Abstract
Carbohydrates play important roles in many biological processes. Chemical synthesis may offer a good solution to get the pure and structurally verified oligosaccharides. The first part of this thesis describes the synthesis of ?-galactosyl ceramide and its C6-derivatives. The phytosphingosine derivative, which was obtained from D-glucosamine, could used to prepare ?-galactosyl ceramide. This strategy can be applied to prepare a variety of a-galactosyl ceramide C6-derivatives. The second part is concerned with the development of phenyl glycosides in the studies of new glycosylation methods and asymmetric intramolecular Diels-Alder reactions of masked o-benzoquinones. Two new and stable types of glycosyl donors, namely 2-allylphenyl and 2-allyloxyphenyl glycosides, were successfully developed, and their coupling with various alcohols in good yields were further investigated. Ease of preparation, handling and storage together with simple reaction set up, and clean glycosylations make these glycosides as attractive donors for the synthesis of oligosaccharides and glycoconjugates, as illustrated by the construction of bleomycin disaccharide. The studies on the synthesis of masked o-benzoquinones embedded with glycopyranoside as chiral auxiliaries to induce new chirality and high diastereoselectivity in asymmetric intramolecular Diels-Alder reaction are also described. The absolute configuration of new compounds is determined by comparison with the X-ray analysis of known compounds and optical rotation values. This convenient methodology can be applied in a wide range of alkenols to prepare a variety of chiral tricyclic ketones.
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