A convenient route to 1-(2-oxiranyl)-1,4-diketones and their application to the synthesis of endo-brevicomin, endo-isobrevicomin, frontalin and related compounds via alkylated 6,8-dioxabicyclo[3.2.1]octan-2-ones

1-(2-Oxiranyl)-1,4-alkanediones were prepared from the ethylene acetals of ethyl 4-oxoalkanoates via the oxidation of the intermediate 1,2-dialkylcyclopropanols having a protected carbonyl group in an aliphatic chain. Intramolecular acetalization of these epoxy dicarbonyl compounds gave alkylated 6,8-dioxabicyclo[3.2.1]octan-2-ones in good yields. The latter were found suitable to be precursors for (±)-endo-brevicomin and its 2-hydroxy derivative, as well as (±)-endo-isobrevicomin and (±)-frontalin.