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.
研究了丝
裂霉素酸
水解机理中的立体选择性。在低 pH 值条件下,1,2-顺式丝
裂霉素降解产物占主导地位,这是因为在降解过程中,中间体质子化的 2-
氨基功能对进入的亲核体产生了导向力,以及在中间体形成之前的一个降解步骤中,C9
脲基取代基的取向产生了立体阻碍。本文讨论了中间体发色团电子密度的差异以及由此导致的相关
氨基功能 pKa 值的差异。