(Rac)-OSMI-1 is a racemate of OSMI-1. OSMI-1 is an inhibitor of O-GlcNAc transferase (OGT) (IC50: 2.7 μM). OSMI-1 inhibits protein O-linked N-acetylglucosaminoglycans (O-GlcNAcylation) in mammalian cell lines and does not qualitatively alter cell surface N- or O-linked glycans.