(3S,4R)-1-Boc-4-(4-chlorophenyl)pyrrolidine-3-carboxylic Acid is used to synthesize pyrrolidinecarboxamide derivatives of piperazines as potent agonists of human melanocortin-4 receptor. It is also an intermediate used to prepare substituted 2H-isoquinolin-1-ones as potent Rho-kinase inhibitors.