The late-stage site-selective activation of C-H bonds in structurally complex, bioactive molecules is a crucial and challenging task. 9,39,45 In this context, our protocol could be employed for the selective isotope labelling of more than 10 pharmaceutical analogues of antibiotic, antiviral, antidepressant, and seizure drugs, rendering the desired product in good to excellent yields with a selectivity of up to 99% (Fig. ). Remarkably, the targeted selectivity could be achieved in the presence of various other α-amine or α-hetero atom positions , e.g. present in the prominent morpholine , piperidine , and piperazine moieties, which would likely be affected in a photocatalytic hydrogen atom abstraction approach. Along the same line, sugar derivatives could be deuterated in good yield and remarkable selectivity as well . Besides this, drug analogues bearing a glutarimide group , adamatane functionality or an extended conjugated system are accepted, too. Functionalized amino acids and more challenging short peptide chains (29) can be deuterated, likewise. In this case, it is worth mentioning that untargeted chiral centers stay untouched , while a classical approach of employing a strong base is expected to lead to a racemization. Reaction conditions: a 0.1 mmol substrate, 5 mol% PC (3DPA2FBN), 2 eq. K2CO3, 15 eq. D2O, 1 mL DMA (0.1 M), 451 nm, 25 °C, 24 h, isolated yields. Deuterium incorporation was calculated based on ESI-MS and 1 H NMR. Selectivity was determined by ESI-MS, 1 H-and 2 H-NMR. PMP = para methoxy phenyl. b same as "a" with a reaction time of 48 h. Reaction conditions: a 0.1 mmol substrate, 5 mol% PC (3DPA2FBN), 2 eq. K2CO3, 15 eq. D2O, 1 mL DMA (0.1 M), 451 nm, 25 °C, 24 h, isolated yields. Deuterium incorporation was calculated based on ESI-MS and 1 H NMR. Selectivity determined by ESI-MS, 1 H-and 2 H-NMR. PMP = para methoxy phenyl.