SYNTHESIS OF ALLOSAMIDIN

The previously prepared disaccharide 2 was deprotected (--> 3) and transformed into the trichloroacetimidate 4. In the presence of Me3SiOTf, 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 (MeNH2, MeOH) of 7 and 8, followed by acetylation, gave 12 (73%) and 13 (74%), respectively (Scheme 2); harsher conditions (NH2NH2. H2O, 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.