Efficient Assembly of an Indole Alkaloid Skeleton by Cyclopropanation:Concise Total Synthesis of(±)-Minfiensine

摘要

Members of the akuammiline alkaloids such as echit-amine,vincorine,and corymine,like indole alkaloid minfiensine,possess a highly congested pentacyclic ring system(Figure 1).These alkaloids exhibit a number of impressive biological activities,including significant anticancer activity.Although the first member of akuammiline alkaloids(echitamine)was characterized more than eighty years ago,only a few successful methods to synthesize the challenging tetracyclic subring system of 9a,4a-iminoethano-carbazole 1 are described because of the synthetic difficulties.