Synthesis and in vitro antibacterial activity of a new series of monobactam derivatives

Using as a model monobactams with a substituted alpha-oxyimino moiety in the side chain (aztreonam), a series of 2-(2-aminothiazol-4-yl)-2-hydrazono-acetamido monobactam (II a, f) were prepared by condensation of the hydrazones (I a, e) (Z form) with tetrabutylammonium 3-amino-4-methyl-2-oxo-1-azetidin-sulphonate. Isomerization occurred during this synthesis and gave the E form of all compounds. Monobactams (II a, f) showed no significant in vitro antibacterial activity when compared with aztreonam and with some cephalosporins bearing the same E-hydrazono side chain.