2-Sulfonylpyrimidines: Reactivity Adjustable Agents for Cysteine Arylation

Abstract

Protein arylation has attracted much attention for developing new classes of bioconjugates with improved properties. Here, we have systematically evaluated 2-sulfonylpyrimidines as covalent warheads for the mild, chemoselective and metal free cysteine S-arylation. 2-sulfonylpyrimidines react rapidly with cysteine, resulting in stable S-heteroarylated adducts at neutral pH. Fine tuning the heterocyclic core and exocyclic leaving group allowed predictable SNAr reactivity with model tripeptide glutathione in vitro, covering 9 orders of magnitude. We achieved extremely fast chemo- and regio- specific arylation of a mutant p53 protein, and confirmed arylation sites by protein X-ray crystallography. Hence, we report the first example of a protein site specifically S-arylated with iodo-aromatic motifs. Overall, this study provides the most comprehensive structure-reactivity relationship to date on heteroaryl sulfones, and highlights 2-sulfonylpyrimidine as a synthetically tractable and protein compatible covalent motif for targeting reactive cysteines, expanding the arsenal of tunable warheads for modern covalent ligand discovery.

Emerging and Re-emerging Warheads for Targeted Covalent Inhibitors: An Update

“…Oral bioavailability, in vivo target engagement, and efficacy were also demonstrated for methyl sulfamate 55c in a mouse CLL model. Sulfamate acetamides were also employed with the aforementioned Pin1 inhibitor sulfopin (54), 32 where a CA electrophile was unsuitable for in vivo administration, while replacement with other electrophiles resulted in a loss of activity. Sulfamate sulfopin derivatives (e.g., 56, Figure 17) exhibited higher labeling efficacy compared to sulfopin despite their lower thiol reactivity, which may be rationalized by additional interactions with a putative sulfamate-accommodating pocket.…”

“…Here, the cysteine-containing tripeptide GSH (thiol p K a ≈ 9.2–9.4) is most commonly applied as the nucleophilic agent, as this compound occurs at millimolar concentrations in cells, where it quenches electrophiles but also acts as an antioxidant and redox regulator. Since GSH assays, in which the reaction rate of the target compound with (reduced) GSH is measured, are most frequently applied (see, for example, refs , − ), many data sets can be found for comparison. Yet, it is also possible to use other cysteine mimics. , These reactivity profiling experiments are often carried out by HPLC (MS or UV detection) or NMR, which limits their throughput.…”

“…Figure54. The three different reactive groups that were coupled to several different amine fragments (here depicted as dotted cyclic structures) in a study carried out to discover new potential sites for covalent modification.…”

“…17. Sulfopin(54) and examples for sulfamate ibrutinib derivatives as well as sulfone and sulfonate analogs (55a−d) and a sulfopin sulfamate analog(56).…”

Erastin-like anti-Warburg compounds X1 and X4 are GLS2-selective covalent glutaminase inhibitors

“…18 X1 is a 2-sulfonyl pyrimidine, a less common electrophile known to react with cysteine by nucleophilic aromatic substitution (SNAr) (Figure 3). 19 2-Sulfonyl pyrimidines are the electrophile of covalent inhibitors of bacterial Sortase A and S. mansoni thioredoxin glutathione reductase. 20,21 2-Sulfonyl pyrimidines are also the electrophile in covalent probes that target cysteine residues of mutant p53.…”