构型转换法制备赤式紫胶桐酸及反应机理分析

Preparation of Erythro Aleuritic Acid by Configuration Transformation and Analysis of Reaction Mechanism

摘要:

探索了苏式紫胶桐酸制备赤式紫胶桐酸的方法及其反应机理。以苏式紫胶桐酸为原料通过构型转换法制备赤式紫胶桐酸，采用FTIR、质谱、核磁（1H /13C-NMR）、TG、DSC、XRD、手性拆分、旋光性等表征手段对所得产物进行了分析确证。在此基础上，对紫胶桐酸苏式到赤式构型的转换机理进行了初步探究。结果表明：FTIR、质谱、核磁显示产物与苏式紫胶桐酸结构一致；XRD、DSC、TG结果表明苏式与产物具有相同晶型，但产物熔点更高，晶胞尺寸更小；手性拆分结果显示产物为紫胶桐酸的光学异构体，从而确定产物为赤式紫胶桐酸。对中间产物的结构表征表明，紫胶桐酸苏式到赤式构型转换的机理为卤素和羟基之间SN2和E2同时发生的反应，羟基和卤素间的两次SN2反应，是发生构型转换反应（瓦尔登转换）的关键；羟基/卤素的E2反应是苏式紫胶桐酸能够彻底转化为赤式的原因。

Abstract:

This paper aims to explore the preparation method and reaction mechanism of erythro aleuritic acid from thero configuration. Erythro aleuritic acid was prepared by configuration transformation method from thero aleuritic acid. And FTIR, mass spectrometry, nuclear magnetic resonance (1H/13C NMR), TG, DSC, XRD, chiral resolution and optical rotation were used to analyze and confirm the structure of reaction products. On these foundations, the transformation mechanism of thero aleuritic acid to erythro aleuritic acid was primary explored. The results showed that the structure of the product was consistent with thero aleuritic acid by FTIR, mass spectrometry. The results including NMR. XRD, DSC and TG show that the thero aleuritic acid and the product have the same crystal type, but the melting point of the product is higher and the crystal cell structure is smaller than thero configuration. The chiral resolution results showed that the product was an optical isomer of aleuritic acid, which was determined to be erythro aleuritic acid. Based on the structural characterization of the intermediates, the mechanism of the transformation from thero aleuritic acid to erythro aleuritic acid is the simultaneous reaction of SN2 and E2 between the halogens and the hydroxides. The twice SN2 reactions are the key to the configuration transformation reaction (Walden transformation). The E2 reaction of hydroxyl/halogen is the reason why thero aleuritic acid can be completely transformed into erythro aleuritic acid.