Synthesis of the Pentacyclic Skeleton of the Aspidosperma Alkaloids Using Rhodium Carbenoids as Reactive Intermediates

摘要: A series of diazo amido keto esters prepared from N-alkenyl-substituted 3-carbalkoxy-2-piperidone derivatives was treated with rhodium(II) acetate. Attack the carbonyl oxygen at resultant rhodium carbenoid center produced a transient push−pull ylide dipole which underwent an intramolecular dipolar cycloaddition reaction. related annulation sequence used to prepare pentacyclic skeleton aspidosperma family alkaloids. Synthesis required imide carried out 3-carboxy-3-ethyl-2-piperidone and N-methyl-3-indoleacetic acid. Treatment acetate afforded 1,3-dipole subsequently across indole π-bond. The resulting cycloadduct is consequence endo respect fully in accord lowest energy transition state. converted three steps into desacetoxy-4-oxo-6,7-dihydrovindorosine. stereochemistry fi...