Part 3: synthesis and biological evaluation of some analogs of the antitumor agents, 2-{4-[(7-chloro-2-quinoxalinyl)oxy]phenoxy}propionic acid, and 2-{4-[(7-bromo-2-quinolinyl)oxy]phenoxy}propionic acid

2-{4-[(7-Chloro-2-quinoxalinyl)oxy]phenoxy}propionic acid (X469) and 2-{4-[(7-bromo-2-quinolinyl)oxy]phenoxy}propionic Acid (SH80) are among the most highly and broadly active antitumor agents to have been developed in our laboratories. However, the mechanism(s) of action of these agents remain to be elucidated, which prompted our continued endeavor to delineate a pharmacophoric pattern, from which a putative target might be deduced. Herein, we provide additional evidence that intact quinoxaline and quinoline rings in XK469 and SH80, respectively, are fundamental to the activities of these structures against transplanted tumors in mice. The consequence of further modification of the heterocyclic ring system in XK469 and SH80, leading to [1,8]naphthyridine; pyrrolo[1,2-a]; imidazo[1,2-a]; and imidazo[1,5-a] derivatives, all deprive the parent structures of antitumor activity. Introduction of CH3, CF3, CH3O, CO2H, or C6H5 substituents at C4 of the quinoline ring of SH80 led to weakly active antitumor agents. Similarly, the phenanthridine analog of SH80 manifested only modest cytotoxicity. Lastly, XK469 and SH80 are both significantly more active than the corresponding regioisomeric structures, 2-{4-[(7-halo-4-quinolinyl)oxy]phenoxy)propionic acids.     

Synthesis and biological evaluation of conformationally constrained analogs of the antitumor agents XK469 and SH80. Part 5

Conformational restriction of bioactive molecules offers the possibility of generating structures of increased potency. To this end, a synthesis has been achieved of (R,S)-2-[(8-chlorobenzofurano[2,3-b]quinolinyl)oxy]propionic acid (12a), a highly rigidified, polycyclic analog of 2-[4-[(7-chloro-2-quinoxalinyl)oxy]phenoxy]propionic acid (2a, XK469). Efforts to effect the same synthesis of the corresponding 8-bromo-derivative led to a mixture of intermediate, 8-chloro (9a), and 8-bromo-2-hydroxybenzofurano[2,3-b]quinoline (9b), generated by halogen-exchange, via an aromatic S(RN)1(A(RN)1) reaction of precursor, 8b, with pyridine hydrochloride. The presumption that conformational restriction of 1b-12a might enhance the antitumor potency of the latter has not been sustained. In fact, 12a proved to be significantly less active than 1b. However, it is apparent that virtually all of the spatial and steric properties of 12a, necessary for improved activity, including the disposition of the 2-oxypropionic acid side chain remain to be identified.     

Synthesis and structure-activity relationships of 6-{4-[(3-fluorobenzyl)oxy]phenoxy}nicotinamide derivatives as a novel class of NCX inhibitors: a QSAR study

The sodium-calcium exchanger (NCX) transports Na+ and Ca2+ ions, and controls the Ca2+ concentration in myocytes. Calcium overload is induced via activation of reverse NCX, and is responsible for reperfusion injury in heart failure. Hence, NCX is an attractive target for prevention and treatment of reperfusion arrhythmias, myocardial contracture, and necrosis. We have synthesized a series of 6-{4-[(3-fluorobenzyl)oxy]phenoxy}nicotinamide derivatives, and evaluated their inhibitory activity against the reverse and forward modes of NCX. N-(3-Aminobenzyl)-6-{4-[(3-fluorobenzyl)oxy]phenoxy}nicotinamide (8) was shown to be a potent inhibitor of reverse NCX activity, with an IC50 value of 0.24 microM. A QSAR study showed that inhibition of reverse NCX activity by 6-{4-[(3-fluorobenzyl)oxy]phenoxy}nicotinamide derivatives is multiply dependent on the hydrophobicity (pi) and the shape (B(iv)) of the substituent at the 3-position of the phenyl ring.     

