The present invention relates to therapeutically active and selective inhibitors of the enzyme DPP-IV, which are of formula I ##STR00001## wherein each n is one or two independently and R.sup.1, R.sup.2, R.sup.3, R.sup.6, R.sup.7, R.sup.9, and R.sup.10 are defined herein. The present invention also relates to pharmaceutical compositions comprising the compounds of formula I and the use of the compounds for treating diseases that are associated with proteins that are subject to inactivation by DPP-IV, such as type-2 diabetes and obesity.