Efficient Synthesis of 3,5-Dicarbamoyl-1,4-dihydropyridines from Pyridinium Salts: Key Molecules in Understanding NAD(P)+/NAD(P)H Pathways.

3,5-Dicarbamoyl-1,4-dihydropyridines were prepared in high yields using a green protocol by reduction of the corresponding pyridinium salts in aqueous buffered sodium dithionite solutions. The pH value is a fundamental parameter for the reduction step and depends on the nature of substituent groups at positions 1, 3, and 5 of the pyridinium salts. These 3,5-dicarbamoyl dihydropyridines show a lower tendency towards oxidation and a higher stability than N-benzyl-3-carbamoyl-1,4-dihydropyridine at low pH values. [ABSTRACT FROM AUTHOR]