Ligands for G-protein coupled receptors

A compound of general formula (I, wherein y is any integer from 1 to 8; z is any integer from 0 to 8 with the proviso that y and z cannot simultaneously be 1; X is -CO-(Y)k-(R )n or SO2-(Y)k-(R )n; k is 0 or 1, Y is a cycloalkyl or polycyloalkyl group (such as an adamantyl, adamantanemethyl, bicyclooctyl, cyclohexyl, cyclopropyl group); or Y is a cycloalkenyl or polycycloalkenyl group; each R is independently selected from hydrogen or an alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, alkynyl, alkylamino, alkylaminoalkyl, alkylaminodialkyl, charged alkylaminotrialkyl or charged alkylcarboxylate radical of 1 to 20 carbon atoms; or each R is independently selected from fluoro, chloro, bromo, iodo, hydroxy, oxyalkyl, amino, aminoalkyl, aminodialkyl, charged aminotrialkyl, or carboxylate radical; and n is any integer from 1 to m, where m is the maximum number of substitutions permissible on the cyclo-group Y; or alternatively R may be selected from a peptido radical, for example having from 1 to 4 peptidic moieties linked together by peptide bonds (for example a peptido radical of 1 to 4 amino acid residues). The compounds may be generated in a library - enriched in agonists/antagonists for the G-proteins coupled class of receptors (GPCRs).