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Stereocontrolled Synthesis of a C n –C n +7 Building Block (“Eastern Moiety”) for the Unnatural Enantiomers of Important Polyol,Polyene Antibiotics Based on a Ring‐Closing Metathesis and an Aldol Addition of a Lactone Enolate
Author(s) -
Kamptmann Sonja B.,
Brückner Reinhard
Publication year - 2013
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201300183
Subject(s) - chemistry , moiety , epoxide , stereoselectivity , stereochemistry , stereocenter , ring closing metathesis , enantiomer , polyene , acetal , metathesis , enantioselective synthesis , organic chemistry , catalysis , polymer , polymerization
A stereocontrolled synthesis of epoxide 6 , which represents the C n –C n +7 or “eastern moiety” building block for the title compounds, has been realized in 19 steps. Our synthesis started from tetrabromoacetone 26 and afforded dibromotriene 33b in six steps. The latter was subjected to a ring‐closing metathesis, which gave the dibromovinyl‐substituted lactone 34 in high yield. A highly stereoselective conjugate addition/enolate aldolization sequence established the additional stereocenters with perfect selectivity. Epoxide 47b was reached in another eight steps, which included a C–SiMe 2 Ph → C–OH oxidation in the presence of an acetal group. The final structure 6 was completed by hydrostannylation/brominolysis.