Synthesis, antifungal activity, and structure-activity relationships of coruscanone A analogues

Coruscanone A, a plant-derived cyclopentenedione derivative, showed potent in vitro antifungal activity against Candida albicans and Cryptococcus neoformans comparable to amphotericin B and fluconazole. A series of analogues have been synthesized by modification of the cyclopentenedione ring, the enolic methoxy functionality, and the side chain styryl moiety of this natural product lead. A structurally close 1,4-benzoquinone analogue was also prepared. All the compounds were examined for their in vitro activity against major opportunistic fungal pathogens including C. albicans, C. neoformans, and Aspergillus fumigatus and fluconazole-resistant C. albicans strains, with several analogues demonstrating potent antifungal activity. Structure-activity relationship studies indicate that the 2-methoxymethylenecyclopent-4-ene-1,3-dione structural moiety is the pharmacophore responsible for the antifungal activity of this class of compounds while the side chain styryl-like moiety plays an important complementary role, presumably contributing to target binding.     

Synthesis and biological activity of substance P C-terminal hexapeptide analogues: structure-activity studies

A series of analogues of the C-terminal hexapeptide of substance P, modified at the glutaminyl residue, was synthesized and their relative activities as spasmogens were determined in the guinea pig ileum and rat colon muscularis mucosae preparations in vitro. In general, when compared to SP6-11, the loss of the carboxamide group has little effect on activity in the colon and reduces activity on the ileum. The exception to this is the Orn6 analogue which retains activity on both preparations and is proposed as a useful tool for structure-activity studies. It is concluded that the hydrogen-bonding potential of the position 6 substituent may be an important determinant of biological activity.     

Synthesis, biological activity, and structure-activity relationships for potent cytotoxic rhodium(III) polypyridyl complexes

The complexes mer-[RhCl 3(DMSO-kappa S)(pp)] 1a- 5a may be prepared by reaction of mer,cis-[RhCl 3(DMSO-kappa S) 2(DMSO-kappa O)] with the appropriate polypyridyl ligand (pp = bpy, phen, dpq, dppz, dppn) in CH 3OH/H 2O solution at 75 degrees C. The mer isomers of 1a- 5a are stable in chloroform solution but those of 1a and 2a isomerize rapidly to a mixture of fac and mer isomers in DMSO. The complexes are potent in vitro cytotoxic agents and exhibit IC 50 values that are strongly dependent on the size of the polypyridyl ligand. IC 50 values of, respectively, 4.0 (0.5) and 1.9 (0.5), 0.40 (0.06) and 0.19 (0.05), and 0.079 (0.012) and 0.069 (0.021) microM are observed for 1a- 3a against the human cell lines MCF-7 (breast cancer) and HT-29 (colon cancer). Cellular uptake studies showed a rapid and high accumulation of the polypyridyl compounds. Treatment of HT-29 and MCF-7 cells with 3a leads to significant decreases in cellular oxygen consumption and the rate of extracellular acidification.     

Design, synthesis, and characterization of new iron chelators with anti-proliferative activity: structure-activity relationships of novel thiohydrazone analogues

Di-2-pyridylketone isonicotinoyl hydrazone Fe chelators utilize the N,N,O-donor set and have moderate anti-proliferative effects. Their closely related N,N,S-thiosemicarbazone analogues, namely, the di-2-pyridylketone thiosemicarbazones, exhibit markedly increased anti-proliferative and redox activity, and this was thought to be due to the inclusion of a sulfur donor atom (Richardson, D. R. et al. J. Med. Chem. 2006, 49, 6510-6521). To further examine the effect of donor atom identity on anti-proliferative activity, we synthesized thiohydrazone analogues of extensively examined aroylhydrazone chelators. The O,N,S-thiohydrazones exhibited decreased anti-proliferative effects compared to their parent aroylhydrazones and reduced redox activity. In contrast, the N,N,S-thiohydrazones showed vastly increased anti-proliferative activity compared to their hydrazone analogues, being comparable to potent thiosemicarbazones. Additionally, N,N,S-thiohydrazone complexes had reversible FeIII/II couples and exhibited increased redox activity. These observations demonstrate that the N,N,S-donor set is critical for potent anti-proliferative efficacy.     

