A Galα1-3LacNAc (α-Gal epitope) ligand equipped with a terminal carboxylic acid through a short butyl spacer. The carboxylic acid can be activated to NHS, sulfo-NHS, or pentafluorophenyl (PFP) esters and reacted with amine-functionalized platforms or lysine residues on proteins and peptides to form stable amide bonds. This compound presents a terminal Galα1-3 linkage on a LacNAc core, corresponding to the α-Gal epitope (Galα1-3Galβ1-4GlcNAc) that is the target of naturally occurring human anti-Gal antibodies and is central to xenotransplantation and anti-Gal immunology research.