“…In a single modification, the heterocyclic carbonyl undergoes chemo- and regioselective amidation, while in the additional presence of a Michael acceptor (e.g., maleimide), a double modification takes place (ring opening, followed by a thiol–X reaction). , The unique reactivity of TLs can be introduced through the commercially available homocysteine thiolactone (HCTL), which can be easily modified through the amine in the α-position (Figure ). Hence, it has been extensively used for postpolymerization modifications, − toward sequence-defined and functional polymers, − surfaces, , hydrogels, , and bioconjugate materials. − …”