Synthesis, characterization, antimicrobial and antioxidant activity of 2- (2′-hydroxyphenyl) -1,3,4-oxadiazolyl-5-amino acid derivatives

The synthesis and biological assessment of 2,5-disubstituted-1,3,4-oxadiazoles derivatives from amino acids as new potential antibacterial and antioxidant agents have been reported. The structures of the new synthesized compounds were characterized based on physicochemical and spectral data UV–Visible, IR, 1HNMR, 13CNMR. All the target compounds were screened for their in vitro antibacterial activity against three Gram-positive bacterial strains, namely Staphylococcus aureus ATCC 25923, Bacillus cereus ATCC 14579, Listeria innocua ATCC 33090, and two Gram-negative bacterial strains, namely Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922, and antifungal activity against Candida albicans ATCC 10231 in comparison with Amoxicillin, Tetracycline, Gentamicin and Oxacillin. The only compound 1-{(4S)-4-amino-4-[5-(2-hydroxyphenyl)-1,3,4-oxadiazol-2-yl]butyl}guanidine 5e with the amine radical that showed excellent results against all bacteria, particularly against L. innocua (IZ = 12 mm), has excellent antifungal activity (IZ = 32 mm). The compounds 2-[5-(1-amino-3-methylbutyl)-1,3,4-oxadiazol-2-yl]phenol 5b and 2-[5-(pyrrolidin-2-yl)-1,3,4-oxadiazol-2-yl]phenol 5j have excellent activities (IZ = 27 and IZ = 28 mm, respectively) against B. cereus and P. aeruginosa. Compounds 2-{5-[(1R)-1-amino-2-sulfanylethyl]-1,3,4-oxadiazol-2-yl}phenol 5c, 2-{5-[(1S)-1-amino-3-(methylsulfanyl)propyl]-1,3,4-oxadiazol-2-yl}phenol 5d with the sulfur radical, 3--[5-(2-3-amino hydroxyphenyl)-1,3,4-oxadiazol-2-yl]propanamide 5g with the amide radical, 5j with the amino radical, and 4-amino-4-[5-(2-hydroxyphenyl)-1,3,4-oxadiazol-2-yl]butanoic acid 5k gave good results against B. cereus, where 19 mm