一種化合物,其結構式如下:其中R1、R2、R3、R4、R5、R6、R7、R8、T、X、Y與Z係如說明書中所定義。本發明亦揭示利用此化合物來抑制二胜肽基胜肽酶Ⅳ或治療Ⅱ型糖尿病之方法。A compound of the following formula: wherein R1 , R2 , R3 , R4 , R5 , R6 , R7 , R8 , T, X, Y, and Z are as defined herein. Also disclosed is a method for inhibiting dipeptidyl peptidase IV or for treating Type II diabetes with such a compound.