[methylpentose structurally derived from galactose; the L isomer occurs naturally in various oligosaccharides and polysaccharides and fucosides and in the carbohydrate portion of some mucopolysaccharides and glycoproteins, including the A, B, and O blood group antigens. ( CSP )] (UMLS (CSP) C0016786) =Carbohydrate; Biologically Active Substance =hexose;