Synthesis and kinetic evaluation of ethyl acrylate and vinyl sulfone derived inhibitors for human cysteine cathepsins

A series of inhibitors targeting human cathepsins have been designed and synthesized following a combinatorial approach. The compounds bear an α,β-unsaturated phenyl vinyl sulfone or ethyl acrylate warhead and a peptidomimetic portion aligned to the non-primed binding region. Biochemical evaluation toward four human cathepsins was carried out and the kinetic characterization confirmed an irreversible mode of inhibition. Compound 6c combining the most advantageous building blocks for cathepsin S inhibition was identified as a potent cathepsin S inactivator exhibiting a second-order rate constant of 30600?M^?1?s^?1.