Discovery and synthesis of rioprostil.

Between 1972 and 1979 a research team at Miles Laboratories produced 1200 prostaglandin analogues as potential pharmaceuticals. Most of these analogues were produced using the Sih synthesis. They were screened in several animal models and a few were found to inhibit gastric acid secretion in the rat. The best compound (TR-4698, rioprostil) is being pursued as an anti-ulcer and cytoprotective agent. An improved synthesis of this compound involves the use of n-butyllithium and copper (I) cyanide in a one-pot conjugate addition of a vinyl tin intermediate with a chiral alkylated cyclopentenone. Multihundred gram lots of rioprostil are produced with only one chromatography, that of the final substance, needed.

The binding of [3H]leukotriene C4 to guinea-pig lung membranes. The lack of correlation of LTC4 functional activity with binding affinity.

High affinity binding sites for [3H]leukotriene C4 ([3H]LTC4) have been identified and characterised in guinea-pig lung membranes. [3H]LTC4 bound to these membranes with a pharmacological specificity totally distinct to that previously observed for [3H]LTD4 binding in guinea-pig lung. Scatchard analysis of saturation binding data showed a single class of binding sites, with a dissociation constant (KD) of 52.6 +/- 4.9 nM and a density (Bmax) of 30 +/- 12 pmol/mg membrane protein. The binding was inhibited with high affinity by a variety of glutathione-containing leukotriene analogues. Most notable was the inhibition by 1,2,3,4-tetranor LTC4 (Ki = 118 nM) and S-decylglutathione (Ki = 154 nM) since neither of these compounds were contractile agonists on guinea-pig parenchymal strips or guinea-pig ileum nor were they antagonists of LTC4-induced contractions of these smooth muscle preparations. These results indicate that the observed binding of [3H]LTC4 to guinea-pig lung membranes is not to a contractile receptor.

Pharmacology of rioprostil, a new gastric cytoprotective/antisecretory agent.

Rioprostil (2-decarboxy-2-hydroxymethyl-15-deoxy-16RS-hydroxy-16-methyl prostaglandin (PG)E1) is a potent orally active inhibitor of gastric acid secretion in both rats and dogs. It prevents gastric lesions in rats induced by ethanol, acetylsalicylic acid, strong acid, strong base, hypertonic saline and thermal injury at doses 100 times less than its antisecretory dose. The cytoprotective effect of rioprostil can be observed when given 4 min before challenge with ethanol and measured 60 min later. The peak antiulcer effect is observed when rioprostil is given 30 min before ethanol challenge and the oral ED50 is 1.93 (1.74-2.15) micrograms/kg. Rioprostil possesses weak PGE-like activity in an isolated tissue cascade, no contragestational activity in rats, hamsters or rabbits, and no remarkable cardiovascular or pulmonary activity in dogs. The animal pharmacology of this compound suggests that it should be useful in the treatment or prophylaxis of peptic ulcer disease and gastric lesions associated with noxious irritants such as ethanol and nonsteroidal antiinflammatory drugs.

The synthesis of dimethylphosphonoprostaglandin analogs.

The synthesis of prostaglandin analogs incorporating the dimethylphosphono or dimethylphosphonomethyl moiety in place of the carboxylic acid moiety is described. These analogs exhibited only very low levels of smooth muscle activity during biological testing.

The synthesis of prostaglandin analogs containing hydroxycyclohexenyl rings.

The synthesis of prostaglandin analogs incorporating the 3-hydroxycyclohexenyl moiety in place of the natural C13-C20 side-chain has been accomplished via copper-assisted conjugate addition of the cycloalkenyllithium 2 to the cyclopentenous intermediates 4, 7 and 10.