RESUMEN
Supramolecular self-assembly is an attractive pathway for bottom-up synthesis of novel nanomaterials. In particular, this approach allows the spontaneous formation of structures of well-defined shapes and monodisperse characteristic sizes. Because nanotechnology mainly relies on size-dependent physical phenomena, the control of monodispersity is required, but the possibility of tuning the size is also essential. For self-assembling systems, shape, size, and monodispersity are mainly settled by the chemical structure of the building block. Attempts to change the size notably by chemical modification usually end up with the loss of self-assembly. Here, we generated a library of 17 peptides forming nanotubes of monodisperse diameter ranging from 10 to 36 nm. A structural model taking into account close contacts explains how a modification of a few Å of a single aromatic residue induces a fourfold increase in nanotube diameter. The application of such a strategy is demonstrated by the formation of silica nanotubes of various diameters.
Asunto(s)
Nanotubos de Péptidos/química , Nanotubos de Péptidos/ultraestructura , Aminoácidos Aromáticos/química , Microscopía Electrónica , Modelos Moleculares , Estructura Molecular , Nanotecnología , Péptidos Cíclicos/química , Dispersión del Ángulo Pequeño , Dióxido de Silicio/química , Somatostatina/análogos & derivados , Somatostatina/química , Difracción de Rayos XRESUMEN
A catalytic enantioselective synthesis of dihydrofurans has been developed. 1,3-Dicarbonyl derivatives react with (E)-ß,ß-bromonitrostyrenes in the presence of a chiral bifunctional thiourea catalyst providing mild and efficient access to diverse polysubstituted dihydrofurans in good yields and enantioselectivities.
RESUMEN
The copper-catalyzed direct alkynylation of azoles with 1,1-dibromo-1-alkenes as electrophiles is described. These easily accessible substrates are a useful addition to the field of direct alkynylations in an efficient and functional group tolerant reaction to provide a straightforward entry to diverse alkynyl heterocycles.
Asunto(s)
Alquenos/química , Alquinos/química , Azoles/química , Compuestos de Bromina/química , Cobre/química , Compuestos Heterocíclicos/química , Catálisis , Estructura MolecularRESUMEN
A copper-catalyzed direct alkenylation of oxazoles with bromoalkenes has been developed. The method is both regio- and stereoselective and tolerates a variety of functional groups. A wide range of 2-E-vinyl-substituted oxazoles were obtained in high yields including the highly fluorescent alkaloid annuloline.
Asunto(s)
Alquenos/química , Bromuros/química , Cobre/química , Oxazoles/química , Catálisis , Estereoisomerismo , Estireno/química , Especificidad por SustratoRESUMEN
An efficient microwave-assisted palladium/copper co-mediated direct arylation of oxazoles with aryl bromides under ligandless conditions has been developed. The method is functional group tolerant and provides rapid access to medicinally relevant compounds in good yields. Coupled to the van Leusen oxazole ring synthesis, this methodology is illustrated by an expedient two-step synthesis of the four 2,5-diaryloxazole alkaloids texamine, texaline, balsoxin, and O-Me-halfordinol from commercially available starting materials.