Mechanistic Analysis of the 3-Methyllumiflavin-Promoted Oxidative Deamination of Benzylamine. A Potential Model for Monoamine Oxidase Catalysis
Author :
J.-M. Kim*, M. A. Bogdan, P. S. Mariano
Journal :
Journal of the American Chemical Society, 115, 10591-10595
Publication Date :
1993-11-01
Papers :
papers
Update Date :
16-07-19 23:22
An investigation designed to probe flavin-promoted oxidative deaminations of amines is described. 3-Methyllumiflavin (3MLF) has been found to promote clean conversion of benzylamine to N-benzylbenzaldimine under acid (HCI or MgCl2 catalyzed, thermal (80 oC) conditions. The reaction is subject to multiple turnover. Amine structure (lo > 2o > 3o) and α-electrofugal group leaving ability (TMS+ > H+) are found to influence reactivity. In addition, the internal d-isotope effect measured for the ground-state reaction by using PhCHDNH2 is found to be 4.3, a value greatly different from the 1.6 measured for the excited-state (SET) reaction run under nearly identical (20 oC rather than 80 oC) conditions. Additional mechanistic information has come from observations which show that benzylamine undergoes instantaneous reaction with N5ethyl-3-methyllumiflavinium perchlorate to produce a stable 4a-adduct. In addition, this adduct is transformed quantitatively to N-benzylbenzaldimine when treated with benzylamine at 60 oC. These results suggest that the ground-state reaction of PhCH2NH2 promoted by 3MLF follows a polar mechanism involving formation of and elimination in a covalent 4a-(N-benzylamino)dihydroflavin intermediate.