Application of the Rh(II) Cyclization/Cycloaddition Cascade for the Total Synthesis of (±)-Aspidophytine
摘要:
A new strategy for the synthesis of (+/-)-aspidophytine has been developed and is based on a Rh(II)-catalyzed cyclization/dipolar cycloaddition sequence. The resulting [3+2]-cycloadduct undergoes an efficient Lewis acid mediated cascade that rapidly provides the complete skeleton of aspidophytine. The synthesis also features a mild decarbomethoxylation reaction.
A dipolar cycloaddition approach toward the kopsifoline alkaloid framework
摘要:
Using a metal-catalyzed domino reaction as the key step, the heterocyclic skeleton of the kopsifoline alkaloid family was constructed by a 1,3-dipolar cycloaddition of a carbonyl ylide dipole derived from a Rh(II)-catalyzed reaction of a diazo ketoester across the indole pi-bond. Ring opening of the resulting 1,3-dipolar cycloadduct followed by a reductive dehydroxylation step resulted in the formation of a critical silyl enol ether necessary for the final F-ring closure of the kopsifoline skeleton. (C) 2007 Elsevier Ltd. All rights reserved.
Total Synthesis of the Alkaloid (±)-Aspidophytine Based on Carbonyl Ylide Cycloaddition Chemistry
作者:José M. Mejía-Oneto、Albert Padwa
DOI:10.1002/hlca.200890034
日期:2008.2
The RhII-catalyzed cycloaddition cascade of an indolyl-substituted α-diazo imide was used for the totalsynthesis of the complex pentacyclic alkaloid (±)-aspidophytine. Treatment of the resulting dipolar cycloadduct with BF3⋅OEt2 induces a domino fragmentation cascade. The reaction proceeds by an initial cleavage of the oxabicyclic ring and formation of a transient N-acyl iminium ion which reacts further