ABSTRACT
Until the late 1970s 0-and N-glycosylated amino acids were constructed and used as standards for structural elucidations of the linkage regions between carbohydrate and peptide parts of glycoproteins [3,4]. However, the synthesis of glycopeptides demanded the development of versatile and selective protecting group techniques [5]. This holds true, in particular, for glycopeptides with complex oligosaccharide portions, which themselves must be formed in laborious multistep syntheses [6,7]. Much attention has to be paid to the glycosidic bond present in all natural glycoproteins. The acetal-type glycosidic and intersaccharidic bonds are potentially sensitive to strong acids and, for 0-glycosyl serine and threonine derivatives (e.g., of 2), also sensitive to bases. Therefore, controlled and selective deblocking of only one functional group of the polyfunctional glycosyl amino acids and glycopeptides is a critical problem in glycopeptide synthesis. Because the synthesis of oligosaccharides and glycosides has been described in a number of reviews [6,7] and is presented in succeeding chapters, this contribution is focused on protecting group techniques in glycopeptide chemistry.
