A series of diazo amido keto esters prepared from N-alkenyl-substituted 3-carbalkoxy-2- piperidone derivatives was treated with rhodium (II) acetate. Attack of the amido carbonyl oxygen at the resultant rhodium carbenoid center produced a transient push-pull carbonyl ylide dipole which underwent an intramolecular dipolar cycloaddition reaction. A related annulation sequence was used to prepare the pentacyclic skeleton of the aspidosperma ...
