<；p>；<；P>；PROBLEM TO BE SOLVED: To provide a method for efficiently and industrially advantageously producing (Z)-11-(3-dimethylaminopropylidene)-6,11-dihydrodibenzo[b, e]oxepine-2-acetic acid without scaling. <；P>；SOLUTION: The method for producing the (Z)-11-(3-dimethylaminopropylidene)-6,11-dihydrodibenzo[b, e]oxepine-2-acetic acid represented by formula [II] or an acid-addition salt thereof includes heating a 6,11-dihydrodibenzo[b, e]oxepine-2-acetic acid ester derivative represented by formula [I] [wherein R<；SP>；1<；/SP>；, R<；SP>；2<；/SP>；, and R<；SP>；3<；/SP>；are each alkyl or the like] in the presence of an acid or the like selected from hydrogen chloride, sulfuric acid, methanesulfonic acid and p-toluenesulfonic acid in a solvent. <；P>；COPYRIGHT: (C)2010,JPO&INPIT <；/p>；[JP2010150226A]
