Synthetic modifications of carboline alkaloid harmine: synthesis of 8-substituted derivatives

Hybrid molecules containing β-carboline and 1-acetylpyrazoline moieties were obtained on the basis of the alkaloid harmine. The synthetic procedure included acetylation of harmine with acetyl chloride in the presence of tin(IV) chloride, Claisen–Schmidt condensation with benzaldehydes under basic conditions, and cyclization of the obtained chalcones by the action of hydrazine hydrate and acetic acid. In addition, a method was proposed for the preparation of 8-formylharmine by treating harmine with dichloromethoxymethane in the presence of tin(IV) chloride. The structures of the synthesized compounds were confirmed by NMR spectra, mass spectra, and X-ray structural analysis.