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Synthesis and biological evaluation of cholecystokinin analogs in which the Asp-Phe-NH2 moiety has been replaced by a 3-amino-7-phenylheptanoic acid or a 3-amino-6-(phenyloxy)hexanoic acid.

Boc-Tyr(SO3H)-Nle-Gly-Trp-Nle-Asp-2-phenylethyl ester (JMV180), an analog of the C-terminal octapeptide of cholecystokinin (CCK-8), shows interesting biological activities behaving as an agonist at the high-affinity CCK binding sites and as an antagonist at the low-affinity CCK binding sites in rat pancreatic acini. Although we did not observe any major hydrolysis of the ester bond of Boc-Tyr(SO3H)-Nle-Gly-Trp-Nle-Asp-2-phenylethyl ester in our in vitro studies, we were aware of a possible and rapid cleavage of this ester bond during in vivo studies. To improve the stability of Boc-Tyr(SO3H)-Nle-Gly-Trp-Nle-Asp-2-phenylethyl ester, we decided to synthesize analogs in which the ester bond would be replaced by a carba (CH2-CH2) linkage. We synthesized the 3-amino-7-phenylheptanoic acid (beta-homo-Aph) with the R configuration in order to mimic the Asp-2-phenylethyl ester moiety and the 3-amino-6-(phenyloxy)hexanoic acid (H-beta-homo-App-OH), an analog of H-beta-homo-Aph-OH in which a methylene group has been replaced by an oxygen. (R)-beta-Homo-Aph and (R)-H-beta-homo-App-OH were introduced in the CCK-8 sequence to produce Boc-Tyr(SO3H)-Nle-Gly-Trp-Nle-(R)-beta-homo-Aph-OH and Boc-Tyr(SO3H)-Nle-Gly-Trp-Nle-(R)-beta-homo-App-OH. Both compounds were able to recognize the CCK receptor on rat pancreatic acini (IC50 = 12 +/- 8 nM and 13 +/- 5 nM, respectively), on brain membranes (IC50 = 32 +/- 2 nM and 57 +/- 5 nM, respectively), and on Jurkat T cells (IC50 = 75 +/- 15 nM and 65 +/- 21 nM, respectively). Like Boc-Tyr(SO3H)-Nle-Gly-Trp-Nle-Asp-2-phenylethyl ester, both compounds produced maximal stimulation of amylase secretion (EC50 = 6 +/- 2 nM and 4 +/- 2 nM, respectively) with no decrease of the secretion at high concentration indicating that these compounds probably act as agonists at the high-affinity peripheral CCK-receptor and as antagonists at the low-affinity CCK-receptor. Replacing the tryptophan by a D-tryptophan in such analogs produced full CCK-receptor antagonists. All these analogs might be more suitable for in vivo studies than Boc-Tyr(SO3H)-Nle-Gly-Trp-Nle-Asp-2-phenylethyl ester.

Amino Acid Sequence↗

Synthesis and biological activity of new HMG-CoA reductase inhibitors. 3. Lactones of 6-phenoxy-3,5-dihydroxyhexanoic acids.

A group of 43 optically active sodium carboxylates (11a-qq and the corresponding lactones 4 were prepared from respective phenols 8 according to Schemes I-III. Phenols 8 were synthesized from commercially available compounds according to Schemes IV-IX. A number of these HMG-CoA reductase inhibitors 11 exceeded mevinolin's activity in vitro (Tables II and III). Selected lactones 4 effectively inhibited hepatic "de novo" cholesterol synthesis in rats in vivo (Table IV). After po administration to rabbits, 4ff(11ff), 4hh, and notably 11jj reduced plasma cholesterol levels more potently than mevinolin (Table V). Whereas 4ff(11ff) displayed the slight superiority expected according to in vitro data, 4hh and 11jj were considerably more potent than expected. Each of these compounds had only moderate activity after po administration to dogs (Table VI). Compound di-11ii, a hybrid of the structural elements of probucol and HMG-CoA reductase inhibitors, after po administration to rats decreased serum lipoproteins and increased HDL/LDL ratio better than probucol (Table VII). HMG-CoA reductase inhibitor 11ll and phenolic building blocks 8, notably 8jj and 8kk, inhibited LDL oxidation in vitro (Table VIII). Chemical structure-activity relationships (Table IX) and the pharmacological profile of phenoxy-type inhibitors 11 diverged from those of known HMG-CoA reductase inhibitors.

