Fluorinated 2-Arylcyclopropan-1-amines – A new class of sigma receptor ligands

Stereoisomeric 2-aryl-2-fluoro-cyclopropan-1-amines have been discovered as a new class of σ receptor ligands showing different selectivity for the two subtypes of the receptor. Generally, compounds substituted in 4-position are much more active than corresponding 3-substituted isomers. trans-2-Fluoro-2-(4-methoxyphenyl)cyclopropan-1-amine (19a) was the most potent (K_i = 4.8 nM) σ₁ receptor ligand, while cis-2-fluoro-2-(4-trifluoromethylphenyl)cyclopropan-1-amine (20b) was the most potent (K_i = 95 nM) σ₂ receptor ligand.     

Novel chemotactic For-Met-Leu-Phe-OMe (fMLF-OMe) analogues based on Met residue replacement by 4-amino-proline scaffold: Synthesis and bioactivity

cis-(2S,4S) 4-Amino-proline (cAmp) and trans-(2S,4R) 4-amino-proline (tAmp) residues, bearing N-For or N-Boc substituents at the two amino groups, have been incorporated into the potent chemotactic agent fMLF-OMe in place of the N-terminal native (S)-methionine to give the analogues 17a–19a and 17b–19b. The new ligands have been examined for their activity (chemotaxis, superoxide anion production and lysozyme release) on human neutrophils as agonists and antagonists. Compounds 19a and 19b, bearing two N-For groups at the proline scaffold, are active and selective chemoattractants. The ligand 18b, containing N-For at the 4-amino group of the N-Boc-tAmp residue, exhibits significant chemotactic antagonism. The influence of the different substitution at the N-terminal position of the new analogues is discussed.     

Discovery of 2-(3,5-difluoro-4-methylsulfonaminophenyl)propanamides as potent TRPV1 antagonists

A series of A-region analogues of 2-(3-fluoro-4-methylsufonamidophenyl) propanamide 1 were investigated as TRPV1 antagonists. The analysis of structure-activity relationship indicated that a fluoro group at the 3- (or/and) 5-position and a methylsulfonamido group at the 4-position were optimal for antagonism of TRPV1 activation by capsaicin. The most potent antagonist 6 not only exhibited potent antagonism of activation of hTRPV1 by capsaicin, low pH and elevated temperature but also displayed highly potent antagonism of activation of rTRPV1 by capsaicin. Further studies demonstrated that antagonist 6 blocked the hypothermic effect of capsaicin in vivo, consistent with its in vitro mechanism, and it showed promising analgesic activity in the formalin animal model.     

Design,synthesis, and pharmacological evaluation of JDTic analogs to examine the significance of replacement of the 3-hydroxyphenyl group with pyridine or thiophene bioisosteres

The potent and selective KOR antagonist JDTic was derived from the N-substituted trans-3,4-dimethyl-4-(3-hydroxyphenyl)piperidine class of pure opioid antagonists. In previous studies we reported that compounds that did not have a hydroxyl on the 3-hydroxyphenyl group and did not have methyl groups at the 3- and 4-position of the piperidine ring were still potent and selective KOR antagonists. In this study we report JDTic analogs 2, 3a–b, 4a–b, and 5, where the 3-hydroxyphenyl ring has been replaced by a 2-, 3-, or 4-pyridyl or 3-thienyl group and do not have the 3-methyl or 3,4-dimethyl groups, remain potent and selective KOR antagonists. Of these, (3R)-7-hydroxy-N-(1S)-2-methyl-[4-methyl-4-pyridine-3-yl-carboxamide (3b) had the best overall binding potency and selectivity in a [³⁵S]GTPγS functional assay, with a K_e = 0.18 nM at the KOR and 273- and 16,700-fold selectivity for the KOR relative to the MOR and DOR, respectively. Calculated physiochemical properties for 3b suggest that it will cross the blood–brain barrier.     

