This paper describes the synthesis of a new class of peptidomimetic cysteine protease inhibitors based on a 1,4-benzodiazepine scaffold and on an electrophilic vinyl sulfone moiety. The former was introduced internally to a peptide sequence that mimics the fragment D-Ser-Gly; the latter was built on the P1-P1' site and reacts as a classical "Michael acceptor", leading to an alkylated enzyme by irreversible