Synthesis and antioxidant activity of some indole-amino acid esters

In the present work, a series of amino acid–indole ester conjugates were prepared by incorporating the pharmacologically significant indole scaffold with amino acid moieties. To achieve this, Z- or Boc-protected amino acids were first activated via either the benzotriazole approach or the DCC-mediated coupling procedure and then esterified with 2-hydroxymethylindole to generate the target indole-based amino acid esters. Structural characterization of the synthesized compounds was accomplished using a combination of spectroscopic and analytical methods, including IR, NMR, mass spectrometry, and elemental analysis. Evaluation of the antioxidant properties revealed that the tryptophan-containing derivative (4) and the methionine-containing derivative (2) displayed the most pronounced antioxidant activity relative to the reference compound BHA.