New propargyl thioquinolines--synthesis,antiproliferative activity in vitro and structure-activity relationships

The series of the propargyl thioquinolines has been prepared on the basis of the reaction of thioquinanthrene (1) (1,4-dithiino[2,3-c:5,6-c']-diquinoline) with sodium alkoxides. Some of these compounds have revealed good antiproliferative activity in vitro against the cells of human and murine cancer lines. 13C NMR spectra were measured for the studied compounds to examine the electronic properties-activity relationships. A regression study on 10 compounds showed a linear correlation of antiproliferative activity with electronic properties, expressed as the 13C NMR chemical shift for C-4 carbon atom (R2 = 0.97). It was found that compounds with chemical shift for C-4 value falling in the range of 135-140 ppm exhibited significant antiproliferative activity, while compounds which possess moderate or low activity are located in the range 140-165 ppm. This finding leads to the expectation that the antiproliferative activity of propargyl thioquinolines can be predicted using the 13C NMR chemical shift value of their C-4 carbon atom.     

Inhibition of superoxide dismutase by 2-methoxyoestradiol analogues and oestrogen derivatives: structure-activity relationships

Superoxide dismutases catalyse the dismutation of highly reactive superoxide ions to produce hydrogen peroxide and several lines of evidence suggest that these enzymes play important roles in the development and response to treatment of human cancers. For example, Mn-containing superoxide dismutase is frequently overexpressed in various cancer types and can contribute to resistance to apoptosis. 2-Methoxyoestradiol is a naturally occurring metabolic product of 17beta-oestradiol that inhibits tubulin polymerization and possesses growth inhibitory and cytotoxic activity in vitro and in vivo. More recently 2-methoxyoestradiol has also been shown to inhibit superoxide dismutase (SOD) in a tetrazolium salt based enzyme assay, suggesting that oestrogen derivatives might be useful starting points for the development of effective, non-toxic enzyme inhibitors. Here we have tested the SOD inhibiting activity of a range of oestrogen derivatives to determine structural features important for enzyme inhibition.     

Design, synthesis, cytoselective toxicity, structure-activity relationships, and pharmacophore of thiazolidinone derivatives targeting drug-resistant lung cancer cells

Ten cytoselective compounds have been identified from 372 thiazolidinone analogues by applying iterative library approaches. These compounds selectively killed both non-small cell lung cancer cell line H460 and its paclitaxel-resistant variant H460 taxR at an IC 50 between 0.21 and 2.93 microM while showing much less toxicity to normal human fibroblasts at concentrations up to 195 microM. Structure-activity relationship studies revealed that (1) the nitrogen atom on the 4-thiazolidinone ring (ring B in Figure 1) cannot be substituted, (2) several substitutions on ring A are tolerated at various positions, and (3) the substitution on ring C is restricted to the -NMe 2 group at the 4-position. A pharmacophore derived from active molecules suggested that two hydrogen bond acceptors and three hydrophobic regions were common features. Activities against P-gp-overexpressing and paclitaxel-resistant cell line H460 taxR and modeling using a previously validated P-gp substrate pharmacophore suggested that active compounds were not likely P-gp substrates.     

Syntheses, resolution, and structure-activity relationships of potent acetylcholinesterase inhibitors: 8-carbaphysostigmine analogues.

The synthesis of a series of 1,2,3,3a,8,8a-hexahydroindeno[2,1-b]pyrrole 5-alkylcarbamates and their resolution are reported. These compounds are structurally related to physostigmine with substitution of a methylene group in place of the NMe group at position 8 of physostigmine. Many of these 8-carbaphysostigmine analogues are more potent acetylcholinesterase inhibitors in vitro and less toxic in vivo than physostigmine. The (-)-enantiomer (e.g., 1d and 1g) possessing the same absolute configuration at C3a and C8a as that of physostigmine, is about 6 to 12-fold more potent at inhibiting acetylcholinesterase than the corresponding (+)-enantiomer (e.g., 1e and 1h).     

Design, synthesis, and biological activity of a novel non-cisplatin-type platinum-acridine pharmacophore.

Platinum-acridine conjugates were prepared from [PtCl2(ethane-1,2-diamine)] and the novel acridinylthioureas MeHNC(S)NMeAcr (6) and MeHNC(S)NMe(CH2CH2)NHAcr (15) by replacing one chloro leaving group in the cisplatin analogue with thiourea sulfur. In HL-60 leukemia cells, IC(50) values for 7 (Pt-tethered 6) and 16 (Pt-tethered 15) were 75 and 0.13 microM, respectively. In the ovarian cell lines 2008 and C13, 16 was active at micromolar concentrations and showed only partial cross-resistance with clinical cisplatin. Possible structure-activity relationships are discussed.     

