Viridiofungins and xeniolide F: target oriented synthesis using different rearrangement reactions of a common substrate class

The present dissertation covers the total synthesis of viridiofungin triesters and studies toward the total synthesis of xeniolide F. In both cases, sigmatropic rearrangements of α-allyloxy substituted α,β-unsaturated esters are employed: for the viridiofungin ester synthesis a [2,3]-Wittig rearrangement and for the xeniolide F synthesis a catalytic asymmetric Claisen rearrangement CAC. For both rearrangement reactions the historical development, main characteristic and important variations are discussed. The viridiofungin triester synthesis represents a convergent and highly flexible route toward these natural products. The [2,3]-Wittig rearrangement allowed the diastereoselective synthesis of the polar head group with two adjacent stereogenic centers. The E-configured double bond was formed by a Julia-Kocienski olefination. During the studies toward the total synthesis of xeniolide F a new, diastereoselective strategy for the generation of allyl vinyl ethers with E-configured vinyl ether double bond was established employing rhodium catalyzed OH-insertion and an E-selective Horner-Wadsworth-Emmons olefination. Under the conditions of the catalytic asymmetric Claisen rearrangement (CAC) this highly substituted allyl vinyl ether rearranged diastero- and enantioselectively to the corresponding a-keto ester. This example clearly illustrates the high potential of the CAC as synthetic tool for natural product synthesis.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Technische Universität Dresden

Year

2006

Author dc:creator

• Pollex, Annett

Contributors dc:contributor

• Hiersemann, Martin
• Metz, Peter
• Brückner, Reinhardt

• rearrangements
• [2,3]-Wittig rearrangement
• Claisen rearrangement
• diterpene
• alkyl citrate
• allyl vinyl ether
• sigmatrope Umlagerungen
• [2,3]-Wittig-Umlagerung
• Claisen-Umlagerung
• Alkylcitrate
• Allylvinylether