click chemistry has been a powerful method for fragment-based drug design since its discovery in 2002. Recently, we demonstrated that the bacterial ribosome can template the azide-alkyne cycloaddition reaction to expedite the discovery of novel antibiotics. We now report this process can be performed in an antibiotic-resistant bacterial cell. The corresponding triazole products formed are potent antibiotics that inhibit bacterial growth; moreover, the potency of each cycloadduct can be visualized using the traditional MIC assay in a 96-well plate format. We characterized the clicked products by independent chemical synthesis and LC-MS analysis, which showed that mass count percent increase was directly proportional to 1/MIC. In other words, potent compounds detected by MIC were formed in greater amounts. Control experiments unambiguously showed the ribosome was responsible for templating triazole formation. Significantly, our method (1) obviates the need to isolate bacterial ribosomes; (2) could be applied to different bacterial strains, which broadens the scope and facilitates the discovery of narrow-spectrum antibiotics; and (3) does not require the knowledge of mode-of-action and thus could uncover novel antibiotic targets. We believe this method could be expanded and implemented as a novel approach for antibiotic drug discovery.
A copper-catalyzed asymmetric aryl CÀ P cross-coupling/cyclization reaction was successfully developed via dynamic kinetic asymmetric transformation (DYKAT) under mild conditions. This study provides a general and simple method for the catalytic enantioselective synthesis of stable six-, seven-and eight-membered P-stereogenic phosphorus heterocycles with excellent enantioselectivities and moderate to high yields. One-pot gram-scale asymmetric synthesis of the Pstereogenic P-heterocycle from commercially available materials was also successfully accomplished with excellent enantioselectivity and high yield.
This paper investigates the microneedle (MN) mediated in vitro transdermal iontophoretic delivery of prochlorperazine edisylate (PE) across dermatomed human skin. The Dermaroller™ induced microchannels were visualized using methylene blue staining and scanning electron microscopy. In vitro skin permeation studies were performed using vertical static Franz diffusion cells. Iontophoretic protocols involved application of direct current at a density of 0.4 mA/cm(2) using Ag as an anode and Ag/AgCl as a cathode. The effect of PE concentration (20, 50 and 100 mg/mL), number of passes of microneedles (0, 5, 10 and 20) on both iontophoretic and passive delivery of PE was studied. The Dermarollertm was found to successfully breach the skin barrier and a linear relationship (r(2) = 0.99) was observed between the number of passes of the Dermaroller™ and the number of microchannels created. Passive transdermal flux of PE (0.060 ± 0.003 µg/cm(2)/h) at 50 mg/mL donor PE concentration) was low and increased (4.15 ± 0.57 µg/cm(2)/h) with the application of direct current. Application of iontophoresis in conjunction with microneedle pre-treatment resulted in enhanced flux (4.90 ± 0.39 µg/cm(2)/h at 50 mg/mL donor PE concentration) of PE. The projected transdermal PE flux indicates that a 9 cm(2) patch could deliver PE in a sufficient amount to maintain therapeutic levels of the drug. In conclusion, microneedles when used in conjunction with iontophoresis significantly enhanced the transdermal delivery of PE and it may be feasible to develop an iontophoretic transdermal patch that could be integrated with MN.
Novel antibacterial drugs that treat multidrug resistant pathogens are in high demand. We have synthesized analogs of solithromycin using Cu(I)-mediated click chemistry. Evaluation of the analogs using Minimum Inhibitory Concentration (MIC) assays against resistant Staphylococcus aureus, Escherichia coli, and multidrug resistant pathogens Enterococcus faecium and Acinetobacter baumannii showed they possess potencies similar to those of solithromycin, thus demonstrating their potential as future therapeutics to combat the existential threat of multidrug resistant pathogens.
A copper-catalysed double O-aylation for enantioselective formation of chiral oxa-spirocycles is described. The method is based on a stepwise process and afforded chiral oxa-spirocycles with good yields and moderate to high enantioselectivities.
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