A sequence to oxo lactones 1 via Barbier-type Gilman-Van-Ess reaction, sonochemical Lemieux oxidation, one-step ether cleavage iodination and phase transfer catalyzed cyclization is presented. Conversion of the oxo lactones 1 into methyl(en)ated macrolides 11 – 13 resulted in highly potent musk fragrances.
involved either the Baeyer-Villiger ring expansion of a cyclic ketone or the macrolactonization of a hydroxy acid to give a lactone. The lactone carbonyl was removed either by conversion to an intermediate thionolactone obtained by reaction with Lawesson's reagent and reduction or by direct reduction using a boron trifluoride etherate mediated sodium borohydride reaction.