Synthesis and Activation of Bench-Stable 3a-Fluoropyrroloindolines as Latent Electrophiles for the Synthesis of C-2-Thiol-Substituted Tryptophans and C-3a-Substituted Pyrroloindolines.

Abstract

Indole dearomatization of tryptophan represents a key approach in the synthesis of indole containing alkaloids. Although the reactivity of C-3a-bromo-, 3a-iodo-, and 3a-chloropyrroloindolines has been explored, the utility and reactivity of C-3a-fluoropyrroloindolines has remained untapped. Here we induce the C-F bond to undergo a Sn1-like reaction. We demonstrate the utility of 3a-fluoropyrroloindoline to access C-2-thiol-substituted tryptophans and C-3a-substituted pyrroloindolines under mild conditions in high yield. A range of Nα-protecting groups and free -COOH are well-tolerated.