Method of Producing an Alkoxyflavone Derivative

A method of producing an alkoxyflavone derivative involves a step of reacting hydroxyflavone derivative which is shown in the below chemical formula and dialkyl sulfate in the presence of dimethyl sulfoxide and an alkali hydroxide. Futher, in the chemical formula below, R11-R14, R21-R25 and R3 are independently one of hydrogen, hydroxyl group, ester group, alkoxy group, alkylenedioxy group, sulfonyl group and alkyl group, respectively. However, at least two of  R21-R25 and R3 are hydroxyl groups.