Investigation of the Unprecedented Reactivity of Spiroepoxyoxinodles Towards the Synthesis of Indole Based Bio Active Molecules

Abstract

Chapter 1. General Introduction, Concept and Aim newline1.1: A general overview of Indole based biologically active compounds newlineFrom the dense forest to the unfathomable oceans, from the simplest microorganisms to the most complex one, mother earth is overflowing with miscellaneous natural alkaloids which constitute of a ubiquitous structurally diverse group of secondary metabolites. The existence of nitrogen in their molecular architecture contributes the unprecedented biological activity to a large fraction of this compound class. Among these prodigious alkaloid family, indole alkaloids held a reputable place; since isatin, indole and oxindole scaffolds are frequently observed in innumerable natural products, bioactive molecules, as well as drugs. Moreover, marine indole alkaloids possess cytotoxic, anti-neoplastic, anti-bacterial, anti-microbial, anti-insecticidal, anti-plasmodial activities, potential for the treatment of neurological disorder and that s why the number is growing dramatically day by day. newline1.2: Concept behind utilization of spiro-epoxyoxindole for the synthesis of indole based small molecules newlineIn this context, we try to understand that unlike the styrene epoxide why the chemistry of this spiro-epoxide is mostly untouched. We then presumed that the different reactivity profile of spiro-epoxyoxindole unique is the reason (Scheme 1). The direct SN2 or SN1 pathway is objectionable considering the congested nature of spiro-center of epoxide and the generation of C3-carbocation which is destabilized by the electron-withdrawing amide carbonyl group. We then envisaged that the ring opening of spiro-epoxide may occur via either SN1 type pathway by the formation of intermediate A or by double inversion via the generation of intermediate B (anchimeric assistance) in presence of Lewis acid catalyst. With this concept in mind, our objective is to unveil the new reactivity pattern of spiro-epoxyoxindole newline