REACTION OF THE TRIMETHYL ESTER OF COENZYME PQQ (PQQTME) AND AMINES IN ORGANIC MEDIA - PRODUCTS AND MECHANISM

The reaction of PQQTME (1, the trimethyl ester of coenzyme PQQ) and various amines in organic media was investigated in order to gain information on the chemistry of PQQ in vitro. The iminoquinone derivatives 2, 3, and 5 were isolated from the reaction of 1 with ammonia, tert-butylamine, and cyclopropylamine, respectively, in CH3CN. The reduction of 2 by methylhydrazine proceeded smoothly to give the aminophenol 2H2 in moderate yield. Detailed analysis of the products from the reaction of 1 (and its 1-methyl derivative 6) with n-propylamine, N-methylpropylamine, triethylamine, and several benzylamines established that the oxidation of amines by PQQTME proceeds via an ionic mechanism (addition-elimination and transamination) that involves a carbinolamine intermediate. PQQTME was also found to be an efficient turnover catalyst of the aerobic oxidation of benzylamines in CH3CN solution.