NADH MIMICS ON DIACETONE-D-GLUCOSE - STEREOSELECTIVE BIOMIMETIC REDUCTION OF BENZOYLFORMATE AND INTERPRETATION OF CHIRALITY TRANSFER DEDUCED BY MOLECULAR-ORBITAL APPROACH

We have prepared novel NADH mimics, in which the 1,4-dihydronicotinami de structure is connected to the dincetone-D-glucose molecule via its C-I nitrogen, e.g, compound 1a and 1b, and through the amide bond, e.g . compound 2-6, and analyzed their ability to stereoselective reductio n of methyl benzoylformate. Although NADH mimics 1-3 and 6 turned out to be less effective in chirality transfer toward methyl benzoylformat e, much higher chirality transfer was observed in the reactions with t he compounds (4 and 5) possessing free hydroxyl groups at 5',6'-positi on of furanose, Importance of an additional intramolecular coordinatin g substituent to bivalent metal ion has been demonstrated in enhancing the stereoselectivity in the reduction of benzoyl,formate with such N ADH mimics. To materialize these observations, transition-states of th e hydride transfer from 1-methyl-1,4-dihydronicotinamide to methyl ben zoylformate in the presence of magnesium (II) ion were calculated by s emi empirical molecular orbital method, MNDO-PM3. Also discussed in th is paper is a general chirality transfer mechanism deduced from the th eoretical transition-state modeling.