Carbohydrates are important organic macromolecules mainly referred to in the context of energy sources, while their essential role in biological systems is rarely interpreted. Information carried in oligosaccharides is determined by the site of the monosaccharide binding s, the configuration of glycosidic bond (α- or β-) and the amount of branching. All this makes them excellent transmitters of biological information. Lectines are proteins that specifically bind sugar structures. A special type of lectins are mannose receptors present on the surface of different immunocompetent cells and are potential targets for binding mannosylated antigens. They can also be used for injection of drugs containing mannose and thus affect the progress of specific reactions in the immune system. The aim of this paper is to develop a method for the preparation of mannosylated carboxylic acid, an important substructure in the synthesis of the compounds used as potential adjuvants. Acetylation of D-mannose with anhydride of acetic acid and iodine as catalyst gave 1,2,3,4,6-penta-O-acetyl-α, β-D-mannopiranose. Anomeric acetate protection, was selectively removed from the obtained compound using three different ways, all resulting in formation of 2,3,4,6-tetra-O-acetyl-α-D-mannopyranose. In the third step, O-mannoside was prepared by reacting tetraacetylated mannose with tert-butyl bromoacetate and potassium carbonate. This reaction gave preferably an α-anomer of O-mannoside. Tert-butyl protection was removed from the pure α-anomer using trifluoroacetic acid in dry dichloromethane giving 2-(2,3,4,6-tetra-O-acetyl-α-D-manopyranosyloxy) acetate in a good yield. The products structures were characterized by \( ^{1}H \) and \( ^{13}C \) NMR spectroscopy.