Synthetic Approaches to Dimeric and Oligomeric Hexahydropyrrolo[2,3-b]indole Alkaloids

Natural product synthesis has been the prime focus for the development of new chemical transformations and the drug discovery. The dimeric and oligomeric hexahydropyrrolo[2,3-b]indole alkaloids represent a architecturally intriguing class of cyclotryptamine alkaloids. These alkaloids share contiguous stereogenic centers with vicinal all-carbon quaternary stereogenic centers. Members of this class of alkaloids are reported to show interesting biological activities. Therefore, there are tremendous synthetic interests not only because of their striking architecture but also due to their important biological activities. In this feature article we have discussed the detailed biogenetic hypothesis of these alkaloids and various elegant strategies from different groups, including our contributions in this area. Special emphasis is given for the synthetic approaches to dimeric, trimeric and tetrameric hexahydropyrrolo[2,3-b]indole alkaloids.