The present invention provides a compound of the Formula II: Formula II wherein X is: R1 is H, -CN, or F; R2 is H or methyl; R3 is H; and R4 is H, methyl, or ethyl; or R3 and R4 joined together form a cyclopropyl ring; or a pharmaceutically acceptable salt thereof.
本发明提供了一种化合物,其
化学式为II:其中X为:R1为H,-CN或F;R2为H或甲基;R3为H;R4为H,甲基或乙基;或者R3和R4结合在一起形成一个环丙基环;或其药用盐。