Alternatively, the starting compound (II) in which either one of R2 and R4 is a lower alkyl group and the other is hydrogen atom and R1 and R3 are hydrogen atom may be prepared by reacting the compound of the formula: ##STR6## wherein Ring A and R7 are the same as defined above, with the compound (VII) in the presence of an alkali metal carbonate in a solvent, reacting the product with a lower alk