Synthesis of Demissidine by a Ring Fragmentation 1,3-Dipolar Cycloaddition Approach

A synthesis of the steroidal alkaloid demissidine from epiandrosterone is reported. A ring fragmentation reaction that efficiently ruptured the D-ring of a diazo ester derivative of epiandrosterone to provide an aldehyde tethered ynoate product was key to this sequence. Incorporation of the indolizidine framework was achieved by an azomethine ylide 1,3-dipolar cycloaddition.