Antioxidant, prooxidant and cytotoxic activity of hydroxylated resveratrol analogues: structure-activity relationship

Resveratrol (trans-3,4',5-trihydroxystilbene), a naturally occurring hydroxystilbene, is considered an essential antioxidative constituent of red wine possessing chemopreventive properties. However, resveratrol and even more its metabolite piceatannol were reported to have also cytostatic activities. In order to find out whether this is related to antioxidative properties of those compounds, we synthesized five other polyhydroxylated resveratrol analogues and studied structure-activity relationships between pro-/antioxidant properties and cytotoxicity. Radical scavenging experiments with O(2)(*-) (5,5-dimethyl-1-pyrroline-N-oxide/electron spin resonance (DMPO/ESR)) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) (photometry) revealed that 3,3',4',5-tetrahydroxystilbene (IC(50): 2.69microM; k(9): 443000M(-1)s(-1)), 3,4,4',5-tetrahydroxystilbene (IC(50): 41.5microM; k(9): 882000M(-1)s(-1)) and 3,3',4,4',5,5'-hexahydroxystilbene (IC(50): 5.02microM), exerted a more than 6600-fold higher antiradical activity than resveratrol and its two other analogues. Furthermore, in HL-60 leukemic cells hydroxystilbenes with ortho-hydroxyl groups exhibited a more than three-fold higher cytostatic activity compared to hydroxystilbenes with other substitution patterns. Oxidation of ortho-hydroxystilbenes in a microsomal model system resulted in the existence of ortho-semiquinones, which were observed by ESR spectroscopy. Further experiments revealed that these intermediates undergo redox-cycling thereby consuming additional oxygen and forming cytotoxic oxygen radicals. In contrast to compounds with other substitution patterns hydroxystilbenes with one or two resorcinol groups (compounds 1 and 3) did not show an additional oxygen consumption or semiquinone formation. These findings suggest that the increased cytotoxicity of ortho-hydroxystilbenes is related to the presence of ortho-semiquinones formed during metabolism or autoxidation.     

Synthesis and structure-activity relationships of N,N'-di-o-tolylguanidine analogues, high-affinity ligands for the haloperidol-sensitive sigma receptor

With an eye toward the development of novel atypical antipsychotic agents, we have studied the structure-affinity relationships of N,N'-di-o-tolylguanidine (DTG, 3) and its congeners at the haloperidol-sensitive sigma receptor. A number of DTG analogues were synthesized and evaluated in in vitro radioligand displacement experiments with guinea pig brain membrane homogenates, using the highly sigma-specific radioligands [3H]-3 and [3H]-(+)-3-(3-hydroxyphenyl)-N-(1-propyl)piperidine and the phencyclidine (PCP) receptor specific compounds [3H]-N-[1-(2-thienyl)-cyclohexyl]piperidine and [3H]-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10- imine. The affinity of N,N'-diarylguanidines for the sigma receptor decreases with increasing steric bulk of ortho substituents larger than C2H5. Hydrophobic substituents are generally preferred over similarly positioned hydrophilic ones. Furthermore, electroneutral substituents are preferred over strongly electron donating or withdrawing groups. Significant binding to the sigma receptor is usually retained as long as at least one side of the guanidine bears a preferred group (e.g. 2-CH3C6H5). Replacement of one or both aryl rings with certain saturated carbocycles (e.g. cyclohexyl, norbornyl, or adamantyl) leads to a significant increase in affinity. By combining the best aromatic and best saturated carbocyclic substituents in the same molecule, we arrived at some of the most potent sigma ligands described to date (e.g. N-exo-2-norbornyl-N'-(2-iodophenyl)guanidine, IC50 = 3 nM vs [3H]-3). All of the compounds tested were several orders of magnitude more potent at the sigma receptor than at the PCP receptor, with a few notable exceptions. This series of disubstituted guanidines may be of value in the development of potential antipsychotics and in the further pharmacological and biochemical characterization of the sigma receptor.     

A new oral cephem, cefdinir: its structure-activity relationships and biological profile]

This article reviews structure-activity relationships and biological properties of a new oral cephem, cefidinir (CFDN). It also describes a hypothesis concerning the absorption mechanism from the intestine. Antibacterial activities and the oral absorption efficiencies were studied with regard to 3-vinyl cephalosporins with various 7-acyl side chains. From the study, 2-(2-aminothiazol-4-yl)-2-hydroxyiminoacetyl group was selected and various 3-substituents were screened. As a result, it was found that the vinyl compound, CFDN, showed excellent antibacterial activity and good oral absorption in rats. In vitro and in vivo antibacterial activities, the affinity for PBPs and the stability to beta-lactamases revealed that CFDN had well balanced antimicrobial activities against Gram-positive and Gram-negative bacteria and good biological properties. The pharmacokinetics of CFDN in healthy volunteers showed that serum concentration and half life were good enough to make CFDN an effective therapeutic agent. The mechanism of intestinal absorption of CFDN and related oral cephems are discussed and a hypothesis for molecular recognition by the carrier protein in the intestine is proposed.     

