Crystal structure and optical activity of 2-(3,4-dimethoxyphenyl)-4-oxo-4H-chromen-3-yl acetate

Key words: 
• flavonoids /
• X-ray single crystal diffraction /
• optical activity

Abstract: Objective To investigate the structure and optical activity of flavonoid derivative:2-(3,4-dimethoxyphenyl) -4-oxo-4H-chromen-3-yl acetate ( 4 ). Methods The absolute configuration was obtained by X-ray single crystal diffraction. The optical rotation of the compound was determined by the SGW^® -1 automatic polarimeter. Results X-ray single crystal diffraction showed that compound 4 belongs to the orthorhombic space group P2₁2₁2₁ with a=7.763 (2)Å, b=13.930 (4)Å and c=14.906 (4), α=β=γ=90.00°, V=1611.91 (8) ų, Z=8. There is no hydrogen bonding between the molecules in this crystal state. The molecules maintain their stable arrangement in space by van der Waals forces. It can be seen from the single-crystal data that there is a 33.9 (2)° torsion of the dimethoxy-substituted benzene ring in the compound 4 with respect to the 4H-chromene skeleton, suggesting that there may exist optical activity. Further experimental results of the optical rotation proved that the compound has a L-rotatory, specific rotation[α]_D^19.1=-5.077°. Conclusion The results of the single crystal indicated that the benzene ring substituted with dimethoxy group in compound 4 has a 33.9 (2)° torsion relative to the 4H-chromene skeleton, which results in chirality and optical activity. This is the first report that non-flavonoid-glycoside has optical activity.