Objective A series of novel, substituted tetracyclic benzothiazepines were designed and prepared in an effort to optimize the potency of this chemical class against drug-resistant strains of the malaria parasite. Methods Tetracyclic benzothiazepines bearing structural modification at seven distinct positions within the structure were synthesized in Knoevenagel condensation reactions followed by sequential intermolecular thio-Michael and then intramolecular imine formation reactions. Following purification and chemical characterization, the novel compounds were tested for in vitro efficacy against blood-stage P. falciparum and liver-stage P. berghei and also for in vivo efficacy against P. berghei. Results Benzothiazepines bearing structural modification at the sulfur atom and at the three carbocycles within the molecule were successfully synthesized. The majority of analogs inhibited blood-stage P. falciparum with submicromolar IC50 values. The potency of an 8-methoxy-substituted analog 12 exceeded that of chloroquine in all three P. falciparum strains tested. The parent benzothiazepine 1 possessed liver-stage activity, inhibiting P. berghei sporozoites infecting HepG2 cells with an IC50 of 106.4 nM and an IC90 of 408.9 nM, but failed to enhance the longevity of P. berghei infected mice compared to the controls. Compounds displayed modest toxicity toward HepG2 cells and were tolerated by mice at the highest dose tested, 640 mg/kg/dose once daily for three days. Conclusion The tetracyclic benzothiazepine described, which inhibits P. berghei infected hepatic cells with an IC50 of 106.4 nM, would appear to warrant further investigation. Optimization of ADME properties may be required since the most active analogs are probably excessively lipophilic.

A versatile synthetic approach toward a series of benzothiazepines with medicinal potential (for example, compound 1) that allows incorporation of structural variation at the three aromatic regions of the structure, and at the sulfur atom, was developed.Knoevenagel condensation of indan-1,3-diones with benzaldehydes, yielded 2-benzylidineindan-1,3-diones, which undewent thio-Michael addition and intramolecular imine formation upon reaction with 2-aminothiophenols, to produce the target benzothiazepines.Use of indan-1,3-diones, benzaldehydes or 2-aminothiophenols bearing further substitution enabled production of novel 5,11-dihydro-12H-benzo[b]indeno [1,2-e][1,4]thiazepin-12-one analogs 1 -14, including compounds bearing substitution at novel positions within the scaffold.

Background Artemisinin-induced dormancy provides a plausible explanation for recrudescence following artemisinin monotherapy. This phenomenon shares similarities with cell cycle arrest where cyclin dependent kinases (CDKs) and cyclins play an important role. Methods Transcription profiles of Plasmodium falciparum CDKs and cyclins before and after dihydroartemisinin (DHA) treatment in three parasite lines, and the effect of CDK inhibitors on parasite recovery from DHA-induced dormancy were investigated. Results After DHA treatment, parasites enter a dormancy phase followed by a recovery phase. During the dormancy phase parasites up-regulate pfcrk1, pfcrk4, pfcyc2 and pfcyc4, and down-regulate pfmrk, pfpk5, pfpk6, pfcrk3, pfcyc1 and pfcyc3. When entering the recovery phase parasites immediately up-regulate all CDK and cyclin genes. Three CDK inhibitors, olomoucine, WR636638 and roscovitine, produced distinct effects on different phases of DHA-induced dormancy, blocking parasites recovery. Conclusions The up-regulation of PfCRK1 and PfCRK4, and down regulation of other CDKs and cyclins correlate with parasite survival in the dormant state. Changes in CDK expression are likely to negatively regulate parasite progression from G1 to S phase. These findings provide new insights into the mechanism of artemisinin-induced dormancy and cell cycle regulation of P. falciparum, opening new opportunities for preventing recrudescence following artemisinin treatment.

Investigation of a series of 2,N-bisarylated 2-ethoxyacetamides resulted in the identification of four inhibitors 5, 20, 24, 29 with single-digit micromolar in vitro efficacy against two drug-resistant Plasmodium falciparum strains. These compounds are analogs of structurally-related 1,3-bisaryl-2-propen-1-ones (chalcones), the latter showing efficacy in vitro but not in a malaria-infected mouse. The 2,N-bisarylated 2-ethoxyacetamides (e.g., 2, 5, 20) were shown to possess significantly greater stability in the presence of metabolizing enzymes than the corresponding 1,3-bisaryl-2-propen-1-ones (e.g., 1, 3, 18).

