EFFICIENT SYNTHESIS OF LACTONEO SERIES ANTIGENS-H, LEWIS-X (LE(X)), AND LEWIS-Y (LE(Y))

Regioselective 6a,6b-di-O-benzoylation of azidolactose 4 furnished der ivative 6 which permitted ensuing regioselective 2b-O-fucosylation, 2b ,3a-di-O-fucosylation, or regioselective 2b-O-benzoylation and then 3a -O-fucosylation, respectively, thus providing directly H, Le(y), and L e(x) antigen building blocks 8a-c. The derived trichloroacetimidates 9 a-c offered regio- and beta-selective glycosylations of partially O-pr otected accepters 5 and 13, affording spacer-linked H, Le(x), Le(y), d imer Le(x) and Le(y) intermediates 12a-c and 14b,c, respectively, whic h could be readily transformed into target molecules 1a-c and 2b,c. Th us, a most straightforward and efficient synthesis of this antigen ser ies is exhibited.