Effects of methy-2[(chloro-4'-benzoyl)-4-phenoxy]-2 propionic acid on the respiratory activity of isolated rat liver mitochondria]

The effects of methyl-2 [(chloro-4' benzoyl)-4 phenoxy]-2 propionic acid (LF 153) on mitochondrial respiration and oxidative phosphorylation are studied in vitro. Its activity is related to that of 3,5,3'-triiodo-L-thyronine (LT3), 3,5,3'-triiodothyroacetic acid (TA3), and to that of clofibrate, LF 153 acts as an inhibitory uncoupler of oxidative phosphorylation. Its uncoupling action is however very intense.     

Effect of various 2-methyl-(4'-chlorobenzoyl)-4-phenoxy)-2 propionic acid (LF 153) analogs on the respiratory activity of rat liver mitochondria]

Seven analogs of methyl-2 [chloro-4' benzoyl)-4 phenoxy]-2 propionic acid, (LF 153) have been tested for their effects on respiration and phosphorylation of rat liver mitochondria suspensions. They differ from one another by the sort of binding between both aromatic cycle as well as by the nature and position of the halogenated substitutions and alpha methylation in the propionic chain. All the compounds which have been tested acted as inhibitors of the electron transport chain and uncouplers of phosphorylations.     

Resolution, absolute stereochemistry, and enantiopharmacology of the GluR1-4 and GluR5 antagonist 2-amino-3-[5-tert-butyl-3-(phosphonomethoxy)-4-isoxazolyl]propionic acid

The phosphono amino acid, (RS)-2-amino-3-[5-tert-butyl-3-(phosphonomethoxy)-4-isoxazolyl+ ++]propio nic acid (ATPO), is a structural hybrid between the NMDA antagonist (RS)-2-amino-7-phosphonoheptanoic acid (AP7) and the AMPA and GluR5 agonist, (RS)-2-amino-3-(5-tert-butyl-3-hydroxy-4-isoxazolyl)propionic acid (ATPA). ATPO has been resolved into (S)-ATPO and (R)-ATPO using chiral HPLC, and the absolute stereochemistry of the two enantiomers was established by an X-ray crystallographic analysis of (R)-ATPO. (S)-ATPO and (R)-ATPO were characterized pharmacologically using rat brain membrane binding and electrophysiologically using the cortical wedge preparation as well as homo- or heteromeric GluR1-4, GluR5-6, and KA2 receptors expressed in Xenopus oocytes. (R)-ATPO was essentially inactive as an agonist or antagonist in all test systems. (S)-ATPO was an inhibitor of the binding of [(3)H]AMPA (IC(50) = 16 +/- 1 microM) and of [(3)H]-6-cyano-7-nitroquinoxaline-2,3-dione ([(3)H]CNQX) (IC(50) = 1.8 +/- 0.2 microM), but was inactive in the [(3)H]kainic acid and the [(3)H]-(RS)-3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid ([(3)H]CPP) binding assays. (S)-ATPO did not show detectable agonist effects at any of the receptors under study, but antagonized AMPA-induced depolarization in the cortical wedge preparation (IC(50) = 15 +/- 1 microM). (S)-ATPO also blocked kainic acid agonist effects at GluR1 (K(i) = 2.0 microM), GluR1+2 (K(i) = 3.6 microM), GluR3 (K(i) = 3.6 microM), GluR4 (K(i) = 6.7 microM), and GluR5 (K(i) = 23 microM), but was inactive at GluR6 and GluR6+KA2. Thus, although ATPO is a structural analog of AP7 neither (S)-ATPO nor (R)-ATPO are recognized by NMDA receptor sites.     

Further optimization of sulfonamide analogs as EP1 receptor antagonists: synthesis and evaluation of bioisosteres for the carboxylic acid group

4-{[2-[(2-Furylsulfonyl)(isobutyl)amino]-5-(trifluoromethyl)phenoxy]methyl}benzoic acid analogs 2a and b and a series of the acid analogs, in which the carboxylic acid residue of 2b was replaced with various kinds of carboxylic acid bioisosteres, were synthesized and evaluated as EP1 receptor antagonists. Compound 2b and its monocyclic acid analogs, in which the carboxylic acid residue of 2b was replaced with monocyclic acid bioisosteres, were found to show potent EP1 receptor antagonist activity. Optimization of the linker Y between the phenyl moiety and the carboxylic acid residue of 2b was also carried out (Table 5). Compounds 2b and 16 and 17 possessing conformationally restricted linker Y were found to show the most optimized potency among the tested compounds. Cytochrome P450 inhibition of optimized compounds was also investigated. Details of the structure-activity relationship study are presented.     

