Ring opening metathesis approach to the isoprostanes

A new route to enantiomerically pure isoprostane analogs is described. Ring opening metathesis of bicyclo[3.2.0]heptene (3) with TBS-protected allyl alcohol generates the syn-disubstituted cyclopentyl product (±)-4. Diene (±)-4 can be converted in a straightforward manner to aldehyde (±)-7. Asymmetric alkylations of aldehyde (±)-7 yield a series of enantiomerically pure isoprostane analogs (2a–d).