An α-D-N-acetylgalactosamine (GalNAcα) ligand equipped with a terminal carboxylic acid through a hydrophilic PEG4 spacer. The carboxylic acid can be activated to NHS, sulfo-NHS, or pentafluorophenyl esters and reacted with amine-functionalized platforms or lysine residues on proteins and peptides to form amide bonds. This compound enables the construction of hepatocyte-targeted therapeutics and research tools that exploit the asialoglycoprotein receptor (ASGPR), which is highly expressed on liver hepatocytes and binds GalNAc-containing ligands with high affinity. The terminal GalNAcα residue is also a substrate for glycosyltransferases, including galactosyltransferases and sialyltransferases, enabling enzymatic chain extension.