',6'-hepta-O-acetyl-beta-lactosyl)-(R,S)-gl ycerols. The most efficient route to 1,2, 3-tri-O-beta-lactosylglycerol (17) involved treatment of 2-O-(2,3,6,2',3',4',6'-hepta-O-acetyl-beta-lactosyl)glycerol with 3 mol. equiv. of 5 followed by removal of the blocking groups, to give 17 (47%).