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 (Ï-oxoalkoxy)carbonylmethylenetriphenylphosphoranes are described. The latter are easily accessible by addition of the appropriate (free or protected) Ï-hydroxyalkanals to the cumulated ylide triphenylphosphoranylideneketene. Examples are then given for the use of these methods in natural product synthesis.
累积
脲 XX.1 通过
三苯基膦亚基
乙烯分子内 Wittig 烯化反应合成 (E)-δ,δ-不饱和大环内酯2 描述了通过 (Ï-氧代烷氧基)羰基亚甲基
三苯基膦分子内 Wittig 反应封闭大环内酯环的两种方法。通过将适当的(游离或受保护的)Ï-羟基
烷烃加入到累积的
三苯基膦亚基
乙烯炔中,很容易获得后者。然后举例说明了这些方法在
天然产物合成中的应用。