Abstract
1,4-Dihydropyridine (1,4-DHP) derivatives have been synthesized and characterized by 1H, 13C, 15N nuclear magnetic resonance (NMR) spectroscopy, secondary proton/deuterium 13C isotope shifts, variable temperature 1H NMR experiments and quantum-chemical calculation. The intramolecular hydrogen bonds NH⋯O=C and CH⋯O=C in these compounds were established by NMR and quantum-chemical studies The downfield shift of the NH proton, accompanied by the upfield shift of the 15N nuclear magnetic resonance signals, the shift to the higher wavenumbers of the NH stretching vibration in the infrared spectra and the increase of the 1J(15N,1H) values may indicate the shortening of the N–H bond length upon intramolecular NH⋯O=C hydrogen bond formation.
Highlights
Since the original discovery of amlodipine, the 2-substituted 1,4dihydropyridines have attracted considerable attention owing to their various biological activities [1]
We propose the two steps procedure from dimethyl 4-substituted 2,6-dimethyl-1,4-dihydropyridine3,5-dicarboxylate via bromination of 2-methyl- or 2,6-dimethyl groups
The rest of the signals in 1H nuclear magnetic resonance (NMR) spectra are in agreement with the nature of aromatic or aliphatic hydrogen atoms
Summary
Since the original discovery of amlodipine, the 2-substituted 1,4dihydropyridines have attracted considerable attention owing to their various biological activities [1]. For the aimed synthesis of novel therapeutic agents, it is important to establish what structural factors influence their biological activity. To this end, the modification of 2,6-Me groups was performed. The original method was elaborated for obtaining both alkyl 4-substituted 2-acetoxymethyl-(3) and 2,6-bis-acetoxymethyl-1,4dihydropyridine-3,5-dicarboxylates (5) (scheme 1). Hydrogen bond interactions are principal forces, which determine the molecular recognition and self-assembly processes as well as the structure of a great variety of chemical and biological systems [2]. The structures of the novel compounds 3 and 5 are interesting because there could be different types of intramolecular interactions
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