Abstract: | Fig. 1. The sialic acids. The nine-carbon backbone common toall sialic acids is shown. Natural substitutions described todate (at C4, C5, C7 C8, and C9,) are indicated. Additional diversityis generated by various types of glycosidic linkage (at R3)by generation of lactones (at C1 ), by dehydro forms (eliminatingR3), and anhydro forms diversity sialic acids neuraminic acids O-acetylation sialidase |