Mitomycin Betaines: Synthesis, Structure, and Solvolytic Reactivity

摘要

7-N-[2-(Methylamino)ethyl]mitomycin C (2b) and 7-N-[2-(ethylamino)ethyl]mitomycin C (2c) underwent rapid C(8) cyclization and oxidation to generate the novel quinoxaline mitomycin betaines 5a,b, respectively. Correspondingly, treatment of mitomycin A with N-methyl-1,2-phenylenediamine gave phenazine mitomycin betaine 17. Similar spectral properties were observed for the three heteroaromatic zwitterionic compounds 5a,b, and 17. We have learned that the formation of 5a,b proceeds by initial cyclization of the terminal amine group to the mitomycin C(8) quinone carbon to generate the corresponding hemiaminal intermediate. Dissolution of 5a,b in buffered methanolic solutions ("pH" 5.5, 7.4) at 25℃ did not lead to aziridine ring opening. The reactivity of 5a,b is briefly discussed in terms of their electronic structures.