Synthesis of Protected N ‐Acetylchitooligosaccharide and Its Analogues: A Versatile Approach for the Synthesis of Complex Oligosaccharides of 2‐Amino‐2‐deoxy Sugar

A stepwise synthesis of oligosaccharide chains containing 2‐amino‐2‐deoxy‐ D ‐glucopyranose units was elaborated as a new versatile approach for preparation of biologically important oligosaccharides having 2‐amino‐ 2‐deoxysugars. Utilizing N ‐phthalic acyl group as the protective group of amine, and phenylthiolate as the leaving group at the reducing terminal, protected N ‐acetylchitooligosaccharide and its analogues, methyl (3‐ O ‐acetyl‐4,6‐ O ‐ benzylene‐2‐deoxy‐2‐phthalimido‐ β ‐ D ‐glucopyranosyl)‐(1→4)‐3‐ O ‐acetyl‐6‐ O ‐benzyl‐2‐deoxy‐2‐phthalimido‐ β ‐ D ‐glucopyranoside 4 , methyl (3‐ O ‐acetyl‐4,6‐ O ‐benzylene‐2‐deoxy‐2‐phthalimido‐ β ‐ D ‐gluco‐pyranosyl)‐(1→4)‐ (3‐ O ‐acetyl‐6‐ O ‐benzyl‐2‐deoxy‐2‐phthalimido‐ β ‐ D ‐glucopyranosyl)‐(1→4)‐3‐ O ‐acetyl‐6‐ O ‐benzyl‐2‐deoxy‐2‐phthalimido‐ β ‐ D ‐glucopyranoside 6 , methyl (3‐ O ‐acetyl‐4,6‐ O ‐benzylene‐2‐deoxy‐2‐phthalimido‐ β ‐ D ‐glucopyranosyl)‐(1→3)‐4,6‐ O ‐benzylene‐2‐deoxy‐2‐phthalimido‐ β ‐ D ‐glucopyranoside 8 , and methyl (3‐ O ‐acetyl‐4,6‐ O ‐benzylene‐2‐deoxy‐2‐phthalimido‐ β ‐ D ‐glucopyranosyl)‐(1→3)‐(4,6‐ O ‐benzylene‐2‐deoxy‐2‐phthalimido‐ β ‐ D ‐glucopyranosyl)‐(1→3)‐4,6‐ O ‐benzylene‐2‐deoxy‐2‐phthalimido‐ β ‐ D ‐glucopyranoside 10 , were designed and synthesized by amino glucose as the starting material, which were all characterized by 1 H NMR, 13 C NMR and HRMS.