Disclosed are process for producing a compound having NPYY5 receptor antagonism and useful crystals. A process for producing a compound represented by the formula (IV): wherein R 1 is substituted or unsubstituted alkyl, R 2 is substituted or unsubstituted alkyl, and n is 1 or 2, or the like, which comprises reacting a compound represented by the formula (II): wherein R 1 and n are as defined, above, and X is a leaving group, or the like and a compound represented by formula (III): wherein R 2 is as defined above, or the like.
