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Inorg Chem ; 58(12): 8130-8139, 2019 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-31124666


An investigation of supramolecular phenomena involving zerovalent transition metal complexes was facilitated by the production of the ditopic isocyanide ligand 1,3-bis( p-isocyanophenyl)urea, which was synthesized via substoichiometric phosgenation of 4-isocyanophenylamine and used to coordinate group VI metal carbonyl fragments. The resulting binuclear organometallic complexes were observed to pack into ladder-like anisotropic arrays in the solid state. Crystallographic and computational evidence suggests that this packing motif can be attributed to a combination of intermolecular π-π and urea-π interactions. Similar to other N, N'-diarylureas bearing electron-withdrawing groups, 1,3-bis( p-isocyanophenyl)urea and the organometallic complexes prepared therefrom also exhibit an affinity toward anion binding in nonaqueous solution. Equilibrium constants ( K) for the formation of host-guest complexes between the organometallic derivatives of 1,3-bis( p-isocyanophenyl)urea and chloride, nitrate, and acetate anions exceed 103, 104, and 105 M-1, respectively.

Chemistry ; 24(63): 16753-16756, 2018 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-30338587


The inthomycins are a family of structurally and biologically rich natural products isolated from Streptomyces species. Herein the implementation of a modular synthetic route is reported that has enabled the enantioselective synthesis of all three inthomycins. Key steps include Suzuki and Sonogashira cross-couplings and an enantioselective Kiyooka aldol reaction.

Org Biomol Chem ; 15(44): 9372-9378, 2017 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-29090723


A simple 1H and 13C NMR spectrometric analysis is demonstrated that permits differentiation of isoleucine and allo-isoleucine residues by inspection of the chemical shift and coupling constants of the signals associated with the proton and carbon at the α-stereocentre. This is applied to the estimation of epimerisation during metal-free N-arylation and peptide coupling reactions.

Isoleucina/química , Espectroscopia de Ressonância Magnética , Peptídeos/química , Estereoisomerismo
Chem Sci ; 7(1): 482-488, 2016 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-28791101


Streptomycetes are a rich source of bioactive specialized metabolites, including several examples of the rapidly growing class of ribosomally-biosynthesized and post-translationally-modified peptide (RiPP) natural products. Here we report the discovery from Streptomyces sp. FXJ1.264 of azolemycins A-D, a complex of novel linear azole-containing peptides incorporating a unique oxime functional group. Bioinformatics analysis of the Streptomyces sp. FXJ1.264 draft genome sequence identified a cluster of genes that was hypothesized to be responsible for elaboration of the azolemycins from a ribosomally-biosynthesized precursor. Inactivation of genes within this cluster abolished azolemycin production, consistent with this hypothesis. Moreover, mutants lacking the azmE and azmF genes accumulated azolemycin derivatives lacking the O-methyl groups and an amino group in place of the N-terminal oxime (as well as proteolysed derivatives), respectively. Thus AzmE, a putative S-adenosyl methionine-dependent methyl transferase, is responsible for late-stage O-methylation reactions in azolemycin biosynthesis and AzmF, a putative flavin-dependent monooxygenase, catalyzes oxidation of the N-terminal amino group in an azolemycin precursor to the corresponding oxime. To the best of our knowledge, oxime formation is a hitherto unknown posttranslational modification in RiPP biosynthesis.

Org Biomol Chem ; 14(4): 1450-4, 2016 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-26691902


The first total syntheses of newly isolated polyazole natural products azolemycins A-D, along with the synthesis of the tetra-oxazole non-natural analogue, are described.

Azóis/síntese química , Produtos Biológicos/síntese química , Azóis/química , Azóis/isolamento & purificação , Produtos Biológicos/química , Produtos Biológicos/isolamento & purificação , Conformação Molecular
Microbiology ; 159(Pt 2): 296-306, 2013 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-23258266


Bacteria contain small non-coding RNAs (ncRNAs) that are responsible for altering transcription, translation or mRNA stability. ncRNAs are important because they regulate virulence factors and susceptibility to various stresses. Here, the regulation of a recently described ncRNA of Pseudomonas syringae pv. tomato DC3000, P16, was investigated. We determined that RpoS regulates the expression of P16. We found that deletion of P16 results in increased sensitivity to hydrogen peroxide compared to the wild-type strain, suggesting that P16 plays a role in the bacteria's susceptibility to oxidative stress. Additionally the P16 mutant displayed enhanced resistance to heat stress. Our findings provide new information on the regulation and role of this ncRNA in P. syringae.

Regulação Bacteriana da Expressão Gênica , Pseudomonas syringae/genética , RNA Interferente Pequeno/genética , Deleção de Genes , Temperatura Alta , Peróxido de Hidrogênio/toxicidade , Lycopersicon esculentum/microbiologia , Estresse Oxidativo , Doenças das Plantas/microbiologia , Pseudomonas syringae/efeitos dos fármacos , Pseudomonas syringae/isolamento & purificação , Pseudomonas syringae/fisiologia , RNA Interferente Pequeno/biossíntese , Estresse Fisiológico