Tunable Aromatic Sulfoxides and Sulfones as Cysteine-Targeting Warheads: Exploring the Structure-Reactivity...

Area of Science:

• Medicinal Chemistry
• Chemical Biology
• Molecular Probes

Background:

• Covalent modalities offer precise protein inhibition and labeling via tunable reactivity.
• Nucleophilic aromatic substitution (S_NAr) is a key reaction for developing covalent modifiers.

Purpose of the Study:

• To design and synthesize a library of aromatic sulfoxide and sulfone warheads for S_NAr reactions.
• To establish structure-reactivity relationships for these covalent warheads.
• To develop ligand-directed covalent probes for targeting specific proteins, such as Bruton's tyrosine kinase (BTK).

Main Methods:

• Synthesis of a 48-member library of aromatic sulfoxide and sulfone compounds.
• Kinetic assays to determine chemoselectivity and reaction rates.
• Incorporation of selected warheads into ligand-directed probes.
• Molecular dynamics simulations to optimize probe-target interactions.

Main Results:

• Systematic structure-reactivity relationship analysis revealed key factors influencing warhead reactivity.
• Demonstrated chemoselectivity for cysteine thiols, with reaction rates dependent on the aromatic scaffold.
• Identified a pyrazine-based warhead suitable for cellular applications.
• Developed an ibrutinib-derived probe (Ibr-2) that achieved potent and traceless BTK labeling in cells without affecting enzymatic activity.

Conclusions:

• Tunable S_NAr warheads are effective tools for developing selective covalent probes.
• These probes show potential for targeting kinases with noncatalytic cysteines, like BTK.
• The developed methodology enables precise protein labeling in cellular environments.