Total Synthesis of Furanether B

Article abstract of DOI:10.1021/jo00285a010

The first total syntheses of furanether B, a member of the lactarane class of sesquiterpenes, have been completed starting from 1-methyl-8-oxabicyclo<3.2.1>oct-6-en-3-one (3).After ketone reduction, Pauson-Khand cycloaddition (propyne-Co2(CO)6, benzene, heat) gives rise to a 75percent yield of stereoisomeric tricyclic enones 5 and 6.Reduction and methylation of enone 5, removal of the ketone (Barton), and oxidation of the remaining alcohol function give 13.The natural product is obtained upon regiospecific formylation, conversion to the S-butyl derivative, and generation of the furan via a modification of Garst's procedure using a thiomethylene ylide under phase-transfer conditions.A similar sequence beginning with 6 also provides access to 13, but most of the steps proceed in somewhat lower yields.