Oxidation-active flavin mimics. Chemical and redox properties of 7,14-diethyl-3,10-dimethylbenzo [1,2-g;4,5-g′]dipteridine-2,4,9,11-(3H,7H,10H,14H)-tetraone(benzo-dipteridine)

Abstract

The chemical and redox properties of benzo-dipteridine (BDP), an oxidation-active flavin mimic, were investigated. It was found that (i) BDP undergoes 2e-redox reaction under conventionl conditions, (ii) pK_a,-values of 2e-reduced BDP (BDP_red), are 3.6 and 8.5, respectively, (iii) a mixture of BDP_OX and BDP_red forms a charge-transfer complex in aqueous solution, (iv) BDP_ox exhibits a remarkably high oidation activity (ca. 10⁷-fold) toward reactions involving nucleophilic attack at the C(4a)-position compared with 3,10-dimethylisoalloxazine (DMI), and (v) the oxidation of an NADH model by BDP_ox is acid-catalysed. As a new model reaction, BDP_ox was found to oxidze sulphite ion via a BDP–SO₃^– adduct, which decomposes unimolecularly to give BDPH^– and [SO₃] in aqueous solution. This is the first example of an APS (adenosine 5′-phosphosulphate) reductase model.