Biogenetically patterned transformation of eudesmanolide to eremophilanolide. I. Angular methyl migration of 5.ALPHA.,6.ALPHA.-epoxy-dihydroalantolactone.
作者:ISAO KITAGAWA、YASUSHI YAMAZOE、HIROTAKA SHIBUYA、REIJI TAKEDA、HIDEKAZU TAKENO、ITIRO YOSHIOKA
DOI:10.1248/cpb.22.2662
日期:——
As a continuation of our study on the biogenetically patterned transformation leading to the natural terpenoids, conversion of an eudesmanolide directing to the related eremophilanolide was investigated and the object was accomplished. After several attempts, treatment of 5α, 6α-epoxy-dihydroalantolactone (15) with HCOOH-acetone (1 : 2) at reflux was found to afford eight products (A-H). Among them, two major products (products A and B) and one minor product (product D), which were obtained in a combined yield of 46%, were elucidated to be the desired eremophilanolides (17, 18, and 23) on the basis of the physicochemical evidence and the chemical conversion of 23 to tetrahydroligularenolide (34). The structure of the product C was assigned 20 on the basis of its physical properties and the chemical derivation. Afterwards, a better reaction condition transforming 15 to give 17 and 18 in a combined 68% yield was found.
作为我们对天然萜类化合物生物基因型转化研究的延续,我们研究了从桉叶内酯向相关的埃瑞莫菲兰内酯的转化,并实现了这一目标。经过多次尝试,发现 5α,6α-环氧二氢金刚烷内酯(15)与 HCOOH-丙酮(1:2)在回流条件下处理可得到八种产物(A-H)。其中,两个主要产物(产物 A 和 B)和一个次要产物(产物 D)的总收率为 46%,根据理化证据和 23 转化为四氢愈创木酚内酯(34)的化学反应,这些产物被确定为所需的愈创木酚内酯(17、18 和 23)。根据产物 C 的物理性质和化学推导,确定了其结构为 20。之后,又找到了一种更好的反应条件,将 15 转化为 17 和 18,总产率为 68%。