Process Development and Good Manufacturing Practice Production of a Tyrosinase Inhibitor via Titanium-Mediated Coupling between Unprotected Resorcinols and Ketones

Abstract

A concise and economically attractive process for the synthesis of a novel tyrosinase inhibitor has been developed and implemented on a multikilogram scale under GMP. A major achievement to the success of the process is the development of a direct coupling between free resorcinol and ketone. First developed under basic conditions, this coupling has been turned to a novel titanium(IV) mediated process allowing good selectivity, easy isolation, and high atom efficiency. Other key steps feature an alkene reduction by palladium catalyzed transfer hydrogenation and a urea formation using N,N′-disuccinimidyl carbonate as the carbonyl source. This route allowed us to produce kilogram batches of the candidate to support preclinical and clinical studies.