A number of 17-aryl trinor and 16-aryloxy tetranor PGF2α derivatives have been approved for the treatment of glaucoma.{8941,9341,8839} These ``ring'' prostaglandin analogs have improved efficacy over the prostaglandins with an n-alkyl lower side chain. Of these, the ones wherein the 13,14-double bond has been hydrogenated retain relatively good potency, but show a significantly reduced incidence of local irritant side effects.{9736} 17-TFM-PGF1α is a typical ``ring'' analog reminiscent of the trifluoromethyl-phenoxy ring of Travoprost. The a chain of 17-TFM-PGF1α is saturated, making this compound a formal member of the one-series PGs. Recent work has shown that in the ``ring'' series of analogs, this modification has little impact on FP receptor binding.{9668} As an ocular hypotensive agent, it is expected that 17-TFM-PGF1α would act very much like the free acid of latanoprost.