8-[2-(4-Aryl-1-piperazinyl)ethyl]-2H-1,4-benzoxazin-3(4H)-ones: Dual-acting 5-HT1 receptor antagonists and serotonin reuptake inhibitors—Part II

8-[2-(4-Aryl-1-piperazinyl)ethyl]-2H-1,4-benzoxazin-3(4H)-ones have been identified as highly potent 5-HT_1A/B/D receptor antagonists with and without additional SerT activity and a high degree of selectivity over hERG potassium channels. Modulation of the different target activities gave compounds with a range of profiles suitable for further in vivo characterization.     

Combined effects of oleic,linoleic and linolenic acids on lactation performance and the milk fatty acid profile in lactating dairy cows

The potential combined effects of oleic, linoleic and linolenic acids supplementation on lactation performance and the milk fatty acid (FA) profile in dairy cows have not been well investigated. Our objective was to examine the effects of supplementation with a combination of these FA as well as the effects of removing each from the combination on lactation performance and the milk FA profile in dairy cows. Eight Holstein cows (101±11 days in milk) received four intravenously infused treatments in a 4×4 Latin square design, and each period lasted for 12 days which consisted of 5 days of infusion and 7 days of recovery. The control treatment (CTL) contained 58.30, 58.17 and 39.96 g/day of C18: 1 cis-9; C18: 2 cis-9, cis-12; and C18: 3 cis-9, cis-12, cis-15, respectively. The other three treatments were designated −−C18: 1 (20.68, 61.17 and 41.72 g/day of C18: 1 cis-9; C18: 2 cis-9, cis-12; and C18: 3 cis-9, cis-12, cis-15, respectively), −C18: 2 (61.49, 19.55 and 42.13 g/day of C18: 1 cis-9; C18: 2 cis-9, cis-12; and C18: 3 cis-9, cis-12, cis-15, respectively) and −C18: 3 (60.89, 60.16 and 1.53 g/day of C18: 1 cis-9; C18: 2 cis-9, cis-12; and C18: 3 cis-9, cis-12, cis-15, respectively). Dry matter intake and lactose content were not affected by the treatments, but the milk protein content was lower in cows treated with −C18: 2 than that in CTL-treated cows. Milk yield as well as milk fat, protein and lactose yields were higher in cows treated with −C18: 3 than the yields in CTL-treated cows, and these yields increased linearly as the unsaturation degree of the supplemental FA decreased. Compared with the CTL treatment, the −C18: 2 treatment decreased milk C18: 2 cis-9 content (by 2.80%) and yield (by 22.12 g/day), and the −C18: 3 treatment decreased milk C18: 3 cis-9, cis-12, cis-15 content (by 2.72%) and yield (by 22.33 g/day). In contrast, removing C18: 1 cis-9 did not affect the milk content or yield of C18: 1 cis-9. The −C18: 2-treated cows had a higher C18: 1 cis-9 content and tended to have a higher C18: 1 cis-9 yield than CTL-treated cows. The yields of C8: 0, C14: 0 and C16: 0 as well as <C16: 0 tended to increase linearly as the unsaturation degree of the supplemental FA decreased (P=0.06, 0.07, 0.07 and 0.09, respectively). These results indicated that supplementation with C18 unsaturated FA might not independently affect the lactation performance and the milk FA profile of dairy cows.     

Design,synthesis, and structure–activity relationships of a series of novel N-aryl-2-phenylcyclopropanecarboxamide that are potent and orally active orexin receptor antagonists

Herein we describe the design, synthesis, and structure–activity relationships (SARs) of a novel phenylcyclopropane series represented by 7 and 33b as antagonists of orexin 1 and orexin 2 receptors. With 4 serving as the initial lead for the development of orexin antagonists, exploration of SAR resulted in improved binding affinity for orexin 1 and orexin 2 receptors. Among the synthesized compounds, 33b ((−)-N-(5-cyanopyridin-2-yl)-2-[(3,4-dimethoxyphenyl)oxymethyl]-2-phenylcyclopropanecarboxamide) exhibited potent in vitro activity and oral efficacy in animal sleep measurement experiments. The results of our study suggest that compound 33b may serve as a valuable template for the development of new orexin receptor antagonists.     