Animals↗

Thromboxane synthase inhibitors. Synthesis and pharmacological activity of (R)-, (S)-, and (+/-)-2,2-dimethyl-6-[2-(1H-imidazol-1-yl)-1-[[(4-methoxyphenyl)- methoxy]methyl]ethoxy]hexanoic acids.

A series of substituted omega-[2-(1H-imidazol-1-yl)ethoxy]alkanoic acid derivatives were synthesized and evaluated for their ability to inhibit thromboxane synthase both in vitro and in vivo. Compound 13 was identified as a potent and selective competitive inhibitor of human platelet thromboxane synthase having a Ki value of 9.6 X 10(-8) M. In collagen-treated human whole blood, 13 potentiated levels of 6-keto PGF1 alpha. Enantiospecific syntheses afforded the R and S enantiomers of 13, of which the S enantiomer 13b was the more potent. Compounds 13 and 13b were potent in vivo inhibitors of thromboxane synthase with good oral activity and duration of action.

6-Ketoprostaglandin F1 alpha↗

A potent, selective inhibitor of matrix metalloproteinase-3 for the topical treatment of chronic dermal ulcers.

The pathology of chronic dermal ulcers is characterized by excessive proteolytic activity which degrades extracellular matrix (required for cell migration) and growth factors and their receptors. The overexpression of MMP-3 (stromelysin-1) and MMP-13 (collagenase-3) is associated with nonhealing wounds, whereas active MMPs-1, -2, -9, and -14 are required for normal wound healing to occur. We describe the synthesis and enzyme inhibition profile of (3R)-3-[([(1S)-2,2-dimethyl-1-(([(1S)-2-methoxy-1-phenylethyl]amino)carbonyl)propyl]amino)carbonyl]-6-(3-methyl-4-phenylphenyl)hexanoic acid (UK-370,106, 7), which is a potent inhibitor of MMP-3 (IC(50) = 23 nM) with >1200-fold weaker potency vs MMP-1, -2, -9, and -14. MMP-13, which may also contribute to the pathology of chronic wounds, was inhibited about 100-fold less potently by compound 7. Compound 7 potently inhibited cleavage of [(3)H]-fibronectin by MMP-3 (IC(50) = 320 nM) but not cleavage of [(3)H]-gelatin by either MMP-2 or -9 (up to 100 microM). Compound 7 had little effect, at MMP-3 selective concentrations, on keratinocyte migration over a collagen matrix in vitro, which is a model of the re-epithelialization process. Following iv (rat) or topical administration to dermal wounds (rabbit), compound 7 was cleared rapidly (t(1/2) = 23 min) from plasma, but slowly (t(1/2) approximately 3 days) from dermal tissue. In a model of chronic dermal ulcers, topical administration of compound 7 for 6 days substantially inhibited MMP-3 ex vivo. These data suggest compound 7 is sufficiently potent to inhibit MMP-3-mediated matrix degradation while leaving unaffected cellular migration mediated by MMPs 1, 2, and 9. These properties make compound 7 a suitable candidate for progression to clinical trials in human chronic dermal wounds, such as venous ulcers.

Administration, Cutaneous↗

Phe-Gly dipeptidomimetics designed for the di-/tripeptide transporters PEPT1 and PEPT2: synthesis and biological investigations.

