Synthesis and Evaluation of Hydropersulfide Activated Hydrogen Selenide Donor

Abstract

Hydrogen selenide (H2Se) is the central metabolic intermediate for selenoprotein bio-synthesis and a potent biological reductant whose controlled intracellular delivery remains an unmet challenge in selenium chemical biology. Persulfides (RSSH/RSS−) are endogenous reactive sulfur species that are elevated under oxidative stress precisely the pathological context in which selenoprotein demand is highest and controlled H2Se supplementation would be most therapeutically meaningful. Motivated by this convergence, we designed a persulfide-activated H2Se donor by exploiting the well-established dual reactivity of persulfides toward benzoyl thioester electrophiles. We first synthesised compound 4, a fluorophore analogue of the PSP3 probe, in which a benzoyl thioester trigger is conjugated to a fluorescein-based fluorophore. Compound 4 exhibited strong, selective fluorescence turn-on in the presence of Na2S4 as a persulfide surrogate, with negligible response toward esterase, validating the benzoyl thioester as an orthogonal, persulfide-selective trigger and establishing proof of concept for persulfide-triggered molecular release as a viable strategy. Building on this, compound 7, a persulfide-activated H2Se donor was synthesised by conjugating the validated benzoyl thioester trigger to the second-generation phenacylselenoester core, which exhibits an approximately ten-fold slower H2Se release rate relative to first-generation donors. TLC-based decomposition studies confirmed that both Na2S4and DTT are required for ketone byproduct formation, consistent with the proposed two-step mechanism of persulfide-triggered unmasking followed by thiol–selenol exchange. Direct evidence for H2Se release was obtained by HPE-IAM trapping, with MALDI-TOF analysis revealing both the selenol–HPE-IAM adduct and the bis-HPE-IAM–H2Se adduct selectively under persulfide and thiol activation conditions. This work presents the first small molecule H2Se donor activated by an endogenous reactive species, establishing a new strategy for stimuli-responsive, oxidative stress directed Hydrogen selenide delivery.