abstract |
Olopatadine, which is useful as a pharmaceutical agent, can be produced with efficiency and in an industrially advantageous manner by heating a dibenzoxepin derivative represented by the formula [I] or a salt thereof in a solvent in the presence of an acid. (I) wherein Me represents a methyl group; and R1, R2 and R3 independently represent an alkyl group having 1 to 4 carbon atoms. |