Synthesis and Antimicrobial Activity of Methoxy- Substituted γ-Oxa-ε-lactones Derived from Flavanones.

Six γ-oxa-ε-lactones, 4-phenyl-3,4-dihydro-2-1,5-benzodioxepin-2-one () and its five derivatives with methoxy groups in different positions of A and B rings (-), were synthesized from corresponding flavanones. Three of the obtained lactones (,,) have not been previously described in the literature. Structures of all synthesized compounds were confirmed by complete spectroscopic analysis with the assignments of signals on H and C-NMR spectra to the corresponding atoms. In most cases, lactones - exerted an inhibitory effect on the growth of selected pathogenic bacteria (, , and ), filamentous fungi (, , and sp.), and yeast (). The broadest spectrum of activity was observed for unsubstituted lactone , which was particularly active against filamentous fungi and yeast. Lactones with methoxy groups in the 3' () and 4' () position of B ring were more active towards bacteria whereas lactone substituted in the 7 position of the A ring () exhibited higher antifungal activity. In most cases, the introduction of lactone function increased the activity of the compound compared to its flavonoid precursors, chalcones -, and flavanones -.