開催日: 2017/09/20 - 2017/09/22
The genus Kopsia, belonging to the family Apocynaceae, is an abundant source of monoterpenoid indole alkaloids possessing structural diversity and significant biological activities. In our chemical studies on novel bioactive alkaloids, we have found several unique monoterpenoid indole alkaloids, such as kopsiyunnanines A-M and andranginine from Kopsia arborea native to Yunnan Province in China. Kopsiyunnanine K (1) has an unprecedented azepane-fused tetrahydro-β- carboline ring skeleton and the structure was confirmed by total synthesis utilizing Ireland-Claisen rearrangement and diastereoselective Pictet-Spengler cyclization as a key step. Kopsiyunnanine L (2) has a novel 2,3,4,5-tetrahydro-1H-benzazepin skeleton rearranged from a Strychnos-type monoterpenoid indole alkaloid. Kopsiyunnanine M (3) is a new type of bisindole alkaloid consisting of Aspidospermatan-type and Strychnos-type alkaloids. Andranginine (4) was first isolated as a racemate from Craspidospermun verticillatum. The first asymmetric total synthesis of 4 utilizing asymmetric Morita-Baylis-Hillman reaction and diastereoselective intramolecular Diels-Alder reaction has revealed that 4 isolated from K. arborea existed as a scalemic mixture.