Enantioselective Approach Towards Potential Substance P Antagonists via Hetero-Ene Reaction of Phenylglycine Derivatives

Abstract

Phenylglycine methyl ester 7 can be converted in a four-step sequence to the aldehyde 11. Lewis acid catalyzed hetero-ene reaction of 11 gave a mixture of 3-hydroxy-2-phenylpiperidines 14a,b with high diastereoselectivity. The major diastereomer 14a was further transformed into 4-isopropyl-3-(2-methoxybenzylamino)-2-phenylpiperidine (19), a compound structurally related to a substance P antagonist, in five steps via azide displacement and reductive amination.