Abstract
Selective tosylation of 1, 6-anhydro-4', 6'-O-benzylidene-β-lactose (1), using 2.2 molar equivalents of tosyl chloride in pyridine at 0°, yielded four tosylates which were designated 2 to 5 in the order of decreasing Rf value on thin-layer chromatography. After column chromatography on silica gel, compounds 2-5 were separated as the 2, 3, 3'-tritosylate (2, 1.3%), 2, 3'-ditosylate (3, 21.9%), 3'-tosylate (4, 15%), and 2-tosylate (5, 25.2%), respectively. Selective tosylation of 3, using 8 molar equivalents of tosyl chloride afforded 2 (29%), 15, and 16, together with 3 (15%). Compounds 15 and 16 were identified as 2, 2', 3, 3'-tetratosylate (15, 38.9%) and 2, 2', 3'-tritosylate (16, 17.1%), respectively. Thus, the order of reactivities of the secondary hydroxyl groups in 1 is 2>3'>3>2'. Compounds 2-5 and 16 have potential value in the chemical modification of lactose or the syntheses of lactose-containing oligosaccharides in human milk.
