Development of an Efficient Manufacturing Process to GSK2248761A API

Amidation of indole 2-carboxylate 1 with ammonia gas via the imidazolide 2 gave GSK2248761A API 3, which was in development for the treatment of HIV. Three significant impurities, namely the phosphinic acid 4, the N-acyl urea 8, and the indoloyl carboxamide 6, were formed during the reaction, and the original process was unable to produce API within clinical specification when run at scale. Investigation into the origin, fate, and control of these impurities led to a new process which was able to produce API within clinical specification.