Synthetic Approach to C-3a Prenylated Hexahydropyrrolo[2,3-b]indole Alkaloids via an Interrupted Fischer Indolization

Goyal, Geeta (2021) Synthetic Approach to C-3a Prenylated Hexahydropyrrolo[2,3-b]indole Alkaloids via an Interrupted Fischer Indolization. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS Dissertation of Geeta Goyal (16MS185),) 16MS185_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (1MB)

Abstract

The natural C-3α prenyl substituted hexahydropyrrolo[2,3b]indole alkaloid with a 3,3 dimethylallyl group adjacent to pseudobenzylic 3a-site, like (-)debromoflustramine E (1a) and related alkaloids, have gained considerable attention due to its interesting structure and potential biological activities. In fact, there are many naturally occurring alkaloids with varying degrees of oxidation pattern, such as (−)- pseudophrynaminol (1b), (−)-pseudophranamine 272A (1c), (−)-pseudophrynamine 270 (1d), and (−)- selaginelic acid (1e). All of them are closely related to the naturally occurring C-3α methylated HPI alkaloid, for example (−)- physostigmine (2a) is a known acetylcholine esterase inhibitor, which is already a drug available in market for the treatment of Alzheimer’s disease, so there is great interest in synthesizing these alkaloids in an enantiomerically enriched form. Biosynthetically, C-3α prenyl substituted HPI alkaloids are generally believed to be derived from L-tryptophan by reacting with 3,3-dimethylallyl pyrophosphate (DMAPP). Attracted by its complex structural ensemble and impressive biological activities, we thought of a very unified approach to these goals following an Interrupted Fischer indolization strategy.

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