The tautomerism of heteroaromatic compounds with five-membered rings—IV

Synthesis, biological evaluation, molecular modeling, and structural analysis of new pyrazole and pyrazolone derivatives as N-formyl peptide receptors agonists

N‐formyl peptide receptors (FPR1, FPR2, and FPR3) play key roles in the regulation of inflammatory processes, and recently, it was demonstrated that FPR1 and FPR2 have a dual role in the progression/suppression of some cancers. Therefore, FPRs represent an important therapeutic target for the treatment of both cancer and inflammatory diseases. Previously, we identified selective or mixed FPR agonists with pyridazinone or pyridinone scaffolds showing a common 4‐(bromophenyl)acetamide fragment, which was essential for activity. We report here new pyrazole and pyrazolone derivatives as restricted analogues of the above 6‐membered compounds, all exhibiting the same 4‐bromophenylacetamide side chain. Most new products had low or absent FPR agonist activity, suggesting that the pyrazole nucleus was not appropriate for FPR agonists. This hypothesis was confirmed by molecular modeling studies, which highlighted that the five‐membered scaffold was responsible for a worse arrangement of the molecules in the receptor binding site.

Final Report on the Safety Assessment of Phenyl Methyl Pyrazolone

Phenyl Methyl Pyrazolone (PMP) is a heterocyclic amine that is used in hair colorants. The phenylhydrazine content in PMP is below the limit of detection. Phenyl Methyl Pyrazolone was slightly toxic to rats, with an oral LD50 of 3.5 g/kg. Feeding rats and mice with PMP-treated feed for 7 weeks was uneventful. A compound containing 500 mg/kg of PMP was, at most, a mild ocular irritant. Phenyl Methyl Pyrazolone was slightly irritating to rabbit skin when tested under occlusive patches. It did not produce a sensitization reaction in guinea pigs. Phenyl Methyl Pyrazolone was nonmutagenic in two assays and noncarcinogenic in oral feeding studies. On the basis of the available data presented in this report, it is concluded that Phenyl Methyl Pyrazolone is safe for use as a cosmetic ingredient in the present practices of use and concentration.

Synthesis, antiviral, cytotoxicity and antitumor evaluations of A4 type of porphyrin derivatives

This manuscript describes the synthesis of a new series of porphyrin structures 4a–4m, 7, 9, 12 and 14. These structures were investigated against two types of viruses such as HIV-1 and HSV-1. Also they were screened for their antitumor activity. Among all tested compounds, it was found that compound 4b showed a high activity against HIV-1 and HSV-1 and against four different tumor cell lines. Most of the tested compounds showed a moderate degree of a potent antimicrobial activity. The structure of these compounds was confirmed on the basis of their analytical and spectral data such as UV-vis, IR, 13 C NMR, 1 H NMR spectroscopy and mass spectral data.

Synthesis and antimicrobial evaluation of novel pyrazolones and pyrazolone nucleosides

The synthesis of a novel series of 4-arylhydrazono-5-methyl-1,2-dihydropyrazol-3-ones 4a-h, and their N (2)-alkyl and acyclo, glucopyranosyl, and ribofuranosyl derivatives is described. K(2)CO(3) catalyzed alkylation of 4a-h with allyl bromide, propargyl bromide, 4-bromobutyl acetate, 2-acetoxyethoxymethyl bromide, and 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide proceeded selectively at the N (2)-position of the pyrazolinone ring. Glycosylation of 4a with 1,2,3,5-tetra-O-acetyl-β-D-ribofuranose under Vorbruggen glycosylation conditions gave the corresponding N (2)-4-arylhydrazonopyrazolone ribofuranoside 9a in good yield. Conventional deprotection of the acetyl protected nucleosides furnished the corresponding 4-arylhydrazonopyrazolone nucleosides in good yields. Selected numbers of the newly synthesized compounds were screened for antimicrobial activity. Compounds 4b, 12a, and 14 d showed moderate activities against Aspergillus flavus, Penicillium sp., and Escherichia coli.