Ab initio molecular orbital calculations on the conformations of some unsaturated fragments of lipid molecules: 1-Butene, cis-2-pentene and 1,4-pentadiene

Conformational energies have been calculated for the title compounds which are basic fragments of physiologically active polyunsaturated fatty acids. For 1-butene extremely good accordance has been obtained with experimental data. In cis-2-pentene a strong influence of the cis methyl group on the potential energies for internal rotation has been found. For 1,4-pentadiene no great influence has been found from a possible coupling of the two rotors on the relative stabilities of the two stable conformations. Reasonable agreement has been observed with similar calculations published recently.     

Tubulin-interactive stilbene derivatives as anticancer agents

Microtubules are dynamic polymers that occur in eukaryotic cells and play important roles in cell division, motility, transport and signaling. They form during the process of polymerization of α- and β-tubulin dimers. Tubulin is a significant and heavily researched molecular target for anticancer drugs. Combretastatins are natural cis-stilbenes that exhibit cytotoxic properties in cultured cancer cells in vitro. Combretastatin A-4 (3′-hydroxy-3,4,4′, 5-tetramethoxy-cis-stilbene; CA-4) is a potent cytotoxic cis-stilbene that binds to β-tubulin at the colchicine-binding site and inhibits tubulin polymerization. The prodrug CA-4 phosphate is currently in clinical trials as a chemotherapeutic agent for cancer treatment. Numerous series of stilbene analogs have been studied in search of potent cytotoxic agents with the requisite tubulin-interactive properties. Microtubule-interfering agents include numerous CA-4 and transresveratrol analogs and other synthetic stilbene derivatives. Importantly, these agents are active in both tumor cells and immature endothelial cells of tumor blood vessels, where they inhibit the process of angiogenesis. Recently, computer-aided virtual screening was used to select potent tubulin-interactive compounds. This review covers the role of stilbene derivatives as a class of antitumor agents that act by targeting microtubule assembly dynamics. Additionally, we present the results of molecular modeling of their binding to specific sites on the α- and β-tubulin heterodimer. This has enabled the elucidation of the mechanism of stilbene cytotoxicity and is useful in the design of novel agents with improved anti-mitotic activity. Tubulin-interactive agents are believed to have the potential to play a significant role in the fight against cancer.     

Stereochemical aspects of the metabolism of the isomeric methylcyclohexanols and methylcyclohexanones

1. The seven isomeric optically inactive forms of methylcyclohexanol (i.e. 1-, and cis- and trans-2-, -3- and -4-) are excreted by rabbits mainly as glucuronides of the thermodynamically more stable forms of the alcohols. The eighth isomer, cyclohexylmethanol, however, undergoes aromatization in vivo, giving rise to benzoic acid and hippuric acid. The (±)-2-, (±-3- and 4-methylcyclohexanones are reduced in the rabbit and excreted mainly as the glucuronides of the thermodynamically more stable forms of the corresponding methylcyclohexanols. 2. Racemic cis- and trans-2-methylcyclohexanol and 2-methylcyclohexanone are all excreted as conjugated trans-2-methylcyclohexanol. However, when the (±)-cis-alcohol or the (±)-ketone is fed, (+)-trans-2-methylcyclohexanol is excreted, whereas when the (±)-trans-alcohol is fed it is excreted as the (±)-trans-alcohol. 3. Racemic cis- and trans-3-methylcyclohexanol and 3-methylcyclohexanone are all excreted as conjugated racemic cis-3-methylcyclohexanol. cis- and trans-4-Methylcyclohexanol and 4-methylcyclohexanone are all excreted as conjugated trans-4-methylcyclohexanol. 4. The metabolic differences between the various methylcyclohexanols are explicable in terms of their conformations and of Vennesland's (1958) hypothesis of the role of NADH in dehydrogenation reactions.     

