A kit for targeted medical imaging and/or therapeutics, comprising at least one Pre-targeting Probe and at least one Effector Probe, wherein the Pre-targeting Probe comprises a Primary Targeting Moiety and a first Bio-orthogonal Reactive Group, and wherein the Effector Probe comprises an Effector Moiety, such as a label or a pharmaceutically active compound, and a second Bio-orthogonal Reactive Group, wherein either of the first and second Bio-orthogonal Reactive Groups is a dienophile and the other of the first and second Bio-orthogonal Reactive Groups is a diene, wherein the dienophile is an 8-member ring dienophile satisfying formula : wherein the position of R is equatorial and the position of R a is axial, wherein X, Y, R 1 , R 1 a , R 6 and R 6 a denote H, and wherein each of R 2 , R 2 a , R 3 , R 3 a , R 4 , R 4 a , R 5 , and R 5 a independently denotes H, or, in at most six instances, a substituent selected from the group consisting of alkyl, aryl, O-aryl, O-alkyl, SO 3 H, OH, NR'R" with R' and R" each independently being H, alkyl, or aryl, C(=O)NR'R" with R' and R" each independently being H, aryl or alkyl, NR'CO-alkyl with R' being H, alkyl or aryl, NR'CO-aryl with R' being H, alkyl or aryl, NR'C(=O)O-alkyl with R' being H, alkyl, or aryl, NR'C(=O)O-aryl with R' being H, alkyl or aryl, OCONR'-alkyl with R' being H, alkyl or aryl, OCONR'-aryl with R' being H, alkyl or aryl, NR'CONR"-alkyl with R' and R" each independently being H, alkyl or aryl, NR'CONR"-aryl with R' and R" each independently being H, alkyl or aryl, NR'CSNR"-alkyl with R' and R" each independently being H, alkyl or aryl, and NR'CSNR"-aryl with R' and R" each independently being H, alkyl or aryl; with one of R a comprised in a Linker Moiety, optionally via a spacer, to the Primary Targeting Moiety or the Effector Moiety; wherein two R or R a moieties together may form a ring; and wherein at least one and maximally four of R a is not hydrogen; and wherein the diene is selected from the group consisting of compounds of the formulae and as defined below: wherein R 1 and R 2 each independently are selected from the group consisting of H, alkyl, and aryl; A is selected from the group consisting of N, C-alkyl, C-aryl, and N + O - ; B is N; X is selected from the group consisting of N, CH, C-alkyl, C-aryl, CC(=O)R', CC(=S)R', CS(=O)R', CS(=O) 2 R′′′, CC(=O)O-R', CC(=O)S-R', CC(=S)O-R', CC(=S)S-R', CC(=O)NR'R", CC(=S)NR'R" , R' and R" each independently being H, aryl or alkyl and R′′′ independently being aryl or alkyl; Y is selected from the group consisting of CH, C- alkyl, C-aryl, N, and N + O - wherein R 1 and R 2 each independently denote a substituent selected from the group consisting of H, 2-pyridyl, 3-pyridyl, 4-pyridyl, 2,6-pyrimidyl, 2,5-pyrimidyl, 3,5-pyrimidyl, 2,4-pyrimidyl , or phenyl, optionally substituted with one or more electron-withdrawing groups such as NO 2 , F, Cl, CF 3 , CN, COOH, COOR, CONH 2 , CONHR, CONR 2 , CHO, COR, SO 2 R, SO 2 OR, NO, Ar, wherein R is C 1 -C 6 alkyl and Ar stands for an aromatic group, particularly phenyl, pyridyl, or naphthyl; and wherein the diene comprises at least one linkage, optionally via a spacer, to the Primary Targeting Moiety or the Effector Moiety. <EOS>