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Highly diastereoselective 5-hexenyl radical cyclizations with Lewis acids and carbohydrate scaffolds
E J Enholm1, J S Cottone, F Allais
1Department of Chemistry, University of Florida, Gainesville, Florida 32611, USA. enholm@chem.ufl.edu
Organic Letters
|June 30, 2001
Abstract:
[figure: see text] Carbohydrates as removable chiral scaffolds for free radical cyclizations were examined for the first time. This investigation illustrates the utility of two inexpensive carbohydrate derivatives as sources of asymmetry for 5-hexenyl radical cyclizations. Diastereomeric ratios as high as 100:1 were achieved with an ester-appended (+)-isosorbide hexose and 70:1 for a diol-protected D-xylose pentose. Temperature dependence, Lewis acids, and solvents were all examined. By correlation with known compounds, the newly generated chiral centers were of the (S)-configuration.