Figure 5.

(a) H-tetrazines modified with a directing group enable complete cleavage of C₂TCO with significantly improved click rates due to decreased steric hindrance. (b) Cleavage experiments at low concentrations (10 μM C₂TCO + 20 μM Tz) revealed instantaneous release upon click (no intermediates detected) and complete overall cleavage (>99%) with HK (20) and PymK (3) after 30 min. (c) Cleavage of C₂TCO triggered by HPA (19) or HK (20) is readily accelerated by increasing the Tz concentration enabling complete bioorthogonal cut in minutes (click = rate-determining). In contrast, the cleavage of a known TCO-linker (cTCO) triggered by DMT (1) requires >1 h to reach completeness (release = rate-determining).