Partial agonism and antagonism of the ionotropic glutamate receptor iGLuR5: structures of the ligand-binding core in complex with domoic acid and 2-amino-3-[5-tert-butyl-3-(phosphonomethoxy)-4-isoxazolyl]propionic acid

More than 50 structures have been reported on the ligand-binding core of the ionotropic glutamate receptor iGluR2 that belongs to the 2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid-type of receptors. In contrast, the ligand-binding core of the kainic acid-type receptor iGluR5 has only been crystallized with three different ligands. Hence, additional structures of iGluR5 are needed to broaden the understanding of the ligand-binding properties of iGluR5, and the conformational changes leading to channel opening and closing. Here, we present two structures of the ligand-binding core of iGluR5; one as a complex with the partial agonist (2S,3S,4S)-3-carboxymethyl-4-[(1Z,3E,5R)-5-carboxy-1-methyl-hexa-1,3-dienyl]-pyrrolidine-2-carboxylic acid (domoic acid) and one as a complex with the antagonist (S)-2-amino-3-[5-tert-butyl-3-(phosphonomethoxy)-4-isoxazolyl]propionic acid ((S)-ATPO). In agreement with the partial agonist activity of domoic acid, the ligand-binding core of the iGluR5 complex is stabilized by domoic acid in a conformation that is 11 degrees more open than the conformation observed in the full agonist (S)-glutamic acid complex. This is primarily caused by the 5-carboxy-1-methyl-hexa-1,3-dienyl moiety of domoic acid and residues Val685-Thr690 of iGluR5. An even larger domain opening of 28 degrees is introduced upon binding of the antagonist (S)-ATPO. It appears that the span of domain opening is much larger in the ligand-binding core of iGluR5 (30 degrees) compared with what has been observed in iGluR2 (19 degrees ). Similarly, much larger variation in the distances between transmembrane linker residues in the two protomers comprising the dimer is observed in iGluR5 as compared with iGluR2.     

6-Acylamino-2-[(alkylsulfonyl)oxy]-1H-isoindole-1,3-dione mechanism-based inhibitors of human leukocyte elastase

A study of various 2-[(alkylsulfonyl)oxy]-6-substituted-1H-isoindole-1,3-diones' inhibition of chymotrypsin compared to inhibition of HLE reveals that acylamino substitution in the 6-position increases selectivity and potency of these inhibitors for HLE. The best HLE inhibitor in this series was 6-(methylglutaryl)amino-2-[(ethylsulfonyl)oxy]-1H-isoindole-1,3-di one with a kobs/[I] = 220,000 M(-1) s(-1).     

Synthesis, hypolipidemic and hypoglycemic activity of some novel 2-(4-(2-substituted aminothiazole-4-yl) phenoxy)-2-methyl propanoic acid derivatives

An improved synthetic protocol for a novel series of 2-(4-(2-substituted aminothiazole-4-yl) phenoxy)-2-methyl propanoic acid derivatives has been developed using different methods of synthesis. The synthesized compounds are evaluated for their hypolipidemic and hypoglycemic activity by high fat diet induced hyperlipidemia and hyperglycemia in Sprague-Dawley rats.     

2-Amino-3-(3-hydroxy-1,2,5-thiadiazol-4-yl)propionic acid: resolution, absolute stereochemistry and enantiopharmacology at glutamate receptors

