Syntheses of 1 , 2 , 4 Triazole Derivatives and their Biological Activity

Cyclisation of [4-(4-oxo-2-phenyl-4H-quinazolin-3-yl)-phenoxy]-acetic acid-N′-(substituted phenyl)-thiosemicarbazides with sodium metal in 99.0 % ethanol gave 3-[4-(4-substituted phenyl-5-thioxo-4,5-dihydro-1H-1,2,4 triazol-3-ylmethoxy)-phenyl]-2-phenyl-3H-quinazolin-4-one . The structures of the newly synthesized compounds have confirmed by IR, H NMR and Mass spectra. The compounds have also been screened for their biological activity.


Introduction
The chemistry of heterocycles is an interesting branch in organic chemistry.Quinazolinone derivatives derived from 2-phenyl-4H-3,1-benzoxazin-4-one are important compounds in chemistry and pharmacology.They have drawn much attention due to their broad range of pharmacological properties 1 , which include anticancer 2 , anti-inflammatory 3 , anticonvulsant 4 , and antidiuretic 5 activities.Also quinazolinone such as tryptanthrin have been found to have remarkable antimalarial activity 6 .

General procedures
Melting points were taken in open capillaries and are uncorrected.IR spectra (KBr in cm -1 ) were recorded on Jasco 410 plus FTIR spectrophotometer. 1 H NMR spectra were recorded on a JEOL 300 MHz FT-NMR spectrophotometer using DMSO-d 6 as solvent and TMS as internal standard (chemical shifts in δ ppm).The mass spectra of compounds were determined with Schimadzu model No.QP 2010.The elemental analysis was carried out on a Perkin Elmer C,H,N analyzer and sulphur analysis was obtained by oxygen-flask method.The purity of the compounds was monitored by thin layer chromatography.TLC was carried out on precoated 0.2 mm silica gel 60 F 254 plates.
(4-Amino-phenoxy)-acetic acid ethyl ester (4)   Compound 3 (11.85g, 0.05 mole) was suspended in 250 mL ethanol and cooled to 10 °C.To this solution, sulphuric acid (3.0 mL, 0.055 mole) was added dropwise with stirring, maintaining the temperature at 10 -15 °C.The reaction mixture was then refluxed for about 2 hours.The excess ethanol was distilled under reduced pressure and then to one-third of the total volume of the solution, 100 mL water was added followed by 20 % of potassium carbonate solution for neutralization.The product was extracted with 3 x 25 mL of dichloromethane.The dichloromethane layer was washed with 3 x 20 mL of water.The compound 4 obtained on distillation of dichloromethane at atmospheric pressure was dried in an oven at 40 °C and recrystallised from benzene, yield 80 %, m.p. 58 °C; IR (KBr) 3382 (NH 2 ), 1740 (C=O ester), 1558, 1509, 1476 (C=C, aromatic).

Biological Activity Antibacterial activity
All the newly synthesized compounds (8a-d) were screened in vitro for their antibacterial activity against Staphylococcus aureus, Escherichia coli and Bacillus subtilis by the ditchplate technique 20 using concentrations of 50 µg/mL.Nutrient agar was employed as culture media and DMF was used as solvent control for antibacterial activity.

Antifungal activity
The compounds (8a-d) synthesized were screened for their antifungal activity against Aspergillus niger, Candida albicans and Cryptococcus neoformans by paper-disc diffusion method 21 at concentrations of 50 µg/mL.Nutrient agar was employed as culture media and DMF was used as solvent control for antifungal activity.
The known compounds, such as ampicillin, amoxicillin, norfloxacin, penicillin and Griseofulvin were used for comparison purpose.The diameter of zone of inhibition was measured in mm.The antibacterial and antifungal screening data are recorded in Table 1.From the Table 1, it can be seen that the compounds 8c and 8d showed remarkable activity against Staphylococcus aureus, compounds 8b and 8c showed remarkable activity against Bacillus subtilis.The compounds 8c showed good activity against A.niger and the compounds 8a and 8c showed maximum activity against cryptococcus neoformans.

Antimalarial activity
The effort to find new antimalarial activity is still a high priority given to the increasing malarial emergency due to chloroquine resistant Plasmodium falciparum strains.The chloroquine-resistant Plasmodium falciparum malarial parasite was cultured in vitro and the sensitivity of parasite to the newly synthesized compounds was evaluated using the tritiated Hypoxanthine incorporation assay 16 .The compounds (8a-d) were tested for antimalarial activity and the only compound 3-{4-[4-(4-fluoro-phenyl)-4H-[1,2,4]triazol-3-yl-methoxy]-phenyl}-2-phenyl-3H-quinazolin-4-one 8b was found to be most active against Plasmodium falciparum strains and its 50 % inhibitor concentration (IC50) values were 1.2µM.

Table 1 .
Biological activity data