Synthesis And Antibacterial Activities Research Of N-Halogenated-O-Hydroxyphenyl-Substituted Amino Acid Derivatives

As well known, the amino acids were used in bactericidal field widely. So the series of N-(2-hydroxyphenyl)-amino acids derivatives and their complexes were synthesized based on the key structures"2-hydroxyphenyl, 2-hydroxy-halophenyl"which played an important role for killing the ptthogenic germs. The inhibitory activities of most compounds were tested. For the difference of structure, the systhesized compounds were classified as below:1. N-(5-chloro-o-hydroxyphenyl) amino acids and its estersSalicylaldehyde or halogenated-salicylaldehyde was condensed with L-α-amino acids or its ester derivatives in the presence of sodium hydroxide to obtain amino acid Schiff bases, then the Schiff bases were reduced by NaBH4 to produce o-hydroxylbenzyl-amino acids and their derivatives. It shows that, the reaction rate was influenced by the space position resistance.The smaller space position resistance was, the faster the reaction rate was. N-(5-hydroxy-o-hydroxyphenyl) glutamic acid, which the substituent is carboxyl, has high inhibitory ratio to Escherichia coli; N-(5-chloro-o-hydroxyphenyl) phenylalanine and N-(5-chloro-2-hydroxyphenyl) tryptophan, which the substituents are aromatic ring and nitrogen heterocycle, the inhibition to Monilia albicans is much higher. The antibacterial property of ester derivatives has obvious selectivity and specificity. N-(5-hydroxy-o- hydroxyphenyl) glutamate methyl has high inhibitory ratio to Monilia albicans, N-(5-hydroxy-o-hydroxyphenyl) glutamate ethyl ester has high inhibitory ratio to Escherichia coli in contrast.2. N-(5-chloro-o-hydroxyphenyl) amino acid copper complexesN-(5-hydroxy-o-benzyl) amino acid and copper nitrate in water and methanol mixed solvents at room temperature to generate complexes, the molar ratio of ligand and copper ion is 1:1. Complexes are green powder; the colors were different for the different groups. The products dissolved difficultly in water but easily in ethanol. It was determined that hydroxyl group, amine group and carboxyl group were coordinate with copper. The inhibition effect to Monilia albicans and Escherichia coli of this kind of complex is far exceeds to its relevant ligand, but the inhibition of complex to Staphylococcus aureus is not higher than its relevant ligand.3. N-(o-hydroxy-benzylacyl) amino acid compoundsAs the starting material, methyl salicylate is brominated and gydrazinolysed, which is produced Schiff base with glyoxylic acid and acetone acid, etc. then reduced by NaBH4. It shows that after the substituted in benzene ring, the rate and conversion of the reaction were enhanced. These kinds of products were exhibited high inhibitory ratio to Escherichia coli and Staphylococcus aureus.Based on the characteristics of compounds, the methods of bactericidal test were revised, the experimental conditions were studied and the neutralizers were selected. It showed that some of the compounds had bactericidal activities; the minimal inhibitory concentration (MIC)was less than the minimal bactericidal concentration (MBC).