A robust process to manufacture AMG 232 was developed to deliver drug substance of high purity. Highlights of the commercial process development efforts include the following: (i) use of a novel bench-stable Vilsmeier reagent, methoxymethylene- N, N-dimethyliminium methyl sulfate, for selective in situ activation of a primary alcohol intermediate; (ii) use of a new crystalline and stable isopropyl calcium sulfinate reagent ensuring robust preparation of a sulfone intermediate; (iii) development of a safe ozonolysis process conducted in an aqueous solvent mixture in either batch or continuous manufacturing mode; and (iv) control of the drug substance purity by crystallization of a salt rejecting impurities effectively. The new process was demonstrated to afford the drug substance (99.9 LC area %) in 49.8% overall yield from starting material DLAC (1).