Evolution of a Strategy for the Enantioselective Synthesis of (−)-Cajanusine

The first enantio­selective synthesis of (−)-cajanusine is presented. Key features of the route include a rapid synthesis of the [4.2.0]­bicyclo­octane core by an enantio­selective isomerization/stereo­selective [2+2]-cycloaddition strategy as well as prominent use of catalytic methods for bond construction. The evolution of the approach is also presented that highlights unexpected roadblocks and how novel solutions were developed.