Abstract: The present invention relates to novel 2-carbonyl-3-acyl-1,3-thiazolidines having a ?-amino group on the acyl chain, in free, prodrug form or pharmaceutically acceptable salt thereof, including their enantiomers, diastereomers and racemates, as efficient inhibitors against DPP-IV. The invention further relates to the pharmaceutical compositions comprising the disclosed compounds. The present invention also relates to methods for preparing the disclosed compounds and for treating DPP-IV-mediated diseases.

Abstract: Novel 4-amino-3-acylnaphthyridine derivatives represented by formula (I), wherein R.sub.1 is hydrogen, C.sub.1 -C.sub.6 lower alkyl group, C.sub.1 -C.sub.6 lower alkoxy group, C.sub.1 -C.sub.6 lower alkoxyalkyl group, C.sub.3 -C.sub.6 cycloalkyl group, C.sub.3 -C.sub.6 cycloalkyl C.sub.1 -C.sub.6 alkyl group, a or phenyl group which maybe substituted with C.sub.1 -C.sub.6 alkyl group; R.sub.2 is hydrogen, C.sub.1 -C.sub.6 lower alkyl group, C.sub.1 -C.sub.6 alkoxy group, C.sub.1 -C.sub.6 alkylthio group, or a group of the formula: NR.sub.6 R.sub.7 wherein R.sub.6 and R.sub.7, identical to or different from each other, are independently hydrogen or C.sub.1 -C.sub.6 lower alkyl group, or R.sub.6 and R.sub.7 may form together 5-membered or 6-membered cycloalkyl group; R.sub.3 is hydrogen, C.sub.1 -C.sub.6 lower alkyl group, C.sub.1 -C.sub.6 alkoxy group, C.sub.1 -C.sub.6 alkylthio group, an amino group substituted with one or two C.sub.1 -C.sub.6 alkyl groups, halogen, cyano group, C.sub.1 -C.sub.