New N-Substituted (E)-4-Arylidene Isoquinoline-1,3-dione Derivatives: NMR Spectroscopic Investigation and Antibacterial Activity

Abstract

New N-substituted 4-arylidene-isoquinoline-1,3-dione derivatives were obtained as one geometrical isomer by aldol condensation of the appropriate aldehyde and the corresponding N-substituted homophthalimides. The structural elucidation of compounds 3a–h was established by infrared and NMR spectroscopy including ¹ H, ¹³ C, CH CORR, and distortionless enhancement by polarization transfer measurements. Compounds 3d–h were evaluated for their antibacterial activity against some strains of bacteria using the disc diffusion method and microdilution tests.

GRAPHICAL ABSTRACT

Keywords:

• Antibacterial activity
• ASIS effect
• (E)-4-arylidene-N-methyl-(2H)-isoquinoline-1,3-diones
• (E)-4-arylidene-N-phenyl-(2H)-isoquinoline-1,3-diones
• IR and NMR spectra

ACKNOWLEDGMENT

The authors are grateful to Direction Générale de la Recherche Scientifique of the Tunisian Ministry of Higher Education Scientific Research and Technology for the financial support of this research.

Notes

^a Yields of isolated products after crystallization.

^a Chemical shifts (in ppm, δ _TMS at 0 ppm) and coupling constants (in Hz) at 300 MHz in CDCl₃ solution. The assignments were supported by 2D-XH CORR measurements.

^b In KBr discs (cm⁻¹).

^c Side chain.

Note. DD, diameter of zone of inhibition (mm) including disc diameter of 6 mm; MIC, minimum inhibitory concentrations; MBC, minimum bactericidal concentrations values given as mg mL¹.

^a Tested at a concentration of 1 mg mL⁻¹.

^b Tested at a concentration of 0.5 mg mL⁻¹.

^c Tested at a concentration of 6 µg/disc.