Syntheses of the four enantiomerically pure diastereoisomers of the phytoprostanes E1 type II and 15-E2t-isoprostanes (1−4) are described. The key steps included the preparation of the Freïmanis (±)-hydroxycyclopentenone 5, enzymatic resolution of this racemic hydroxycyclopentenone, Wittig and Horner−Wadsworth−Emmons (HWE) coupling reactions and finally enantioselective reductions.