Abstract: Provided is a compound represented by the formula (1): wherein R1 and R2 are each independently a hydrogen atom or a straight chain alkyl group having a carbon number of 1-3, R3 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, which has, unlike known PGI2 analogs, a selective EP4 agonist action, and a medicament containing the compound, which is useful for the prophylaxis and/or treatment of immune diseases, diseases of the digestive tract, cardiovascular diseases, cardiac diseases, respiratory diseases, neurological diseases, ophthalmic diseases, renal diseases, hepatic diseases, bone diseases, skin diseases and the like.