RESUMO
Polyketides are secondary metabolites which display both valuable pharmaceutical and agrochemical properties. Biosynthesis is performed by polyketide synthases (PKSs), and the acyl carrier protein (ACP), a small acidic protein, that transports the growing polyketide chain and is essential for activity. Here we report the synthesis of two aromatic probes and a linear octaketide mimic that have been tethered to actinorhodin ACP. These experiments were aimed at probing the ACP's capacity to sequester a non-polar versus a phenolic aromatic ring (that more closely mimics a polyketide intermediate) as well as investigations with extended polyketide chain surrogates. The binding of these mimics has been assessed using high-resolution solution NMR studies and high-resolution structure determination. These results reveal that surprisingly a PKS ACP is able to bind and sequester a bulky non-polar substrate containing an aromatic ring in a fatty acid type binding mode, but the introduction of even a small degree of polarity favours a markedly different association at a surface site that is distinct from that employed by fatty acid ACPs.
RESUMO
The tyrosine kinase A (TrkA) receptor is a validated therapeutic intervention point for a wide range of conditions. TrkA activation by nerve growth factor (NGF) binding the second extracellular immunoglobulin (TrkAIg2) domain triggers intracellular signaling cascades. In the periphery, this promotes the pain phenotype and, in the brain, cell survival or differentiation. Reproducible structural information and detailed validation of protein-ligand interactions aid drug discovery. However, the isolated TrkAIg2 domain crystallizes as a ß-strand-swapped dimer in the absence of NGF, occluding the binding surface. Here we report the design and structural validation by nuclear magnetic resonance spectroscopy of the first stable, biologically active construct of the TrkAIg2 domain for binding site confirmation. Our structure closely mimics the wild-type fold of TrkAIg2 in complex with NGF ( 1WWW .pdb), and the (1)H-(15)N correlation spectra confirm that both NGF and a competing small molecule interact at the known binding interface in solution.
Assuntos
Descoberta de Drogas , Espectroscopia de Ressonância Magnética/métodos , Receptor trkA/química , Amitriptilina/metabolismo , Sítios de Ligação , Desenho de Fármacos , Fator de Crescimento Neural/metabolismo , Estrutura Terciária de Proteína , Receptor trkA/metabolismo , Proteínas Recombinantes , Relação Estrutura-AtividadeRESUMO
A versatile method for the synthesis of orthogonally protected D-xylose 1-thioethers is described using unusual silyl group migrations which were pivotal in the synthesis of 4,8-dimethyl-6-O-(2',4'-di-O-methyl-ß-D-xylopyranosyl)hydroxyquinoline confirming the structure and absolute configuration of the natural product.
Assuntos
Alcaloides/síntese química , Hidroxiquinolinas/síntese química , Silanos/química , Xilose/análogos & derivados , Xilose/química , Xilose/síntese química , Alcaloides/química , Produtos Biológicos/química , Hidroxiquinolinas/química , Espectroscopia de Ressonância Magnética , Conformação Molecular , Estrutura MolecularRESUMO
An efficient strategy for the total synthesis of (-)-blepharocalyxin D and an analogue is described. The key step involves an acid-mediated cascade process in which reaction of methyl 3,3-dimethoxypropanoate with γ,δ-unsaturated alcohols possessing diastereotopic styrenyl groups gives trans-fused bicyclic lactones with the creation of two rings and four stereocenters in one pot.
Assuntos
Álcoois/química , Lactonas/síntese química , Piranos/síntese química , Alpinia/química , Lactonas/química , Estrutura Molecular , Piranos/química , EstereoisomerismoRESUMO
trans-2,8-Dioxabicyclodecanes were prepared in high yield with the creation of up to three stereocenters in a single pot by the acid-mediated reaction of γ,δ-unsaturated alcohols with aldehydes (see scheme, Bn=benzyl). This versatile reaction enables the stereoselective introduction of substituents at the C3, C4, C7, and C9 positions of the bicyclic framework.