Search Results (5)

According to our quantum and chemical calculations 4-methyl-2,2-dioxo-1H-2λ⁶,1-benzothiazine-3-carboxylic acid imidazolide is theoretically almost as reactive as its 2-carbonyl analog, and it forms the corresponding N-pyridyl-4-methyl-2,2-dioxo-1H-2λ⁶,1-benzothiazine-3-carboxamides with many aminopyridines. However, in practice, the sulfo group introduces significant changes at times and prevents the acylation of sterically hindered amines. One of these products was 2-amino-6-methylpyridine. Thus, it has been concluded that aminopyridines interact with imidazolide in aromatic form where the target for the initial electrophilic attack is the ring nitrogen. To confirm the structure of all substances synthesized, ¹H-NMR spectroscopy and X-ray diffraction analysis were used. From X-ray diffraction data it follows that in the crystalline phase the carbonyl and sulfo group may occupy different positions with respect to the plane of the benzothiazine bicycle: this position may be unilateral, typical for 4-methyl-2,2-dioxo-1H-2λ⁶,1-benzothiazine-3-carboxamides, versatile, and not yet encountered in compounds of this type. A comparison of these data with the results of the pharmacological screening conducted on the standard model of carrageenan inflammation showed that the N-pyridylamides of the first group demonstrated a direct dependence of their analgesic and anti-inflammatory activity on the mutual arrangement of the planes of the benzothiazine and pyridine fragments. The new molecular conformation of the benzothiazine nucleus provides a sufficiently high level of analgesic (but not anti-inflammatory) properties in all N-pyridylamides of the second group with an extremely weak dependence on the spatial arrangement of the pyridine cycle. All substances presented this article proved themselves in varying degrees as analgesics and antiphlogistics. Moreover, two of them—N-(5-methylpyridin-2-yl)- and N-(pyridin-3-yl)-4-methyl-2,2-dioxo-1H-2λ⁶,1-benzothiazine-3-carboxamides—exceeded the most effective drug of oxicam type Lornoxicam by these indicators. Full article

In order to detect new structural and biological patterns in a series of hetaryl-3-carboxylic acid derivatives, the optically pure (S)- and (R)-enantiomers of N-(1-arylethyl)-4-methyl- 2,2-dioxo-1H-2λ⁶,1-benzothiazine-3-carboxamides, their true racemates, and mechanical racemic mixtures have been synthesized in independent ways. The particular features of the ¹Н- and ¹³С-NMR spectra of all synthesized substances, liquid chromato-mass spectrometric behavior thereof under electrospray ionization conditions, and also the results of polarimetric and X-ray diffraction studies have been discussed. Pharmacological screening on a model of carrageenan inflammation has found a clear relationship between the spatial structure of the studied objects and biological activity thereof. Enantiomers with chiral centers having (S)-configuration showed weak inhibition of pain and inflammatory reactions, while their mirror (R)-isomers exhibited very powerful analgesic and antiphlogistic properties under the same conditions, with the level of specific activity exceeding that of Lornoxicam and Diclofenac. Taking obtained data into account, a noticeable decrease in the activity of mechanical racemic mixtures, consisting of one-half of the “wrong” (S)-enantiomers, is quite natural. The true racemate of N-(1-phenylethyl)-amide proved itself in a similar way, while 4-methoxy-substituted analog thereof stood out against this background with unexpectedly high analgesic and anti-inflammatory activities. A comparative analysis of X-ray diffraction data has found that crystalline and molecular structure of racemic N-[1-(4-methoxyphenyl)ethyl]-4-methyl-2,2-dioxo-1H-2λ⁶,1-benzothiazine-3-carboxamide is completely different from that of the original enantiomers and, moreover, very unusual for racemates. Obviously, it is the factor determining the unique character of the biological effects of the said substance. Full article

