Abstract
More than ever, it is a challenging objective in synthetic chemistry
to create efficient access to biologically active compounds. In
particular, one structural element which is frequently incorporated
in the framework of complex natural products is a β-hydroxy
ketone. In this context, the aldol reaction as the most important
transformation to generate this structural element not only creates
new C-C bonds but also establishes stereogenic centers.
In recent years, a large variety of highly selective methodologies
for aldol and aldol-type reactions has been put forward. On this
background, the vinylogous Mukaiyama aldol reaction became a pivotal transformation
since it also allows for the immediate transformation of the olefin
which is simultaneously introduced. This Account covers the application
of various (vinylogous) aldol reactions from our laboratories in
the syntheses of natural products with important bio-logical activities.
1 Introduction
2 Polyketides: Selected Natural Products
3 Vinylogous Mukaiyama Aldol Reaction (VMAR)
3.1 Triarylboranes in the Substrate-Controlled VMAR in the Synthesis
of Ratjadone
3.1.1 Suppression of the Silyl Cation Catalyzed Pathway
3.1.2 Substrate-Controlled VMAR in the Synthesis of Oleandolide
3.1.3 Substrate-Controlled VMAR in the Synthesis of Amphidi-nolide
H2 and Tedanolide
3.2 Oxazaborolidinones as Chiral Lewis Acids in the Enantio-selective
VMAR
4 Aldol Reactions in Natural Product Syntheses
4.1 Tedanolide
4.2 Chivosazole
4.3 Disorazole
4.4 Epothilone
4.5 Spirangien
5 Conclusions and Outlook
Key words
aldol reactions - vinylogy - stereoselectivity - natural product synthesis
