Synthesis of (±)-prostaglandin I2 methyl ester and its 15-epimer from 2-(cyclopent-2-enyl)-1-(2-oxocyclopentyl)ethanol derivatives

Abstract

The threo-2-(cyclopent-2-enyl)-1-(2-oxocyclopentyl)ethanol derivatives (2) and (3) have been converted into (±)-prostaglandin I₂ methyl ester and its 15-epimer. The route involved halogenoetherification, hydrodehalogenation, Baeyer–Villiger oxidation, and methanolysis, to give the 5-hydroxyprostaglandin I₁ derivatives (17) and (18). These hydroxy esters were mesylated, the 11- and 15-hydroxy groups were deprotected, and the resulting 15-epimeric alcohols were separated. The final elimination, accomplished by means of neat 1,8-diazabicyclo[5.4.0]undec-7-ene, gave the required Δ⁵-olefin with a high degree of regioselectivity, and was stereospecifically trans, giving the required Z-configuration (25).