Preparation of the HIV Attachment Inhibitor BMS-663068. Part 4. Synthesis of the 6-Azaindole Core

We report research focused on the construction of the 6-azaindole core, a key intermediate in the synthesis of the clinical candidate BMS-663068. The work describes an efficient and scalable method to access the 6-azaindole from a protected 3-ketopyrrole via a Pictet–Spengler cyclization and a radical-mediated aromatization. The process reported herein has been successfully implemented on the multikilogram scale to support preclinical development and clinical studies of BMS-663068.