Synthesis of novel МТ3 receptor ligands via an unusual Knoevenagel condensation.

New 5-acetamido-substituted melatonin derivatives were efficiently synthesized in excellent yields via Knoevenagel condensation. The relative binding affinity of new synthesized compounds to MT3 receptor was tested via enzymatic assays and the X-ray structures of the most potent compounds were determined in complex with MT3.