BENZOCARBAPENEMS FROM INDOLES

The 8,8a-dihydroazeto[l,2-a]indol-2(1H)-ones (benzocarbapenems) 1a, 16 , 17, 22, 27, 35 and 36 have been prepared by cyclodehydration of the corresponding beta-amino acids, these amino acids being obtained by re duction of the analogous 2-substituted or 2,7-disubstituted indoles. T he hydroxy group of compound 36 is designed to mimic the carboxylic ac id function of the carbapenems on the basis of molecular modelling. Th e azetidinones 1a and 27, which are unsubstituted at the methylene gro up of the four-membered ring, are unstable and highly susceptible to r ing opening by nucleophiles but the compounds 22, 35 and 36 with two m ethyl substituents at this position are much more stable. The carbonyl stretching frequency in the IR is close to 1770 cm(-1) for all the az etidinones except the phenol 36 for which the absorption is at 1735 cm (-1). An X-ray crystal structure of compound 36 is reported.