Stereoselective C-Glycosylation Reactions of Ribose Derivatives: Electronic Effects of Five-Membered Ring Oxocarbenium Ions
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- 作者：Catharine H. Larsen ; Brian H. Ridgway ; Jared T. Shaw ; Deborah M. Smith ; and K. A. Woerpel
- 刊名：Journal of the American Chemical Society
- 出版年：2005
- 出版时间：August 10, 2005
- 年：2005
- 卷：127
- 期：31
- 页码：10879 - 10884
- 全文大小：142K
- 年卷期：v.127,no.31(August 10, 2005)
- ISSN：1520-5126
文摘
The factors controlling the highly 
-selective C-glycosylation of ribose derivatives were determinedby examining the stereoselective reactions of 18 ribose analogues differing in substitution at C-2, C-3, andC-4. The lowest energy conformers of the intermediate oxocarbenium ions display the C-3 alkoxy group ina pseudoaxial orientation to maximize electrostatic effects. To a lesser extent, the C-2 substituent prefersa pseudoequatorial position, and the alkyl group at C-4 has little influence on conformational preferences.In all cases, the product was formed by stereoelectronically preferred inside attack on the lowest energyconformer.
-selective C-glycosylation of ribose derivatives were determinedby examining the stereoselective reactions of 18 ribose analogues differing in substitution at C-2, C-3, andC-4. The lowest energy conformers of the intermediate oxocarbenium ions display the C-3 alkoxy group ina pseudoaxial orientation to maximize electrostatic effects. To a lesser extent, the C-2 substituent prefersa pseudoequatorial position, and the alkyl group at C-4 has little influence on conformational preferences.In all cases, the product was formed by stereoelectronically preferred inside attack on the lowest energyconformer.