Amino Acid-Based Cinnamoyl Thiourea Ligands and Their Copper(II) Complexes: Synthesis, in Silico, and Antibacterial Evaluation

Brandon Sanday, Mominn and Maya Asyikin, Mohamad Arif (2025) Amino Acid-Based Cinnamoyl Thiourea Ligands and Their Copper(II) Complexes: Synthesis, in Silico, and Antibacterial Evaluation. ChemistrySelect, 10 (47). pp. 1-11. ISSN 2365-6549

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Abstract

Three amino acid-based cinnamoyl thiourea compounds (1–3) as potential antimicrobial agents has been synthesized, focusing on optimizing their pharmacokinetic profiles. Molecular docking simulations against the DNA gyrase enzyme (PDB ID: 1KZN) yielded encouraging results, with docking scores between −5.7 and −7.1 kJ mol−1. The ligands also demonstrated favorable drug-like properties, obeying Lipinski's rule of five and showing predictions for high gastrointestinal absorption and low blood–brain barrier (BBB) permeability. Interestingly, the corresponding Cu(II) complexes (1a–3a) exhibited even stronger binding affinities, with docking scores ranging from −7.2 to −8.2 kJ mol−1. The successful synthesis of the thiourea ligands was confirmed by FTIR spectroscopy which displayed characteristic N─H and C═S stretches at 3165–3056 cm−1 and 1293–1269 cm−1, respectively. In the 1H NMR spectra, the presence of CONH and CSNH signals in the δ 11.43–11.13 ppm region further supported the proposed structures. The formation of the Cu(II) complexes was confirmed by the disappearance of the carbonyl band of the carboxylate group at 1731–1716 cm−1 in the FTIR spectra indicated that the carboxylate group coordinated with the Cu(II) center. Antibacterial assays showed that compound 2, complexes 1a and 2a, possessed promising activity against the E. coli strain, producing clear inhibition zones of 10–13 mm.

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