Diastereoselective synthesis of trans-4-arylpiperidine-3-carboxylic acid derivatives from 4-aryl-1,4-dihydropyridine

A convenient procedure for the preparation of trans-3,4-disubstituted piper idines from dr-aryl-l,4-dihydropyridine is described. The diastereoselectiv e synthesis of an unnatural amino acid, trans-4-arylpiperidine-3 carboxylic acid, and its derivatives is exemplified. The key steps include the constr uction of a trans-3,4-disubstituted piperidine moiety in compound (5), N-me thyl carbamate of trans-4-aryl-piperidine-3-carboxylic acid, from 4-aryl-1, 4-dihydropyridine-3-carboxylic acid methyl ester (2) via hydrogenation, red uction, and hydrolysis. Reduction of acid (5) with lithium aluminum hydride or with sodium borohydride provided the corresponding carbinol (7) or (8).