PURPOSE: To obtain the titled compound which is a synthetic intermediate for medicines, etc., in high purity, by de-tert-butylating a readily available 3-(3,5- ditertiary butyl-4-hydroxyphenyl)propionic acid as a raw material in the presence of an acidic substance.

CONSTITUTION: 3-(3,5-Ditertiary butyl-4-hydroxyphenyl)propionic acid or an ester thereof is used as a raw material and de-tert-butylated in the presence of an acidic substance, such as sulfuric acid or trifluoroacetic acid, in a solvent, such as benzene or chloroform, while cooling or at a temperature of room temperature W boiling point of the solvent used to afford the aimed compound expressed by the formula (R1 is H or tertiary butyl; R2 is H or alkyl).