Facile and Effective Synthesis of Glucopyranosyl Oligosacchardes with Alternative (1 →3)‐α‐ and ‐β‐Linkages in the Presence of C‐2 Ester Capable of Neighboring Group Participation

Coupling of acetylated α‐(1 → 3)‐linked glucobiosyl trichloroacetimidate with acetylated α‐(1→3)‐linked glucobioside acceptor gave a β‐linked tetrasaccharide, while coupling of acetylated β‐(1→3)‐linked glucobiosyl trichloroacetimidate with acetylated β‐(1→3)‐linked glucobioside acceptor gave an α‐linked tetrasaccharide in spite of the C‐2 neighboring group participation. Two hexasaccharides with alternative (1→3)‐α‐and ‐β‐linkges were synthesized by these reactions via remote control exerted by the glycosylation bond in either donor or acceptor.