Synthesis and antimalarial activity of new 1,12-bis(N,N'-acetamidinyl)dodecane derivatives

I2-Catalyzed Oxidative Coupling of Ketone Oximes and Dialkyl/Diarylphosphine Oxides

A new protocol for the oxidative coupling of ketone oximes with dialkyl/diarylphosphine oxides to synthesize O-(dialkylphosphinyl)ketone oximes has been developed. Hydrogen peroxide is used as a green oxidizing agent, and molecular iodine is used as a nonmetal catalyst. The reaction has a high atom economy, with water as the only byproduct. O-(Dialkylphosphinyl)ketone oximes with 26 examples have been obtained with high yields. Furthermore, the product may be transformed into other molecules, i.e., by reduction.

Evaluation of amidoxime derivatives as prodrug candidates of potent bis-cationic antimalarials

Plasmodium falciparum is responsible for most of the cases of malaria and its resistance to established antimalarial drugs is a major issue. Thus, new chemotherapies are needed to fight the emerging multi-drug resistance of P. falciparum malaria, like choline analogues targeting plasmodial phospholipidic metabolism. Here we describe the synthesis of amidoxime derivatives as prodrug candidates of reverse-benzamidines and hybrid compounds able to mimic choline, as well as the design of a new series of asymmetrical bis-cationic compounds. Bioconversion studies were conducted on amidoximes in asymmetrical series and showed that amidoxime prodrug strategy could be applied on C-alkylamidine moieties, like benzamidines and that N-substituents did not alter the bioconversion of amidoximes. The antimalarial activity of the three series of compounds was evaluated in vitro against P. falciparum and in vivo against P. vinckei petteri in mice.

Development of the first oral bioprecursors of bis-alkylguanidine antimalarial drugs

Plasmodium falciparum is responsible of the most severe form of malaria, and new targets and novel chemotherapeutic scaffolds are needed to fight emerging multidrug-resistant strains of this parasite. Bis-alkylguanidines have been designed to mimic choline, resulting in the inhibition of plasmodial de novo phosphatidylcholine biosynthesis. Despite potent in vitro antiplasmodial and in vivo antimalarial activities, a major drawback of these compounds for further clinical development is their low oral bioavailability. To solve this issue, various modulations were performed on bis-alkylguanidines. The introduction of N-disubstituents on the guanidino motif improved both in vitro and in vivo activities. On the other hand, in vivo pharmacological evaluation in a mouse model showed that the N-hydroxylated derivatives constitute the first oral bioprecursors in bis-alkylguanidine series. This study paves the way for bis-alkylguanidine-based oral antimalarial agents targeting plasmodial phospholipid metabolism.

Design and synthesis of N¹,N⁵-bis[4-(5-alkyl-1,2,4-oxadiazol-3-yl)phenyl]glutaramides as potential antifungal prodrugs

A facile three step synthesis of a group of N1,N5-bis[4-(5-alkyl-1,2,4-oxadiazol-3-yl)phenyl]glutaramides, N1,N5-bis[4-(1,2,4-oxadiazol-3-yl)phenyl]glutaramide and N1,N5-bis[4-(5-oxo-4,5-dihydro-1,2,4-oxadiazol-3-yl)phenyl]glutaramide is described. These products are designed to function as masked bis-amidine prodrugs of a promising N1,N5-bis[4-(N'-(carbamimidoyl)phenyl]glutaramide antifungal lead.

Evaluation of bis-alkylamidoxime O-alkylsulfonates as orally available antimalarials

The main threat to controlling malaria is the emerging multidrug resistance of Plasmodium sp. parasites. Bis-alkylamidines were developed as a potential new chemotherapy that targets plasmodial phospholipid metabolism. Unfortunately, these compounds are not orally available. To solve this absorption issue, we investigated a prodrug strategy based on sulfonate derivatives of alkylamidoximes. A total of 25 sulfonates were synthesized as prodrug candidates of one bis-N-alkylamidine and of six N-substituted bis-C-alkylamidines. Their antimalarial activities were evaluated in vitro against P. falciparum and in vivo against P. vinckei in mice to define structure-activity relationships. Small alkyl substituents on the sulfonate group of both C-alkyl- and N-alkylamidines led to the best oral antimalarial activities; alkylsulfonate derivatives are chemically transformed into the corresponding alkylamidines.

Qualitative structure-metabolism relationships in the hydrolysis of carbamates

The aims of this review were 1) to compile a large number of reliable literature data on the metabolic hydrolysis of medicinal carbamates and 2) to extract from such data a qualitative relation between molecular structure and lability to metabolic hydrolysis. The compounds were classified according to the nature of their substituents (R³OCONR¹R²), and a metabolic lability score was calculated for each class. A trend emerged, such that the metabolic lability of carbamates decreased (i.e., their metabolic stability increased), in the following series: Aryl-OCO-NHAlkyl >> Alkyl-OCO-NHAlkyl ~ Alkyl-OCO-N(Alkyl)₂ ≥ Alkyl-OCO-N(endocyclic) ≥ Aryl-OCO-N(Alkyl)₂ ~ Aryl-OCO-N(endocyclic) ≥ Alkyl-OCO-NHAryl ~ Alkyl-OCO-NHAcyl >> Alkyl-OCO-NH₂ > Cyclic carbamates. This trend should prove useful in the design of carbamates as drugs or prodrugs.

