| Autor: |
Beaver MG; Department of Chemistry, University of California, Irvine, California 92697-2025, USA., Woerpel KA |
| Jazyk: |
angličtina |
| Zdroj: |
The Journal of organic chemistry [J Org Chem] 2010 Feb 19; Vol. 75 (4), pp. 1107-18. |
| DOI: |
10.1021/jo902222a |
| Abstrakt: |
Nucleophilic substitution reactions of 2-deoxyglycosyl donors indicated that the reactivity of the oxygen nucleophile has a significant impact on stereoselectivity. Employing ethanol as the nucleophile resulted in a 1:1 (alpha:beta) ratio of diastereomers under S(N)1-like reaction conditions. Stereoselective formation of the 2-deoxy-alpha-O-glycoside was only observed when weaker nucleophiles, such as trifluoroethanol, were employed. The lack of stereoselectivity observed in reactions of common oxygen nucleophiles can be attributed to reaction rates of the stereochemistry-determining step that approach the diffusion limit. In this scenario, both faces of the prochiral oxocarbenium ion are subject to nucleophilic addition to afford a statistical mixture of diastereomeric products. Control experiments confirmed that all nucleophilic substitution reactions were performed under kinetic control. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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