Process Development for a Key Synthetic Intermediate of LY2140023, a Clinical Candidate for the Treatment of Schizophrenia

To fuel clinical development of the experimental CNS medicine LY2140023, we developed a scalable route for the multistep synthesis of a pivotal synthetic intermediate. The core of the conformationally restricted glutamic acid-based amino acid analogue was built via a Rh-catalyzed cyclopropanation of thiophene. Regioselective functionalization of the remaining double bond was achieved by a hydroboration/oxidation sequence followed by a Bucherer-Bergs reaction to give a hydantoin with the targeted L-glutamic acid configuration. Subsequent resolution, oxidation state, and protecting group manipulations gave the key intermediate in an overall nine-step scalable streamlined route starting from thiophene.