Design, synthesis and in vitro antimalarial evaluation of triazole-linked chalcone and dienone hybrid compounds.

A targeted series of chalcone and dienone hybrid compounds containing aminoquinoline and nucleoside templates was synthesized and evaluated for in vitro antimalarial activity. The Cu(I)-catalyzed cycloaddition of azides and terminal alkynes was applied as the hybridization strategy. Several chalcone-chloroquinoline hybrid compounds were found to be notably active, with compound 8b the most active, exhibiting submicromolar IC(50) values against the D10, Dd2 and W2 strains of Plasmodium falciparum.

Novel tetracyclic structures from the synthesis of thiolactone-isatin hybrids.

A simple and straightforward synthetic approach to potential anti-infective thiolactone-isatin hybrids led to the discovery of novel tetracyclic compounds which bear a macrocylic motif containing an unusual bridged amide bond.

Chloroquine resistance: proposed mechanisms and countermeasures.

Malaria has been, and remains, one of the biggest global health concerns as far as infectious diseases are concerned, with yearly incidence and mortality figures running into millions. One of the major drawbacks to the control of this disease has been the emergence of drug resistant strains of the causative agent, which limits the successful use of many clinically available antimalarial drugs. This review discusses chloroquine resistance; it highlights some of the proposed molecular mechanisms of chloroquine resistance, but dwells more on efforts at reversing chloroquine resistance and the concept of chloroquine resistance-reversal agents.

CRIMALDDI: a co-ordinated, rational, and integrated effort to set logical priorities in anti-malarial drug discovery initiatives.

Despite increasing efforts and support for anti-malarial drug R&D, globally anti-malarial drug discovery and development remains largely uncoordinated and fragmented. The current window of opportunity for large scale funding of R&D into malaria is likely to narrow in the coming decade due to a contraction in available resources caused by the current economic difficulties and new priorities (e.g.

Synthesis and in vitro evaluation of gold(I) thiosemicarbazone complexes for antimalarial activity.

The reaction of thiosemicarbazones (TSCs) with [Au(I)(THT)Cl], THT=tetrahydrothiophene, has been investigated. The resulting gold(I) complexes have been characterized by a range of spectroscopic techniques: NMR spectroscopy, mass spectrometry, microanalysis and infrared spectroscopy. The in vitro antimalarial data for gold(I) TSC complexes suggests that coordination of gold(I) to TSCs enhanced their efficacy against the malaria parasite Plasmodium falciparum and their inhibition of the parasite cysteine protease falcipain-2.

Comparison of the antiplasmodial and falcipain-2 inhibitory activity of beta-amino alcohol thiolactone-chalcone and isatin-chalcone hybrids.

The synthesis and biological evaluation of two novel series of natural-product-like hybrids based on the chalcone, thiolactone and isatin scaffolds is herein described. Results for a 36-member beta-amino alcohol triazole library showed that the thiolactone-chalcones, with IC(50)s ranging from 0.68 to 6.

Gold(I) derived thiosemicarbazone complexes with rare halogen-halogen interaction-reduction of [Au(damp-C1,N)Cl2].

An attempt to prepare gold(III) complexes of thiosemicarbazones with the starting material gold(III) [Au(damp-C(1),N)Cl(2)] led instead to gold(I) complexes with a rare Cl...

Synthesis, antimalarial and antitubercular activity of acetylenic chalcones.

A series of acetylenic chalcones were evaluated for antimalarial and antitubercular activity. The antimalarial data for this series suggests that growth inhibition of the W2 strain of Plasmodium falciparum can be imparted by the introduction of a methoxy group ortho to the acetylenic group. Most compounds were more active against non-replicating than replicating cultures of Mycobacterium tuberculosis H(37)Rv, an unusual pattern with respect to existing anti-TB agents.

Synthesis and evaluation of phenylequine for antimalarial activity in vitro and in vivo.

