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Glycans are substantially more complex than other important biological macromolecules such as nucleic acids and proteins. The linkages between individual subunits in glycans are not identical whereas nucleic acids and proteins are linear molecules in which the individual subunits are linked by identical phosphate and peptide bonds. Consequently, glycans may be linear or branched and may be covalently attached to a protein or lipid. Glycans are therefore highly efficient vehicles for information storage. Efficient chemical assembly of glycans has been a major concern in synthetic organic chemistry over the past decade due to important roles of complex glycans in many fundamental life-sustaining processes. Development of efficient and stereoselective glycosylation methodologies is crucial for the efficient synthesis of glycans. The selection of an appropriate glycosyl donor is one of the key processes for the successful glycosylation in terms of efficiency and stereoselectivity. Lecture starts with simple transformations of polyhydroxy compounds such as the selective oxidation of diols or triols and the selective protection or deprotection of polyols. Lecture also includes the synthesis of higher-carbon sugars, higher-carbon sugar nucleosides, branched-chain sugars, and inositols. Lecture continues with describing our works on development of new glycosyl donors and stereoselective glycosylations with the new glycosyl donors such as 2´-carboxybenzyl (CB) glycosides, glycosyl pentenoates/PhSeOTf, and C-1 hydroxy sugars/phthalic anhydride/Tf2O. Complexoligosaccharides, which were synthesized by our new glycosylation methods, are listed Lecture also includes the effect of remote protecting groups of glycosyl donors on glycosylation stereochemistry. Mannosylations of various acceptors with donors possessing an electron-withdrawing group at O-3, O-4, or O-6 positions were found to be b-selective except when donors had 3-O-acyl and 6-O-acetyl groups, which afforded a-mannosides as major products. Directing effect of remote protecting groups of other glycosyl donors was found to be quite different from the directing effect of those of mannosyl donors.