A reliable and efficient synthesis of SR 142801

A convenient synthesis of the potent human NK-3 receptor antagonist SR 142801, (S)-(+)-N-{{3-[1-benzoyl-3-(3,4-dichlorophenyl)piperidin-3-yl]prop-1-yl}-4-phenylpiperidin-4-yl}-N-methylacetamide [(S)-(+)-(15)], is described. Improvements over the previously reported procedure are the preparation of the intermediate 5via the novel imide 3 and subsequent reaction with the nucleophile 14, which reacts, regioselectively, at the endocyclic nitrogen.