In situ NAD+ regeneration using 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) as an electron transfer mediator

Electrochemical oxidation of reduced nicotinamide adenine dinucleotide (NADH) proceeds very effectively at 0.585 V versus Ag ∣ AgCl in pH 9.0 buffered solution at ambient temperature using ABTS2− (2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) as an electron transfer mediator. The electrochemistry of ABTS2− and its oxidized form ABTS−, as well as the coupled homogeneous reactions were studied, and the rate constants were estimated using cyclic voltammetry and photometric methods (kapp,NADH=5.6–6.45×103 M−1 s−1). The mediated electrochemical oxidation was successfully coupled to horse liver alcohol dehydrogenase catalyzed oxidation of a meso-diol to a chiral lactone (yield 93.5%, ee>99.5%).