Infoscience

Journal article

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.

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