Novel synthesis of antibacterial pyrone derivatives using kinetics and mechanism of oxidation of azithromycin by alkaline permanganate

Abstract

Dimethylamino-2H-5-dihydropyrane-6-methyl-4-one (DADHP) is a novel antibacterial pyrones derivatives and potential pharmaceutical that was quantitatively synthesized by oxidizing azithromycin (AZ) antibiotic with potassium permanganate in an alkaline medium (pH > 12). The oxidation reaction was kinetically studied using spectrophotometric technique at ionic strength equal to 0.02 mol dm−3. The redox reaction was discovered to have two separate stages that could be measured. The first stage was relatively fast and corresponding to the formation of coordination intermediate complexes involving blue hypomanganate (V) and/or green manganate (VI) transient species. Variable parameters like as the concentration of permanganate ion and AZ substrate, as well as pH and ionic strength, have been studied to see how they affect oxidation rates. The experimental results showed a first-order dependency in [MnO4-] and fractional first-order kinetics in each of [AZ] and alkali concentration under pseudo-first-order reaction conditions of [AZ] ≫ 10 [MnO4-]. The oxidation process was base-catalyzed, and the oxidation rates increased as the alkali concentration increased. The product was confirmed by Fourier Transform Infrared spectroscopy (FTIR), elemental analysis, condensation tests with 2,4-dinitrophenyl haydrazine and hydroxyl amine, and GC-Mass. The oxidation product obtained can be employed as interesting class of organic compounds with diverse chemical and pharmacological applications.