alkyl group having 1 to 3 carbon atoms, --COOH, --COOR (wherein R is an alkyl group having 1 to 3 carbon atoms), B is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; and Z is a hydroxy group, an alkoxy group having 1 to 3 carbon atoms or an alkyl group having 1 to 3 carbon atoms; particularly preferred are in the case where A is a hydrogen atom, a methyl group, --COOH, B is a hydroge