Synthesis of Allosamidin

The previously prepared disaccharide 2 was deprotected (→ 3 ) and transformed into the trichloroacetimidate 4 . In the presence of Me 3 SiOTf, 4 reacted regioselectively with the racemic allosamizoline benzyl ether 5 , to yield (61%) the pseudotrisaccharides 7–10 (44:40:9:7) and the elimination product 6 ( Scheme 1 ). Selective dephthaloylation (MeNH 2 , MeOH) of 7 and 8 , followed by acetylation, gave 12 (73%) and 13 (74%), respectively ( Scheme 2 ); harsher conditions (NH 2 NH 2 .H 2 O, EtOH, reflux), followed by acetylation, transformed 7 into 11 . Deacetylation of 11–13 yielded 14–16 , respectively. Allosamidin ( 1 ) was obtained in high yield by hydrogenation of 15 under acidic conditions ( Scheme 3 ). Similarly, 16 and 14 were transformed into 17 and 18 , respectively. Preliminary data on the inhibition of endochitinases by 1 and 17 are reported.