STUDY OF THE MECHANISM OF THE HYDRIDE TRANSFER WITH A HIGHLY REACTIVEAND STEREOSELECTIVE NADH MODEL

The H-1 and C-13 NMR spectra of the chiral NADH models 3 and 4 were st udied both in the presence or absence of Mg2+ ions, These two compound s have a chiral carboxamide part derived from (S)-phenylalaninol but c ontrary to 3, compound 4 has the ability to free-rotate about the C-3- C=O bond. Careful analysis of the spectral results and comparison with some other studies recently published in the literature allowed the f ollowing assumptions: 1-the 1,4-dihydropyridine structure is planar bo th in the absence or presence of magnesium ions. 2-in the case of the rigid model 3, the C=O is out of the plane of the dihydropyridine stru cture. S-with Mg2+ the chiral amino alcohol moiety adopts a quasi-cycl ic conformation in the case of 4 but not in the case of 3. The observe d enantioselectivities are explained by the mean of ternary complexes between the model, Mg2+ and the substrate