In order to identify new subtype-selective (S)-glutamate (Glu) receptor ligands we have synthesized (RS)-2-amino-3-(3-hydroxy-1,2,5-thiadiazol-4-yl)propionic acid [(RS)-TDPA]. Resolution of (RS)-TDPA by chiral chromatography was performed using a Crownpac CR(+) column affording (R)- and (S)-TDPA of high enantiomeric purity (enantiomeric excess=99.9%). An X-ray crystallographic analysis revealed that the early eluting enantiomer has R-configuration. Both enantiomers showed high affinity as well as high agonist activity at (RS)-2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid (AMPA) receptors, determined using a [(3)H]AMPA binding assay and an electrophysiological model, respectively. The affinities and agonist activities obtained for (R)-TDPA (IC(50)=0.265 microM and EC(50)=6.6 microM, respectively) and (S)-TDPA (IC(50)=0.065 microM and EC(50)=20 microM, respectively) revealed a remarkably low AMPA receptor stereoselectivity, (S)-TDPA showing the highest affinity and (R)-TDPA the most potent agonist activity. In addition, (S)-TDPA was shown to interact with synaptosomal Glu uptake sites displacing [(3)H](R)-aspartic acid (IC(50 ) approximately 390 microM). An enantiospecific and subtype-selective agonist activity was observed for (S)-TDPA at group I metabotropic Glu (mGlu) receptors (EC(50)=13 microM at mGlu(5) and EC(50)=95 microM at mGlu(1)).     

Effects of phenoxy acid herbicides and glyphosate on nitrogenase activity (acetylene reduction) in root-associated Azospirillum, Enterobacter and Klebsiella

Abstract Nitrogenase activity (C₂H₂ reduction) in root-associated Azospirillum lipoferum, Klebsiella pneumoniae, Enterobacter agglomerans and Pseudomonas sp. isolated from roots of Finnish grasses was assayed in the presence of glyphosate, the phenoxy acid herbicides 2-methyl-4-chlorophenoxy acetic acid (MCPA), 2,4-dichlorophenoxy acetic acid (2,4-D), (±)-2-(2-methyl-4-chlorophenoxy)propionic acid (mecoprop) and (±)-2-(2,4-dichlorophenoxy)propionic acid (dichlorprop), and the commercial products Roundup, Nurmikko-Hedonal, Mepro, and Dipro. In the presence of the phenoxy acid herbicides the nitrogenase activity of K. pneumoniae was significantly inhibited, but that of E. agglomerans was stimulated. With the exception of Mepro and mecoprop no phenoxy acid herbicides inhibited the nitrogenase activity of A. lipoferum and none that of Pseudomonas sp. Nurmikko-Hedonal considerably stimulated the nitrogenase activity of E. agglomerans , and Pseudomanas sp. On the other hand, the nitrogenase activity of both K. pneumoniae and E. agglomerans was considerably repressed by glyphosate and Roundup, which also inhibited the growth of the bacteria. These chemicals had no effect on the growth of A. lipoferum and Pseudomonas sp., but stimulated their nitrogenase activity.     

Synthesis of N(1)-substituted analogues of (2R,4R)-4-amino-pyrrolidine-2,4-dicarboxylic acid as agonists, partial agonists, and antagonists of group II metabotropic glutamate receptors.

The chemical synthesis of a series of N(1)-substituted derivatives of (2R,4R)-4-aminopyrrolidine-2,4-dicarboxylic acid [(2R,4R)-APDC] as constrained analogues of gamma-substituted glutamic acids is described. Appropriate substitution of the N(1)-position results in agonist, partial agonist, or antagonist activity at mGluR2, mGluR3, and/or mGluR6.     

Synthesis and Herbicidal Activity of Phenoxypropionic Acid Derivatives with Imidazo[1,2-α]pyridine Moiety

Phenoxypropionic acid derivatives (Ia-s) with an imidazo[1,2-a]pyridine moiety were synthesized and their herbicidal activities were examined. The activities were affected dramatically by the substituents on the imidazo[1,2-a]pyridine ring, and good substituents to enhance the herbicidal activity were a cyano group at the 3-position and a chlorine atom at the 6-position. Among the compounds, n-propyl 2-[4-(6-chloro-3-cyano-2-imidazo[1,2-a]pyridinyloxy)phenoxy]propionate(Iq) was most active against gramineous weeds and the activity was comparable to that of the commercial herbicide fluazifop-butyl.     