Clotrimazole scaffold as an innovative pharmacophore towards potent antimalarial agents: design, synthesis, and biological and structure-activity relationship studies

We describe herein the design, synthesis, biological evaluation, and structure-activity relationship (SAR) studies of an innovative class of antimalarial agents based on a polyaromatic pharmacophore structurally related to clotrimazole and easy to synthesize by low-cost synthetic procedures. SAR studies delineated a number of structural features able to modulate the in vitro and in vivo antimalarial activity. A selected set of antimalarials was further biologically investigated and displayed low in vitro toxicity on a panel of human and murine cell lines. In vitro, the novel compounds proved to be selective for free heme, as demonstrated in the beta-hematin inhibitory activity assay, and did not show inhibitory activity against 14-alpha-lanosterol demethylase (a fungal P450 cytochrome). Compounds 2, 4e, and 4n exhibited in vivo activity against P. chabaudi after oral administration and thus represent promising antimalarial agents for further preclinical development.     

Synthesis of aniline-type analogues of farnesyl diphosphate and their biological assays for prenyl protein transferase inhibitory activity

Stable analogues of farnesyl diphosphate, possessing an aniline-type portion in the prenyl-mimic moiety and phosphonoacetamido(oxy) groups in the place of the metabolically unstable diphosphate unit, were synthesised and submitted to biological assays. The enzyme inhibition tests performed on FTase and GGTase I show that the newly synthesised compounds based on a combination of the aniline-containing portions with (phosphonoacetamido)oxy groups do not afford potent inhibitors.     

海洋来源 (+)-sclerotiorin衍生物的半合成、抗结核活性与初步构效关系研究

目的 结核病仍然是世界范围内一个重要的公共卫生问题,因此迫切需要寻找新型抗结核分子。以海洋天然产物(+)-sclerotiorin为原料半合成一系列衍生物,其中包含18个新化合物,通过考察它们的抗结核等活性,探究其初步构效关系。方法 利用Mycobacterium marinum 和 Mycobacterium tuberculosis 菌株对衍生物的生物活性进行测定。结论 衍生物4, 5, 8?10和12的抗海分枝杆菌活性与阳性药相当,MIC90值在16.1?18.9 μM之间。此外,衍生物9, 11, 12和15也显示出中等的抗结核活性。初步构效关系表明喹啉、异喹啉、联苯和联苯醚等基团有利于提升(+)-sclerotiorin衍生物的抗结核活性。衍生物12在结核杆菌蛋白酪氨酸磷酸酶B抑制试验中显示出最强的活性,分子对接的结果表明,它与蛋白的Phe98残基之间存在苯环与苯环间的π-π相互作用。该研究证实了(+)-sclerotiorin衍生物作为抗结核候选药物的潜力。     

Antitumor agents. 2. Synthesis,structure-activity relationships,and biological evaluation of substituted 5H-pyridophenoxazin-5-ones with potent antiproliferative activity

New antiproliferative compounds, 5H-pyrido[3,2-a]phenoxazin-5-ones (1-10), 5H-benzophenoxazin-5-one (11), 5H-pyrido[2,3-a]phenoxazin-5-one (12), 5H-pyrido[3,4-a]phenoxazin-5-one (13), and 5H-pyrido[4,3-a]phenoxazin-5-one (14), were synthesized and evaluated against representative human neoplastic cell lines. The excellent cytotoxic activity of these polycyclic phenoxazinones, structurally related to the actinomycin chromophore, is discussed in terms of structural changes made to rings A and D (Chart 1). Electron-withdrawing or electron-donating substituents were introduced at different positions of ring A to probe the electronic and positional effects of the substitution. A nitro group in R(2) or in R(1) increases the cytotoxic activity, whereas electron-donating methyl groups in any position lead to 10- to 100-fold decreasing of the activity. The low antiproliferative activity of benzophenoxazinone 11 and pyridophenoxazinones 13 and 14 confirms the crucial role of pyridine nitrogen in the W position of ring D in DNA binding. The unexpected high activity exhibited by 12, which has the nitrogen in the X position, could be ascribed to a different mechanism of action, which needs further investigation.     

A review of molecular modeling approaches to pharmacophore models and structure-activity relationships of ion channel modulators in CNS.

Through pharmacophore models and providing quantitative analysis of structure-activity relationships (QSAR), molecular modeling techniques can be useful tools to study the interactions of ion channels and their modulators. The present review focuses on molecular modeling approaches that defined pharmacophore models of ion channel modulators in the CNS. The commonality and subtlety of the pharmacophore models of various ion channel modulators are discussed which can be used as a framework for the design of ion channel modulators.