Stereocontrol in Diels-Alder cycloaddition to unsaturated sugars: reactivities of acyclic seven-carbon trans dienophiles derived from aldopentoses.
Acyclic trans-2,3-unsaturated aldoheptonate derivatives (1-9) obtained from D-aldopentoses by Wittig chain-extension served as dienophiles for a detailed comparative study of their asymmetric Diels-Alder cycloaddition with cyclopentadiene. Cycloaddition under uncatalyzed thermal conditions gave mixtures of the four possible stereoisomeric norbornene adducts. The endo:exo ratios and the diastereofacial selectivities in the formation of the adducts were determined by NMR spectroscopy and by chemical transformations. The quantitative distribution of adducts as a function of stereochemistry of the dienophile is discussed.
Horton
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Department of Chemistry, Ohio State University, Columbus 43210.
Koh
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D002236:Carbohydrate Conformation; D003517:Cyclopentanes; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D015394:Molecular Structure; D009904:Optical Rotation; D010429:Pentoses; D013237:Stereoisomerism
D003517:Cyclopentanes; D007202:Indicators and Reagents; D010429:Pentoses; C004709:1,3-cyclopentadiene