Stereochemical and Biochemical Mechanisms in Lignan Biosynthesis

在本研究开始之前，已有多篇关于连翘属植物中木脂素生物合成的论文发表，并对其立体化学机制进行了概述。另一方面，很少有人知道在其他植物中的木酚素的生物合成，特别是那些产生的木酚素是相反的对映体的连翘植物中发生的。本研究旨在阐明各种植物中木脂素生物合成的立体化学机制。首先，进行文献综述，总结迄今为止从各种植物中分离的各种木脂素的旋光度标志。在此基础上，本文选取牛蒡（Arctium lappa）、新疆蜡菊（Wikstroemia sikokiana）和叶下珠（Phyllanthus sp.）三种植物作为研究木脂素生物合成的立体化学机制的植物材料。其次，从这些植物中分离得到了多种木脂素类化合物，手性HPLC分析表明，它们中的许多是对映异构体。 ...更多信息 对映体与连翘属（Forsythia spp.）例如，（+）-开环异落叶松树脂酚（78% e.e.）其为连翘属（Forsythia spp.）的（-）-对映体的对映体。第三，发现来自牛蒡的酶制剂催化（+）-开环异落叶松树脂酚（20% e.e.）由非手性松柏醇制得。这是对映选择性地产生（+）-开环异落叶松树脂酚的酶促反应的第一个实例。根据酶促反应和氘标记化合物的补料实验结果，建立了木脂素的生物合成途径，对结果的分析表明，不同植物中形成的对映体不同，产生光学纯木脂素的代谢步骤可能不同。综上所述，本研究揭示了连翘、牛蒡和王香属植物中木脂素生物合成的立体化学机制存在很大的差异。少

Before the present investigation was started, several papers had been published on lignan biosynthesis in Forsythia plants, and outline of its stereochemical mechanisms was elucidated. On the other hand, little was known about lignan biosynthesis in other plants, especially those producing the lignans which are the opposite enantiomers to those occurring in Forsythia plants. The present investigation has dealt with elucidation of stereochemical mechanisms for lignan biosynthesis in various plants.First, literature survey was carried out to summarize sign of optical rotation of various lignans which were isolated so far from various plants. Based on the analysis of the data three plants were selected for plant materials to investigate stereochemical mechanisms in lignan biosynthesis in the present investigation : Arctium lappa, Wikstroemia sikokiana, and Phyllanthus sp. Second, various lignans were isolated from the plants, and chiral HPLC analysis showed that many of them are the oppos … More ite enantiomers to those occurring in Forsythia spp. For instance, (+) -secoisolariciresinol (78% e.e.) which is the opposite enantiomer to the (-) -antipode from Forsythia spp.was isolated from Arctium lappa. Third, an enzyme preparation from Arctium lappa was found to catalyze enantioselective formation of (+) -secoisolariciresinol (20% e.e.) from achiral coniferyl alcohol. This is the first example of an enzymatic reaction to produce (+) -secoisolariciresinol enantioselectively. Based on the results of the enzymatic reaction and feeding experiments with deuterium-labelled compounds biosynthetic pathways of the lignans were established.Analysis of the results indicated that different enantiomers are formed in different plants and that metabolic steps to produce the optically pure lignans are probably different in the plants. In conclusion, the present investigation revealed that there is a great diversity in stereochemical mechanisms for lignan biosynthesis in Forsythia, Arctium and Wikstroemia plants. Less