Dipeptidyl peptidase IV (DPP-IV)-inhibiting compounds are provided that have formula I: wherein n is 1 to 3； X is CH 2 ； S； O； CF 2 or C(CH 3 ) 2 ； Z is H； halogen； hydroxyl； (C 1-6 )alkoxy； (C 1-12 )alkyl； (C 3-12 )cycloalkyl； phenyl； or heteroaryl； where the phenyl and heteroaryl groups are optionally mono- or independently plurisubstituted with R 7 ； optionally, X together with an adjacent ring carbon and Z form a fused cyclopropyl； and optionally, one of the bonds in the ring containing X is a double bond； and CR i R ii , R 1 , R 2 , R 3 , R 4 and R 5 are as described herein.
