Abstract: Compounds of general formula I X1 is a CD2 group or a CT2 group; X2 is oxygen or a group (CZ1Z2)n, wherein Z1 and Z2 on each occurrence independently each are hydrogen, deuterium, or tritium and n is an integer from 1 to 12; X3 is a CD2 group or a CT2 group; and R is selected from the group consisting of hydroxy, -NO2, halogen, a diazonium ion, a diazonium salt, a trialkylammonium ion, a trialkylammonium salt, a dialkoxyarene, a sulphoxide, a boronic acid, a boronic acid ester, an organotin compound, an iodonium ion, an iodonium salt, an iodonium ylide, and a sulphonate.

Abstract: A compound of general formula I Residues X1a, X1b, X2a, X2b, X3a, X3b, X4a, X4b, X5a, and X5b each independently are hydrogen or deuterium, with the provision that at least one of residues X1a, X1b, X2a, X2b, X3a, X3b, X4a, X4b, X5a, and X5b is deuterium.