Synthesis, bioassay, crystal structure and ab initio studies of Erlenmeyer azlactones

Several 4-arylidene-2-phenyl-5(4H)-azlactones have been synthesized via Erlenmeyer method. The synthesized compounds have been characterized on the basis of systematic spectral studies (IR, (1)H NMR, (13)C NMR, and MS). The compound (4Z)-4-(3,5-dimethoxybenzylidene)-2-phenyl-1,3-oxazol-5(4H)-one, C(18)H(15)NO(4), (5), crystallizes in the orthorhombic system, space group P2(1)2(1)2(1), with a=5.6793(3) Å, b=15.2038(7) Å, c=17.6919(10) Å, Mr=309.31, V=1527.64(14) Å(3), Z=4 and R=0.0547. The compound (4Z)-2-phenyl-4-(3,4,5-trimethoxybenzylidene)-1,3-oxazol-5(4H)-one, C(19)H(17)NO(5), (6) crystallizes in triclinic geometry with space group P-1, having unit cell parameters a=7.3814(3) Å, b=8.1446(3) Å, c=13.9845(5) Å, α=86.918(3), β=83.314(2), γ=82.462(3), Mr=339.34, V=827.16(5) Å(3), Z=2 and R=0.0433. The DFT calculations of compounds (5) and (6) have been carried out to ascertain the stability of Z-conformer. The in vitro antimicrobial activity of all the compounds (1-6) was evaluated by the disk diffusion method against gram +ve and gram -ve microorganism and fungal strains. The MIC of the synthesized compounds was determined by agar well diffusion method in 96-well microtiter plate. All the synthesized compounds were also screened for their free radical scavenging activity by DPPH method.