STUDIES ON SYNTHESIS OF 6, 8-DIMETHYL-5, 7, 4′-TRI HYDROXYL FLAVANONE

Farrerol (Ⅴ) has been isolated from the leaves of Rhododendron dauricurn L. (Man-Shan-Hong) of Heilongjiang province. Its structure is ascertained s 6, 8-dimethyl-5,7,4′-trihydroxyflavanone, which is a phlegm-reducing principle.We report here two routes of syntheses for farrerol (Ⅴ). The first is condensation of compound Ⅰ with compound Ⅳ to give compound Ⅵ, followed by a Fries reaction and cyclization. The second route makes use of the condensation of compound (ⅩⅣ) with p-hydroxybenzaldehyde (Ⅻ) in the presence of boric acid using ethylene glycol as a diluent.Synthetic (±)-farrerol was found to be identical with the natural specimen by IR and NMR spectra. They were also comparable pharmacologically, toxicologically and clinically.