A fully unprotected (free amine, free acid) L-threonine glycoamino acid carrying a Galβ1-3GalNAcα disaccharide. This deprotected building block is suited to use as a reference standard, an enzymatic substrate/acceptor, or for conjugation and analytical work rather than direct Fmoc-SPPS. The installed glycan is the T antigen / core 1 structure (Galβ1-3GalNAcα-O-Ser/Thr), a tumor-associated carbohydrate antigen and ligand for galectins and the macrophage galactose lectin, used to build glycopeptides for cancer immunology and O-glycobiology research.