Synthesis of (±)-cryptofauronol and related valerane sesquiterpenes via rearrangement of bicyclo[5.3.0]decane precursors

Abstract

Alkenyl-substituted furfuryl alcohols have been converted into the corresponding alkenyl-substituted pyrylium species which undergo intramolecular cycloaddition to produce highly functionalised perhydroazulenes. These products, epoxybicyclo[5.3.0]decanones and the corresponding alcohols, can undergo acid-catalysed rearrangement reactions to give cis-fused bicyclo [4.4.0] decanes. The scope and limitations of these rearrangement reactions have been explored. The process has been adapted for use in the synthesis of the sesquiterpenes (±)-cryptofauronol, (±)-fauronyl acetate, (±)-valeranone, and (±)-valerane.