Abstract
In the redox reaction by coenzyme NAD(P)+-NAD(P)H, it has been suggested that the orientation of carbamoyl group at 3-position are associated with the stereoselectivity in the reaction. In order to elucidate the effect of this orientation, 2-N-bridged NAD+ analogues with axial chirality at 3-position by the steric hindrance of the 2-aryl ortho substituent which stuck out to 3-position was proposed and synthesized. In this paper, the reaction of 2-N-bridged NAD+ analogues with H2NC(=NH)SO2H is reported. In the reaction, 1,4-reductant was obtained mainly, and a small amount of 1,6-reductant was also formed. However, unidentified compound was generated about 5 times than 1,4- reductant. Secondly, 2-N-bridged NAD+ analogues was treated with H2NC(=NH)SO2H in heavy water to elucidated the regioselectivity of the reduction. As the result, it was revealed that this analogues was reduced at C-4 position directly from the only decrease of integral value of proton at C-4 position on 1H-NMR spectrum. Furthermore, the isotope effect on kinetic rate and product ratio was observed, and the unidentified compound observed in H2O was not generated in D2O.
