2002 Fiscal Year Final Research Report Summary
Regioselective Glycosylation of Non-protected Methyl Hexopyranosides Using the Stannylene Activation Method
| Project/Area Number |
12672059
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Chemical pharmacy
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| Research Institution | Kitasato University |
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Principal Investigator |
KAJI Eisuke Kitasato University, School of Pharmaceutical Sciences, Professor, 薬学部, 教授 (60050598)
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| Co-Investigator(Kenkyū-buntansha) |
HIROTANI Seiko Assistant, 薬学部, 助手 (20050594)
YAGO Kazuo Professor, 薬学部, 教授 (10276157)
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| Project Period (FY) |
2000 – 2002
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| Keywords | glycosylation / oligosaccharide / dibutyltin oxide / Stannylene acetal / sugar hydroxyl group / Ag(I) silica alumina / glycosyl bromide / regioselectivity |
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| Research Abstract |
Developing a new method for regioselective glycosylation of unprotected sugars is highly desired, since the conventional protection-deprotection method renders the overall synthetic scheme lengthy and impractical. Chemical reactions should be much more selective, rapid, and productive.
In this context, very few precedents have revealed that the stannylene-mediated regioselective glycosylation of unprotected hexopyranosides makes it possible to provide one-pot assembly of some oligosaccharides. However, the previous methods were limited to afford α / β-(1 → 6)-linked disaccharides only, I.e., glycosylation of the primary hydroxyl group of hexoses is preferred, and the yields of the glycosylation reaction are not always high. Therefore, it is necessary to develop a novel regioselective glycosylation applicable to the secondary hydroxyl groups even in the presence of the primary hydroxyl one, giving for example, α / β-(1→3)-linked disaccharides.
We have developed a novel methodology of regio- and stereoselective glycosylation for fully unprotected methyl hexopyranosides by the stannylene activation method. Ag(I)-silica alumina-promoted glycosylation of stannylated sugars in the one-pot process was shown to yield β-(1 → 6)-linked disaccharides predominantly. Furthermore, addition of some tetra butylammonium salts to the reaction medium provides a significant regioselectivity shift on the glycosylation of unprotected methyl β-D-galactopyranoside, affording glucosyl-β-(1 → 3) -galactoside in preference to the corresponding β-(1→6)-linked disaccharide.
Since glycosyl β-(1→ 3)-galactoside moiety is well known as a core disaccharide unit of many immunologically relevant oligosaccharides, the method reported here would contribute to synthetic carbohydrate chemistry, which can be an alternative to the conventional "protection-deprotection" method.
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