Preparation of ethynylsulfonamides and study of their reactivity with nucleophilic amino acids

The development of covalent drugs, particularly those utilizing Michael acceptors, has garnered significant attention in recent pharmaceutical research due to the ability of such molecules to irreversibly inhibit protein function. This study focusses on the synthesis and evaluation of ethynylsulfonamides, which are predicted to have superior covalent binding ability, metabolic stability, and water solubility compared to traditional amides. We developed a straightforward synthesis method for ethynylsulfonamides and comprehensively evaluated the covalent binding abilities of these compounds using NMR with various nucleophilic amino acids in different solvents. Our results revealed that ethynylsulfonamides exhibit rapid and selective reactivity with cysteine residues, particularly in phosphate-buffered saline (PBS), where the reaction progressed quantitatively within five minutes. Notably, propynylsulfonamide demonstrated high reactivity and selectivity toward cysteine, suggestive of the significant potential of this molecule for applications in antibody-drug conjugates (ADCs) and other therapeutic areas where metabolic stability, water solubility, and selective reactivity are crucial.