Controlled Sulfane Sulfur Delivery via Allyl Disulfide Rearrangement-Mediated Thiosulfoxide Formation

Protein S-persulfidation is a key post-translational modification in redox signaling. In this process, hydropersulfides (RSSH) and hydrogen persulfide (H₂S₂) act as regulatory sulfane sulfur species, transferring their electrophilic sulfane sulfur (S⁰) atoms to protein thiols (P-SH) to form protein persulfides (P-SSH). Due to the high reactivity and instability of RSSH/H₂S₂, controllable donors are essential chemical tools for inducing protein S-persulfidation. Existing donors are primarily disulfide-based; however, this structural feature leads to a major limitation, as disulfide-based donors are known to undergo unavoidable disulfide exchange reactions with cellular thiols (e.g., glutathione (GSH), cysteine (Cys)) and subsequently lose their ability to release the desired RSSH/H₂S₂. In this work, we proposed that thiosulfoxides [R-S(═S)-R'] could serve as equivalents of RSSH/H₂S₂ for protein S-persulfidation and that controlled thiosulfoxide formation is an alternative way for the design of RSSH/H₂S₂ donors. To prove the hypothesis, we studied spontaneous [2,3]-sigmatropic allyl disulfide rearrangements with a variety of allyl disulfide substrates. We identified structural elements that promote the rearrangement to form thiosulfoxide adducts and demonstrated that the resulting transient thiosulfoxide intermediates were effective S⁰ transfer agents. Based on this discovery, we developed stable allyl disulfide reagents (such as 3i) that could be selectively activated by cellular thiols via the inevitable disulfide exchange, followed by a [2,3]-sigmatropic rearrangement cascade to induce protein S-persulfidation. Our results present a conceptually new way to deliver reactive sulfane sulfur species in biological systems.