Unexpected stability of δ-lactones with axial substituents rather than equatorial ones. Conformational evaluation by molecular mechanics and molecular orbital calculations
作者:Yoshiki Morimoto、Haruhisa Shirahama
DOI:10.1016/s0040-4020(96)01138-6
日期:1997.2
trisubstituted δ-lactones 5a and 5b was subjected to thermodynamically equilibrated conditions to give predominantly 5b with axial substituents rather than 5a with all equatorial ones, in contrast to the Prelog-Djerassi lactone derivatives 3a and 3b. Further surprisingly, it has been found that the disubstituted lactone 15 also adopts a half-chair conformation with axial substituents. The conformational analyses
与Prelog-Djerassi内酯衍生物3a和3b相反,将三取代的δ-内酯5a和5b的1:1混合物置于热力学平衡的条件下,主要得到具有轴向取代基的5b而不是所有赤道取代基5a。进一步令人惊奇地发现,二取代的内酯15也采用带有轴向取代基的半椅构型。通过分子力学和分子轨道计算对这些化合物进行的构象分析强调了网状效应和静电相互作用,这是偏向于轴向构象异构体的原因。