Provided are a compound which is superior in metabolic stability, and selectively binds to an EP4 receptor, and a medicament containing same. It has been found that a compound represented by the formula (1): wherein R 1 and R 2 are each independently a hydrogen atom or a straight chain alkyl group having a carbon number of 1 - 3, R 3 is a hydrogen atom, an alkyl group having a carbon number of 1 - 4, an alkoxyalkyl group, an aryl group, a halogen atom or a haloalkyl group, or a pharmaceutically acceptable salt thereof, has, unlike known PGI 2 analogs, a selective EP4 agonist action, and therefore, a medicament containing the compound is useful for the prophylaxis and/or treatment of immune diseases, cardiovascular diseases, cardiac diseases, respiratory diseases, ophthalmic diseases, renal diseases, hepatic diseases, bone diseases, diseases of the digestive tract, neurological diseases, skin diseases and the like.本發明提供一種代謝安定性優良且選擇性地結合到EP4受體之化合物及含有該化合物之醫藥。即，一種式(1)所表示之化合物或其藥學上容許之鹽類(式中，R1及R2各自獨立表示氫原子或碳原子數為1～3之直鏈烷基；R3表示氫原子、碳原子數為1～4之烷基、烷氧基烷基、芳基、鹵原子或鹵化烷基)：其被發現與已知之PGI2類不同，具有選擇性EP4促效劑作用，因此，含有該化合物之醫藥可用於預防及/或治療免疫疾病、循環器官疾病、心臟疾病、呼吸器官疾病、眼部疾病、腎臟疾病、肝臟疾病、骨骼疾病、消化道疾病、神經疾病及皮膚疾病等。
