Synthesis of some new phosphate esters containing three 1,3,4-oxadiazole units and studying their biological activity

Abstract EN

Condensation of three equivalents of p-cresol with phosphorus oxychloride afforded tri (p-cresyl) phosphate [1].

Oxidation of the three methyl groups in compound [1] was carried out using potassium permanganate in pyridine yielded tri (4-carboxyphenyl) phosphate [2].

This compound underwent addition–cyclodehydration reactions with 4-methoxybenzoyl hydrazine to produce tri-[4-(5-p-methoxyphenyl-1,3,4-oxadiazol-2-yl) phenyl] phosphate [3].

The 5-(4-hydroxyphenyl)-1,3,4-oxadiazole-2-thiol [5] was obtained by the reaction of 4-hydroxybenzoyl hydrazine [4] with carbon disulfide under basic condition.

Reaction of compound [5] with appropriate alkyl halide afforded 5-(4-hydroxyphenyl)-1,3,4-oxadiazol-2-thio alkyl [6 – 8].

Condensation of three equivalents of appropriate phenolic compounds [6 – 8] with phosphorus oxychloride in the presence of pyridine as proton accepter yielded tri-[4-(5-alkyl thio-1,3,4-oxadiazol-2-yl) phenyl] phosphate [9 – 11].

All the synthesized compounds were characterized by their melting points, and spectral (FT-IR, mass, 1H-NMR and UV) data.

The newly phosphate esters synthesized compounds were subjected to in vitro testing against two strains of pathogenic microorganism viz., Staphylococcus aureus and Escherichia coli.

The results obtained revealed that compounds [2,9,10 and 11 ] showed considerable activity against the two types of bacteria, while compounds [1 and 3] showed considerable activity against Escherichia coli.