Microwave assisted synthesis of novel spiro diarylidenes and their antimicrobial assay Scientific paper

Abstract

A rapid and high yield microwave assisted synthesis of a series of novel 7,9-bis-(arylidene)-4-methyl-2,6,10-triphenyl-2,3-diazaspiro[4,5]dec-3-ene-1,8-dione has been explored. The spiro diarylidene derivatives having nit­rogen atom and α,β-unsaturated ketone moiety were synthesized by aldol con­densation between 4-methyl-2,6,10-triphenyl-2,3-diazaspiro[4,5]dec-3-ene-1,8-dione and corres­pon­d­ing aryl aldehydes followed by dehydration. The syn­thesized series of novel spirodiarylidene derivatives were characterized using IR, ¹H- and ¹³C-NMR and mass spectra. Density functional theory (DFT) study was performed by Gaussian 09 software. The antimicrobial activities of the synthesized derivatives were evalu­ated against two pathogenic Gram-positive and Gram-negative bacterial strain and three pathogenic fungal species by disk diffusion method. The minimum inhi­bitory concentration was determined by the microbroth dilution technique. The results of the present study demon­strated that the examined compounds marked 5a and 5c, possessing 4-NO₂ and 5-Br-2-OH substituents, are found to be more active against Gram-positive bacterium Staphylococcus aureus, 8 and 16 µg mL^-1, respectively, and moder­ately active against Gram-negative bacteria Pseudomonas aeruginosa and Escherichia coli, compared to other synthetic derivatives. However, none of the synthesized derivatives showed any activity against Streptococcus pyro­genes. Compound 5e, possessing 2,4,6-(OCH₃)₃C₆H₃ moiety, exhibited broad spectrum activity against all fungal strains under study, but showed no anti­bacterial activity.