Lisa A. Peterson, Anthony Trevor, and Neal Castagnoli, Jr.* Department of Pharmaceutical Chemistry, School of Pharmacy, University of California, San Francisco, San Francisco, California 94143. Received March 20, 1986 ... Mammals metabolize the tobacco alkaloid (S)-nicotine primarily to the lactam (S)-cotinine by a pathway involving an initial cytochrome P-450 catalyzed two-electron oxidation at the prochiral 5'-carbon atom. The stereochemical course of this oxidation was ...