5-deoxy-4-epi-2,3-dehydro-Kdo-(4->8)-alpha-Kdo is a carbohydrate acid comprising 3-deoxy-alpha-D-manno-oct-2-ulopyranosonic acid (Kdo) having a 5-deoxy-4-epi-2,3-dehydro-Kdo moiety attached via an unusual (4->8) non-glycosidic linkage. It derives from a 3-deoxy-alpha-D-manno-oct-2-ulopyranosonic acid.