Pairs of Thiol-Substituted 1,2,4-Triazole-based Isomeric Covalent Inhibitors with Tunable Reactivity and Selectivity

Covalent bioactive compounds are successfully used in clinic and attracted intense research efforts in the fundamental study as well as drug development. The advantageous effects of covalent compounds compared with non-covalent ones are highly dependent on electrophilic warheads. Hence, electrophilic warheads with tunable reactivity and selectivity are highly demanded in fields of medicinal chemistry and chemical biology. Herein, we report a novel electrophilic warhead, chloromethyl group activated by thiol-substituted 1,2,4-triazole. Interestingly, a pair of regioisomers could be simultaneously occurred in the step of alkylation during the synthesis of this unique motif. This is a rare example that the alkylation could simultaneously generate these two separable regioisomers of 1,2,4-triazole at the nitrogen or sulfur atom. The covalent-working mechanism of this new warhead is confirmed by various chemoproteomics experiments including target identification and binding site mapping. Importantly, the reactivity and selectivity of this new electrophilic warhead could be efficiently tuned by virtue of stereo effect. Interestingly, one pair of regioisomers (19S and 19X) induced distinct modes of cell death. Isomer 19S could induce apoptosis of colon cancer cells while 19X could induce both apoptosis and ferroptosis. Together, this study provides pairs of novel electrophilic warheads that could be useful not only in supporting the design of covalent compounds for drug discovery but also in providing chemical probes for the fundamental biological study.