Transformations of the 2,7-<i>Seco Aspidosperma</i> Alkaloid Leuconolam, Structure Revision of <i>epi</i>-Leuconolam, and Partial Syntheses of Leuconoxine and Leuconodines A and F

Several transformations of the seco Aspidosperma alkaloid leuconolam were carried out. The based-induced reaction resulted in cyclization to yield two epimers, the major product corresponding to the optical antipode of a (+)-meloscine derivative. The structures and relative configuration of the products were confirmed by X-ray diffraction analysis. Reaction of leuconolam and epi-leuconolam with various acids, molecular bromine, and hydrogen gave results that indicated that the structure of the alkaloid, previously assigned as epi-leuconolam, was incorrect. This was confirmed by an X-ray diffraction analysis, which revealed that epi-leuconolam is in fact 6,7-dehydroleuconoxine. Short partial syntheses of the diazaspiro indole alkaloid leuconoxine and the new leuconoxine-type alkaloids leuconodines A and F were carried out.本研究针对裂环白坚木类生物碱（seco Aspidosperma alkaloid）白坚木碱（leuconolam）开展了数种转化反应。碱诱导反应可引发环化，生成两种差向异构体（epimer），其中主要产物为(+)-meloscine衍生物的光学对映体。产物的结构与相对构型经X射线衍射分析（X-ray diffraction analysis）得以确证。白坚木碱与表白坚木碱（epi-leuconolam）分别与多种酸、单质溴及氢气发生反应的实验结果显示，此前被指定为表白坚木碱的该生物碱的结构实为错误。该结论经X射线衍射分析验证后得到确认：表白坚木碱实际为6,7-脱氢白坚木辛碱（6,7-dehydroleuconoxine）。本研究还完成了二氮杂螺环吲哚类生物碱（diazaspiro indole alkaloid）白坚木辛碱（leuconoxine），以及新型白坚木辛碱类生物碱白坚木定A与F（leuconodines A and F）的简短半合成。