A series of five Phe-Gly dipeptidomimetics containing different amide bond replacements have been synthesized in a facile way from the readily available unsaturated ketoester 1, and their affinities for the di-/tripeptide transporters hPEPT1 (Caco-2 cells) and rPEPT2 (SKPT cells) were tested. The compounds contained the amide bond isosteres ketomethylene (2a), (R)- and (S)-hydroxyethylidene (3a and 4a), and (R)- and (S)-hydroxyethylene (5a and 6a) to provide information on the conformational and stereochemical requirements for hPEPT1 and rPEPT2 affinity. The affinity studies showed that for rPEPT2 there is no significant difference in affinity between the ketomethylene isostere 2a and the natural substrate Phe-Gly (K(i) values of 18.8 and 14.6 microM, respectively). Also the affinities for hPEPT1 are in the same range (K(i) values of 0.40 and 0.20 mM, respectively). This corroborates earlier findings that the amide bond as such is not essential for binding to PEPTX, but the results also reveal possible differences in the binding of ketomethylene isosteres to hPEPT1 and rPEPT2. The trans-hydroxyethylidene and hydroxyethylene isosteres proved to be poor substrates for PEPTX. These results provide new information about the importance of flexibility and of the stereochemistry at the C(4)-position for this class of compounds. Furthermore, the intracellular uptake of 2a-4a in Caco-2 cells was investigated, showing a 3-fold reduction of the uptake of 2a in the presence of the competetive inhibitor Gly-Pro, indicating contribution from an active transport component. No active uptake of 3a and 4a was observed. Transepithelial transport studies also indicated active transport of 2a across Caco-2 monolayers.

Animals↗

5-substituted tetrazoles as bioisosteres of carboxylic acids. Bioisosterism and mechanistic studies on glutathione reductase inhibitors as antimalarials.

Plasmodium parasites are exposed to elevated fluxes of reactive oxygen species during intraerythrocytic life. The most important antioxidative systems are based on the glutathione reductases of the malarial parasite Plasmodium falciparum and the host erythrocyte. The development of menadione chemistry has led to the selection of the carboxylic acid 6-[2'-(3'-methyl)-1',4'-naphthoquinolyl] hexanoic acid M(5) as an inhibitor of the parasitic enzyme. As reported here, revisiting the mechanism of M(5) action revealed an uncompetitive inhibition type with respect to both NADPH and glutathione disulfide. Masking the polarity of the acidic function of M(5) by ester or amide bonds improved antiplasmodial activity. Bioisosteric replacement of the carboxylic function by tetrazole to increase bioavailability and to maintain comparable acidity led to improved antimalarial properties as well, but only with the cyanoethyl-protected tetrazoles. Using computed ab initio quantum methods, detailed analyses of the electronic profiles and the molecular properties evidenced the similarity of M(5) and the bioisoteric tetrazole T(4). The potential binding site of these molecules is discussed in light of the recently solved crystallographic structure of P. falciparum enzyme.

Animals↗

Design, synthesis, and binding studies of new potent ligands of cannabinoid receptors.

Despite their different chemical structures, delta9-tetrahydrocannabinol (THC) and anandamide (AEA) have common pharmacological properties. This study was aimed at finding new cannabinoid receptor ligands that overcome the instability of AEA and its analogues. To this end we planned the synthesis of a series of compounds which retained both a rigid structure, like that of plant cannabinoids, and a flexible portion similar to that of anandamide. Binding studies on CB1 and CB2 receptors, anandamide membrane transporter (AMT), and fatty acid amide hydrolase (FAAH) showed that some of the newly developed compounds have high affinity and specificity for cannabinoid CB1 and CB2 receptors. Compound 25 is a potent CB1 and CB2 ligand, with affinity constants significantly lower than AEA and similar to WIN 55-212, compound 52 is a potent CB2 ligand, although not very selective over CB1 receptors, and compound 43 is CB2 ligand, with at least a 26-fold selectivity over CB1 receptors. Compound 25 behaved as a inverse agonist at CB1 receptors as assessed in the cyclic AMP functional assay.