Synthesis of the potent antiplasmodial 4-aminoquinoline, phenylequine (PQ), is reported for the first time. PQ and the two analogues show increased efficacy in moving from the chloroquine sensitive D10 to the chloroquine resistant K1 strain in vitro. The in vivo efficacy of PQ, and salts thereof, have been determined in Plasmodium berghei ANKA and Plasmodium yoelii.

Cycloaddition and one-carbon homologation studies in the synthesis of advanced iridoid precursors.

A Diels-Alder cycloaddition approach to the sweroside aglycone intermediate of iridoids was explored using silylated butenolides and levoglucosenone as dienophiles under both Lewis acid and thermal conditions. Results of this study reveal no evidence that using less sterically demanding derivatives compromise the diastereofacial selectivity of the cycloaddition using silylated butenolides. Further chemistry performed on cycloadducts concentrated on the identification and management of methodologies suitable for its conversion into sweroside aglycone.

Synthesis of novel 2-alkoxy-3-amino-3-arylpropan-1-ols and 5-alkoxy-4-aryl-1,3-oxazinanes with antimalarial activity.

A variety of novel syn-2-alkoxy-3-amino-3-arylpropan-1-ols was prepared through LiAlH(4)-promoted reductive ring-opening of cis-3-alkoxy-4-aryl-beta-lactams in Et(2)O. The latter gamma-aminoalcohols were easily converted into cis-5-alkoxy-4-aryl-1,3-oxazinanes using formaldehyde in THF. Both series of compounds were evaluated against a chloroquine sensitive strain of Plasmodium falciparum (D10), revealing micromolar potency for almost all representatives.

Novel web-based tools combining chemistry informatics, biology and social networks for drug discovery.

A convergence of different commercial and publicly accessible chemical informatics, databases and social networking tools is positioned to change the way that research collaborations are initiated, maintained and expanded, particularly in the realm of neglected diseases. A community-based platform that combines traditional drug discovery informatics with Web2.0 features in secure groups is believed to be the key to facilitating richer, instantaneous collaborations involving sensitive drug discovery data and intellectual property.

Synthetic medicinal chemistry of selected antimalarial natural products.

Natural products remain a rich source of novel molecular scaffolds for novel antimalarial agents in the fight against malaria. This has been well demonstrated in the case of quinine and artemisinin both of which have served as templates for the development of structurally simpler analogues that either served or continue to serve as effective antimalarials. This review will expound on these two natural products as well as other selected natural products that have served either as antimalarial agents or as potential lead compounds in the development of antimalarial drugs.

Antiplasmodial, beta-haematin inhibition, antitrypanosomal and cytotoxic activity in vitro of novel 4-aminoquinoline 2-imidazolines.

A novel series of 4-aminoquinoline-containing 2-imidazolines were synthesized via a one-pot 3-component condensation reaction of amine, aldehyde and isocyanoacetate. The products were obtained in high yield as well as purity and were evaluated directly against two strains of Plasmodium falciparum and Trypanosoma brucei. Compound was the most active across all parasites with ED(50) = 3.

Meclonazepam analogues as potential new antihelmintic agents.

New analogues of the potent antihelmintic meclonazepam were prepared and evaluated against Schistosoma mansoni. The biological data suggests substitution at positions 2 and 4 of meclonazepam could provide promising analogues for prophylactic and therapeutic activity against S. mansoni.

Metallocene antimalarials: the continuing quest.

Over the last decade, a significant body of research has been developed around the inclusion of a metallocene moiety into known antimalarial compounds. Ferroquine is the most successful of these compounds. Herein, we describe our contribution to metallocene antimalarials.

Studies in iridoid synthesis. Chemoselective transformations of cis-1,2,4,6-tetrahydrophthalic anhydride.

