| abstract |
The present invention relates to a compound 7 or a pharmaceutically acceptable salt thereof, wherein R1, R2, R3, R4, and R5 represent H (hydrogen) or D (deuterium), and at least one of them is D. The invention also relates to a preparation method of the compound, a pharmaceutical composition in which the compound is an active ingredient, and an application of the compound of the invention or a pharmaceutically acceptable salt thereof in the preparation of medicines for treating insomnia, inducing sleep and maintaining sleep. |