Formation of (-⊃-1′,2′-epi-2-cis-xanthoxin acid from a precursor of abscisic acid

Tomato shoots and avocado mesocarp supplied with (±)-[2-¹⁴C]-5-(1,2-epoxy-2,6,6-trimethylcyclohexyl)-3-methylpenta-cis-2-trans-4-dienoic acid metabolize it into (+)-abscisic acid and a more polar material that was isolated and identified as (?)-epi-1′(R),2′(R)-4′(S)-2-cis-xanthoxin acid. The (+)-1′(S),2′(S)-4′(S)-2-cis-xanthoxin acid recently synthesized from natural violaxanthin, has the 1′,2′-epoxy group on the opposite side of the ring to that of the 4′(S)-hydroxyl group and the compound is rapidly converted into (+)-abscisic acid. The 1′,2′-epoxy group of (?)-1′,2′-epi-2-cis-xanthoxin acid is on the same side of the ring as the 4′(S) hydroxyl group: the compound is not metabolized into abscisic acid. The configuration of the 1′,2′-epoxy group probably controls whether or not the 4′(S) hydroxyl group can be oxidized. (+)-2-cis-Xanthoxin acid is probably not a naturally occurring intermediate because a ‘cold trap’, added to avocado fruit forming [¹⁴C]-labelled abscisic acid from [2-¹⁴C]mevalonate, failed to retain [¹⁴C] label.     

Flavour biogenesis. Partial purification and properties of a fatty acid hydroperoxide cleaving enzyme from fruits of cucumber

A membrane-bound enzyme, which catalyses the cleavage of fatty acid hydroperoxides to carbonyl fragments, has been partially purified from cucumber fruit. The isomeric 9- and 13-hydroperoxydienes (but not the hydroxydienes) derived from both linoleic and linolenic acids are cleaved by the enzyme but a mixture of 9- and 10-hydroperoxymonoenoic derivatives of oleic acid was not attacked. No evidence was obtained for free intermediates between fatty acid hydroperoxides and the cleavage products. Major volatile products were: cis-3-nonenal and hexanal (from 9- and 13-hydroperoxides of linoleic acid respectively) or cis-3,cis-6-nonadienal and cis-3-hexenal (from 9- and 13-hydroperoxides of linolenic acid). The increase in the ratio of cis-3- to trans-2-enal products with enzyme purification indicated that cis-3-enals are the immediate cleavage products and that the trans-2- forms are produced by subsequent isomerization.     

Identification of N-acyl 4-(5-pyrimidine-2,4-dionyl)phenylalanine derivatives and their orally active prodrug esters as dual-acting alpha4–beta1 and alpha4–beta7 receptor antagonists

N-Acyl 4-(5-pyrimidine-2,4-dionyl)phenylalanine derivatives of type 4 were designed to replace the 2,6-dichlorobenzoylamine portion of compound 1 in order to identify novel compounds with improved potency against α4-integrins. Several derivatives were identified as very potent dual-acting α4-integrin, α4β1 and α4β7 antagonists. Investigation of a limited number of prodrug esters led to the discovery of the ethyl ester prodrug 42, which demonstrated good intestinal fluid stability and good permeability. Despite low solubility, 42 gave acceptable blood levels of 30 when dosed orally in non-human primates. Additionally, 42 had an overall excellent profile and was selected for clinical trials. Investigation of N-acyl 4-(5-pyrimidine-2,4-dionyl)phenylalanine derivatives led to the discovery of several very potent dual-acting α4-integrin antagonists. Ethyl ester prodrug 42 advanced to human clinical trials based on the excellent intestinal fluid stability, good permeability and superior efficacy in non-human primates.     

