Progress in Synthesis of 3,4-Fused Indole Alkaloids

The indole nucleus is one of the most important heterocycles for its presence in a vast number of bioactive natural products, pharmaceuticals, and agrochemicals. Due to their widest spectrum of biological activity and some of them have been used in clinical trials, construction and functionalization of indoles have attracted considerable interests from synthetic and medicinal chemists for over a hundred years. Among the naturally occurring indole alkaloids, those containing 3,4-fused indole skeleton possess a major part and have been especially considered attractive synthetic targets because of their unique structure and biological activities. This review emphasized on the methodologies and strategies of construction of 3,4-fused indole skeleton, and their application in total synthesis of natural products.