Syntheses of (5E)-PGE2 and New 6-Functionalized Derivatives by the Use of Palladium-Catalyzed Decarboxylative Allylic Alkylation

Abstract

(5 E )-Prostaglandin E 2 ( 7) was synthesized fron ( R )-4- t -butyldimethylsilyloxy-2-cyclopentenone ( 1) by in situ 2-alkenyloxycarbonylatlon of the organocopper conjugate-addition adduct ( 3) followed by intramolecular palladium-catalyzed decarboxylative allylic alkylation. The (5 E )-prostaglandin E 2 skeleton was also obtained from the β-keto allylic ester ( 11) by a similar decarboxylative allylic alkylation. The decarboxylative allylic alkylation of another type of the three-component coupling product ( 12) gave new 6-methyleneprostaglandin E1 skeleton ( 15a), which was converted into new 6-methylprosta-glandin I methyl ester ( 20) via 6-methyleneprostaglandin F 1α derivative ( 16) by two different ways. The stereochemistry of this intramolecular decarboxylative allylic alkylation was discussed in the reaction of 2-[( E )- or ( Z )-2-butenyloxy-carbonyl] cyclopentanone systems.