Amine-free melanin-concentrating hormone receptor 1 antagonists: Novel 1-(1H-benzimidazol-6-yl)pyridin-2(1H)-one derivatives and design to avoid CYP3A4 time-dependent inhibition

Melanin-concentrating hormone (MCH) is an attractive target for antiobesity agents, and numerous drug discovery programs are dedicated to finding small-molecule MCH receptor 1 (MCHR1) antagonists. We recently reported novel pyridine-2(1H)-ones as aliphatic amine-free MCHR1 antagonists that structurally featured an imidazo[1,2-a]pyridine-based bicyclic motif. To investigate imidazopyridine variants with lower basicity and less potential to inhibit cytochrome P450 3A4 (CYP3A4), we designed pyridine-2(1H)-ones bearing various less basic bicyclic motifs. Among these, a lead compound 6a bearing a 1H-benzimidazole motif showed comparable binding affinity to MCHR1 to the corresponding imidazopyridine derivative 1. Optimization of 6a afforded a series of potent thiophene derivatives (6q–u); however, most of these were found to cause time-dependent inhibition (TDI) of CYP3A4. As bioactivation of thiophenes to form sulfoxide or epoxide species was considered to be a major cause of CYP3A4 TDI, we introduced electron withdrawing groups on the thiophene and found that a CF₃ group on the ring or a Cl adjacent to the sulfur atom helped prevent CYP3A4 TDI. Consequently, 4-[(5-chlorothiophen-2-yl)methoxy]-1-(2-cyclopropyl-1-methyl-1H-benzimidazol-6-yl)pyridin-2(1H)-one (6s) was identified as a potent MCHR1 antagonist without the risk of CYP3A4 TDI, which exhibited a promising safety profile including low CYP3A4 inhibition and exerted significant antiobesity effects in diet-induced obese F344 rats.     

Synthesis and biological evaluation of novel N-substituted nipecotic acid derivatives with a cis-alkene spacer as GABA uptake inhibitors

To discover new, potent, and selective inhibitors for the murine gamma-aminobutyric acid transporter 4 (mGAT4), the structure-activity relationship (SAR) study of a new cis-alkene analog family based on DDPM-1457 [(S)-2], which previously showed promising inhibitory potency at and subtype selectivity for mGAT4, was conducted. To uncover the importance of the differences between the trans- and the cis-alkene moiety in the spacer, the present publication describes the synthesis of the new compounds via catalytic hydrogenation with Lindlar’s catalyst. The biological results collected by the SAR study revealed that analog rac-7j characterized by a four-instead of a three-carbon atom spacer with a cis double bond applying to the majority of the studied compounds displays a surprisingly high potency at mGAT1 (pIC₅₀?=?6.00?±?0.04) and at the same time a reasonable potency at mGAT4 (pIC₅₀?=?4.82).     

1,1-Dioxo-5,6-dihydro-[4,1,2]oxathiazines,a novel class of 11ß-HSD1 inhibitors for the treatment of diabetes

Racemic cis-1,1-dioxo-5,6-dihydro-[4,1,2]oxathiazine derivative 4a was isolated as an impurity in a sample of a hit from a HTS campaign on 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). After separation by chiral chromatography the 4a-S, 8a-R enantiomer of compound 4a was identified as the true, potent enzyme inhibitor. The cocrystal structure of 4a with human and murine 11ß-HSD1 revealed the unique binding mode of the oxathiazine series. SAR elucidation and optimization in regard to metabolic stability led to monocyclic tetramethyloxathiazines as exemplified by compound 21g.     

Discovery of novel pyrazolo[1,5-a]pyridine-based EP1 receptor antagonists by scaffold hopping: Design,synthesis, and structure-activity relationships

A scaffold-hopping strategy towards a new pyrazolo[1,5-a]pyridine based core using molecular hybridization of two structurally distinct EP₁ antagonists, followed by structure-activity relationship-guided optimization, resulted in the identification of potent EP₁ antagonists exemplified by 4c, 4f, and 4j, which were shown to reduce pathological intravesical pressure in rats when administered at 1 mg/kg iv.     

