Total Asymmetric Syntheses of beta-Hydroxy-delta-lactones via Umpolung with Sulfur Dioxide
Cyclic stereotriads and stereotetrads of the beta-hydroxy-delta-lactone type, e.g. prelactones B and E, common in polyketides and polypropionates, are prepared via SO2-induced oxyallylations of enoxysilanes with (1E,3Z)-1-(1-phenylethoxy)penta-1,3-dien-3-yl carboxylates. Using (Z)- or (E)-enoxysilanes both 4,5-cis- or 4,5-trans-delta-lactones are obtained. Depending on the reduction method applied to the obtained aldol intermediates 5,6-trans or 5,6-cis-derivatives are formed. The delta-lactones can be prepared in both their enantiomeric forms depending on the (1R)- or (1S)-configuration of the starting 1-(1-phenylethoxy)penta-1,3-dienes.
Keywords: Modular Polyketide Synthase ; Precursor-Directed Biosynthesis ; Ring-Closing Metathesis ; Marine Natural-Products ; Enantioselective Synthesis ; Prelactone-B ; Erythromycin Biosynthesis ; Stereoselective-Synthesis ; Polypropionate Synthesis ; Antibiotic Kendomycin
Record created on 2011-12-16, modified on 2016-08-09