Detection of the 15‐acetate of prostaglandin E 2 methyl ester as a prominent component of the prostaglandins in the gorgonian coral Plexaura homomalla

15 R ‐Prostaglandin E 2 (PGE 2 ) methyl ester 15‐acetate ( 1 ) was isolated from the R ‐variety of the Caribbean sea whip coral, Plexaura homomalla collected in the Florida Keys. It was present in coral samples from separate collections in 2–10% of the abundance of the major prostaglandin component, PGA 2 methyl ester 15‐acetate. The structure of 1 was assigned based on one‐ and two‐dimensional 1 H NMR, HPLC, and LC‐MS analyses. A sample of the S ‐variety of P. homomalla was found to contain a similar abundance of the corresponding 15 S product, prostaglandin E 2 methyl ester 15‐acetate. The significance of PGE acetylation is discussed in relation to the proposed mechanism of PGA synthesis in the coral.