Design and synthesis of a selective EP4-receptor agonist.: Part 3:: 16-phenyl-5-thiaPGE1 and 9-β-halo derivatives with improved stability

To identify a new selective EP4-agonist with improved chemical stability, further chemical modification of those reported previously was continued. We focused our attention on chemical modification of the alpha chain of 3,7-dithiaPGE(1), and selected 5-thiaPGE(1), as a new chemical lead, Introduction of an optimized omega to chain to the 5-thiaPG skeleton afforded in-methoxymethyl derivative 33a, which showed the most potent EP4-receptor agonist activity and good subtype-selectivity both in vitro and in vivo. 9beta-HaloPGF derivatives were also synthesized and biologically evaluated in an attempt to block self-degradation of the beta-hydroxyketone moiety. Among these series, 39a and 39b showed potent agonist activity and good subtype-selectivity. Structure-activity relationships (SARs) are also discussed. (C) 2002 Elsevier Science Ltd. All rights reserved.