An overview of triazoloquinazolines: Pharmacological significance and recent developments

Nitrogen heterocyclic rings have participated to constitute most of the drugs and several pharmacologically related compounds. The existence of such hetero atoms/groups in heterocyclic systems privileged specificities in their biological objectives. Particularly, quinazoline and triazole are biologically imperative platforms known to be linked with various pharmacological activities. Some of the prominent pharmacological responses ascribed to these systems are analgesic, antiinflammatory, anticonvulsant, hypnotic, antihistaminic, antihypertensive, anticancer, antimicrobial, antitubercular, antiviral and antimalarial activities. This diversity in the pharmacological outputs for both triazole and quinazoline systems has encouraged the medicinal chemistry researchers to create several chemical routes aiming at the incorporation of two rings in one molecule named triazoloquinazoline system. This system has shown multiple potential activities against numerous targets. Correlation the specific structural features of triazoloquinazoline system with its pharmacological purposes has successively been achieved by performing several pharmacological examinations and structure-activity relationship studies. The development of triazoloquinazoline derivatives and the understanding of their pharmacological targets offer opportunities for novel therapeutics. This review mainly emphases on the medicinal chemistry aspects of triazoloquinazolines including synthesis, reactivity, biological activity and structure activity relationship studies (SARs). Moreover, this review collates literature reported by researchers on triazoquinazolines and provides detailed attention on their analogs pharmacological activities in the perspective of drug development and discovery.

Biological effects of a new set 1,2,4-triazolo[1,5-a]quinazolines on heart rate and blood pressure

BACKGROUND

Several quinazoline and triazole derivatives are reported to possess a wide-range of interesting pharmacological effects. Although various triazoloquinazoline subclasses having been synthesized and studied, the preparation of 1,2,4-triazolo[1,5-a]quinazolines as antihypertensive agent is still relatively unexplored. In continuation of our earlier research, we aimed at the synthesis and development of various potent antihypertensive 1,2,4-triazoloquinazoline derivatives.

RESULTS

A new series of 1,2,4-triazolo[1,5-a]quinazoline derivatives have been synthesized. Their structures were mainly established by spectroscopic methods of analysis (IR, MS, 1H and 13C NMR). Their in vivo antihypertensive activity was evaluated by tail cuff method using Muromachi Blood Pressure Monitor (Model MK 2000) for rats and mice. Some of the tested compounds were found to exhibit valuable effects in terms of heart rate and blood pressure. According to the biological results, some of tested derivatives have abolished completely the tachycardia of the parent compounds and may be studied and modified as potential adrenoblockers and cardiac stimulant.

CONCLUSION

New series of fifteen 1,2,4-triazolo[1,5-a]quinazolines were synthesized by convenient methodology from four key molecules, whereby their structures were established by advanced spectroscopic analyses. Some lead compounds have abolished completely the tachycardia of the parent compounds, that may be examined as potent adrenoblockers and some other compounds seem to be a cardiac stimulant or may be modified to enhance their hypotensive activity.

Antimicrobial activity of newly synthesized methylsulfanyl-triazoloquinazoline derivatives

OBJECTIVE

The aim of this research was to study and evaluate the antimicrobial activity of a novel 2-methylsulfanyl-[1,2,4]triazolo[1,5-a]quinazoline and its derivatives. Antibacterial activity of the target compounds was tested against a variety of species of Gram-positive bacteria such as Staphylococcus aureus ATCC 29213, Bacillus subtilis ATCC6633, and Gram-negative bacteria such as Pseudomonas aeruginosa ATCC27953 and Escherichia coli ATCC 25922. In addition some yeast and fungi, Candida albicans NRRL Y-477 and Aspergillus niger, respectively, were screened.

METHODS

Antimicrobial tests were carried out by the agar well diffusion method, using 100 μl of suspension containing 1 × 10(8)  CFU/ml of pathological tested bacteria, 1 × 10(6)  CFU/ml of yeast, and 1 × 10(4)  spore/ml of fungi spread on nutrient agar (NA), Sabourand dextrose agar (SDA), and potato dextrose agar (PDA), respectively.

KEY FINDINGS

The minimum inhibitory concentration (MIC) of the tested compounds was determined using the broth double dilution method (serially diluted technique) in proper nutrient. For comparison, ciprofloxacin and ketoconazole were used as antibacterial and antifungal reference drugs, respectively. Compounds 6, 9, 13, 14, and 11 were found to have the highest broad-spectrum antibacterial activity against S. aureus ATCC 29213, B. subtilis ATCC6633 and Gram-negative bacteria such as P. aeruginosa ATCC27953 and E. coli ATCC 25922 with MIC values of 6.25 and 12.50 μg/ml.

CONCLUSIONS

It was clear that many of the synthesized compounds exhibited good antimicrobial activity. This study has revealed that compounds 6, 9, 13, 14, and 11 have been disclosed as moderate antimicrobial agents. These compounds could be useful as templates for further development through modification or derivatization to design more potent antimicrobial agents.

Synthesis and Reactivity of [1,2,4]Triazolo-annelated Quinazolines

This paper reports the synthesis of phenyl-substituted 2-alkoxy(methylsulfanyl)-1,2,4-triazolo[1,5-a]quinazolines starting from N-cyanoimidocarbonates and substituted hydrazinobenzoic acids as building blocks. Thionation or chlorination of the inherent lactam moiety in the target compounds followed by treatment with multifunctional nucleophiles provided access to a variety of derivatives.