Key building blocks for the production of fully synthetic macrolides have been scaled-up in first time pilot plant and kilo-lab campaigns. These building blocks have supported the discovery of new macrolide antibiotics as well as ongoing preclinical studies.
View Article and Find Full Text PDFThe C-8 position of the tetracyclines has been largely underexplored because of limitations in traditional semisynthetic techniques. Employing a total synthetic approach allowed for modifications at the C-7 and C-8 positions, enabling the generation of structure-activity relationships for overcoming the two most common tetracycline bacterial-resistance mechanisms: ribosomal protection (tet(M)) and efflux (tet(A)). Ultimately, several compounds were identified with balanced activity against both Gram-positive and Gram-negative bacteria, including pathogens bearing both types of tetracycline-resistance mechanisms.
View Article and Find Full Text PDFUtilizing a fully synthetic route to tetracycline analogues, the C-9 side-chain of the fluorocyclines was optimized for both antibacterial activity and oral efficacy. Compounds were identified that overcome both efflux (tet(K), tet(A)) and ribosomal protection (tet(M)) tetracycline-resistance mechanisms and are active against Gram-positive and Gram-negative organisms. A murine systemic infection model was used as an oral efficacy screen to rapidly identify compounds with oral bioavailability.
View Article and Find Full Text PDFAn efficient route to the complex L-kedarosamine alpha-glycosidic ether 2, a synthetic precursor to kedarcidin chromophore, is described. Central to the route, which is suitable for the preparation of multigram amounts of material, is a short synthetic sequence from D-threonine to protected L-kedarosamine derivatives and methodology for their alpha-selective coupling with appropriate hydroxyl acceptors.
View Article and Find Full Text PDFA convergent, enantioselective synthesis of the proposed structure of kedarcidin chromophore () is described. The route is 24 steps in the longest linear sequence (beginning with the commercial reagent 2,3--isopropylidene-d-erythronolactone) with an average yield of 75% per step (overall yield: 0.1%).
View Article and Find Full Text PDFA new and effective proteasome inhibitor, beta-lactam 3, has been accessed enantioselectively by multistep synthesis from the readily prepared intermediates 7 and 8 which were joined by a [2 + 2]-cycloaddition reaction to form the spiro beta-lactam 9 stereoselectively. The intermediate 9 was converted to 3 in seven steps and 30% overall yield. The beta-lactam 3 is stable for many days in water at pH 7, in contrast to the natural beta-lactones salinosporamide A (1) and omuralide (2).
View Article and Find Full Text PDFThe kinetics and thermodynamics of atropisomerism within the protected kedarcidin chromophore aglycon 8, as well as a series of ansa-bridged synthetic intermediates leading to 8, were determined by 1H NMR spectroscopy. The data show that the ratio of atropisomeric forms of chloropyridine-bridged ansa intermediates is subject to wide variation with seemingly subtle structural variation. The vinyl bromide 4, for example, in the first X-ray structure determination of a kedarcidin ansa-bridged system, was found to exist as a single atropisomer in the solid state, but a nearly equal mixture (K = 0.
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