Synthesis, Structure, and Analgesic Activity of Picolylamides of 2-Hydroxy-4-Oxo-4H-Pyrido-[1,2-a]Pyrimidine-3-Carboxylic Acids

Crystal structure and Hirshfeld surface analysis of 6-amino-8-(2,6-di-chloro-phen-yl)-1,3,4,8-tetra-hydro-2H-pyrido[1,2-a]pyrimidine-7,9-dicarbo-nitrile

In the mol-ecular structure of the title compound, C16H13Cl2N5, the 1,4-di-hydro-pyridine ring of the 1,3,4,8-tetra-hydro-2H-pyrido[1,2-a]pyrimidine ring system adopts a screw-boat conformation, while the 1,3-diazinane ring is puckered. In the crystal, inter-molecular N-H⋯N and C-H⋯N hydrogen bonds form mol-ecular sheets parallel to the (110) and (10) planes, crossing each other. Adjacent mol-ecules are further linked by C-H⋯π inter-actions, which form zigzag chains propagating parallel to [100]. A Hirshfeld surface analysis indicates that the most significant contributions to the crystal packing are from N⋯H/H⋯N (28.4%), H⋯H (24.5%), C⋯H/H⋯C (21.4%) and Cl⋯H/H⋯Cl (16.1%) contacts.

Molecular Conformations and Biological Activity of N-Hetaryl(aryl)alkyl-4-methyl-2,2-dioxo-1H-2λ6,1-benzothiazine-3-carboxamides

The analysis of our previous studies on the search for synthetic analgesics among N-R-amides of bicyclic hetaryl-3-carboxylic acids has been performed; on its basis N-hetaryl(aryl)-alkyl-4-methyl-2,2-dioxo-1H-2λ6,1-benzothiazine-3-carboxamides have been selected as new study objects. The “one pot synthesis” of these compounds, which is simple to perform and at the same time highly effective, has been offered. The method consists in the initial reaction of 4-methyl-2,2-dioxo-1H-2λ6,1-benzothiazine-3-carboxylic acid and N,N′-carbonyldiimidazole in anhydrous N,N-dimethylformamide with the subsequent amidation of imidazolide formed with hetarylalkyl- or benzylamines in the same solvent. The peculiarities of 1H- and 13C-NMR spectra of the substances obtained, as well as their electrospray ionization liquid chromato-mass spectra are discussed. According to the results of the pharmacological tests carried out on the model of carrageenan inflammation it has been found that all without exception N-hetaryl(aryl)alkyl-4-methyl-2,2-dioxo-1H-2λ6,1-benzothiazine-3-carboxamides demonstrate the statistically significant analgesic and anti-inflammatory properties. Among the substances presented in this article analgesics and antiphlogistics, which increase the pain threshold and suppress the inflammatory response more effectively than Lornoxicam and Diclofenac in the same doses, have been identified. The molecular and crystal structures of a large group of the substances synthesized have been studied by X-ray diffraction analysis. Comparison of these data with the results of biological tests has revealed the fact of excellent correlation between the molecular conformations of N-hetaryl(aryl)alkyl-4-methyl-2,2-dioxo-1H-2λ6,1-benzothiazine-3-carboxamides recorded in the crystal and the potency of their analgesic effect. N-Thiophen-2-ylmethyl- and N-4-methoxybenzyl-amides of 4-methyl-2,2-dioxo-1H-2λ6,1-benzothiazine-3-carboxylic acid has shown a high analgesic and anti-inflammatory effect, therefore, they deserve more careful research.