Triterpenoids from Sanguisorba officinalis

Seven triterpenoids, i.e., 3beta-[(alpha-L-arabinopyranosyl)oxy]-19beta-hydroxyurs-12,20(30)-dien-28-oic acid (1), 3beta-[(alpha-L-arabinopyranosyl)oxy]-urs-11,13(18)-dien-28-oic acid beta-D-glucopyranosyl ester (2), 2alpha,3alpha,23-trihydroxyurs-12-en-24,28-dioic acid 28-beta-D-glucopyranosyl ester (3), 3beta-[(alpha-L-arabinopyranosyl)oxy]-urs-12,19(20)-dien-28-oic acid (4), 3beta-[(alpha-L-arabinopyranosyl)oxy]-urs-12,19(29)-dien-28-oic acid (5), 3beta-[(alpha-L-arabinopyranosyl)oxy]-19alpha-hydroxyolean-12-en-28-oic acid (6), 2alpha,3beta-dihydroxy-28-norurs-12,17,19(20),21-tetraen-23-oic cid (7), together with three known ones (8-10), were isolated from the roots of Sanguisorba officinalis. Their structures were determined by spectroscopic and chemical methods. Compounds 7 and 10 showed marginal inhibition activity against the growth of tumor cell lines.     

New glycosides from Tetracentron sinense and their cytotoxic activity

One novel neolignan (tetracentronsine; 1), one new indole alkaloid (=3-(2-hydroxyethyl)-1H-indole-5-O-beta-D-glucopyranoside; 2), and two new phenol derivatives, 3-{2-[(beta-glucopyranosyl)oxy]-4,5-(methylenedioxy)phenyl}propanoic acid (3) and methyl 3-{2-[(beta-glucopyranosyl)oxy]-4,5-(methylenedioxy)phenyl}propanoate (4), together with six known compounds were isolated from the stem bark of Tetracentron sinense. Their structures were determined by spectral analysis, including 1D- and 2D-NMR, and MS analyses. These compounds were tested for their cytotoxic activity against human leukaemia cells in vitro. Among them, compound 2, (E)-3-(4-hydroxyphenyl)-N-[2-(4-hydroxyphenyl)ethyl]prop-2-enamide (5), and maslinic acid (6) showed significant inhibitory activities against human leukaemia cells CCRF-CEM and its multidrug-resistant sub-line, CEM/ADR5000, with IC50 values in a range of 7.1 to 29.7 microM.     

Design, synthesis, and pharmacological evaluation of some 2-[4-morpholino]-3-aryl-5-substituted thiophenes as novel anti-inflammatory agents: generation of a novel anti-inflammatory pharmacophore

Compounds incorporating a thiophene moiety, a pi excess five membered heterocycle, have attracted a great deal of research interest owing to the therapeutic utility of the template as useful drug molecular scaffolding. Recently we reported the anti-inflammatory activity profile exhibited by two thiophene analogs, AP84 and AP82 in acute and chronic models of inflammation. The good activity profile exhibited by AP84, a 3-(substituted aryl)-2-(4-morpholino)-5-heteroaryl substituted analog of thiophene, in the formalin induced rat paw edema chronic model as compared to a weak activity in acute carrageenin induced rat paw edema, and the slightly better protection exhibited in the acute model by AP82 (27%), the 5-aroyl analog provided an impetus for a proper exploration of their structural types. In this paper we report the synthesis and pharmacological evaluation of some novel, 2-(4-morpholino)-3-(substituted aryl)-5-substituted thiophenes, as possible anti-inflammatory leads. The 3-(4-chlorophenyl)-2-(4-morpholino) thiophene analogs AP49, AP158, and AP88 provided a protection of 20%, 23%, and 20%, respectively, when screened for anti-inflammatory activity in carrageenin induced rat paw edema, an acute in vivo model, comparable to that of AP82, at a dose level of 100mg/kg body weight p.o. compared to ibuprofen as standard. The replacement of the 3-(4-chlorophenyl) moiety with the 3-phenyl moiety gave rise to AP50 (30%), AP159 (38%), AP27 (0%), and AP92 (38%), with three analogs being more active in the acute model. Alteration of the group para to the phenyl ring at third position, from chloro, to methyl mercapto gave rise to the 3-(4-methylmercapto-phenyl) analogs AP54 (20%), AP160 (0%), and AP73 (52%), with only one analog appearing to be better than AP82. These results indicate that 4-methane sulfonyl aroyl group at 5-position and other substituents of different quadrants of Craig plot on the phenyl moiety at the third position could lead to more potent candidates. However, alteration of aroyl to substituted pyridyl at 5-position with a phenyl group at the third position as in AP26 gave rise to much better protection (66%) again reinforcing the importance of the heteroaryl ring at the fifth position and implying its utility in the composition of a novel pharmacophore for designing better trisubstituted thiophenes as anti-inflammatory agents.     

