PRODUCTION OF BENZOFURO(3,2-C)QUINOLINE DERIVATIVE

PURPOSE:To obtain, with industrial advantage, the subject compound, having bone absorb-depression and forming-efacient effects and useful as a remedy for osteroporosis, by treating a specified compound with hydrobromic acid. CONSTITUTION:Preferably, 200-1000 equivalents hydrobromic acid is added to a compound represented by formula I (R is H or lower alkyl; R2 is H or lower alkoxy) [e.g., 3-(2,4-dimethoxyphenyl)-4-hydioxy-7-methoxy-1H-quinolin-2- one], refluxed while being heated for 5-6days, allowed to cool and subsequently filtered to collect precipitated crystals. The obtained crystals are washed using water and ethanol and dried, thus obtaining the aimed compound expressed by formula II (R3 is H or OH).