| Abstract
| - 3,4-Disubstituted 6,7-indolequinones[1,3-dimethyl-4-(3‘-methylindol-2‘-yl)indole-6,7-dione (2),3-methyl-4-phenylindole-6,7-dione (3), and 3,4-dimethyl-6,7-dione(4)] and a 3,7-disubstituted 4,5-indolequinone [3,7-dimethylindole-4,5-dione (5)] have beensynthesized as models for the novel organiccofactor TTQ of bacterial amine dehydrogenases. The substituentand structural effects on thephysicochemical properties of the quinones have been investigated indetail by comparing thespectroscopic data (UV−vis, IR, 1H- and13C-NMR), pKa values of the pyrroleproton, and the two-electron redox potentials with those of model compound 1[3-methyl-4-(3‘-methylindol-2‘-yl)indole-6,7-dione] previously reported (ref ). Reactivity of each quinonein the transamination process[iminoquinone formation (k1), rearrangement toproduct−imine (k2), and aminophenolformation(k3)] has been investigated kinetically,revealing that the substituent and structural effects ontheamine-oxidation reaction are not so significant. In the aerobiccatalytic oxidation of benzylamine,however, the aromatic substituents on the quinone ring play animportant role to protect the quinonefrom the deactivation process of a Michael-type addition by the amine,making it act as an efficientturnover catalyst.
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