DBCO-NHCO-C4-NHS ester

This DBCO-NHCO-C4-NHS ester is a bifunctional PROTAC linker designed to combine a strained cyclooctyne handle for rapid bioorthogonal conjugation with an activated N-hydroxysuccinimide ester for efficient amide-bond formation. Its dual reactivity enables modular assembly of targeted protein degraders by connecting ligands under mild conditions while preserving functional group compatibility. The following points describe the linker’s structure and practical reactivity considerations in PROTAC construction.

Structure: The linker contains a DBCO (dibenzocyclooctyne) moiety for strain-promoted cycloaddition and a carbamate-linked spacer terminating in an NHS ester. It features an amide/carbonyl-rich connectivity and an activated succinimide leaving group, supporting selective formation of stable conjugates under aqueous-compatible conditions.

Reactivity: The NHS ester reacts with primary amines (e.g., lysine residues or amine-functional ligands) to form amide bonds via nucleophilic acyl substitution, typically in buffered aqueous media with controlled pH to maintain NHS reactivity. The DBCO handle undergoes strain-promoted azide–alkyne cycloaddition with azide-functional partners without added catalysts. For PROTAC assembly, sequential conjugation is commonly used to minimize cross-reactivity, using standard protein-compatible buffers and avoiding strong nucleophiles that quench NHS esters.