The first total synthesis of 15 (R)-Me-PGD2 3 is reported. The synthesis is based on the enantioselective and stereospecific syntheses of synthon 17 and its attachment to the five- membered ring by a olefin cross metathesis reaction. This approach permits the introduction of a side chain with a predetermined stereogenic center into the prostanoid ring, resulting in the synthesis of 15 R-methyl prostaglandin D2 and allows rapid access to other ...