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. Full article

Continuing the search for new potential analgesics among the derivatives of 4-methyl-2,2-dioxo-1H-2λ⁶,1-benzothiazine-3-carboxylic acid, the possibility of obtaining its esters by the alkylation of the corresponding sodium salt with iodoethane in dimethyl sulfoxide (DMSO) at room temperature was studied. It was found that under such conditions, together with the oxygen atom of the carboxyl group, a heteroatom of nitrogen is also alkylated. Therefore, the product of the reaction studied is a mixture of ethyl 4-methyl-2,2-dioxo-1H-2λ⁶,1-benzothiazine-3-carboxylate (major) and its 1-ethyl-substituted analog (minor). A simple but very effective method of preparative separation of these compounds was proposed. Moreover, the heterogeneous crystallization from ethanol was revealed to result in a monoclinic polymorphic form of ethyl 4-methyl-2,2-dioxo-1H-2λ⁶,1-benzothiazine-3-carboxylate, while the homogeneous crystallization results in its orthorhombic form. The molecular and crystal structures of both forms were confirmed by X-ray diffraction analysis, and the phase purity by powder diffraction study. The pharmacological tests carried out on the model of a carrageenan edema showed that the screening dose of 20 mg/kg of 1-ethyl-substituted ester and the orthorhombic form of its analog unsubstituted in position 1 exhibited weak anti-inflammatory and moderate analgesic effects. At the same time, the monoclinic form of ethyl 4-methyl-2,2-dioxo-1H-2λ⁶,1-benzothiazine-3-carboxylate appeared to be both a powerful analgesic and an anti-inflammatory agent that exceeded Piroxicam and Meloxicam in the same doses by these indicators. A detailed comparative analysis of the molecular and crystal structures of two polymorphic forms of ethyl 4-methyl-2,2-dioxo-1H-2λ⁶,1-benzothiazine-3-carboxylate was carried out using quantum chemical calculations of the energies of pairwise interactions between molecules. An explanation of the essential differences of their biological properties based on this was offered. Full article

In order to determine the regularities of the structure–analgesic activity relationship, the peculiarities of obtaining, the spatial structure, and biological properties of 4-methyl-2,2-dioxo-1H-2λ⁶,1-benzothiazine-3-carboxylic acid and some of its derivatives have been studied. Using nuclear magnetic resonance (NMR) spectroscopy and X-ray diffraction analysis, it has been proven that varying the reaction conditions using alkaline hydrolysis of methyl 4-methyl-2,2-dioxo-1H-2λ⁶,1-benzothiazine-3-carboxylate makes it possible to successfully synthesize a monohydrate of the target acid, its sodium salt, or 4-methyl-2,2-dioxo-1H-2λ⁶,1-benzothiazine. The derivatographic study of the thermal stability of 4-methyl-2,2-dioxo-1H-2λ⁶,1-benzothiazine-3-carboxylic acid monohydrate has been carried out; based on this study, the optimal conditions completely eliminating the possibility of unwanted decomposition have been proposed for obtaining its anhydrous form. It has been shown that 4-methyl-2,2-dioxo-1H-2λ⁶,1-benzothiazine is easily formed during the decarboxylation of not only 4-methyl-2,2-dioxo-1H-2λ⁶,1-benzothiazine-3-carboxylic acid, but also its sodium salt, which is capable of losing СО₂ both in rather soft conditions of boiling in an aqueous solution, and in more rigid conditions of dry heating. The NMR spectra of the compounds synthesized are given; their spatial structure is discussed. To study the biological properties of 4-methyl-2,2-dioxo-1H-2λ⁶,1-benzothiazine-3-carboxylic acid and its sodium salt, the experimental model of inflammation caused by subplantar introduction of the carrageenan solution in one of the hind limbs of white rats was used. The anti-inflammatory activity and analgesic effect were assessed by the degree of edema reduction and the ability to affect the pain response compared to the animals of control groups. According to the results of the tests performed, it has been found that after intraperitoneal injection, the substances synthesized demonstrate a moderate anti-inflammatory action and simultaneously increase the pain threshold of the experimental animals very effectively, exceeding Lornoxicam and Diclofenac in a similar dose by their analgesic activity. Full article