Amides↗

Wortmannin-C20 conjugates generate wortmannin.

We report on C20-6-(N-methylamino)hexanoic conjugates of wortmannin featuring a tertiary enamine attached to the C20 that inhibit phosphoinositol-3-OH kinase (PI3K) by producing wortmannin (Wm) through an intramolecular attack. The generation of Wm by these conjugates permits the design of Wm based PI3K inhibitors that need not fit into the ATP pocket of PI3K, including Wm conjugates of BSA, IgG, or beads. Wm generating WmC20-N(Me)-hexanoate conjugates offer an approach to the design of targeted or slow release forms of Wm which may inhibit PI3K in tissues more selectively than the parent Wm, a compound which has desirable anti-inflammatory and anti-proliferative activities but which also has a variety of toxic effects.

Androstadienes↗

S-alkylated homocysteine derivatives: new inhibitors of human betaine-homocysteine S-methyltransferase.

A series of S-alkylated derivatives of homocysteine were synthesized and characterized as inhibitors of human recombinant betaine-homocysteine S-methyltransferase (BHMT). Some of these compounds inhibit BHMT with IC50 values in the nanomolar range. BHMT is very sensitive to the structure of substituents on the sulfur atom of homocysteine. The S-carboxybutyl and S-carboxypentyl derivatives make the most potent inhibitors, and an additional sulfur atom in the alkyl chain is well tolerated. The respective (R,S)-5-(3-amino-3-carboxy-propylsulfanyl)-pentanoic, (R,S)-6-(3-amino-3-carboxy-propylsulfanyl)-hexanoic, and (R,S)-2-amino-4-(2-carboxymethylsulfanyl-ethylsulfanyl)-butyric acids are very potent inhibitors and are the strongest ever reported. We determined that (R,S)-5-(3-amino-3-carboxy-propylsulfanyl)-pentanoic acid displays competitive inhibition with respect to betaine binding with a Kappi of 12 nM. Some of these compounds are currently being tested in mice to study the influence of BHMT on the metabolism of sulfur amino acids in vivo.

Betaine-Homocysteine S-Methyltransferase↗

Design and synthesis of substrate and intermediate analogue inhibitors of S-ribosylhomocysteinase.

S-Ribosylhomocysteinase (LuxS) catalyzes the cleavage of the thioether linkage in S-ribosylhomocysteine (SRH) to produce homocysteine and 4,5-dihydroxy-2,3-pentanedione, the precursor of autoinducer 2. Inhibitors of LuxS should interfere with bacterial interspecies communication and potentially provide a novel class of antibacterial agents. LuxS utilizes a divalent metal ion as a Lewis acid during catalysis. In this work, a series of structural analogues of the substrate SRH and a 2-ketone intermediate were designed and synthesized. Kinetic studies indicate that the compounds act as reversible, competitive inhibitors against LuxS, with the most potent inhibitors having K(I) values in the submicromolar range. These represent the most potent LuxS inhibitors that have been reported to date. Cocrystal structures of LuxS bound with two of the inhibitors largely confirmed the design principles, i.e., the importance of both the homocysteine and ribose moieties in high-affinity binding to the LuxS active site.

Amides↗

Structure-activity relationships of (4-acylpyrrol-2-yl)alkanoic acids as inhibitors of the cytosolic phospholipase A2: variation of the substituents in positions 1, 3, and 5.

