Remote stereochemical control of the ring conformation of 2-bromo-3-methyl-4-alkyl-butyrolactones
作者:Gilbert Dana、Estera Touboul、Mariam Mellot-Srour
DOI:10.1016/s0040-4020(01)88720-2
日期:1992.2
conformation. Inspection of the NMR spectra of , compared to , shows a evident flattening of the butyrolactone ring and an axial orientation of the side-chain, which is a new type of this remote effect, with the 3-methyl trans to the side-chain. These special features arise from the steric interaction which would occur in the regular conformation between the 3-methyl and the substituents at C5. During
内酯和内酯仅通过侧链的碳原子C5的构型而不同,但是在环构象中呈现出完全不同的特征。与相比,对NMR谱的检查表明,丁内酯环明显展平并且侧链的轴向取向(这是这种远程效应的一种新型形式),带有3-甲基反式到侧链。这些特殊特征是由空间相互作用产生的,该空间相互作用会在3-甲基和C5的取代基之间的规则构象中发生。在这些内酯的合成过程中,在向手性醛中添加手性烯丙基格氏试剂的过程中或在aa'中具有两个不对称中心的酮的氢化物还原过程中,观察到了惊人的立体化学行为。