PREPARATION OF AZA-ANALOGS OF APLYSINOPSINS AND ZWITTERIONIC BY REACTIONS OF HETEROCUMULENES IN NAPHTHYRIDINES SERIES

Imidazo[1,2-a][1,8]naphthyridines (9a,b) having the carbodiimide moiet y on the position 1 lead to (Z)-aza-aplysinopsins (10a,b) by solid sup ported reaction on neutral alumina. By flash chromatography these hete rocumulenes are stereospecifically converted to the corresponding meth oxyimidazol-4-ones (11a,b) in good yields. In contrast, tandem aza-Wit tig-cyclization reaction of imidazo[1,2-a][1,8]naphthyridine (13) havi ng iminophosphorane moiety on the position 2 gives zwitterionic compou nds (14a,b 15) by N-annulation under thermal conditions.