Design and Synthesis of Polyheterocyclic Compounds Containing Pyrazolopyridopyrimidine Nucleus with Antimicrobial Activities.

This study reports the design, synthesis, and antibacterial evaluation of a library of novel polyheterocyclic derivatives featuring a unique fused pyrimidopyridopyrazole moiety. A cyclocondensation reaction between an amino-pyrazolopyridopyrimidine precursor and malonates afforded a series of pyrimidopyridopyrazolopyrimidine derivatives. Further diversification was achieved through nucleophilic cyclocondensation, yielding a collection of complex polyheterocyclic systems encompassing various ring structures. All synthesized compounds were rigorously characterized using spectroscopic techniques and elemental analysis. The antibacterial activity of the newly synthesized compounds was assessed against a panel of Gram-positive and Gram-negative bacteria. Notably, several compounds exhibited promising antibacterial activity, highlighting their potential as leads for the development of novel antibiotics.

Discovery of Quinazoline-2,4(1H,3H)-Dione Derivatives as Potential Antibacterial Agent: Design, Synthesis, and Their Antibacterial Activity.

In this paper, we report on the design and synthesis of a novel series of quinazoline-2,4(1H,3H)-dione derivatives as fluoroquinolone-like inhibitors of bacterial gyrase and DNA topoisomerase IV to identify and develop antimicrobial agents to prevent bacterial resistance problems. Their structures were confirmed using spectroscopic analyses (IR, NMR, and EI-MS). The novel quinazoline-2,4(1H,3H)-dione derivatives were evaluated for their antimicrobial activities against Gram-positive and Gram-negative bacterial strains using the Agar well diffusion method to study the antimicrobial activities and compared them with the standard drugs. Most compounds displayed moderate activity. Among the tested compounds, the most promising compounds 13 and 15 provided broad bioactive spectrum against Gram-positive and Gram-negative strains compared to the standard drugs.

Synthesis and Antibacterial Activities of Different Five-Membered Heterocyclic Rings Incorporated with Pyridothienopyrimidine.

Certain pyridothienopyrimidine derivatives exhibit antiatheroscleorotic, antibacterial, antiviral, antidepressant, antidiabetic, antihypertensive, anticancer, antihistaminic, antiallergic, anti-inflammatory, spasmolytic, analgesic, and neurotropic activities. 4-Hydrazino-7,9-dimethylpyrido[3',2':4,5]thieno[3,2-d]pyrimidine (1) is a reported pyridothienopyrimidine derivative. In the current study, (1) has been reacted with different reagents to obtain 12 new pyridothienopyrimidine derivatives. The newly synthesized five-membered heterocyclic rings incorporated with pyridothienopyrimidines have been screened for their antibacterial activities. The results encourage further studies on other possible biological activities.

Anti-HIV activity of new substituted 1,3,4-oxadiazole derivatives and their acyclic nucleoside analogues.

A number of new 5-[(naphthalen-5-yloxy)methyl]-1,3,4-oxadiazole derivatives, 2-5 and 8-11, were synthesized. The 2-{5-[(naphthalen-5-yloxy)methyl]-1,3,4-oxadiazol-2-ylthio}acetohydrazones 6a and 6b were synthesized by the reaction of the hydrazide 4 with the corresponding monosaccharides. Cyclization of the sugar hydrazones 6a and 6b with acetic anhydride afforded the substituted oxadiazoline derivatives 7a and 7b. The synthesized compounds were evaluated for their antiviral activity against, the human immunodeficiency virus (HIV-1) and some of these compounds showed moderate to high antiviral activity.

Rapid and efficient synthesis of 4-substituted pyrazol-5-one under microwave irradiation in solvent-free conditions.

New heterocyclic compounds containing pyrazol-5-one coupled with benzimidazole, benzothiazole, benzoxazole, quinoline, naphthyridin, and pyrazole were synthesized. Comparative investigations to synthesize these interesting classes of heterocyclic compounds through conventional heating or under microwave-irradiation conditions were presented. Synthesized compounds 1a, 2a, 4k, 3a, c, 5a, b, 6b, 7a, b, d, 8a, and 9a were evaluated for their antitumor activity. Some of these compounds exhibited promising antitumor activity.

Synthesis of novel acyclonucleosides analogs of pyridothienopyrimidine as antiviral agents.

Nucleoside analogs of pyridothienopyramidines were prepared by condensing the sodium salt 2a,b with an acyclic side chain in the form of acetylated haloalkoxyalcohol, and subsequent removal of the protecting acetyl group in ammonia/methanol afforded 4a,b. The O-tosyl derivative of 4a could then be modified to azido- and amino derivatives. Reaction of the sodium salt of 2b with halo-ether, benzyl halo-ether and/or halo-thioether gave N- and S-alkylated products, 8 and 9, respectively. Coupling of 10 with the sodium salt of 2a,b gave the corresponding dioxolane derivatives 11, 13, and 14, which were treated with 80% acetic acid at room temperature to give diols 12, 15, and 16. Treatment of 16 with tosyl chloride afforded the ditosylate 17 and this could then be modified to diazido and diamino derivatives. Some of the products were screened for their biological activity.

Intercalating nucleic acids: the influence of linker length and intercalator type on their duplex stabilities.

Six new examples of intercalating nucleic acids were synthesized in order to evaluate the dependence of the length of the linker between oligo and intercalator on the thermal stability of their corresponding duplexes and triplexes.