Preparation of ent-Prostaglandin E2

The enantiomeric prostaglandins, exemplified by ent-PGE2, are apparently produced in vivo by the nonenzymatic oxidation of arachidonic acid. To assess the physiological activity of ent-PGE2, it was necessary to prepare it by total synthesis. The key transformation in this synthesis was the equilibration of the kinetically prepared ent-15-E2t-isoprostane to ent-PGE2.