RESUMO
Oxygen-tolerant, aqueous copper-mediated polymerization approaches are combined with click chemistry in either a sequential or a simultaneous manner, to enable the synthesis of multifunctional protein-polymer conjugates. Propargyl acrylate (PgA) and propargyl methacrylate (PgMA) grafting from a bovine serum albumin (BSA) macroinitiator is thoroughly optimized to synthesize chemically addressable BSA-poly(propargyl acrylate) and BSA-poly(propargyl methacrylate) respectively. The produced multifunctional bioconjugates bear pendant terminal 1-alkynes which can be readily post-functionalized via both [3+2] Huisgen cycloaddition and thiol-yne click chemistry under mild reaction conditions. Simultaneous oxygen-tolerant, aqueous copper-catalyzed polymerization, and click chemistry mediate the in situ multiple chemical tailoring of biomacromolecules in excellent yields.
Assuntos
Química Click , Cobre , Cobre/química , Polimerização , Polímeros/química , Soroalbumina Bovina , Acrilatos , Metacrilatos , Alcinos/química , Azidas/química , Reação de CicloadiçãoRESUMO
The first example of gold-catalyzed silaboration of alkynes with PhMe2SiBpin is documented in the presence of supported gold nanoparticles. In the case of terminal alkynes, the reaction proceeds at ambient conditions in very good yields and the regioselectivity is opposite to that observed in the presence of Pd or Pt catalysts. The abnormal regioselectivity is attributed to steric factors imposed by the Au nanoparticle during the 1,2-addition of silylborane to the alkyne.
RESUMO
Supported gold nanoparticles on metal oxides (1 mol %) catalyze for the first time the cis-selective disilylation of terminal alkynes by 1,2-disilanes in isolated yields up to 94%. It is likely that the reaction proceeds through oxidative insertion of the σ Si-Si bond of disilanes on gold followed by 1,2-addition to the alkyne.
RESUMO
Gold nanoparticles supported on TiO(2) catalyze under mild conditions the activation of a series of 1,2-disilanes towards hydrolysis and alcoholysis, with concomitant evolution of H(2) gas. For the case of tert-benzyl alcohols, the main or only pathway is reduction to the corresponding alkanes.
Assuntos
Álcoois/química , Ouro/química , Nanopartículas Metálicas/química , Silanos/química , Silanos/síntese química , Alcanos/síntese química , Alcanos/química , Catálise , Hidrólise , Estrutura Molecular , Oxirredução , Titânio/químicaRESUMO
Gold nanoparticles supported on TiO(2) (1.2 mol %) catalyze, for the first time under heterogeneous conditions, the cycloisomerization of a series of 1,6-enynes in high yields. In several cases, the product selectivity differs significantly as compared to homogeneous Au(I)-catalysis. Based on product analysis and stereoisotopic studies it is proposed that the major or exclusive pathway involves a 5-exo cyclization mode to form stereoselectively gold cyclopropyl carbenes that undergo a single cleavage pathway, in contrast to homogeneous Au-catalysis where the double cleavage pathway operates substantially.
RESUMO
Photooxygenation of (ß-keto)-2-substituted furans leads, in a one pot operation, to functionalized 3(2H)-furanones with good to excellent yields. This methodology was applied as a key-step to the concise and biomimetic synthesis of the sesquiterpene merrekentrone C. The precursor to merrekentrone C, keto difuran, was synthesized using a cross coupling of α-iodo-3-acetylfuran with an alkenyl furan under Fenton-type conditions.
Assuntos
Produtos Biológicos/síntese química , Biomimética/métodos , Convolvulaceae/química , Furanos/química , Sesquiterpenos/síntese química , Furanos/síntese químicaRESUMO
The dimeric metabolite acremine G was synthesized featuring a highly regioselective and stereoselective Diels-Alder reaction between a TBS-protected hydroquinone diene and a structurally related alkenyl quinone. The major endo [4 + 2] adduct slowly transforms to acremine G by the atmospheric air under the deprotection conditions (in situ generated HF).