Derivatives of 3-(1,3,5-trimethyl-4-octadecanoylpyrrol-2-yl)propionic acid (1) and (1,3,5-trimethyl-4-octadecanoylpyrrol-2-yl)acetic acid (4) were prepared and evaluated for their ability to inhibit the cytosolic phospholipase A2 of intact bovine platelets. While replacement of one of the methyl groups in position 1, 3, or 5 of the acetic acid 4 by a benzyl residue did not influence the inhibitory potency significantly, the introduction of a dodecyl chain led to compounds which even enhanced the enzymatic activity. Stepwise elongation of the alkyl substituent in position 1 showed that the ability to inhibit the enzyme was lost when the alkyl chain exceeded a length of five carbons in case of compound 1 or six carbons in case of compound 4. Introduction of a polar functional group at the end of the 1-alkyl chain of these inactive pyrroles, however, restored or even elevated inhibitory potency. The most preferable of the polar terminal functions investigated was the carboxylic acid moiety. 6-[2-(2-Carboxyethyl)-4-dodecanoyl-3,5-dimethylpyrrol-1-yl]hexanoi c acid (65c) and 6-[2-(carboxymethyl)-4-dodecanoyl-3,5-dimethylpyrrol-1-yl]nonanoic acid (66f) were the synthesized inhibitors with the greatest potency. With IC50 values of 3.4 and 3.3 microM, respectively, they were about 3-fold more active than the standard cPLA2 inhibitor arachidonyl trifluoromethyl ketone (IC50: 11 microM).

Animals↗

New alkenyldiarylmethanes with enhanced potencies as anti-HIV agents which act as non-nucleoside reverse transcriptase inhibitors.

Twenty-two new alkenyldiarylmethanes (ADAMs) were synthesized and evaluated for inhibition of HIV-1 replication. The most potent compound proved to be methyl 3',3"-dichloro-4',4"-dimethoxy-5', 5"-bis(methoxycarbonyl)-6,6-diphenyl-5-hexenoate (ADAM II), which displayed an EC50 of 13 nM for inhibition of the cytopathic effect of HIV-1RF in CEM-SS cells. ADAM II inhibited HIV-1 reverse transcriptase with an IC50 of 0.3 microM but was inactive as an inhibitor of HIV-1 attachment/fusion to cells, protease, integrase, and the nucleocapsid protein. Molecular target-based and cell-based assays revealed that ADAM II acted biologically as a nonnucleoside reverse transcriptase inhibitor (NNRTI). ADAM II inhibited replication of a wide variety of laboratory, clinical, and clade-representative isolates of HIV-1 in T cell lines and cultures of peripheral blood mononuclear cells or monocyte/macrophages. Mutations that conferred resistance to ADAM II clustered at residues 101, 103, 108, 139, 179, 181, and 188, which line the nonnucleoside binding pocket of HIV-1 reverse transcriptase. However, HIV-1 NL4-3 strain expressing a mutation at residue 100 of reverse transcriptase, and an AZT-resistant virus, displayed increased sensitivity to ADAM II. Thus, ADAM II could serve as an adjunct therapy to AZT and NNRTIs that select for L100I resistance mutations.

Alkanes↗

Novel modifications in the alkenyldiarylmethane (ADAM) series of non-nucleoside reverse transcriptase inhibitors.

In an effort to obtain more insight into the interaction between HIV-1 reverse transcriptase and the alkenyldiarylmethanes (ADAMs), a new series of compounds has been synthesized and evaluated for inhibition of HIV-1 replication. The modifications reported in this new series include primarily changes to the alkenyl chain. The most potent compound proved to be methyl 3',3' '-dibromo-4',4' '-dimethoxy-5',5' '-bis(methoxycarbonyl)-6,6-diphenyl-5-hexenoate (28), which displayed an EC(50) of 1.3 nM for inhibition of the cytopathic effect of HIV-1(RF) in CEM-SS cells. ADAM 28 inhibited HIV-1 reverse transcriptase with an IC(50) of 0.3 microM. Mutations that conferred greater than 10-fold resistance to ADAM 28 clustered at residues Val 106, Val 179, Tyr 181, and Tyr 188. Results derived from this series indicate that ADAMs containing chlorines in the aromatic rings might bind to HIV-1 reverse transcriptase in a slightly different mode when compared with those analogues incorporating bromine in the aromatic rings.

Anti-HIV Agents↗