Regeneration of dihydronicotinamide cofactors

A key step in developing efficient practical processes with NAD-dependent enzymes may well be the generation and regeneration of NADH from NAD+ (eq. 3.15)  

NADH can be regenerated by enzymatic [334], electrochemical [334, 335] or chemical [334] reduction, however, all these methods have some drawbacks. Strong reducing agents act on a non-selective way, i.e. in 

This reaction is catalyzed by [Rh(r 5-C5Me5)(bipy)]2+ with a TOF = 80 h 1 

Reduced 1-benzylnicotinamide (BNAH) is capable for reduction of carbonyl compounds in the presence of divalent ions such as Mg2+ and Zn2+. It can be (regenerated from BNA+ by a photochemically assisted hydrogen transfer from ascorbate, using [Ru(bipy)3]3+ as photosensitizer and [RhCl(TPPMS)3] as catalyst. The BNAH, generated continously in this reaction, was used for the reduction of benzil to benzoin [339], 

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