title: Stereocontrol in Diels-Alder cycloaddition to unsaturated sugars: reactivities of acyclic seven-carbon trans dienophiles derived from aldopentoses.
abstract: 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.
authors.affiliation: Department of Chemistry, Ohio State University, Columbus 43210.
authors.forename: D
authors.initials: D
authors.lastname: Horton
authors.forename: D
authors.initials: D
authors.lastname: Koh
mesh_terms: 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
chemical_list: D003517:Cyclopentanes; D007202:Indicators and Reagents; D010429:Pentoses; C004709:1,3-cyclopentadiene