Whereas mammalian oligosaccharides consist of only ten different monosaccharide units (e.g. Glc, Gal, Man, GlcNAc etc.) bacteria present a plethora of different monosaccharides. Many of them are highly desoxygenated, bear amino groups, quaternary carbon centers or longer carbon chains. This feature allows to detect bacteria by carbohydrate-specific antibodies since many of these sugars are not found in mammals. One of these bacterial monosaccharides found in the flagellum of Helicobacter pylori and other bacteria is pseudaminic acid (Pse). Pse is crucial for the assembly of functional flagella, and is required for bacterial motility and invasion of the host intestinal tract. The talk will tackle our synthetic endeavors towards the synthesis of a building block for pseudaminic acid, its incorporation into a trisaccharide found in pilins (Figure 1) and biological studies with azido derivatives.