Synthesis of <i>ent</i>-[3]-Ladderanol: Development and Application of Intramolecular Chirality Transfer [2+2] Cycloadditions of Allenic Ketones and Alkenes

An enantioselective synthesis of ent-[3]-ladderanol is presented. The ladderanes are an interesting class of molecules for their unique structure of fused cyclobutane rings as well as their perceived biological function of organism protection. The route hinges on the development and application of a chirality transfer [2+2] cycloaddition of an allenic ketone and alkene. Further stereocontrolled transformations allowed for completion of the synthesis. The scope of the chirality transfer [2+2] cycloaddition is also presented.