C(7)-Substituted Diaminomitomycins: Synthesis, Structure, and Chemical Reactivity
作者:Shuang Wang、Harold Kohn
DOI:10.1021/jo970675t
日期:1997.8.1
Five mitomycins (23-27) were prepared to determine if an appended C(7) diamine substituent would promote C(1) nucleophilic substitution transformations by covalent modification of the C(8) quinone group. The appended C(7) diamine units varied in the basicity of the terminal amine and in the type and length of the carbon backbone. The mitomycins were prepared in high yield by treatment of mitomycin A (28) with selected diamines. Mitomycin 25, which contained a C(7) 3-amino-2,2-dimethylpropylamine unit, underwent rapid conversion to the corresponding albomitomycin-type adduct 34 in which the C(8) quinone group was converted to the corresponding C(8) imine. Dissolution of each mitomycin (23, 24, 26, 27, and 34) in methanol (''pH'' 5.5, 25 degrees C) led to the production of the cis- and trans-C(1) methoxymitosenes. The rates of salvolysis were monitored by HPLC and followed pseudo-first-order kinetics. Modest rate enhancements (5.1-15.2-fold), compared with mitomycin C(1), were observed for 7-N-(2-aminobenzyl)mitomycin C (23) and 7-N(2-anilinoethyl)mitomycin C(24), the two mitomycins containing terminal aniline groups. Solvolysis of 23 gave the C(1) methoxymitosenes 37 and 38, in which the C(8) site was converted to the cyclized C(8) imine; solvolysis of 24 gave C(1) methoxy products 39 and 40, in which the C(8) quinone unit was not modified. No appreciable rate enhancements over 1 were observed for 26 and 27, the two mitomycins containing terminal-substituted aliphatic amine groups. Albomitomycin 34 solvolyzed 6.9 times faster than 1. The observed rate data indicated that the aniline units in 23 and 24 promoted solvolysis by modifying the C(8) quinone group to give either the C(8) hemiaminal or the C(8) imine adduct, Formation of these adducts disrupted the delocalization of the indoline N(4) electrons with the C(5a)-C(8a)-C(8)-O conjugated system, permitting the sequential activation of the C(1) site toward nucleophilic substitution. The significance of these findings for the mode of action of KW-2149 and BMS-181174 is briefly discussed.