The present invention relates to novel pyrrolidine compounds or pharmacologically acceptable salts thereof, which have melanocortin receptor agonist activity, and medical use of the same. The present invention relates to pyrrolidine derivatives of the general formula [I] wherein Ring A is an optionally substituted aryl group, for example； R1 is an optionally substituted alkyl group, for example； R2 is a halogen atom, for example； R3 is an alkyl group substituted by an optionally substituted aryl group, for example, and R4 is hydrogen atom, for example； or R3 and R4 bind each other at their ends to form a nitrogen-containing aliphatic heterocycle together with the nitrogen atom to which these groups attach, the heterocycle optionally partly containing a double bond and being optionally substituted, or a pharmacologically acceptable salt thereof.本發明係關於具有黑皮質素受體促效活性之新穎吡咯啶化合物或其藥理上可容許之鹽以及其醫藥用途。本發明係關於通式[I]所示之吡咯啶衍生物、或其藥理上可容許之鹽：[式中，環A表示可經取代之芳基等；R1表示可經取代之烷基等；R2表示鹵素原子等；R3為經可經取代之芳基所取代之烷基等，且R4為氫原子等；或者，R3及R4互相以末端鍵結，並與該等所鍵結之氮原子共同形成可部分包含雙鍵且可經取代之含氮脂肪族雜環]。
