Synthesis and antioxidant activities of novel N-aryl (and N-alkyl) gamma- and delta-imino esters and ketimines

Novel N-aryl (and N-alkyl) gamma- and delta-imino esters 2a-g (3a-g) and N-aryl (and N-alkyl) ketimines 2h-j (3h-j) were synthesized in high yields (80-99%) from their corresponding gamma- and delta-keto esters and ketones in this study. The structures of the synthesized compounds were clarified by Fourier transform infrared (FT-IR), NMR (H-1 and C-13), mass spectrometry, and elemental analyses. Isomerizations [E/Z] were also determined by their H-1 NMR spectra. The free-radical scavenging activity of imines was evaluated using the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) method. The relationships between the structure and antioxidant activity of these compounds are discussed. Among these compounds, 2a-c (at the concentration 1000 mu g/mL) exhibit high antioxidant activity similar to those of the standards (butylated hydroxyanisole [BHA], butylated hydroxytoluene [BHT], and ascorbic acid).