New Synthesis of Thiophene-3,4-Imido Amino Acid Esters and Investigation of Their Electrochemical Behaviors

Benzotriazole-mediated thiophene-3,4-imido-L-amino acid esters (L-phenylalanine methyl ester, L-tyrosine methyl ester, and L-aspartic acid methyl ester) were synthesised from thiophene-3,4- dicarboxylic acid via thiophene-3,4-anhydride to model the reactions of aromatic, phenolic, and polar amino acids, respectively. In synthetic studies, L-amino acids were first reacted with thiophene-3,4- anhydride to produce thiophene intermediates with a carboxylic acid group in the 3-position and an amide group in the 4-position. These intermediates' carboxylic acid functions were then activated using the N-acylbenzotriazole method. This resulted in an in situ cyclisation reaction that was distinct from conventional N-acylbenzotriazole reactions. This reaction formed the target products -thiophene- 3,4-imido-L-amino acid esters- in good yields. The electrochemical properties of the thiophene-3,4- imido amino acid ester derivatives, which are free from the 2,5-position of thiophene, were investigated. The structures of thiophene-3,4-imido amino acid esters were examined using 1H and 13C NMR spectroscopy.