Development of the arming participating group.

The last few decades have shown the importance that carbohydrates play in physiological processes. It has been shown that carbohydrates are responsible for processes such as metabolism, cell-cell recognition, cell adhesion, immune response, metastasis and for viral and bacterial infection (for cell membrane penetration). They have also shown promise as antibiotic and anti-cancer drugs. Biological studies require significant quantities of chirally pure compounds. Isolation of pure material from natural sources, however, remains a daunting task. One approach to overcome this is to chemically synthesize the required compounds. In line with recent developments in the area of synthetic chemistry, there is a demand to synthesize these compounds in the most straightforward way. One of the most efficient, Fraser-Reid's armed-disarmed glycosylation strategy, is based on the chemoselectivity principle, in which an armed glycosyl donor is activated over a disarmed acceptor to afford a 1,2- cis-linked disaccharide. The armed-disarmed glycosylation strategy simplifies the synthesis of cis-trans or cis-cis -linked oligosaccharides. It is not, however, applicable for the synthesis trans-cis or trans-trans sequences. This dissertation focuses on a novel glycosylation approach that minimizes protective group manipulations between glycosylation steps, by utilizing a new class of protective group, the so-called "arming participating substituent". This group has permitted the development of the "Inverse Armed-Disarmed Strategy" which allows for synthesis of trisaccharides bearing all four possible glycosylation patterns.