Complete assignment of the 1H and 13C NMR spectra of antimicrobial 4-arylamino- 3-nitrocoumarin derivatives

Abstract

Herein, we describe the synthesis and complete assignment of the (1)H and (13)C NMR chemical shifts of a series of antimicrobial 4-arylamino-3-nitrocoumarin derivatives based on a combination of (1)H and (13)C NMR, (1)H-(1)H-COSY, NOESY, HSQC and HMBC experiments. Conformational effects upon the chemical shifts of the coumarin moiety arising from the anisotropy of the aryl side group are briefly discussed. This study provides the first complete and fully assigned NMR data for this important group of antimicrobial compounds and bridges the gap existing in the literature with regard to NMR structural data for 4-arylamino-3-nitrocoumarins.