A Diastereoselective Synthesis of the ABCD Ring System of Rubriflordilactone B

A novel 9-step diastereoselective route to the ABCD ring system of the natural product rubriflordilactone B is reported. Use of an a-substituted butenolide derived from maleic anhydride facilitated a 1,4-conjugate addition to provide a diene. The order in which a ring-closing metathesis and enolate oxidation were performed on this compound dictate the relative stereochemistry of the target. The final product exhibited anisotropic effects during room temperature NMR studies, requiring elevated temperature experiments to confirm its identity.