ASYMMETRIC SYNTHESIS--STRUCTURE, STEREOCHEMISTRY AND NMR

在开发制备手性醇和制备手性醇的方法方面 它们的绝对立体化学的初步归属(基于它们的 制备方法)，我们继续考察对映体选择性。 酯的水解性。这些水解物由体内的酶催化 霉菌黑色根霉，所形成的醇的构型可以 从考虑取代基的有效大小预测的 甲醇碳。而关于绝对立体化学的数据更多 快速水解酯的对映体符合规律，a 进行了定量分析，以确定相对分子质量 电子、空间位阻和极化率因素对 与酶-底物复合体的形成和相对速率有关 对映体的水解性。关于光学纯度的数据 用生成的醇类和水解度来计算 “E”值，描述两者的相对水解率 醋酸酯对映体。这些数据显示了立体的相对重要性， 电子和极化率因素，并证明了它是可能的 预测使用标准值形成的酒精的光学纯度 取代基的大小、电负性和极化率。至 补充手性烯丙基的制备方法学 酒精，我们进行了一项初步研究，以证明 缩酮克莱森重排(烯丙基乙烯基醚的重排 醇)，一种以前没有得到太多关注的反应，可以 用于合成几种倍半萜，铜烯，月桂烯， 巴扎烯和三环二烯。这些天然产品中的每一个都含有 季碳原子。我们建议使用已建立的手性 一种用来控制四元化合物绝对立体化学的烯丙醇 在重排过程中形成碳原子。

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. While data on the absolute stereochemistry of the more rapidly hydrolyzed enantiomer of the ester were consistent with the rule, a quantitative analysis was carried out to determine the relative contributions that electronic, steric and polarizability factors make both to the formation of the enzyme-substrate complex and to the relative rates of hydrolysis of the enantiomers. Data on the optical purities of the alcohols formed and the percent hydrolysis were employed to calculate an "E" value which describes the relative rates of hydrolysis of the two acetate enantiomers. The data show the relative importance of steric, electronic and polarizability factors and demonstrate that it is possible to predict the optical purity of an alcohol formed using standard values of the size, electronegativity and polarizability of substituents. To complement the methodology developed for the preparation of chiral allylic alcohols described, we carried out a preliminary study to demonstrate that the ketal Claisen rearrangement (a rearrangement of vinyl ethers of allylic alcohols), a reaction that had not previously received much attention, can be used for the synthesis of several sesquiterpenes, cuparene, laurene, bazzanene and trichodiene. Each of these natural products contain a quaternary carbon atom. We propose to employ the established chirality of an allylic alcohol to control the absolute stereochemistry of a quaternary carbon atom formed in the rearrangement.