Design and synthesis of novel benzimidazole derivatives as phosphodiesterase 10A inhibitors with reduced CYP1A2 inhibition

A novel class of phosphodiesterase 10A (PDE10A) inhibitors with reduced CYP1A2 inhibition were designed and synthesized starting from 2-{[(1-phenyl-1H-benzimidazol-6-yl)oxy]methyl}quinoline (1). Introduction of an isopropyl group at the 2-position and a methoxy group at the 5-position of the benzimidazole ring of lead compound 1 resulted in the identification of 2-{[(2-isopropyl-5-methoxy-1-phenyl-1H-benzimidazol-6-yl)oxy]methyl}quinoline (25b), which exhibited potent PDE10A inhibitory activity with reduced CYP1A2 inhibitory activity compared to compound 1.     

Discovery of novel 4-(2-fluorophenoxy)quinoline derivatives bearing 4-oxo-1,4-dihydrocinnoline-3-carboxamide moiety as c-Met kinase inhibitors

A series of novel 4-(2-fluorophenoxy)quinoline derivatives containing 4-oxo-1,4-dihydrocinnoline-3-carboxamide moiety were designed, synthesized and evaluated for their in vitro biological activities against c-Met kinase and six typical cancer cell lines (A549, H460, HT-29, MKN-45, U87MG and SMMC-7721). All the prepared compounds showed moderate to excellent antiproliferative activity, and the analysis of their structure–activity relationships indicated that 2-chloro or 2-trifluoromethyl substituted phenyl group on the 1-position of cinnoline ring was more favorable for antitumor activity. In this study, a promising compound 33, with a c-Met IC₅₀ value of 0.59 nM, was identified as a multitargeted receptor tyrosine kinase inhibitor.     

Design and Synthesis of Novel Arylisoxazole‐Chromenone Carboxamides: Investigation of Biological Activities Associated with Alzheimer's Disease

A novel series of hybrid arylisoxazole‐chromenone carboxamides were designed, synthesized, and evaluated for their cholinesterase (ChE) inhibitory activity based on the modified Ellman's method. Among synthesized compounds, 5‐(3‐nitrophenyl)‐N‐{4‐[(2‐oxo‐2H‐1‐benzopyran‐7‐yl)oxy]phenyl}‐1,2‐oxazole‐3‐carboxamide depicted the most acetylcholinesterase (AChE) inhibitory activity (IC₅₀=1.23 μm ) and 5‐(3‐chlorophenyl)‐N‐{4‐[(2‐oxo‐2H‐1‐benzopyran‐7‐yl)oxy]phenyl}‐1,2‐oxazole‐3‐carboxamide was found to be the most potent butyrylcholinesterase (BChE) inhibitor (IC₅₀=9.71 μm ). 5‐(3‐Nitrophenyl)‐N‐{4‐[(2‐oxo‐2H‐1‐benzopyran‐7‐yl)oxy]phenyl}‐1,2‐oxazole‐3‐carboxamide was further investigated for its BACE1 inhibitory activity as well as neuroprotectivity and metal chelating ability as important factors involved in onset and progress of Alzheimer's disease. It could inhibit BACE1 by 48.46 % at 50 μm . It also showed 6.4 % protection at 25 μm and satisfactory chelating ability toward Zn²⁺, Fe²⁺, and Cu²⁺ ions. Docking studies of 5‐(3‐nitrophenyl)‐N‐{4‐[(2‐oxo‐2H‐1‐benzopyran‐7‐yl)oxy]phenyl}‐1,2‐oxazole‐3‐carboxamide and 5‐(3‐chlorophenyl)‐N‐{4‐[(2‐oxo‐2H‐1‐benzopyran‐7‐yl)oxy]phenyl}‐1,2‐oxazole‐3‐carboxamide confirmed desired interactions with those amino acid residues of the AChE and BChE, respectively.