Antiparasitic compounds that target DNA

Designed, synthetic heterocyclic diamidines have excellent activity against eukaryotic parasites that cause diseases such as sleeping sickness and leishmania and adversely affect millions of people each year. The most active compounds bind specifically and strongly in the DNA minor groove at AT sequences. The compounds enter parasite cells rapidly and appear first in the kinetoplast that contains the mitochondrial DNA of the parasite. With time the compounds are also generally seen in the cell nucleus but are not significantly observed in the cytoplasm. The kinetoplast decays over time and disappears from the mitochondria of treated cells. At this point the compounds begin to be observed in other regions of the cell, such as the acidocalcisomes. The cells typically die in 24-48h after treatment. Active compounds appear to selectively target extended AT sequences and induce changes in kinetoplast DNA minicircles that cause a synergistic destruction of the catenated kinetoplast DNA network and cell death.

Lipidomic analysis of Toxoplasma gondii reveals unusual polar lipids

Analysis of the polar lipids of Toxoplasma gondii by electrospray ionization tandem mass spectrometry provides a detailed picture of the lipid molecular species of this parasitic protozoan. Most notably, T. gondii contains a relatively high level, estimated to about 2% of the total polar lipid, of ceramide phosphoethanolamine. The ceramide phosphoethanolamine has a fatty amide profile with only 16- and 18-carbon species. Compared with the host fibroblasts in which it was grown, T. gondii also has higher levels of phosphatidylcholine but lower levels of sphingomyelin and phosphatidylserine. Analysis at the molecular species level indicated that T. gondii has greater amounts of shorter-chain fatty acid in its polar lipid molecular species than the host fibroblasts. Shorter-chain fatty acids with a combined total of 30 or fewer acyl carbons make up 21% of Toxoplasma's, but only 3% of the host's, diacyl phosphatidylcholine. Furthermore, diacyl phosphatidylcholine with two saturated acyl chains with 12, 14, or 16 carbons make up over 11% of parasite phosphatidylcholine but less than 3% of the host phosphatidylcholine molecular species. The distinctive T. gondii tachyzoite lipid profile may be particularly suited to the function of parasitic membranes and the interaction of the parasite with the host cell and the host's immune system. Combined with T. gondii genomic data, these lipidomic data will assist in elucidation of metabolic pathways for lipid biosynthesis in this important human pathogen.

Carbamate prodrugs of N-alkylfuramidines

The synthesis and evaluation of 2,5-bis[4-(N-ethoxycarbonyl-N'-isopropyl)amidinophenyl]furan, 2,5-bis[4-(N-2,2,2-trichloroethoxycarbonyl-N'-isopropyl)amidinophenyl]furan and 2,5-bis[4-(N-cyclopentyl-N'-2,2,2-trichloroethoxycarbonyl)amidinophenyl]furan as prodrugs of bis-N-alkylamidines are reported. The results show that the bis-2,2,2-trichloroethyl carbamates function effectively in a rat model for Pneumocystis pneumonia.

Prodrugs for the treatment of neglected diseases

Recently, World Health Organization (WHO) and Medicins San Frontieres (MSF) proposed a classification of diseases as global, neglected and extremely neglected. Global diseases, such as cancer, cardiovascular and mental (CNS) diseases represent the targets of the majority of the R&D efforts of pharmaceutical companies. Neglected diseases affect millions of people in the world yet existing drug therapy is limited and often inappropriate. Furthermore, extremely neglected diseases affect people living under miserable conditions who barely have access to the bare necessities for survival. Most of these diseases are excluded from the goals of the R&D programs in the pharmaceutical industry and therefore fall outside the pharmaceutical market. About 14 million people,mainly in developing countries, die each year from infectious diseases. From 1975 to 1999,1393 new drugs were approved yet only 1% were for the treatment of neglected diseases[3]. These numbers have not changed until now, so in those countries there is an urgent need for the design and synthesis of new drugs and in this area the prodrug approach is a very interesting field. It provides, among other effects, activity improvements and toxicity decreases for current and new drugs, improving market availability. It is worth noting that it is essential in drug design to save time and money, and prodrug approaches can be considered of high interest in this respect. The present review covers 20 years of research on the design of prodrugs for the treatment of neglected and extremely neglected diseases such as Chagas' disease (American trypanosomiasis), sleeping sickness (African trypanosomiasis), malaria, sickle cell disease, tuberculosis, leishmaniasis and schistosomiasis.