STUDIES ON AN UNUSUAL N-DEALKYLATION REACTION. II. CHARACTERISTICS OF THE ENZYME SYSTEM AND A PROPOSED PATHWAY FOR THE REACTION

¹ Hoffmann-La Roche Inc., Research Division, Nutley, New Jersey

The characteristics of the enzyme system which catalyzes the N-dealkylation of N-tert.-butylnorchlorcyclizine have been studied. The reaction requires oxygen, reduced nicotinamide adenine dinucleotide phosphate, nicotinamide adenine dinucleotide, microsomes and cytoplasm and is inhibited by cyanide, semicarbazide, o-phenanthroline, disulfiram, pyrazole, SKF 525A and carbon monoxide. The requirement for cytoplasm can be replaced by alcohol or aldehyde dehydrogenase. The reaction is induced by pretreatment with phenobarbital and is inhibited by pretreatment with carbon tetrachloride. A reaction pathway is proposed which involves hydroxylation of a methyl group on the N-tert.-butyl side chain by the microsomal mixed function oxidase system followed by stepwise oxidation to a carboxylic acid by soluble enzymes which require nicotinamide adenine dinuncleotide. The carboxylic acid is decarboxylated and the resulting N-isopropyl derivative is N-dealkylated by microsomal mixed function oxidases to norchlorcyclizine.