The present invention provides: a methyl 1-{2-[(3S,4R)-1-[(3R,4R)-1-cyclopentyl-3-fluoro-4-(4-methoxyphenyl)pyrrolidine-3-carbonyl]-4-(methoxymethyl)pyrrolidin-3-yl]-5-(trifluoromethyl)phenyl}piperidine-4-carboxylate 1/2 ethane-1,2-disulfonic acid which is represented by formula (1) and is excellent in crystallinity； and a method for producing the same； and a production intermediate thereof； and a production method using this compound.
