作者:A. Chatterjee、D. Banerjee、R. Mallik
DOI:10.1016/0040-4020(77)80437-7
日期:1977.1
the novel cyclopropane carboxylic acid 12. What is more significant is that although the formation of the trans-lactone on the whole is favoured in the ring opening of epoxides 4, at least in two cases, 4b and 4c, there is considerable formation of cis-lactones, a result that remains unexplained. Attempted synthesis of the model cis-lactone 3c always resulted in the formation of a 1:1 mixture of the
4型环氧化物会与碳离子一起开环;尽管位点的空间位阻增加,但亲核试剂无一例外地攻击C-1(如在具有环取代基的环氧化物4b和4e中)。在回流的叔丁醇中,环氧化物4b与甲基丙二酸二乙酯的阴离子相互作用,除其他产品外,还提供了新型环丙烷甲酸12。更为重要的是,尽管整体上反式内酯的形成有利于环氧化物4的开环,但至少在两种情况下4b和4c,形成了相当大的顺式内酯,这一结果尚无法解释。尝试合成模型顺式内酯3c总是导致顺式3c和反式内酯2a的1:1混合物的形成。从这些γ-内酯的3a-质子信号在其NMR光谱中的位置已明确确定了本文所述的顺-和反-内酯的立体化学。