Amino-PEG3-t-butyl ester

Amino-PEG3-t-butyl ester, provides a hydrophilic, flexible polyethylene glycol spacer with an amino handle and a protected carboxyl functionality. Such bifunctional linkers are widely used to assemble PROTACs by enabling reliable conjugation to ligands while maintaining solubility and conformational adaptability. The amino group supports coupling strategies, and the t-butyl ester protection supports controlled downstream functionalization. Detailed structural and synthetic considerations are provided below.

Structure: Amino-PEG3-t-butyl ester is a PEG-based linker featuring an ether-rich, flexible backbone, an amino substituent for nucleophilic coupling, and a tert-butyl ester that masks a carboxylic acid. Its structure contains amide-compatible functional groups, ether linkages, and an acid-labile ester moiety, contributing to improved aqueous compatibility.

Reactivity: The amino group can participate in common PROTAC assembly reactions such as amide-bond formation with activated carboxylic acid derivatives, or coupling to electrophilic carbonyls under standard peptide-conjugation conditions. The tert-butyl ester is typically retained during base-neutral coupling steps and can be selectively deprotected under acid-promoted conditions to reveal a carboxylic acid for subsequent activation. Suitable solvents include polar aprotic systems for coupling, while deprotection commonly uses acidic media compatible with PEG-containing linkers.