Borch R F, Valente R R
Department of Chemistry, University of Rochester, New York 14642.
J Med Chem. 1991 Oct;34(10):3052-8. doi: 10.1021/jm00114a014.
A series of perhydrooxazine analogues of aldophosphamide has been prepared, and their 31P NMR kinetics and in vitro cytotoxicity have been evaluated. These compounds were developed on the basis of the idea that ring opening and tautomerization to an enamine intermediate might provide a mechanistic alternative to the beta-elimination reaction for release of phosphoramide mustard. The 4,4,6-trimethyltetrahydro-1,3-oxazine moiety was selected on the basis of its rapid rate of iminium ion generation and relatively slow rate of hydrolysis. These analogues underwent phosphorodiamidate release by three distinct mechanisms: hydrolysis to aldophosphamide and subsequent beta-elimination; cyclization to produce the 4-hydroxycyclophosphamides, which release phosphorodiamidate by ring opening and elimination; and tautomerization to the enamine with rapid expulsion of phosphorodiamidate. Kinetic studies demonstrated that hydrolysis to the aldehyde contributed minimally to the overall activation process and that the enamine pathway represented the major route of activation. For those analogues that could undergo cyclization, this pathway competed effectively with enamine release, and these analogues were essentially equivalent to their 4-hydroxycyclophosphamide counterparts in cytotoxicity. A series of tetra-N-substituted phosphorodiamidates that cannot undergo cyclization was prepared to explore the effects of cyclization on the cytotoxicity of these analogues. The tetrakis(chloroethyl)phosphorodiamidates were highly potent in vitro against both cyclophosphamide-sensitive and -resistant L1210 and P388 cell lines, and one of these analogues had significant antitumor activity against L1210 leukemia in vivo. These results demonstrate that the enamine mechanism provides a viable pathway for delivery of phosphorodiamidates and that this approach can be used to deliver phosphorodiamidates that are non-cross-resistant in cyclophosphamide-resistant cell lines.
已制备了一系列醛磷酰胺的全氢恶嗪类似物，并评估了它们的³¹P NMR动力学和体外细胞毒性。这些化合物是基于这样的想法开发的，即开环并互变异构为烯胺中间体可能为磷酰胺氮芥的释放提供一种替代β-消除反应的机制。4,4,6-三甲基四氢-1,3-恶嗪部分是根据其亚胺离子生成速率快和水解速率相对较慢而选择的。这些类似物通过三种不同机制释放磷二酰胺：水解为醛磷酰胺并随后进行β-消除；环化生成4-羟基环磷酰胺，通过开环和消除释放磷二酰胺；互变异构为烯胺并快速排出磷二酰胺。动力学研究表明，水解为醛对整体活化过程的贡献最小，烯胺途径是主要的活化途径。对于那些可以进行环化的类似物，该途径与烯胺释放有效竞争，并且这些类似物在细胞毒性方面与它们的4-羟基环磷酰胺对应物基本相当。制备了一系列不能进行环化的四-N-取代磷二酰胺，以探索环化对这些类似物细胞毒性的影响。四（氯乙基）磷二酰胺在体外对环磷酰胺敏感和耐药的L1210和P388细胞系都具有高效活性，其中一种类似物在体内对L1210白血病具有显著的抗肿瘤活性。这些结果表明，烯胺机制为磷二酰胺的递送提供了一条可行的途径，并且这种方法可用于递送在环磷酰胺耐药细胞系中无交叉耐药性的磷二酰胺。
