The derivation of 1a-demethylmitomycin G from mitomycin C

Mitomycin G (2) was derived from porfiromycin (10b) in 3 steps via the methanesulfonate (14b) in an overall yield of 39%. On the basis of the established method for the introduction of an exomethylene group in mitomycins with a 9a-methoxy group, the preparation of biologically more important 1a-demethylmitomycin G (5) from mitomycin C (1) was accomplished by the use of a protective acetyl group on the aziridine in an overall yield of 57%. 1a-Demethylmitomycin K (6) was obtained from 5 in a yield of 42%. In a preliminary evaluation of their antitumor activity, compound 5 showed superior activity against sarcoma 180 (sc-ip) to its 1a-methyl congener, i.e., mitomycin G (2).