Stereodivergent Construction of [5,5]-Oxaspirolactones of Phainanoids

A stereodivergent synthesis of [5,5]-oxaspirolactones of phainanoids is presented herein. Through precisely tuning the inherent substitution differences on cyclopropanol, a palladium-catalyzed cascade carbonylative lactonization enables the stereodivergent synthesis of [5,5]-oxaspirolactones of phainanoids.