Enantioselective total synthesis of eunicenone A

An enantioselective, stereocontrolled total synthesis of eunicenone A (1) i s described starting from geranylgeranylacetylene (9) in 14 steps via inter mediates 10-20. The most critical construction in the synthesis is the high ly effective Diels-Alder combination of the achiral components 2-bromoacrol ein and diene 13 in the presence of the chiral Lewis acid catalyst 14 to fo rm 15 (85% yield, 97% ee, >98:2 endo-exo ratio). The synthesis utilizes a n ovel reagent (12) for introduction of silicon, which serves to activate and direct the diene 13 for Diels-Alder reaction and to provide for eventual o xygen functionality of homoallylic alcohol 17 under mild conditions. Other noteworthy steps include the position selective and diastereoselective epox idation 17 --> 18, the methoxycarbonylation with allylic transposition 19 - -> 20, and the alpha,beta -enone unmasking 20 --> 1.