Biotin-PEG4-amino-t-Bu-DADPS-C6-azide

Biotin-PEG4-amino-t-Bu-DADPS-C6-azide, is engineered to integrate a biotin handle with a flexible polyethylene glycol spacer and a functional azide for modular conjugation. Its design supports reliable attachment to biorecognition or capture motifs while maintaining linker mobility that can improve productive ternary complex formation. The subsequent sections describe the structural features and the practical reactivity considerations for assembling PROTAC constructs using this versatile azide-bearing scaffold.

Structure: The linker contains a biotin-derived moiety connected through a PEG-based hydrophilic spacer, an amino-functional handle, and a tert-butyl-protected DADPS-derived segment. An azide group provides a terminal, chemically addressable functionality. Multiple amide and ether linkages confer polarity and conformational flexibility.

Reactivity: The terminal azide is suited for copper-free or copper-catalyzed azide–alkyne cycloaddition, enabling efficient “click” conjugation to alkyne-functional PROTAC arms under biocompatible conditions. Alternatively, azide can participate in strain-promoted cycloaddition with cyclooctyne reagents. The amino group can be leveraged for amide coupling or carbamate formation when paired with activated carboxylic acids or carbonyl transfer reagents, typically using standard peptide-coupling chemistries in polar aprotic solvents with base.