A series of chemically stable TXA2/PGH2 analogues modeled after the structure of the natural products was prepared in search of useful inhibitors of TXA2/PGH2-mediated pathophysiology. Each of the 16 isomers implied in structure 1 was prepared in chiral form and evaluated for activity in vitro in platelets and smooth muscle. Depending on relative side chain and carbinol stereochemistry, TXA2/PGH2 agonist and antagonist and, surprisingly, ...