Abstract: This invention concerns a process for producing phenolic substances with beneficial biological activities in a high yield, which comprises: subjecting a glycose of which an OH group at the 1 position is substituted for a halogen atom and of which other groups are substituted for acyl groups, and a phenol of which at least one of the ortho-positions in regard to phenolic OH groups is substituted to reaction with an alkali metal hydride in dimethylsulfoxide or dimethylformamide in the presence of or non-presence of a quat-ammonium salt and then hydrolyzing said acyl groups with an alkaline substance.