DBCO-PEG9-DBCO

This DBCO-PEG9-DBCO linker is designed for modular PROTAC assembly by enabling efficient, orthogonal conjugation through strain-promoted azide–alkyne cycloaddition (SPAAC). Its PEG-based spacer improves solubility and conformational flexibility, which can help optimize ternary complex formation and targeted protein degradation performance. The molecule’s two DBCO termini allow sequential or parallel functionalization of PROTAC-relevant warheads and E3 ligands. Detailed structural and reactivity considerations are provided below.

Structure: The linker contains two DBCO (dibenzocyclooctyne) moieties connected by a PEG-based chain, providing an ether-rich, flexible spacer. It features strained cyclooctyne alkynes poised for rapid cycloaddition, along with stable carbon–carbon and carbon–oxygen connectivity that supports aqueous-compatible conjugation.

Reactivity: DBCO groups react selectively with azides via SPAAC, typically proceeding under catalyst-free conditions. Suitable conjugation is commonly performed in polar solvents such as aqueous buffers or mixed aqueous media, with mild temperatures to preserve sensitive ligands. The mechanism relies on strain release upon cycloaddition to form a stable triazole linkage, enabling efficient attachment of azide-functionalized PROTAC components without the need for copper catalysts.