The invention relates inter alia to a compound of general formula (I) or (I'): wherein z is 1,2 or 4； X is -CO-Y k -(R 1 ) n or SO 2 -Y k -(R 1 ) n ； k is 0 or 1； Y is a cycloalkyl or polycyloalkyl group (such as an adamantyl, adamantanemethyl, bicyclooctyl, cyclohexyl, cyclopropyl group)； or is a cycloalkenyl or polycycloalkenyl group； each R 1 is independently selected from hydrogen or an alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, alkynyl or alkylamino radical of 1 to 20 carbon atoms (for example of 5 to 20 carbon atoms, of 8 to 20 carbon atoms, of 9 to 20 carbon atoms, of 10 to 18 carbon atoms, of 12 to 18 carbon atoms, of 13 to 18 carbon atoms, of 14 to 18 carbon atoms, of 13 to 17 carbon atoms)； or each R 1 is independently selected from fluoro, chloro, bromo, iodo, hydroxy, oxyalkyl, amino, aminoalkyl or aminodialkyl radical； and n is any integer from 1 to m, where m is the maximum number of substitutions permissible on the cyclo-group Y (such that n=1 if k=0, such that the R 1 group is bonded directly to the carbonyl or sulfonyl group)； provided that simultaneously X cannot be an undec-10-en-1-oyl group and z be equal to 1 or 2； or alternatively R 1 is selected from a peptido radical having from 1 to 4 peptidic moieties linked together by peptide bonds.
