Sayed M. Riyadh

New pyrazoles incorporating pyrazolylpyrazole moiety: Synthesis, anti-HCV and antitumor activity

Three series of novel pyrazole derivatives 2b-d, 4a-d and 6a-d were synthesized via two step procedure that utilizes hydrazonoyl chlorides 1a-d and enaminones 3a-d and 5a-d, respectively as starting materials. The structures of all the newly synthesized products have been established on the basis of analytical and spectral data. Moreover, some of the products 2-6 were tested against HCV and Subacute Sclerosing Panencephalitis (SSPE). In addition, compounds 2-6 were also tested for the inhibition of peroxynitrite-induced tyrosine nitration and antioxidant activity. The tested compounds are highly effective at very low concentration as anti-HCV, SSPE antioxidant and anticancer in the following ascending order 2d, 4c, 6b, 3b, 6c, 4d, 2b, 2c, 2a, 6a, 5b, 5a, 3a, 4b and 5c. It is worth to mention that all tested compounds are more potent than the reference standards used for comparing activity. All the measurements revealed that the mechanism of action of the anti cancer activities of all the tested compounds is topoisomerase I inhibitor.

ENAMINES AS PRECURSORS TO POLYFUNCTIONAL HETEROAROMATIC COMPOUNDS; A DECADE OF DEVELOPMENT

Recent synthesis and utilization of enamines as precursors for heterocyclic and carbocyclic compounds are reviewed. Two general synthetic routes for preparation of enamines based on condensation and addition reactions. Enamines and azaenamines can be used as building blocks for carbocyclic, five-and six-membered heterocyclic as well as fused heterocyclic compounds.

Synthesis under microwave irradiation of [1,2,4]triazolo[3,4-b] [1,3,4]thiadiazoles and other diazoles bearing indole moieties and their antimicrobial evaluation.

Microwave-assisted synthesis of some novel compounds, namely, 3-(2-methyl-1H-indol-3-yl)-6-aryl-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles 5a,b was accomplished via bromination of 2-methyl-3-[4-(arylideneamino)-5-mercapto-4H-[1,2,4]triazol-3-yl]-1H-indoles 3a,b. Also, new [1,3,4]thiadiazoles 12a,b, [1,2,4]triazoles 15a,b and [1,3,4]oxadiazoles 19a,b, with indole moieties, were prepared by cyclization of 1-[(2-methyl-1H-indole)-3-carbonyl]thiosemicarbazides 8a,b under microwave irradiation using different reaction conditions. Moreover, reaction of acid hydrazide 7 with ethyl 2-(N-phenylhydrazono)-3-oxobutanoate (20) gave the respective phenylhydrazonopyrazole derivative 21 under the reaction conditions employed. The structures of the synthesized compounds were assigned based on elemental analyses and spectral data (IR, 1H-NMR, 13C-NMR, MS). The antifungal and antibacterial activities of the new products were also evaluated.

Enaminones as Building Blocks for the Synthesis of Substituted Pyrazoles with Antitumor and Antimicrobial Activities

Novel N-arylpyrazole-containing enaminones 2a,b were synthesized as key intermediates. Reactions of 2a,b with active methylene compounds in acetic acid in the presence of ammonium acetate afforded substituted pyridine derivatives 5a-d. Enaminones 2a,b also reacted with aliphatic amines such as hydrazine hydrate and hydroxylamine hydrochloride to give bipyrazoles 8a,b and pyrazolylisoxazoles 9a,b, respectively. On the other hand, treatment of 2a,b with a heterocyclic amine and its diazonium salt yielded the respective [1,2,4]triazolo[4,3-a]pyrimidines 12a,b and pyrazolylcarbonyl[1,2,4]triazolo-[3,4-c][1,2,4]triazines 14a,b. Moreover, 2-thioxo-2,3-dihydro-1H-pyrido[2,3-d]pyrimidin-4-one (17) was prepared via reaction of enaminone 2a with aminothiouracil (15). Cyclocondensation of 17 with the appropriate hydrazonoyl chlorides 18a-c gave the corresponding pyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidin-5-ones 21a-c. The cytotoxic effects of compounds 2b, 14a and 17 against human breast cell line (MCF-7) and liver carcinoma cell line (HEPG2) were screened and in both lines they showed inhibition effects comparable to those of 5-fluorouracil, used as a standard. The antimicrobial activity of some products chosen as representative examples was also evaluated.

