The present invention relates to compounds comprising an oxazole or thiazole moiety of formula (I), processes for preparing them, pharmaceutical compositions comprising said compounds and their uses as H.sub.3-receptor ligands, Formula (I), wherein, A.sup.1 is CH, C(alkyl), C-halogen or N; R.sup.1 is hydrogen, halogen, C.sub.1-6 alkyl or alkoxy; R.sup.2 is, Formula (II'), A.sup.3 is O or S; R.sup.3 is hydrogen, halogen, C.sub.1-6 alkyl or alkoxy; R.sup.4 is hydrogen, halogen, C.sub.1-6 alkyl, alkoxy or --O-L; R.sup.5 is hydrogen or --O-L, wherein L is an aminoalkyl group and at least one of R.sup.4 and R.sup.5 should be --O-L.