Insights into the activation patterns of 1,2-dithiolane unit in biofunctional molecules

The cyclic five-membered disulfide 1,2-dithiolane, known for its moderate reactivity and ease of preparation, holds significant promise as a recognition unit in probe design and drug development. However, potential limitations in activation specificity-most notably the diminished selectivity toward thioredoxin reductase (TrxR) caused by nonspecific reactions with abundant low-molecular-weight (LMW) thiols such as glutathione (GSH)-raise concerns about its reliability in biological settings. Here we systematically evaluate the activation behavior of 1,2-dithiolane by synthesizing a panel of prodrugs and fluorescent probes incorporating either amine- or hydroxyl-linked cargoes. Our results reveal that TrxR-mediated selective activation of the 1,2-dithiolane unit is achievable when the cargo is incorporated within an amine-based framework. In contrast, hydroxyl-linked conjugates undergo rapid cleavage by physiological GSH levels, resulting in a pronounced loss of TrxR selectivity. Generally, the recognition site 1,2-dithiolane, the linker unit and the leaving group in a cargo coordinate to determine the selectivity activated by TrxR. Overall, this study resolves ambiguities in previous reports, reconciles conflicting observations, and provides new conceptual guidance for the use of the 1,2-dithiolane scaffold in the design of biofunctional molecules.