Synthesis and anticancer activity of arylazothiazoles and 1,3,4-thiadiazoles using chitosan-grafted-poly(4-vinylpyridine) as a novel copolymer basic catalyst

A novel series of 4-substituted 5-arylazo-2-[1-(pyrrol-3-yl)ethylidenehydrazinyl]thiazoles and 5-arylazo-2-[1-(pyrrol-3-yl)ethylidenehydrazinyl]-2,3-dihydrothiazol-3-amines was prepared by cyclocondensation of α-oxohydrazonoyl halides with 1-(pyrrol-3-yl)-ethylidenethiosemicarbazide and 1-(pyrrol-3-yl)ethylidenethiocarbohydrazide, respectively. These cyclocondensation reactions were achieved by using chitosan-grafted-poly(4-vinylpyridine) as a novel basic catalyst under microwave irradiation. Furthermore, the reaction of the above mentioned thiosemicarbazide and thiocarbohydrazide with N-phenylbenzenecarbohydrazonyl chlorides (bereft of the α-oxo group) using chitosan-grafted catalyst proceeded via a similar mechanism and afforded the same 2-hydrazono-1,3,4-thiadiazoles. The structures of the newly synthesized compounds were established on the basis of spectroscopic evidences as well as by their synthesis via alternative methods. Finally, the appraisal of the newly synthesized products for their anticancer activity against a colon carcinoma cell line (HCT-116) and liver carcinoma cell line (HEPG2-1) revealed promising activity, especially 4-phenyl- and 4-(thiophen-2-yl)-substituted 1,3-thiazole derivatives.

Novel polyazaheterocyclic systems: Synthesis, antitumor, and antimicrobial activities

A series of new polyazaheterocyclic ring systems was synthesized via the reaction of enaminone 5 with active methylene compounds, hydrazine hydrate, hydroxylamine, and heterocyclic amines. The structures of the newly synthesized compounds were substantiated on the basis of spectral data and elemental analyses. The antitumor activity of the enaminone 5 against the human breast cell line MCF-7, the liver carcinoma cell line HEPG2-1, and HELA cells was determined. In addition, the antimicrobial activity of some selected products was evaluated.

Studies with beta-oxoalkanonitriles: simple novel synthesis of 3-[2,6-diaryl-4- pyridyl]-3-oxopropanenitriles.

Heteroaromatization of ethyl 2-cyano-4-oxo-2-(2-oxo-2-arylethyl)-4-aryl-butanoates 3a,b with ammonium acetate gave ethyl 2,6-diarylisonicotinates 4a,b.Treatment of the latter with acetonitrile afforded novel β-oxoalkanonitriles 6a,b. Reactions of 6a,b with phenyl hydrazine and hydroxylamine gave the corresponding pyridyl aminopyrazoles 8a,b and pyridyl aminoisoxazoles 10a,b, respectively.

Cellulose Sulfuric Acid as an Eco-Friendly Catalyst for Novel Synthesis of Pyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidin-5-ones

A novel synthesis of a series of pyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidin-5-ones has been developed from reactions of 1-(5-methyl-1-phenyl-1H-pyrazol-4-yl)-3-arylprop-2-en-1-ones and 7-amino-1,3-disubstituted[1,2,4]triazolo[4,3-a]pyrimidin-5(1H)-ones in dioxane under thermal conditions, using cellulose sulfuric acid as an eco-friendly acid catalyst. The reaction mechanism was proposed and the structures of the newly synthesized compounds were established on the basis of spectral data (mass spectrometry, infrared, 1H and 13C nuclear magnetic resonance) and elemental analyses.

Synthesis, anticancer, and antimicrobial activities of some new antipyrine-based heterocycles

A facile and convenient synthesis of [1,2,3]triazole, [1,2,4]triazolo[5,1-c][1,2,4]triazine, and pyrazolo[5,1-c][1,2,4]triazine derivatives incorporating an antipyrin-4-yl or antipyrin-4-ylcarboxamide moiety via the versatile, readily accessible 2-cyano-N-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)acetamide is described. Structures of the synthesized compounds were elucidated by means of IR, 1H NMR, 13C NMR, and mass spectral data. The biological activity of the newly synthesized compounds was examined and some of them were found to possess anticancer and antimicrobial activities.Graphical abstract

Rational design, synthesis, pharmacophore modeling, and docking studies for identification of novel potent DNA-PK inhibitors

Drugs of cancer based upon ionizing radiation or chemotherapeutic treatment may affect breaking of DNA double strand in cell. DNA-PK enzyme has emerged as an attractive target for drug discovery efforts toward DNA repair pathways. Hence, the search for potent and selective DNA-PK inhibitors has particularly considered state-of-the art and several series of inhibitors have been designed. In this article, a novel benchmark DNA-PK database of 43 compounds was built and described. Ligand-based approaches including pharmacophore and QSAR modeling were applied and novel models were introduced and analyzed for predicting activity test for DNA-PK drug candidates. Based upon the modeling results, we gave a report of synthesis of fifteen novel 2-((8-methyl-2-morpholino-4-oxo-4H-benzo[e][1,3]oxazin-7-yl)oxy)acetamide derivatives and in vitro evaluation for DNA-PK inhibitory and antiproliferative activities. These fifteen compounds overall are satisfied with Lipinskis rule of five. The biological testing of target compounds showed five promising active compounds 7c, 7d, 7f, 9e and 9f with micromolar DNA-PK activity range from 0.25 to 5µM. In addition, SAR of the compounds activity was investigated and confirmed that the terminal aryl moiety was found to be quite crucial for DNA-PK activity. Moreover flexible docking simulation was done for the potent compounds into the putative binding site of the 3D homology model of DNA-PK enzyme and the probable interaction model between DNA-PK and the ligands was investigated and interpreted.