Kumulierte Ylide XX.¹ Synthesen (E)-α,β-ungesättigter macrocyclischer Lactone durch intramolekulare Wittig-Olefinierung via Triphenylphosphoranylidenketen²

Cumulated Ylides XX.¹ Syntheses of (E)-α,β-Unsaturated Macrocyclic Lactones by Intramolecular Wittig-Olefination via Triphenylphosphoranylideneketene² Two methods for closure of macrocyclic lactone rings by intramolecular Wittig reaction of (ω-oxoalkoxy)carbonylmethylenetriphenylphosphoranes are described. The latter are easily accessible by addition of the appropriate (free or protected) ω-hydroxyalkanals to the cumulated ylide triphenylphosphoranylideneketene. Examples are then given for the use of these methods in natural product synthesis.