Stereoselectivity in the Mechanism of Acid Hydrolysis of Mitomycins

The stereoselectivity in the acid hydrolysis mechanism of mitomycins was studied. The predominance of the 1, 2-cis-mitosene degradation products occurring at low pH was ascribed to the directing force exterted on the incoming nucleophile by the protonated 2-amino function of an intermediate in the process as well as to steric hindrance due to the orientation of the C9 urethane substituent in one of the degradation steps preceding the formation of the intermediate. The differences in electron density in the intermediate chromophore and the resulting differences in pKa value of the amino function involved are discussed.