An Improved Synthesis of Apigenin

Two routes for the synthesis of the flavone apigenin are described. In the first, taxicatigenin was converted to 2-hydroxy-4,6-dimethoxyacetophenone and then by condensation with anisaldehyde to 2′-hydroxy-4,4′,6′-trimethoxychalcone. The latter was cyclised with iodine and demethylated with pyridine hydrochloride to form apigenin in 53% overall yield. In the second route, a single step for the preparation of the chalcone was used in which 1,3,5-trimethoxybenzene was acylated with p-methoxycinnamic acid. Although the synthesis of apigenin was achieved in a lower overall yield of 34%, the process was simpler.