Fusobacterium nucleatum is an oral bacteria related to various types of diseases. As Gram-negative bacteria, lipopolysaccharide (LPS) of Fusobacterium nucleatum could be a potential virulence factor. Recently, the structure of O-antigen in LPS of Fusobacterium nucleatum strain 25586 was elucidated to contain a trisaccharide repeating unit -(4-β-Nonp5Am-4-α-L-6dAltpNAc3PCho-3-β-D-QuipNAc)-. The nonulosonic acid characterized as 5-acetamidino-3,5,9-trideoxy-L-glycero-L-gluco-non-2-ulosonic acid (named as fusaminic acid), and 2-acetamido-2,6-dideoxy-L-altrose are the novel monosaccharides isolated. Herein we report the de novo synthesis of 5-N-acetyl fusaminic acid and the thioglycoside derivative in order to further investigate the biological significance of nonulosonic acids for bacterial pathogenesis.