A compound of interest whose R3 is a halogen atom, for example, a compound whose R3 is fluorine atom, can be obtained by treating a compound having a hydroxyl group at the 7-position with diethylaminosulfur trifluoride in tetrahydrofuran, methylene chloride, ethyl ether, toluene, 1,1-dimethoxyethane or a mixture solvent thereof.