The present invention is concerned with novel compounds of formula (I) which are inhibitors of a membrane tripeptidyl peptidase responsible for the inactivation of endogenous neuropeptides such as cholecystokinis (CCKs). The invention further relates to methods for preparing such compounds, pharmaceutical compositions comprising said compounds as well as the use as a medicine of said compounds. ##STR00001## wherein n is an integer 0 or 1; X represents O; S; or --(CR.sup.4R.sup.5).sub.m-- wherein m is an integer 1 or 2; R.sup.4 and R.sup.5 are each independently from each other hydrogen or C.sub.1-4alkyl; R.sup.1 is C.sub.1-6alkylcarbonyl optionally substituted with hydroxy; C.sub.1-6alkyloxycarbonyl; aminoC.sub.1-6alkylcarbonyl wherein the C.sub.1-6alkyl group is optionally substituted with C.sub.3-6cycloalkyl; mono- and di(C.sub.1-4alkyl)aminoC.sub.1-6alkylcarbonyl; aminocarbonyl substituted with aryl; C.sub.1-6alkylcarbonyloxyC.sub.1-6alkylcarbonyl; C.sub.1-6alkyloxycarbonylaminoC.sub.1-6alkylcarbonyl wherein the amino group is optionally substituted with C.sub.1-4alkyl; an amino acid; C.sub.1-6alkyl substituted with amino; or arylcarbonyl; R.sup.2 is an optionally substituted 5-membered heterocycle, or R.sup.2 is optionally substituted benzimidazole; R.sup.3 is a bivalent radical --CH.sub.2CH.sub.2-- optionally substituted with halo or phenylmethyl; or R.sup.3 is a bivalent radical of formula ##STR00002##