Design and synthesis of an EP2-receptor selective agonist began with the chemical modification of α-and ω-chains of butaprost 1a, which exhibits an affinity for the IP-receptor. Two series of prostaglandin (PG) analogues with a 16-hydroxy-17, 17-trimethylene moiety as an ω-chain were identified. Among those tested, 4a, b, e, f, h and 6a, b, e, f, h were found to be highly selective EP2-receptor agonists. Structure–activity relationships are ...