STEREOCHEMISTRY OF ASYMMETRIC (NET) HYDRIDE TRANSFER IN AN INTERCOENZYME MODEL REACTION SYSTEM

X-ray crystal structure analysis revealed the absolute configuration of compound 2 and thus proved the absolute configuration of 5-deazaflavin (+)-1 possessing both axial and planar chirality to be (S). Model reactions of ''(net) hydride transfer'' between 1 and Me2PNPH enanatiomers revealed that (S)-(+)-1 oxidizes (4S)-Me2PNPH more rapidly than its (4R) isomer and that (R)-(-)-1 oxidizes (4R)-Me2PNPH more rapidly than its (4S) isomer. These results strongly suggest that an enatioselectivity on Me2PNPH by chiral 1 is not solely determined by the availability of C(4) hydrogen but by the ''(net) hydride donor-acceptor'' interactions involving the interaction between the pyrimidine site of 5-deazaflavin molecule and the carbamoyl group of the NAD(P)H model as the important contributor.