Semisynthesis of bioactive flavonols and aurones from naringin

Abstract

Four natural flavonols kaemferol (1), 3-hydroxy-5,7,4'-trimethoxy flavone (2), 3,5-dihydroxy-7,4'-dimethoxyflavone (3), rhamnocitrin (4) and two novel aurones 4,6,4'-trihydroxydihydroaurone (5), 4-hydroxy-6,4'- dimethoxydihydroaurone (6) were semisynthesized by reaction steps including glycoside hydrolysis, dehydrogenation, benzyl protection, O-methylation, dimethyldioxirane (DMDO) oxidation or Algar-Flynn-Oyamade (AFO) reaction and debenzylation. The synthetic methods of DMDO oxidation for flavones to flavonols and AFO reaction for chalcones to aurones were efficient improved in the key steps. The structures of all synthetic compounds have been confirmed by NMR, IR and MS techniques. The synthetic methods have the advantages of easy availability of starting materials, simple operation and good yields, so it has considerable practical value. © 2012 Chinese Chemical Society & SIOC, CAS.