REGIOSELECTIVE ADDITION OF 2-NITROPROPANE ANION TO NAD+ ANALOGS

Various NAD+ analogues have been reduced regioselectively by the tetra methylammonium salt of 2-nitropropane anion in acetonitrile at 298 K t o yield the corresponding 4-alkylated NADH analogues. The one-electron oxidation potential of the tetramethylammonium salt of 2-nitropropane anion has been determined as 0.10 V (vs. SCE) by using second harmoni c ac voltammetry as well as by analysing the cyclic voltammograms at v arious sweep rates. The rate constants for the reduction of NAD+ analo gues by 2-nitropropane anion (>1 x 10(6) dm3 mol-1 s-1) are much large r than those estimated for outer-sphere electron transfer from 2-nitro propane anion to NAD+ analogues based on the one-electron oxidation po tential of 2-nitropropane anion and the one-electron reduction potenti als of NAD+ analogues. The origin of the regioselectivity is discussed in terms of the HSAB (hard and soft acids and bases) principle.