N-DBCO-N-bis(PEG2-C2-NHS ester)

N-DBCO-N-bis(PEG2-C2-NHS ester), is designed to connect a DBCO-bearing handle to two NHS-activated ester sites, enabling modular assembly of targeted protein degradation constructs. Its PEG-containing spacer promotes solubility and configurational flexibility, while the NHS esters provide reliable electrophilic coupling points to amine-bearing ligands. The molecule is therefore well suited for stepwise PROTAC synthesis, where orthogonal conjugation strategies improve control over linker architecture.

Structure: The linker contains a DBCO moiety for strain-promoted azide–alkyne cycloaddition, coupled to two PEG2-extended arms terminating in NHS ester functionalities. It features stable carbamate/amide-forming reactive groups, ether-rich PEG segments, and ester-linked leaving groups that enable controlled nucleophilic substitution under mild conditions.

Reactivity: NHS ester groups react with primary amines via nucleophilic acyl substitution, typically requiring mildly basic conditions and anhydrous, amine-compatible solvents such as aqueous buffer systems with controlled pH. The DBCO handle enables catalyst-free cycloaddition with azide-functional partners, commonly performed in aqueous or mixed solvent media. Orthogonal use of NHS coupling followed by azide–DBCO ligation supports sequential PROTAC assembly without cross-reactivity.