Isothiocyanates as H₂S Donors Triggered by Cysteine: Reaction Mechanism and Structure and Activity Relationship

Isothiocyanates are reported as H₂S donors, yet the mechanisms are not clear. Herein, we reported that isothiocyanates (ITCs, R-NCS) rapidly formed adducts with cysteine. These adducts underwent intramolecular cyclization followed by releasing organic amine R–NH₂ and raphanusamic acid (RA) as major products with formation of H₂S and 2-carbylamino-4,5-dihydrothiazole-4-carboxylic acids as minor products. The ratios of the two groups of products are dependent on the R groups which have strong impact on H₂S releasing rates.