N-Boc-N-bis(PEG2-propargyl)

N-Boc-N-bis(PEG2-propargyl), is designed to provide a protected, bifunctional scaffold that enables efficient conjugation of two targeting components through orthogonal click-compatible handles. Its PEG-containing segments support solubility and conformational flexibility, while the propargyl termini facilitate copper-catalyzed azide–alkyne cycloaddition for modular assembly. The Boc-protection strategy helps maintain controlled reactivity during synthesis, and the molecule will be described in detail below.

Structure: The linker contains a Boc-protected nitrogen center connected to two PEG2-terminated propargyl arms. It features ether linkages within the PEG segments, carbamate functionality from the Boc group, and terminal carbon–carbon triple bonds suitable for click chemistry. These elements collectively increase hydrophilicity and provide flexible spacing.

Reactivity: The propargyl groups participate in copper-catalyzed azide–alkyne cycloaddition, enabling rapid formation of stable triazole linkages under mild conditions. Typical approaches use Cu(I) generated in situ from copper salts with a reducing agent, in polar organic or mixed solvent systems compatible with biomolecule conjugation. The Boc group can be retained during coupling steps and removed under standard acid-mediated deprotection when subsequent amide or amine functionalization is required.