Mechanistic aspects of the formation of anhydrovinblastine by Potier-Polonovski oxidative coupling of catharanthine and vindoline. Spectroscopic observation and chemical reactions of intermediates
作者:Richard J. Sundberg、Kumar G. Gadamasetti、Phyllis J. Hunt
DOI:10.1016/s0040-4020(01)88140-0
日期:——
by trifluoroacetic anhydride has been carried out under conditions which allow observation of intermediates and comparison of reactivity by low temperature NMR. These studies have confirmed or revealed the following facets of the mechanism of the reaction: (1) fragmentation of an intermediate derived from catharanthine-N-oxide which otherwise is stable at −40°C occurs rapidly on addition of vindoline;
三氟乙酸酐对金刚烷胺和长春新碱的断裂偶联反应是在允许观察中间体并通过低温NMR比较反应性的条件下进行的。这些研究已经证实或揭示了反应机理的以下几个方面:(1)加入长春花碱后,在-40°C时稳定的衍生自Catharanthine-N-氧化物的中间体发生断裂。(2)其他的碱,包括三- Ñ-丁胺,N,N-二甲基-3-甲氧基苯胺,N,N-二甲基-2-(2,4-二甲氧基苯基)乙胺和10-三氟乙酰基-长春花碱也促进了裂解; (3)偶合的立体选择性部分受长春花碱与脱水长春碱和16′-表-脱水长春碱的单独前体的不同反应速率控制;(4)N一个-methylcatharanthine-N b的方式类似于catharantine -N-氧化物-氧化物经受碎裂,但有不能在后者的情况下被检测到可观察到的中间体; (5)将N碎片的速率一个-methylcatharanthine-N b氧化物还受到碱的加速;(6)由最