Cytokinins: synthesis and biological activity of geometric and position isomers of zeatin

Geometric and position isomers of zeatin and of ribosylzeatin and other compounds closely related to zeatin have been tested in the tobacco (Nicotiana tabacum var. Wisconsin No. 38) bioassay. None was more active than zeatin itself. There was a much greater difference in activity (> 50-fold) between trans- and cis-zeatin than between trans-isozeatin [6-(4-hydroxy-2-methyl-trans-2-butenylamino) purine] and cis-isozeatin [6-(4-hydroxy-2-methyl-cis-2-butenylamino) purine], the latter being less active than cis-zeatin and trans-isozeatin. Higher concentrations were required for equivalent callus growth stimulated by the 9-ribosyl derivatives, which followed an order of decreasing activity: ribosyl-trans-zeatin > ribosyl-cis-zeatin > ribosyl-trans-isozeatin > ribosyl-cis-isozeatin, corresponding roughly to that of the bases. The effect of side chain, double bond saturation was to diminish the activity, and in the dihydro series the shift of the methyl group from the 3- to the 2-position in going from dihydrozeatin to dihydroisozeatin [6-(4-hydroxy-2-methylbutylamino) purine] resulted in a 70-fold decrease in activity. cis-Norzeatin [6-(4-hydroxy-cis-2-butenylamino) purine], which was less than one-fifth as active as cis-zeatin, showed the effect of complete removal of the side chain methyl group, and cyclic-norzeatin [6-(3,6-dihydro-1,2-oxazin-2-yl) purine] was about 1/100 as active as cis-norzeatin. These findings delineate completely the effect on the cytokinin activity of zeatin of variation in side chain geometry, presence and position of the methyl substituent, presence and geometry of hydroxyl substitution, presence of the double bond, and of side chain cyclization.     

A criterion to determine whether cis-4-hydroxyproline is produced in animal tissues

Hydrolyzates of tissues that had been labeled with [¹⁴C]proline often contain significant amounts of cis-4-hydroxy[¹⁴C]proline. Since animal cells do not contain an enzyme which can effect formation of cis-4-hydroxyproline, there are only two possible explanations for its presence. Either it is formed during acid hydrolysis of trans-4-hydroxyproline (which is synthesized by cells and is a common constituent of connective tissues), or it is produced by a nonenzymatic mechanism such as attack by oxygen radicals. It is important to resolve this issue because if a nonenzymatic mechanism is active in connective tissues, then it will be necessary to reevaluate currently accepted ideas about production of hydroxyproline. This communication describes a method for distinguishing between the two alternate explanations. Tissues or cells are labeled with [¹⁴C]proline, and then a known amount of trans-4-hydroxy[³H]proline is added to each sample before hydrolysis; the relative amounts of [¹⁴C]- and [³H]-cis-4-hydroxyproline are compared after hydrolysis. It is known from a separate series of measurements with mixtures of [¹⁴C]- and [³H]-trans-4-hydroxyproline standards that there is a very high correlation (r = 0.998) between acid-induced formation of the [¹⁴C]- and [³H]-cis epimers. One can thus compare the amount of cis-4-hydroxy[¹⁴C]proline in a hydrolyzate from a biological system with the amount that would be expected if it were all formed during acid hydrolysis. This method was used to show that fibroblasts cultured under conditions commonly used to study collagen metabolism do not produce cis-4-hydroxyproline. This result strongly suggests that nonenzymatic hydroxylation does not normally occur in cell culture systems.     

Key structural features of cis-cinnamic acid as an allelochemical

1-O-cis-cinnamoyl-β-d-glucopyranose is one of the most potent allelochemicals isolated from Spiraea thunbergii Sieb. It is suggested that it derives its strong inhibitory activity from cis-cinnamic acid, which is crucial for phytotoxicity. It was synthesized to confirm its structure and bioactivity, and also a series of cis-cinnamic acid analogues were prepared to elucidate the key features of cis-cinnamic acid for lettuce root growth inhibition. The cis-cyclopropyl analogue showed potent inhibitory activity while the saturated and alkyne analogues proved to be inactive, demonstrating the importance of the cis-double bond. Moreover, the aromatic ring could not be replaced with a saturated ring. However, the 1,3-dienylcyclohexene analogue showed strong activity. These results suggest that the geometry of the C–C double bond between the carboxyl group and the aromatic ring is essential for potent inhibitory activity. In addition, using several light sources, the photostability of the cinnamic acid derivatives and the role of the C–C double bond were also investigated.