American Chemical Society
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Flexible Approach to Stemona Alkaloids: Total Syntheses of (−)-Stemospironine and Three New Diastereoisomeric Analogs

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posted on 2012-09-21, 00:00 authored by Nuria Bardají, Francisco Sánchez-Izquierdo, Ramón Alibés, Josep Font, Félix Busqué, Marta Figueredo
Total syntheses of (−)-stemospironine and three new diastereoisomeric analogs have been completed through a flexible strategy devised for Stemona alkaloids. The azabicycle 7 is the pivotal intermediate, from which the sequence splits according to each particular target. The most remarkable differential feature for stemospironine is the installation of the spiranic γ-lactone through an intramolecular Horner–Wadsworth–Emmons olefination. The configuration of the stereogenic center at C-11 was controlled by fine-tuning of the synthetic sequence.