Boger D L, Johnson D S, Palanki M S, Kitos P A, Chang J, Dowell P
Department of Chemistry, Scripps Research Institute, La Jolla, CA 92037.
Bioorg Med Chem. 1993 Jul;1(1):27-38. doi: 10.1016/s0968-0896(00)82100-8.
The DNA alkylation properties and in vitro cytotoxic activity of a series of analogs of CC-1065 and the duocarmycins incorporating the 9a-chloromethyl-1,2,9,9a-tetrahydrocyclopropa[c]benz[e]indol-4-one (C2BI) alkylation subunit are detailed. The C2BI-based agents have been shown to alkylate DNA within the minor groove in a fashion analogous to CC-1065 or duocarmycin. The stereoelectronically-controlled adenine N3 addition to the least substituted cyclopropane carbon occurs with a selectivity that represents a composite of the two enantiomers of the corresponding CBI-based agents. Additional high affinity alkylation sites were detected which were not prominent alkylation sites for either enantiomer of the CBI-based agents. Such sites may represent induced high affinity alkylation sites resulting from DNA cross-linking following complementary strand alkylation at a high affinity alkylation site and each such site detected proved consistent with predicted models of an adenine-adenine cross-linking event. Further, consistent with this interpretation, the C2BI agents were shown to constitute efficient cross-linking agents with DNA cross-linking being observed at the same concentrations as DNA alkylation. In comparison to the parent CBI-based agents, the C2BI-based agents proved to be approximately 100-10,000x less effective at DNA alkylation and 100-10,000x less potent in cytotoxic assays. This is suggested to be the consequence of a significant steric deceleration of the adenine N3 alkylation reaction attributable to the additional 9a-chloromethyl substituent. Consistent with this interpretation, the noncovalent binding constant of C2BI-CDPI2 for poly[dA]-poly[dA]-poly[dT] proved nearly identical to that of CDPI3 under kinetic binding conditions, and prolonged incubation of C2BI-CDPI2 with poly[dA]-poly[dT] (72 h, 25 degrees C) provided covalent complexes with a helix stabilization comparable to that observed with (+)- or (-)-CPI-CDPI2 indicating that the size of the C2BI subunit inhibits but does not preclude productive DNA alkylation.
详细介绍了一系列CC - 1065类似物以及包含9a - 氯甲基 - 1,2,9,9a - 四氢环丙[c]苯并[e]吲哚 - 4 - 酮（C2BI）烷基化亚基的双环霉素的DNA烷基化特性和体外细胞毒性活性。已证明基于C2BI的试剂以类似于CC - 1065或双环霉素的方式在小沟内使DNA烷基化。立体电子控制的腺嘌呤N3加成到取代最少的环丙烷碳上，其选择性代表了相应基于CBI的试剂的两种对映体的组合。检测到了额外的高亲和力烷基化位点，这些位点对于基于CBI的试剂的任何一种对映体都不是突出的烷基化位点。这些位点可能代表在高亲和力烷基化位点进行互补链烷基化后，由于DNA交联而诱导产生的高亲和力烷基化位点，并且检测到的每个此类位点都与腺嘌呤 - 腺嘌呤交联事件的预测模型一致。此外，与此解释一致的是，基于C2BI的试剂被证明是有效的交联剂，在与DNA烷基化相同的浓度下观察到DNA交联。与母体基于CBI的试剂相比，基于C2BI的试剂在DNA烷基化方面的效率约低100 - 10000倍，在细胞毒性测定中的效力也低100 - 10000倍。这被认为是由于额外的9a - 氯甲基取代基导致腺嘌呤N3烷基化反应显著的空间位阻减速的结果。与此解释一致的是，在动力学结合条件下，C2BI - CDPI2与聚[dA] - 聚[dA] - 聚[dT]的非共价结合常数被证明与CDPI3几乎相同，并且将C2BI - CDPI2与聚[dA] - 聚[dT]长时间孵育（72小时，25℃）提供了与（+） - 或（ - ） - CPI - CDPI2观察到的螺旋稳定性相当的共价复合物，表明C2BI亚基的大小抑制但不排除有效的DNA烷基化。
