Luteolytic prostaglandins. Synthesis and biological activity

Design and synthesis of 13,14-dihydro prostaglandin F(1alpha) analogues as potent and selective ligands for the human FP receptor

The in vitro evaluation of a new class of potential bone anabolic agents for the treatment of osteoporosis is described. These compounds are potent and selective ligands for the human prostaglandin F receptor (hFP receptor). The compounds lack the olefin unsaturation required for potency in the natural ligand PGF(2)(alpha) yet retain binding affinity for the hFP receptor in the nanomolar to micromolar range. Removal of the alkenes also results in a better selectivity ratio for the hFP receptor over the other prostaglandin receptors tested. A rationale for the selectivity differences of various analogues, based on ligand docking experiments to a putative hFP receptor model, is also described.

Luteolytic potency of 16-phenoxy-derivatives of prostaglandin F2 alpha

The binding of 16-phenoxy derivatives of prostaglandin (PG) F2 alpha to rat luteal membranes, and also their abortifacient potency in pregnant rats, have been studied. Competitive binding studies with various PG-analogues were performed in ovaries of juvenile rats pretreated with PMSG and HCG, and in parallel studies the abortifacient potency of these substances was tested in pregnant rats. It was observed that this class of derivatives bound to the PGF2 alpha receptor as well as, or even better than the parent compound PGF2 alpha. Modifications in the carboxyl group at C-1 yielded derivatives with a higher affinity for the receptor, in decreasing order of effectiveness as follows: -COOR greater than COOH greater than OH. The data obtained from the binding studies also compared well with data on the abortifacient potency in pregnant rats. It is concluded that the addition of a phenoxy group to either the lower or upper side chain of PGF2 alpha may augment the binding to the receptor as well as the biological responses induced by the post receptor effect.

Synthesis and biological properties of 16(S)-amino-PGF2 alpha methyl ester

A synthesis of 16-amino-derivatives of PGF2 alpha is reported. Introduction of an amino group into position 16 of PGF2 alpha has decreased the sensitivity of the compound to metabolic degradation. 16(S)-amino-PGF2 alpha methyl ester shows high abortifacient activity with reduced diarrhoeic side effect.

Antihypertensive activity of 16, 16-dimethyl-oxa-alkyl-prostaglandins of the PGA2, PGE2 and trans-delta 2-11-deoxy-PGE1 series: structure-activity relationships

Utilizing Corey's synthesis, a variety of prostaglandins (PGs) with a modified omega-side chain were prepared. The 16, 16-dimethyl-oxa-alkyl analogues of PGA2 had potent antihypertensive activity. HR 466 (16, 16-dimethyl-18-oxa-PGA2), the best compound out of this series was active for 5-6 hours after oral administration of 0, 1 mg/kg to conscious renal hypertensive dogs. The corresponding analogues of PGE2 were also potent anti-hypertensive compounds, but were much more spasmogenic. Structural variations within the trans-delta 2-11-deoxy-PGE1-series, in both side chains, gave HR 601 (trans-delta2-15alpha-acetoxy-16, 16-dimethyl-18-oxa-11-deoxy-PGE1-methylester) which was orally active in the hypertensive dog with similar activity to HR 466.

Vasodilation and inhibition of platelet aggregation by prostacyclins with modified omega-side chain

Prostacyclin analogs with modified omega-side chain were synthetized in search of therapeutically useful agents. To characterize the vasodilator and platelet-antiaggregating properties, prostacyclin analogs were tested on systemic blood pressure in anesthetized rats, relaxation of bovine coronary artery and inhibition of arachidonic acid induced human platelet aggregation. The sodium salt of prostacyclin induced a dose dependent decrease of blood pressure with an ED25 of 0.23 microgram/kg i.v., a marked relaxation of bovine coronary artery with an IC50 of 5.9 ng/ml and a strong inhibition of platelet aggregation with an ED50 of 3x10(-9) M. Similar results were obtained with prostacyclin-methylester. Replacement of the n-pentyl moiety attached to C-15 of prostacyclin by cyclohexyl, 2-(2-furyl)ethyl, 2-(3-thienyl)ethyl and especially by 3-thienyl-oxymethyl yielded analogs with comparable prostacyclin properties, while substitution by 1,1-dimethyloxaalkyl residues was followed by a marked loss of activity. The order of potency among the analogs of the sodium salt and methylester of prostacyclin with strong vasodepressor and antiaggregatory properties was identical in all three models used. The three test systems used for evaluation have demonstrated that suitable modifications of the omega-side chain of prostacyclin result in potent vasodilator and platelet-antiaggregating agents.