ASYMMETRIC SYNTHESIS--STRUCTURE, STEREOCHEMISTRY AND NMR

在开发制备手性醇的方法和 其绝对立体化学的暂定分配（基于其 制备方法），我们继续研究了对映选择性 酯的水解。 这些水解是由酶催化的， 霉菌黑根霉，并且形成的醇的构型可以是 从考虑取代基上的有效大小预测 甲醇碳 这些研究扩展到一系列共轭 烯丙基醇，其中发现一种手性醇已经形成， 一个意想不到的配置。 这个绝对的立体化学 通过X射线晶体结构严格确定了化合物 保持战略定力 为了确定其他的醇类， 我们进行了一系列的研究， 对应的DC曲线的符号之间的关系 对溴苯甲酸酯和这些分子的绝对立体化学。 这些研究表明，直流测量可用于独立的 配置的分配。 化合物，其中这些分配和 基于微生物方法的那些不同需要进一步研究。 在合成一系列中环2-溴-2-环烯基乙酸酯的同时， 改进了银催化溶剂分解反应的反应条件 与文献中描述的不同。 我们的改造改变了 由先前形成的化合物的双键的几何形状 报道 现在可以制备顺式或 反式-2-溴环烯烃的制备方法 反应条件 这些环烯烃被用来表明，三键 质子-碳耦合常数，使用最近开发的2D 核磁共振技术可以用来分配几何相似 三取代的双键。 这些任务以前非常 很难制作。

In developing methodologies to prepare chiral alcohols and to make tentative assignments of their absolute stereochemistry (based on their method of preparation) we have continued to examine the enantioselective hydrolysis of esters. These hydrolyses are catalyzed by enzymes in the mold Rhizopus nigricans, and the configuration of the alcohol formed can be predicted from considerations of the effective sizes of substituents on the carbinol carbon. These studies were extended to a series of conjugated allylic alcohols where it was found that one chiral alcohol had formed with an unanticipated configuration. The absolute stereochemistry of this compound was rigorously established by an x-ray crystallographic structure determination. In order to identify other alcohols that form with unexptected configurations, we undertook a series of studies of the relation between the sign of the DC curves of the corresponding p-bromobenzoates and the absolute stereochemistry of these molecules. These studies demonstrated that DC measurements can be used for independent assignments of configuration. Compounds in which these assignments and those based on the microbial method differ require further study. While preparing a series of medium-ring 2-bromo-2-cycloalkenyl acetates, we modified the reaction conditions of a silver catalyzed solvolysis reaction from that described in the literature. Our modification altered the geometry about the double bond of the compound formed from that previously reported. It is now possible to prepare either cis- or trans-2-bromocycloalkenes from the same starting material by adjusting the reaction conditions. These cycloalkenes were used to show that three-bond proton-carbon coupling constants, obtained using a recently developed 2D NMR technique could be used to assign the gometry about similarly tri-substituted double bonds. These assignments previously have been very difficult to make.