Synthesis of 4,5-Diaryl-1H-pyrazole-3-ol Derivatives as Potential COX-2 Inhibitors

4,5-Diaryl-1H-pyrazole-3-ol was utilized as a versatile template to synthesize several classes of compounds such as pyrazolo-oxazines 7, pyrazolo-benzooxazines 9, pyrazolo-oxazoles 10, and its analogues 11a-c as potential COX-2 inhibitors. Compounds 11b,c were successfully synthesized with use of pyridinium p-toluenesulfonate mediated cyclization of the ketal intermediate. Diaryl-pyrazolo-benzooxazepine analogues were synthesized by using Cu-mediated cyclization of the O-alkylated arylbromide intermediate. Arylsulfonamides were synthesized efficiently on a large scale with 4-[4-(4-fluorophenyl)-5-hydroxy-2H-pyrazol-3-yl]benzenesulfonamide 31 template readily synthesized from commercially available 4-sulfamoyl benzoic acid 29. The structure of a representative compound from each class was confirmed by X-ray crystallography. Selected compounds tested for inhibitory activity against COX-1 and COX-2 enzymes showed good selectivity for COX-2 versus COX-1 enzyme.

IR-spectral study of photoinduced tautomerization in 1,3-diphenyl-pyrazol-5-one

The UV-photoinduced prototropic isomerization of 1,3-diphenyl pyrazol-5-one (DPhP) embedded in polyvinyl chloride (PVC) film is studied by means of difference in IR spectral analysis. The initially existing CH-form in non-irradiated compound is transformed to NH-form, and a hydrochloride salt is stabilized because of the photodegradation of the PVC. An additional comparative IR spectral study of DPhP in different solutions as well as of its hydrochloride salts in solid state is also carried out.

Structures and Chemical Equilibria of Some N-Heterocycles Containing Amide Linkages

Structures and chemical equilibria of 5-carboxy-2-thiouracil (1), 5,6-diphenyl-3-hydroxy-1,2,4-triazine (2),  1-phenyl-3-methyl-5-pyrazolone (3) and 2-mercapto-4,6-dimethylpyrimidine hydrochloride (4) are reported. Their electronic transitions are assigned and pK values are evaluated and discussed.

Metal-induced cyclization of thiosemicarbazones derived from beta-keto amides and beta-keto esters: open-chain and cyclized ligands in zinc(II) complexes

The reactions of Zn(OAc)(2) with acetoacetanilide, methyl acetoacetate, o-acetoacetanisidide, and ethyl 2-methylacetoacetate thiosemicarbazones (HTSC(1), HTSC(2), HTSC(3), and HTSC(4), respectively) were explored in methanol. With HTSC(1), HTSC(2), and HTSC(3), following isolation of the corresponding zinc(II) thiosemicarbazonates [Zn(TSC(x))(2)] (x = 1, 2, 3), the mother liquors afforded pyrazolonate complexes [ZnL(1)(2)(H(2)O)] (HL(1) = 2,5-dihydro-3-methyl-5-oxo-1H-pyrazole-1-carbothioamide) that had been formed by cyclization of the corresponding TSC(-). The reaction of HTSC(4) with zinc(II) acetate gave only the pyrazolonate complex [ZnL(2)(2)(H(2)O)] (HL(2) = 2,5-dihydro-3,4-dimethyl-5-oxo-1H-pyrazole-1-carbothioamide). All compounds were studied by IR and NMR spectroscopy, and HTSC(3), [Zn(TSC(3))(2)] x DMSO, [ZnL(1)(2)(H(2)O)] x 2DMSO, and [ZnL(2)(2)(H(2)O)] x 2DMSO were also studied by X-ray diffractometry, giving a thorough picture of the cyclization process. In preliminary tests of the effects of HL(1) and [ZnL(1)(2)(H(2)O)] on rat paw inflammatory edema induced by carrageenan, HL(1) showed antiinflammatory activity.

Heterocyclic derivatives of sugars: the formation of 1-glycosyl-3-methylpyrazol-5-ones from hydrazones

Conditions to effect the conversion of monosaccharide and disaccharide hydrazones to 1-glycosyl-3-methylpyrazol-5-ones were examined. The sugar pyrazolone derivatives were sensitive to oxidation, but high yields were achieved with 2,2,2-trifluoroethyl acetoacetate in mildly acidic solution. Azo coupling of the pyrazolones produced highly coloured azopyrazolone derivatives that prevented further degradation, and these may prove useful labels for chromatographic analysis of carbohydrates.