Five membered ring analogues of nifedipine - Part 3: synthesis and reactions of 1,4-dihydropyridines with 4-(4-nitro-5-imidazolyl)-substituents

in the Hantzsch pyridine synthesis the 4-nitro-5-imidazolylcarbaldehydes 4 react with methyl 3-aminocrotonate or 3-aminocrotononitrile in acetic acid to yield the 1,4-dihydropyridines (DHP) 5 and 6. The corresponding pyridine s 7 and 8 are obtained by oxidation with cerium(IV) or chromium(VI), respec tively. Reduction of the nitro group in 7 with iron in acetic acid leads to the lactames 9, while from 8a the imidazolylamine 10 is isolated. Compound 8a reacts with dithionite to yield the cyclic amidine 11. Irradiation of t he DHP 5 and 6b with UV-A light affords the 4-nitroso-5-imidazolyl pyridine s 12 and 13. The half wave potentials E-1/2 of the DHP 5 were determined by anodic oxidation using difference pulse voltammetry (DPV); nifedipine was used as reference substance. The DHP 5 inhibit the growth of Staphylococcus aureus in the platelet diffusion test.