A practical route to both enantiomers of bicyclo[3.3.0]oct-2-en-7-one and their use for the synthesis of key trisubstituted cyclopentanes

We describe new methodology for the synthesis of both enantiomers of 7,7-dichlorobicyclo[3.2.0]hep-2-en-6-one and conversion of these compounds into stereochemically defined bicyclo[3.3.0]oct-2-en-7-ones and thence trisubstituted cyclopentanes. These are key intermediates for the synthesis of prostanoids, brefeldin and other cyclopentane-containing natural products.