利用Glycals 進行位相選擇性合成的2,3-Unsaturated glycals 和Spiro-glycosides
| Autor: | Yen-Bo Chen, 陳彥伯 |
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| Rok vydání: | 2016 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 104 Glycosides play an important rule in an organism, and it is very important to develop the methods to synthesis them. Among them, the O-glycosylation and C-arylglycosylation products display diverse biological activities, such as anti-timor, anti-bacterial, anti-virus, and inhibition of enzyme. In this program, we have developed two methods to synthesize the α-2,3-Unsaturated galactosides and Spiro bis-C,C-α-arylglycosides. In part 1, α-2,3-Unsaturated galactosides were synthesized in good to excellent yields by the initial activation of D-galactals with diethyl phosphorochloridite and the subsequent glycosyl addition via Ferrier rearrangement with various O-nucleophiles in the presence of AlCl3. The two-step reactions were carried out in one-pot and finished within 60 min in 81-95% yield to give the glycoside products with excellent α-stereoselectivity. On the other hands, spiro bis-C,C-α-arylglycosides were synthesized in three steps in 78−85% overall yields starting from exo-glycals. The initial Heck type C-aryl addition of exo-glycals with arylboronic acids afforded α-aryl-β-substituted C-glycosides with exclusive α-stereoselectivity. Among the products, β-ethanal α-aryl C-glycosides further reacted with alkylthiol in the presence of InCl3, followed by in situ Friedel−Crafts cyclization to yield the desirable final products. We proposed a mechanism to explain how the α-aryl group serves as a main determinant of the cyclization. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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