Synthesis of Xanthanolides including new acylations and their synthetic applications

Xanthanolides were synthesized with intramolecular acylation of organolithium forming a sevenmembered carbocycle and one-pot acylation-Wittig lactonization as key steps. The Cu(II) complex efficiently catalyzed the acylation of thioester in Wittig lactonization under neutral conditions. Using the Cu(II) catalyst, symmetric dithiomalonates were converted into dissymmetric S,O-malonates via selective monoacylation. The key step in this reaction was the thermal formation of an acylketene, the stability of which would contribute to selectivity.