Synthesis of Aminomethylene-gem-bisphosphonates Containing an Aziridine Motif: Studies of the Reaction Scope and Insight into the Mechanism.

A broad range of N-carbamoylaziridines were obtained and then treated by the diethyl phosphonate anion to afford α-methylene-gem-bisphosphonate aziridines. Study of the reaction's scope and additional experiments indicates that the transformation proceeds via a new mechanism involving the chelation of lithium ion. This last step is crucial for the reaction to occur and disfavors the aziridine ring-opening. A phosphonate-phosphate rearrangement from a α-hydroxybisphosphonate aziridine intermediate is also proposed for the first time. This reaction provides a simple and convenient method for the synthesis of a highly functionalized phosphonylated aziridine motif.

Isoxazolidine: A Privileged Scaffold for Organic and Medicinal Chemistry.

The isoxazolidine ring represents one of the privileged structures in medicinal chemistry, and there have been an increasing number of studies on isoxazolidine and isoxazolidine-containing compounds. Optimization of the 1,3-dipolar cycloaddition (1,3-DC), original methods including electrophilic or palladium-mediated cyclization of unsaturated hydroxylamine, has been developed to obtain isoxazolidines. Novel reactions involving the isoxazolidine ring have been highlighted to accomplish total synthesis or to obtain bioactive compounds, one of the most significant examples being probably the thermic ring contraction applied to the total synthesis of (±)-Gelsemoxonine. The unique isoxazolidine scaffold also exhibits an impressive potential as a mimic of nucleosides, carbohydrates, PNA, amino acids, and steroid analogs. This review aims to be a comprehensive and general summary of the different isoxazolidine syntheses, their use as starting building blocks for the preparation of natural compounds, and their main biological activities.

Divalent Amino-Acid-Based Amphiphilic Antioxidants: Synthesis, Self-Assembling Properties, and Biological Evaluation.

We report herein the synthesis of a divalent amphiphilic carrier onto which α-phenyl-N-tert-butyl nitrone (PBN) and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) antioxidants were grafted to give the divalent derivative called FATxPBN. The divalent carrier consists of two lysine amino acids as a scaffold upon which the antioxidant moieties are grafted, a perfluorinated chain that supplies hydrophobicity, and a sugar-based polar headgroup that ensures water solubility. For the sake of comparison, a divalent PBN derivative called FADiPBN was also synthesized. The self-aggregation properties of FATxPBN and FADiPBN were studied by means of surface tension, dynamic light scattering, and transmission electron microscopy methods, and showed they form small micelles (i.e., 12 and 6 nm diameter, respectively) at submillimolar concentrations (i.e., 0.01 and 0.05 mM, respectively), in agreement with partition coefficient values. The superior antioxidant properties of FATxPBN over FADiPBN and the parent compounds PBN and Trolox were demonstrated using in vitro ABTS(•+) reduction (98%) and soybean lipoxygenase inhibition (94%) assays. Finally, FATxPBN was found to significantly inhibit hyperglycemia-induced toxicity on an ex-vivo rat model, demonstrating its potency as a bioactive antioxidant against oxidative stress-induced damage.

ß-Hydroxy- and ß-Aminophosphonate Acyclonucleosides as Potent Inhibitors of Plasmodium falciparum Growth.

Malaria is an infectious disease caused by a parasite of the genus Plasmodium, and the emergence of parasites resistant to all current antimalarial drugs highlights the urgency of having new classes of molecules. We developed an effective method for the synthesis of a series of ß-modified acyclonucleoside phosphonate (ANP) derivatives, using commercially available and inexpensive materials (i.e., aspartic acid and purine heterocycles). Their biological evaluation in cell culture experiments and SAR revealed that the compounds' effectiveness depends on the presence of a hydroxyl group, the chain length (four carbons), and the nature of the nucleobase (guanine). The most active derivative inhibits the growth of Plasmodium falciparum in vitro in the nanomolar range (IC50 = 74 nM) with high selectivity index (SI > 1350). This compound also showed remarkable in vivo activity in P. berghei-infected mice (ED50 ∼ 0.5 mg/kg) when administered by the ip route and is, although less efficient, still active via the oral route. It is the first ANP derivative with such potent antimalarial activity and therefore has considerable potential for development as a new antimalarial drug.

Plasmodium Purine Metabolism and Its Inhibition by Nucleoside and Nucleotide Analogues.

Malaria still affects around 200 million people and is responsible for more than 400,000 deaths per year, mostly children in subequatorial areas. This disease is caused by parasites of the Plasmodium genus. Only a few WHO-recommended treatments are available to prevent or cure plasmodial infections, but genetic mutations in the causal parasites have led to onset of resistance against all commercial antimalarial drugs. New drugs and targets are being investigated to cope with this emerging problem, including enzymes belonging to the main metabolic pathways, while nucleoside and nucleotide analogues are also a promising class of potential drugs. This review highlights the main metabolic pathways targeted for the development of potential antiplasmodial therapies based on nucleos(t)ide analogues, as well as the different series of purine-containing nucleoside and nucleotide derivatives designed to inhibit Plasmodium falciparum purine metabolism.