stereocontrolled strategy toward the total synthesis of isoprostanes based on a bicyclic alpha,beta-epoxy ketone intermediate 6. Bicyclo[3.3.0]octene scaffold permitted stereodirection of reagents allowing stereoselective epoxidation, diastereoselective ketone reduction, and regioselective epoxide opening otherwise not accessible with a simple cyclopentene framework.
Total Synthesis of (15<i>R</i>)- and (15<i>S</i>)-F<sub>2t</sub>-Isoprostanes by a Biomimetic Process Using the Cyclization of Acyclic Dihydroxylated Octa-5,7-dienyl Radicals
We report a new route to F-2t-IsoP (formerly named 8-epi-PGF(2alpha)) using a biomimetic radical cyclization of a highly functionalized C20 precursor. The strategy employed gives a beta-hydroxy free radical followed by molecular oxygen trapping, which is an unusual method for quenching carbon free radicals. We observed the formation of unique diastereoisomers (15R)- and (15S)-F-2t-IsoP. This result is consistent with a strong stereoelectronic control associated with a steric effect initiated by the side chains alpha and omega on the cyclopentane ring.