Multikilogram Synthesis of a Potent Dual Bcl-2/Bcl‑xL Antagonist. 2. Manufacture of the 1,3-Diamine Moiety and Improvement of the Final Coupling Reaction

This paper describes the synthesis of kilogram quantities of the sulfonamide moiety 3 involved in a coupling reaction with acid moiety 2 to provide batches of drug candidate 1 for preclinical studies and first-in-human clinical trials. A first approach relying on a chiral separation furnished the desired enantiomer of 1,3-diamine 20, precursor of sulfonamide 3. An enantiomeric synthesis of 20 using the Ellman’s chiral auxiliary coupled with an aza-Reformatsky reaction to control the stereochemistry is also discussed. Coupling conditions of the final step involving EDCI to provide 1 under a cGMP process are detailed. An alternative approach using N-(1-methanesulfonyl)­benzotriazole is also presented.