The present invention aims to provide a novel compound which has an OX2R
agonist activity.The present invention relates to a
cyclopentane compound represented by the following formula (I) or a pharmaceutically acceptable salt thereof. The compound of the present invention or a pharmaceutically acceptable salt thereof has an
agonist activity on OX2R and is useful as an agent for the treatment of sleep disorders involving OX2R (for example,
narcolepsy, idiopathic hypersomnia, Kleine-Levin syndrome, hypersomnia due to physical diseases, hypersomnia due to psychiatric disorders, hypersomnia due to drugs or substances,
circadian rhythm sleep-wake disorder, insufficient sleep syndrome and
long sleep) or the like.