Stable multisubstrate adducts as enzyme inhibitors. Potent inhibition of ornithine decarboxylase by N-(5'-phosphopyridoxyl)-ornithine.

The synthesis of several N-(5'-phosphopyridoxyl)-amino acids is described. These compounds, analogs of the Schiff base intermediate involved in enzyme-catalyzed decarboxylation, are potent inhibitors of the cognate amino acid decarboxylases. Kinetic studies using partially purified rat liver ornithine decarboxylase, have shown that N-(5'-phosphopyridoxyl)-ornithine inhibits the enzyme in a non-competitive manner with respect to both ornithine and pyridoxal-5'-phosphate. These findings suggest that the inhibitor binds to the holoenzyme active site in place of the Schiff base intermediate.

Synthesis and evaluation of some stable multisubstrate adducts as inhibitors of catechol O-methyltransferase.

A new series of methylase inhibitors has been designed in which the nucleophilic methyl acceptor is attached to the adenosine and/or homocysteine fragments of the methyl donor, S-adenosylmethionine, to form a "multisubstrate adduct". In the present case, catecholamine analogues attached through a phenethyl sulfide linkage to 5'-thioadenosine or homocysteine have been synthesized, together with the corresponding methylsulfonium salts. These compounds were assayed as inhibitors of catechol O-methyltransferase, and the adenosylsulfonium salts (4) were found to be inhibitors of the enzyme.

Glucose transport-enhancing and hypoglycemic activity of 2-methyl-2-phenoxy-3-phenylpropanoic acids.

A series of 2-phenoxy-3-phenylpropanoic acids has been prepared which contains many potent hypoglycemic agents as demonstrated by assessing glucose lowering in ob/ob mice. Some compounds (32, 33, 59) normalize plasma glucose in this diabetic model at doses of approximately 1 mg/kg. The mechanism of action of these drugs may involve enhanced glucose transport, especially in fat cells, but the compounds do not stimulate GLUT4 translocation and do not increase the levels of GLUT1 or GLUT4 in vivo. Thus, these compounds may enhance the intrinsic activity of the glucose transporter GLUT1 or GLUT4. Some compounds also modestly decrease hepatocyte gluconeogenesis in vitro, but this is not likely to be a major contributor to the hypoglycemic effect observed in vivo. Likewise, a modest decrease in food consumption observed with some of these compounds was shown by a pair-feeding experiment not to be the primary cause of the hypoglycemia observed.

Hydantoin bioisosteres. In vivo active spiro hydroxy acetic acid aldose reductase inhibitors.

The hypothesis that clinical side effects of the aldose reductase inhibitor (ARI) sorbinil were related to its hydantoin ring led to a bioisosteric analysis and replacement of the hydantoin by a spiro hydroxy acetic acid moiety as in 40. These hydroxy acids, compared to hydantoins, showed a similar potency increase on chroman 2-methyl substitution, a similar orthogonal relationship of acidic to aromatic moieties, and similar ARI enantioselectivity. In this series the six-membered spiro hydroxy acetic acid anion array is a bioisostere for a spiro hydantoin anion and leads to ARIs with excellent in vivo activity. In vitro and in vivo activity was improved over 40 by chroman cis 2-methylation as in 4 and by aromatic 6,7-halogen substitution. Compounds with the best acute in vivo activity in rats were compared for chronic in vivo activity. The highest tissue levels and best chronic in vivo activities were found in the racemic 6,7-dichloro and 6-fluoro-7-chloro analogues 18 and 23. ARI activity was enantioselective for 58 and 60, the 2R,4R-enantiomers of 18 and 23. 7-Chloro-6-fluoro-cis-4-hydroxy-2(R)-methyl-chroman-4-acetic acid (60) was selected for phase 1 clinical trials and did not exhibit sorbinil-like hypersensitivity side effects.

Synthesis of [3H]- and -[14C]-labeled sulprostone.

The synthesis of N-methanesulfonyl 16-phenoxy-omega-tetranor PGE2 carboxamide (sulprostone--CP-34,089/ZK-57,671) labeled with tritium and carbon-14 is described. Sulprostone labeled with tritium in the phenoxy moiety by means of catalytic hydrogenolysis was obtained in a 17% radiochemical yield with a specific activity of 1.0 Ci/mmol. The methanesulfonamide-14C derivative of sulprostone was prepared from methyl-14C iodide in an 11.8% radiochemical yield having a specific activity of 18.8 mCi/mmol.