Synthesis, structural determination, and biological activity of new 7-hydroxy-3-pyrazolyl-4H-chromen- 4-ones and their o-β-D-glucosides

A convenient route to synthesize some new medicinally important 7-hydroxy-3-pyrazolyl chromones (3ai) is described. The interaction of 7-hydroxy-3-formyl chromone (1) with various substituted acetophenones and further cyclization with hydrazine hydrate in an aprotic solvent followed by condensation with 2, 3, 4, 6-tetra-o-acetyl-α-d-glucopyranosyl bromide afforded 2, 3, 4, 6-tetra-o-acetyl-β -d- glucopyranosyloxy- 3-(3-aryl-1H-pyrazol-5-yl)-4H-chromen-4-ones (4a-i). Later deacetylation with anhydrous zinc acetate in methanol gave 7-o-β -d-glucopyranosyloxy-3-(3-aryl-1H -pyrazol-5-yl)-4H-chromen-4-ones (5a-i). These compounds were evaluated for their in vitro antimicrobial and anti-oxidant activity. The structures of these newly synthesized o-glucosides were established by IR, NMR, mass spectra, elemental analysis, and chemical analysis.