| Summary: | 碩士 === 國立清華大學 === 化學系 === 97 === Globo-H hexasaccharide is a tumor-associated carbohydrate antigen that is highly expressed on the surface of breast cancer cells. This hexasaccharide has been aimed at development of anti-breast cancer vaccine. In recent study, the pentasaccharide precursor of Globo-H, SSEA-3, was found that its expression in breast cancer stem cells was higher than Globo-H. As a result, SSEA-3 has become another candidate for anti-breast cancer vaccine.
In this thesis we focus on the synthetic methods of Globo-H and SSEA-3. Our strategy is base on one-pot glycosylation method and we want synthesize these two oligosaccharides by using well-know protocols. In the synthesis of α-D-Gal-(1→4)-β-D-Gal-(1→4)-β-D-Glc trisaccharide, we can get exclusive α product by using benzyl-protected lactose acceptor, and no β isomer was observed. In the synthesis of β-D-Gal-(1→3)-β-D-GalNAc disaccharide, we use cheap and commercial available galactose as starting material of GalNAc acceptor, and we used azide group at C-2 position. The exclusive β disaccharide can be synthesized by using benzoyl group at C-2 position of galactose donor. We use the benzoyl- and Troc-protected GalNAc acceptor to improve the efficiency of glycosylation. The pentasaccharide compound has been synthesized by using our building blocks. In this thesis, the α/β selectivity is good in every glycosylation reaction. We established a simple and efficient pathway to achieve the synthesis of this oligosaccharide.
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