Recent Trends in Biomimetic NADH Regeneration

Nicotinamide adenine dinucleotide (NADH) and nicotinamide adenine dinucleotide phosphate constitute a major cost factor in preparative biotransformations. The development of efficient methods for their regeneration with cheap reducing equivalents has been an area of intense research in the last decades. Methods explored include chemical, electrochemical, and photochemical approaches. None of the methods to regenerate NADH has reached an efficiency comparable with enzymatic regeneration (e.g. formate dehydrogenase) which remains the method of choice for most applications. In this review, we summarize primarily organometallic-based approaches for NADH regeneration methods which include non-enzymatic steps, before moving on to the most recent developments in synthetic NADH related transformations. We highlight the frequent problem of mutual inactivation between the organometallic catalyst for NADH regeneration and the corresponding NADH dependent downstream enzyme. Potential remedies are discussed, such as the compartmentalization of the organometallic complex.