In the course of synthetic studies towards the development of diastereoselective routes to secoiridoid aglycones, cis-1,2,4,6-tetrahydrophthalic anhydride was transformed into the corresponding lactone cis-3a,4,7,7a-tetrahydro-3H-isobenzofuran-1-one, which served as a key precursor for a variety of chemoselective synthetic manipulations. Unsuccessful formylation of an ester intermediate resulted in a (E/Z) mixture of vinyl alcohols which were protected as acetates and as a single p-methoxybenzyl (PMB) ether (E) isomer. Dihydroxylation of the cyclohexene motif using OsO(4) led to the unexpected deprotection of the PMB ether.

Design, synthesis, and antimalarial activity of structural chimeras of thiosemicarbazone and ferroquine analogues.

The design, synthesis, and antimalarial activity of chimeras of thiosemicarbazones (TSC) and ferroquine (FQ) is reported. Key structural elements derived from FQ were coupled to fragments capable of coordinating metal ions. Biological evaluation was conducted against four strains of the malaria parasite Plasmodium falciparum and against the parasitic cysteine protease falcipain-2.

Synthesis of new 7-chloroquinolinyl thioureas and their biological investigation as potential antimalarial and anticancer agents.

New 7-chloroquinolinyl thiourea derivatives derived from the corresponding 4,7-dichloroquinoline isothiocyanate were synthesized and evaluated for in vitro antimalarial and anticancer activity. The most active compound from the series displayed an inhibitory IC(50) value of 1.2 microM against the D10 strain of Plasmodium falciparum.

Metallocene-based antimalarials: an exploration into the influence of the ferrocenyl moiety on in vitro antimalarial activity in chloroquine-sensitive and chloroquine-resistant strains of Plasmodium falciparum.

To establish the role of the ferrocenyl moiety in the antiplasmodial activity of ferroquine, compounds in which this moiety is replaced by the corresponding ruthenium-based moieties were synthesized and evaluated. In both the sensitive (D10) and resistant (K1) strains of Plasmodium falciparum, ruthenoquine analogues showed comparable potency to ferroquine. This suggests that a probable role of the ferrocenyl fragment is to serve simply as a hydrophobic spacer group.

Application of multicomponent reactions to antimalarial drug discovery. Part 3: discovery of aminoxazole 4-aminoquinolines with potent antiplasmodial activity in vitro.

The synthesis and antimalarial activity of a novel series of first generation 4-aminoquinoline-containing 2,4,5-trisubstituted aminoxazoles against two strains of the Plasmodium falciparum parasite in vitro is described. A number of compounds significantly more potent than the standard drug chloroquine were identified.

Antiplasmodial hirsutinolides from Vernonia staehelinoides and their utilization towards a simplified pharmacophore.

The dichloromethane extract of the leaves of Vernonia staehelinoides Harv. (Asteraceae) showed in vitro activity (IC(50) approximately 3 microg/ml) against the chloroquine-sensitive (D10) and the chloroquine-resistant (K1) strains of Plasmodium falciparum. Through conventional chromatographic techniques and bioassay-guided fractionation two structurally-related hirsutinolides displaying in vitro antiplasmodial activity (IC(50) approximately 0.

Novel inhibitors of the trypanosome alternative oxidase inhibit Trypanosoma brucei brucei growth and respiration.

African trypanosomiasis is a deadly disease for which few chemotherapeutic options are available. The causative agents, Trypanosoma brucei rhodesiense and T. b.

Purification of human malaria parasite hypoxanthine guanine xanthine phosphoribosyltransferase (HGXPRT) using immobilized Reactive Red 120.

Malaria is caused by Plasmodium parasite infection. The human malarial parasite does not have a de novo pathway for synthesis of nucleotides and the purine salvage pathway enzyme hypoxanthine guanine xanthine phosphoribosyltransferase (HGXPRT) is critical for survival. In our efforts to find inhibitors of the malarial parasite HGXPRT, we have developed a simple but effective purification protocol for this protein expressed in Escherichia coli without an affinity tag.