No abstract

New pseudotrisaccharide derivatives of aminoglycosides that exploit additional interaction on the shallow groove face of the decoding-site rRNA of eukaryotic ribosome were designed, synthesized and biologically evaluated. Novel lead structures (6 and 7 with an additional 7′-OH), exhibiting enhanced specificity to eukaryotic cytoplasmic ribosome, and superior nonsense mutation suppression activity than those of gentamicin, were discovered. The comparative benefit of new leads was demonstrated in four different nonsense DNA-constructs underling the genetic diseases cystic fibrosis, Usher syndrome, and Hurler syndrome.

Leishmaniasis comprises an array of diseases caused by pathogenic species of Leishmania, resulting in a spectrum of mild to life-threatening pathologies. Currently available therapies for leishmaniasis include a limited selection of drugs. This coupled with the rather fast emergence of parasite resistance, presents a dire public health concern. Paromomycin (PAR), a broad-spectrum aminoglycoside antibiotic, has been shown in recent years to be highly efficient in treating visceral leishmaniasis (VL)—the life-threatening form of the disease. While much focus has been given to exploration of PAR activities in bacteria, its mechanism of action in Leishmania has received relatively little scrutiny and has yet to be fully deciphered. In the present study we present an X-ray structure of PAR bound to rRNA model mimicking its leishmanial binding target, the ribosomal A-site. We also evaluate PAR inhibitory actions on leishmanial growth and ribosome function, as well as effects on auditory sensory cells, by comparing several structurally related natural and synthetic aminoglycoside derivatives. The results provide insights into the structural elements important for aminoglycoside inhibitory activities and selectivity for leishmanial cytosolic ribosomes, highlighting a novel synthetic derivative, compound 3, as a prospective therapeutic candidate for the treatment of VL.

Mild oxidation of sulfur-containing chemical warfare agents was performed in organic medium by electrophilic iodine reagents. Kinetic experiments on sulfur mustard (HD) showed rapid (t 1/2 < 3 min) and selective oxidation to the nonvesicant sulfoxide product (HD-SO) in acetonitrile or propylene carbonate solutions (9% water added) containing excess N-iodosuccinimide (NIS). Molecular iodine solutions in these solvents led to similar results as with NIS but at much slower rates (t 1/2 ∼ 90 min). Higher donor number solvents, such as THF, DMF, or DMSO, showed slower rates with both iodine and NIS. The oxidation of the nerve agent O-ethyl-S-2-(N,N-diisopropylaminoethyl)­methyl­phos­phono­thioate (VX) selectively to the nontoxic ethyl methylphosphonic acid product exhibited fast rates (t 1/2 = 6 min) using NIS in DMSO solution. In all other solvents tested with VX, rates were slower (t 1/2 ∼ 30–70 min). Oxidation experiments under the same conditions with chloroethyl ethyl sulfide (HD simulant) and O,S-diethyl methylphosphonothioate (VX simulant) led to much faster reaction rates. These transformations are believed to proceed through electrophilic iodine attack on the sulfur moiety and display solvent dependency based on the agents’ structural and chemical properties.

The emergence of multidrug‐resistant pathogens that are resistant to the majority of currently available antibiotics is a significant clinical problem. The development of new antibacterial agents and novel approaches is therefore extremely important. We set out to explore the potential of catalytic antibiotics as a new paradigm in antibiotics research. Herein, we describe our pilot study on the design, synthesis, and biological testing of a series of new derivatives of the natural aminoglycoside antibiotic neomycin B for their potential action as catalytic antibiotics. The new derivatives showed significant antibacterial activity against wild‐type bacteria and were especially potent against resistant and pathogenic strains including Pseudomonas aeruginosa and methicillin‐resistant Staphylococcus aureus. Selected compounds displayed RNase activity even though the activity was not as high and specific as we would have expected. On the basis of the observed chemical and biochemical data, along with the comparative molecular dynamics simulations of the prokaryotic rRNA decoding site, we postulate that the rational design of catalytic antibiotics should involve not only their structure but also a comprehensive analysis of the rRNA A‐site dynamics.