Relaxant activity of 4-amido-3,4-dihydro-2H-1-benzopyran-3-ols and 4-amido-2H-1-benzopyrans on guinea pig isolated trachealis.

A series of 4-amido-3,4-dihydro-2H-1-benzopyran-3-ols and 4-amido-2H-1-benzopyrans related to the potassium channel activator cromakalim have been prepared and evaluated for their relaxant activity in guinea pig isolated tracheal spirals. Several analogues show enhanced relaxant activity relative to cromakalim in this preparation and the rank order of potency for those substituents investigated at C-6 was CF3 greater than CN greater than C2H5 greater than aza greater than or equal to CH3. One compound, trans-3,4-dihydro-2,2-dimethyl-4-(2-oxopiperidin-1-yl)-7-(trifluor omethyl)-2H- 1-benzopyran-3-ol (24), was resolved into its two enantiomers and the activity was shown to reside essentially in the (+)-isomer, adding further support to the suggestion that the smooth muscle receptor for these potassium channel activators is stereoselective.

Inhibition of cyclic nucleotide phosphodiesterase by derivatives of 1,3-bis(cyclopropylmethyl)xanthine.

Alkylation of the selective type IV phosphodiesterase inhibitor, 8-amino-1,3-bis(cyclopropylmethyl)-xanthine (1, BRL 61063), led exclusively to the N-7 substituted derivatives 2-9, which showed varying selectivities for the PDE type IV isoenzyme relative to PDE Va. The 4-methoxybenzyl derivative 6 in particular was a highly potent PDE Va inhibitor (IC50 0.14 microM) and showed a 24-fold selectivity for this isoenzyme relative to PDE IV. Sulfonation of 1 was more complex, with the product profile being highly dependent on the reaction conditions. As with alkylation, sulfonation at N-7 generally increased potency against PDE Va, especially in the aryl-containing moieties lacking strongly electron-withdrawing substituents (12, 15-17, 19). Bis-arylsulfonation at the exocyclic amino group generally reduced inhibitory potency against both PDE IV and Va. An 8-amidino compound 33, formed by the unusual reaction of 1 with N-methylpyrrolidinone in the presence of benzenesulfonyl chloride, had an IC50 value of 0.05 microM against PDE Va and is believed to be the most potent inhibitor of this isoenzyme reported. No correlation of PDE IV inhibition with displacement of [3H]rolipram from its high-affinity binding site was demonstrated. This suggests that either the catalytic site and the rolipram binding site are not the same or that PDE IV can exist in two conformations, only one of which binds to rolipram with high affinity, and that the compounds described vary in their selectivity for this isoform.

Cyclic ketone inhibitors of the cysteine protease cathepsin K.

Cathepsin K (EC 3.4.22.38), a cysteine protease of the papain superfamily, is predominantly expressed in osteoclasts and has been postulated as a target for the treatment of osteoporosis. Crystallographic and structure--activity studies on a series of acyclic ketone-based inhibitors of cathepsin K have led to the design and identification of two series of cyclic ketone inhibitors. The mode of binding for four of these cyclic and acyclic inhibitors to cathepsin K is discussed and compared. All of the structures are consistent with addition of the active site thiol to the ketone of the inhibitors with the formation of a hemithioketal. Cocrystallization of the C-3 diastereomeric 3-amidotetrahydrofuran-4-one analogue 16 with cathepsin K showed the inhibitor to occupy the unprimed side of the active site with the 3S diastereomer preferred. This C-3 stereochemical preference is in contrast to the X-ray cocrystal structures of the 3-amidopyrrolidin-4-one inhibitors 29 and 33 which show these inhibitors to prefer binding of the 3R diastereomer. The 3-amidopyrrolidin-4-one inhibitors were bound in the active site of the enzyme in two alternate directions. Epimerization issues associated with the labile alpha-amino ketone diastereomeric center contained within these inhibitor classes has proven to limit their utility despite promising pharmacokinetics displayed in both series of compounds.

Diastereoselective synthesis, activity and chiral stability of cyclic alkoxyketone inhibitors of cathepsin K.

The diastereoselective synthesis of a novel class of cathepsin K inhibitors together with their cathepsin K affinity and stability towards aqueous buffer is reported.

Endothelin-converting enzyme: substrate specificity and inhibition by novel analogs of phosphoramidon.

Endothelin converting enzyme was partially purified by detergent extraction and ion exchange chromatography from porcine aortic endothelial cells. This kinetically homogeneous preparation catalyzes the hydrolysis of porcine big endothelin-1 to endothelin-1 with a pH optimum of 7. Human big endothelins-1, -2, and -3 are also hydrolyzed, but at progressively lower rates. Fragments of big porcine endothelin-1 comprising residues 16-39 and 16-29 are good substrates, but additional C-terminal truncations are devoid of substrate activity. Endothelin converting enzyme is characteristically inhibited by phosphoramidon and other metalloproteinase inhibitors including EDTA, o-phenanthroline, and diethylpyrocarbonate, but not by inhibitors of other classes of proteases or thiorphan. The inhibition by phosphoramidon is competitive with big porcine endothelin-1 suggestive of a common binding site for substrate and inhibitor. A number of novel analogs of phosphoramidon were synthesized by modifying various regions of the molecule and tested for inhibitory activity. The most potent of these, a methylphosphonic acid, has an IC50 of 0.05 microM.

Solid-phase synthesis of cyclic alkoxyketones, inhibitors of the cysteine protease cathepsin K.

Using solid-phase synthesis, a library of novel cyclic alkoxyketones has been constructed which show strong inhibitory activity against the cysteine protease, cathepsin K (EC 3.4.22.38).

3-Anilino-4-arylmaleimides: potent and selective inhibitors of glycogen synthase kinase-3 (GSK-3).

Potent 3-anilino-4-arylmaleimide glycogen synthase kinase-3 (GSK-3) inhibitors have been prepared using automated array methodology. A number of these are highly selective, having little inhibitory potency against more than 20 other protein kinases.