No abstract

Herein, we report the application of nanoparticulate platinum (nPt) to enhancing the heterogeneous electron transfer between NAD + (nicotinamide adenine dinucleotide, oxidized form) and electrodes in the presence of an organometallic mediator.(Pentamethylcyclopentadienyl-2,2'-bipyridinechloro)rhodium(III) (M = [Cp*Rh(bpy)Cl] + ; Cp* = C 5 Me 5 , bpy = 2,2'-bipyridine) was used as a primary mediator to shuttle electrons between NAD + and electrodes. nPt functioned as a homogeneous catalyst and also as a secondary mediator to improve the turnover kinetics of M.Pyridine nucleotides (NAD(P)H) or their oxidized counterparts (NAD(P) + ) are used as cofactors that are critically required for redox reactions catalyzed by various oxidoreductases. [1,2] In biocatalytic reactions, NADH should be regenerated to allow the enzymes to continue their turnover. Electrochemical regeneration has been chosen as an attractive strategy that is an alternative to enzymatic regeneration.[3] In electrochemical regeneration, however, the first drawback to overcome is the slow electron transfer between NAD + and the electrodes, even at a potential where the reduction of NAD + into NADH is thermodynamically favorable. The use of a homogeneous mediator to shuttle electrons between electrodes and NAD + can be one solution to solve the problem. [4][5][6] The rhodium complex M was successfully used as an electron shuttle for NAD + in electrolyte, which improved the kinetics of NADH regeneration. [7][8][9] The active reduced form M red2 that enables NADH to be generated is made through a typical electrochemical/chemical (EC) process (Scheme 1).M ox is reduced to M red1 by accepting two electrons from the electrodes (E step). Successively, M red1 is chemically converted into M red2 without any change in the total number of electrons, by taking up one proton from solution (C step). NADH is generated from NAD + with the active form M red2 by accepting one proton plus two electrons from M red2 and returning M red2 to the initial state M ox (Scheme 2).The chemical step from M red1 to M red2 (the uptake of a proton into the ligand sphere of M red1 ) is the rate-determining step of NADH generation, specifically at high rates, even though it was reported to proceed quite fast.[8] Figure 1 a shows cyclic voltammograms obtained at various scan rates. The intensity of the anodic peak increased with scan rate, whereas the peak was not apparently observed at scan rates

A direct one-pot synthesis of phenanthrene lactams, which employs a Suzuki-Miyaura coupling/aldol condensation cascade reaction of isoindolin-1-one with 2-formylphenylboronic acid, has been developed. The approach is used to efficiently produce a number of natural aristolactams, such as aristolactam BII (cepharanone B), aristolactam BIII, aristolactam FI (piperolactam A), N-methyl piperolactam A, and sauristolactam.

Herein, we report the application of nanoparticulate platinum (nPt) to enhancing the heterogeneous electron transfer between NAD + (nicotinamide adenine dinucleotide, oxidized form) and electrodes in the presence of an organometallic mediator.(Pentamethylcyclopentadienyl-2,2'-bipyridinechloro)rhodium(III) (M = [Cp*Rh(bpy)Cl] + ; Cp* = C 5 Me 5 , bpy = 2,2'-bipyridine) was used as a primary mediator to shuttle electrons between NAD + and electrodes. nPt functioned as a homogeneous catalyst and also as a secondary mediator to improve the turnover kinetics of M.Pyridine nucleotides (NAD(P)H) or their oxidized counterparts (NAD(P) + ) are used as cofactors that are critically required for redox reactions catalyzed by various oxidoreductases. [1,2] In biocatalytic reactions, NADH should be regenerated to allow the enzymes to continue their turnover. Electrochemical regeneration has been chosen as an attractive strategy that is an alternative to enzymatic regeneration.[3] In electrochemical regeneration, however, the first drawback to overcome is the slow electron transfer between NAD + and the electrodes, even at a potential where the reduction of NAD + into NADH is thermodynamically favorable. The use of a homogeneous mediator to shuttle electrons between electrodes and NAD + can be one solution to solve the problem. [4][5][6] The rhodium complex M was successfully used as an electron shuttle for NAD + in electrolyte, which improved the kinetics of NADH regeneration. [7][8][9] The active reduced form M red2 that enables NADH to be generated is made through a typical electrochemical/chemical (EC) process (Scheme 1).M ox is reduced to M red1 by accepting two electrons from the electrodes (E step). Successively, M red1 is chemically converted into M red2 without any change in the total number of electrons, by taking up one proton from solution (C step). NADH is generated from NAD + with the active form M red2 by accepting one proton plus two electrons from M red2 and returning M red2 to the initial state M ox (Scheme 2).The chemical step from M red1 to M red2 (the uptake of a proton into the ligand sphere of M red1 ) is the rate-determining step of NADH generation, specifically at high rates, even though it was reported to proceed quite fast.[8] Figure 1 a shows cyclic voltammograms obtained at various scan rates. The intensity of the anodic peak increased with scan rate, whereas the peak was not apparently observed at scan rates