Mechanistic aspects of oxidation of N-substituted 5H-dibenz[c,e]azepines by aldehyde oxidase

Article abstract of DOI:10.1002/jhet.5570210427

5H-Dibenz[c,e]azepine (2) and its N-ethyl and N-(2-ethoxyethyl) analogues 3 and 4 were prepared and evaluated as substrates for aldehyde oxidase. Quaternization of 2 with ethyl iodide furnished 3, while 4 was prepared by lithium aluminum hydride reduction of N-(2-ethoxy)ethyldiphenimide followed by mercuric acetate oxidation of the resultant amine. The rates of oxidation of 2 and 3 were similar, suggesting a lack of selectivity by the enzyme for the respective imine and iminium functional groups in these compounds. The rate of oxidation of 3 decreased with increasing pH while the extent of 'hydration' of this substrate increased over a similar pH range, signifying a preference by the enzyme for 3 over its carbinolamine equilibrium partner. Experiments with deuterium labelled analogues of 2 and 3 indicated that azomethine hydrogen loss from these substrates during enzymatic oxidation was not rate determining. Thus 5H-dibenz[c,e]azepine-5,5,7-d₃ prepared by lithium aluminum deuteride reduction of diphenimide and its N-ethyl analogue, had respective enzymatic oxidation rates which did not differ from those of their non-deuterated counterparts.