New Phosphoramidate Derivatives of 5-Nitroquinolin-8-ol: Synthesis, Spectral Characterization, and Evaluation of Biological Activity

GRAPHICAL ABSTRACT

Abstract

Synthesis of a series of new 14 phosphoramidate derivatives, 4-nitrophenyl-5-nitroquinolin-8-yl-substituted amino phosphonates/phosphoramidates 11(a–g) and 4-chlorophenyl-5-nitroquinolin-8-yl-substituted amino phosphonates/phosphoramidates 12(a–g) from 5-nitroquinolin-8-ol (5) was accomplished for biological interest. The structures of the newly synthesized compounds were elucidated by spectroscopic data and elemental analysis. Their antimicrobial (100 and 200 μg/mL) and antioxidant (50 and 100 μg/mL) activities were evaluated, and their minimum inhibitory concentration (MIC) and IC₅₀ values were also examined. A few of the compounds, namely 11d, 11e, 11g, and 12d, showed potent antimicrobial activity against tested microbial pathogens, and compounds 11d, 12c, 12d, and 12g exhibited promising radical (DPPH and NO) scavenging activity in the two tested methods. The overall biological activity results disclosed that 1-(4-nitrophenyl)piperazine (11d and 12d)-, 4-fluorophenyl methanamine (11e and 12e)-, and pyridine-3-yl methanamine (11g and 12g)-substituted compounds exhibited potential activity. The majority of the title compounds acted as promising antimicrobial agents as compared with antioxidant agents.

Keywords:

• Phosphoramidates
• 5-nitroquinolin-8-ol
• 4-nitrophenyl dichlorophosphate
• 4-chlorophenyl dichlorophosphate
• antimicrobial activity
• minimum inhibitory concentrations
• antioxidant activity
• half-maximal inhibitory concentrations