title: Highly substituted tetrahydropyrones from hetero-Diels-Alder reactions of 2-alkenals with stereochemical induction from chiral dienes.
abstract: [reaction: see text] A new method for the stereoselective synthesis of libraries of 2,3,5-trisubstituted tetrahydro-gamma-pyrones and the corresponding tetrahydropyran-4-ols is reported. Dienes with a chiral moiety at position 5 were synthesized starting from (triphenylphosphoranylidene)acetone. In hetero-Diels-Alder (HDA) reactions, especially with alpha,beta-unsaturated aldehydes, they induce diastereomeric ratios from 4:1 to 14:1. Through selective epimerization and reduction, further building blocks are available. These constitute ideal starting points for their use in the total synthesis of complex polyketide macrocycles, especially with the vinyl group available for metathetic coupling.
authors.affiliation: Department of Bioorganic Chemistry, Leibniz Institute of Plant Biochemistry, Weinberg 3, 06120 Halle (Saale), Germany.
authors.forename: Eelco
authors.initials: E
authors.lastname: Ruijter
authors.forename: Heike
authors.initials: H
authors.lastname: Schültingkemper
authors.forename: Ludger A
authors.initials: LA
authors.lastname: Wessjohann