5,8,11,14-Tetraoxa-2-azahexadecanedioic acid

Fmoc-NH-PEG4-CH2COOH is a PEG linker containing an Fmoc-protected amine and a terminal carboxylic acid. The hydrophilic PEG spacer increases solubility in aqueous media. The Fmoc group can be deprotected under basic condition to obtain the free amine which can be used for further conjugations. The terminal carboxylic acid can react with primary amine groups in the presence of activators (e.g. EDC, or HATU) to form a stable amide bond.

Fmoc-NH-PEG4-CH2COOH is a degradable ADC linker for antibody drug conjugate (ADC) synthesis. It is also a PEG-based PROTAC linker, which can be used for PROTAC synthesis.