A series of ten new 2,3,6-substituted quinazolin-4(3H)-one derivatives (10a-j) were prepared from anthranilic acid (1) in a simple and economical path in a series of reactions and screened for their anticancer activity against pancreatic cancer cell line (PANC-1) using MTT assay. The results reveal that at concentration 100 µM/L, compounds 10b, 10f, 10g and 10h exhibited potential anticancer activity by inhibiting the growth of PANC-1 cells by >75% and remaining compounds showed moderate anticancer activity. The structural characterization of the synthesized compounds was elucidated by 1H & 13C NMR, LC-MS, FT-IR and elemental analysis. As potential anti-tumor agents, these new derivatives show promise for further research. Keywords: 2-Ethoxyacetamide, 2-ethoxyphenylacetamide, ethylation, phenylacetic acid.

A synthetic approach to novel series of alpha-ethoxy-alpha-phenylacetamides and alpha-ethoxy-alpha-quinolinylacetamides was developed. Aryl aldehydes were converted to cyanohydrins, which were then hydrolyzed or alcoholyzed. Following ethylation of the alpha-hydroxy group, peptide-coupling protocols were used to produce the target amides. These amides, together with the alpha-ethoxy intermediates, have significant potential for a broad range of application including as antimalarial, fungicidal, bactericidal, anticoagulant, hypolipidemic and sleep-promoting agents.

AbstractA series of new α‐ethoxy‐α‐phenylacetamides and α‐ethoxy‐α‐quinolinylacetamides is prepared from anthranilic acid in a simple and economical path.

A series of 1,7-diaminoisoquinolinamines, that are expected to mediate antimalarial activity by the same mechanism employed by the chalcones, were produced. Six 7-benzylamino-1-isoquinolinamines were found to be submicromolar inhibitors in vitro of drug-resistant Plasmodium falciparum, with the best possessing activity comparable to chloroquine. Despite being developed from a lead that is a DHFR inhibitor, these compounds do not mediate their antimalarial effects by inhibition of DHFR.

4′-n-Butoxy-2,4-dimethoxy-chalcone (MBC) has been described as protecting mice from an otherwise lethal infection with Plasmodium yoelii when dosed orally at 50 mg/kg/dose, daily for 5 days. In contrast, we found that oral dosing of MBC at 640 mg/kg/dose, daily for 5 days, failed to extend the survivability of P. berghei-infected mice. The timing of compound administration and metabolic activation likely contribute to the outcome of efficacy testing in vivo. Microsomal digest of MBC yielded 4′-n-butoxy-4-hydroxy-2-methoxy-chalcone and 4′-(1-hydroxy-n-butoxy)-2,4-dimethoxy-chalcone. We propose that the latter will hydrolyze in vivo to 4′-hydroxy-2,4-dimethoxy-chalcone, which has greater efficacy than MBC in our P. berghei-infected mouse model and was detected in plasma following oral dosing of mice with MBC. Pharmacokinetic parameters suggest that poor absorption, distribution, metabolism and excretion properties contribute to the limited in vivoefficacy observed for MBC and its analogs.

The cyclin dependent protein kinases, Pfmrk and PfPK5, most likely play an essential role in cell cycle control and differentiation in Plasmodium falciparum and are thus an attractive target for antimalarial drug development. Various 1,3-diaryl-2-propenones (chalcone derivatives) which selectivity inhibit Pfmrk in the low micromolar range (over PfPK5) are identified. Molecular modeling shows a pair of amino acid residues within the Pfmrk active site which appear to confer this selectivity. Predicted interactions between the chalcones and Pfmrk correlate well with observed potency. Pfmrk inhibition and activity against the parasite in vitro correlate weakly. Several mechanisms of action have been suggested for chalcone derivatives and our study suggests that kinase inhibition may be an additional mechanism of antimalarial activity for this class of compounds.

Malaria, the most important of the human parasitic diseases, causes about 500 million infections worldwide and over I million deaths every year. The search for novel drug candidates against specific parasitic targets is an important goal for antimalarial drug discovery. Recently the antimalarial activity of chalcones has generated great interest. These compounds are small non-chiral molecules with relative high lipophilicity (clogP similar to 5-7), have molecular weights in the range of 300 to 600 g/mol, and possess in vivo efficacy against both P. berghei and P. yeolii. Preliminary data on our ongoing chalcone synthesis project indicate that these compounds are active in vitro against P. falciparum, but are rapidly metabolized in liver microsome assays. Structurally-related compounds not including the enone linker are found to be much more metabolically stable and yet have comparable in vitro efficacy. In this study, we have utilized the efficacy data from an in-house on-going chalcone project to develop a 3D pharmacophore for antimalarial activity and used it to conduct virtual screening (in silico search) of a chemical library which resulted in identification of several potent chalcone-like antimalarials. The pharmacophore is found to contain an aromatic and an aliphatic hydrophobic site, one hydrogen bond donor site, and a ring aromatic feature distributed over a 3D space. The identified compounds were not only found to be potent in vitro against several drug resistant and susceptible strains of P. falciparum and have better metabolic stability, but included one with good in vivo efficacy in a mouse model of malaria.