Inhibition of prostaglandin synthetase by di- and triphenylethylene derivatives: a structure-activity study

The syntheses of new di- and triphenylethylene derivatives are described along with their X-ray analysis and NMR study, which have helped to establish their conformation. Screening of over 50 derivatives for inhibition of prostaglandin synthetase (PGS) activity in bovine seminal vesicle microsomes has revealed that many of the triphenylethylene derivatives are potent inhibitors of PGS. Several even show marked activity at the extremely low concentration (IC50) of about 4 X 10(-8) M, which is two orders of magnitude lower than the active concentration of the majority of known nonsteroidal antiinflammatory agents (IC50 approximately equal to 10(-6) M). Unlike the latter, these compounds are not carboxylic acids. Furthermore, in contrast to biphenyl, diphenylmethane, or unsymmetrical, alpha, alpha'-diphenylethylene PGS inhibitors, the presence of a beta-phenyl ring was an essential requirement for high potency. The best inhibitors possessed a cyanide group (acids, amides, and amines were poor inhibitors), methoxy in preference to hydroxy groups on the alpha-phenyl rings, and a halogen (F or Cl) in a para position on the beta-phenyl ring. These data provide additional insight into the nature of the PGS binding site.