RESUMO
The monophosphino-boranes o-iPr(2)P(C(6)H(4))BR(2) (1: R = Ph and 3: R = Cy) and diphosphino-boranes [o-R(2)P(C(6)H(4))](2)BPh (5: R = Ph and 6: R = iPr) readily react with CuCl to afford the corresponding complexes {[o-iPr(2)P(C(6)H(4))BPh(2)]Cu(mu-Cl)}(2) 2, {[o-iPr(2)P(C(6)H(4))BCy(2)]Cu(mu-Cl)}(2) 4, {[o-Ph(2)P(C(6)H(4))](2)BPh}CuCl 7, and {[o-iPr(2)P(C(6)H(4))](2)BPh}CuCl 8. The presence of Cu-->B interactions supported by arene coordination within complexes 2, 7, and 8 has been unambiguously evidenced by NMR spectroscopy and X-ray diffraction studies. The unique eta(2)-BC coordination mode adopted by complexes 7 and 8 has been thoroughly analyzed by density-functional theory (DFT) calculations.
Assuntos
Boranos/química , Calixarenos/química , Cobre/química , Compostos Organometálicos/síntese química , Cristalografia por Raios X , Modelos Moleculares , Estrutura Molecular , Compostos Organometálicos/químicaRESUMO
Several (amino)(aryl)carbenes have been shown to be stable at room temperature in solution and in the solid state. Electroneutrality of the carbene center is ensured by the amino group, which has both pi-donor and final sigma-acceptor electronic character. The aryl group remains a spectator substituent, as shown by single-crystal x-ray analysis and by its chemical behavior. Because only one electron-active substituent is needed, numerous stable carbenes will become accessible, which will open the way for new synthetic developments and applications in various fields.
RESUMO
The disulfonimide (R)-1 enables enantio-differentiation of a large scope of chiral O-heterocycles, thanks to the formation of diastereomeric adducts. The underlying H-bond has been investigated by NMR. (R)-1 has been used as a chiral solvating agent (CSA) to determine the stereochemical purity of D/L lactide by (1)H NMR.
RESUMO
The treatment of patients suffering from advanced Parkinson's disease is highly challenging, because the efficacy of the "gold standard" levodopa declines with time. Co-administration of the dopamine receptor agonist apomorphine is beneficial, but difficult due to the poor oral bioavailability and short half-life of this drug. In order to overcome these restrictions, PLGA-based microparticles allowing for controlled parenteral delivery of this morphine derivative were prepared using (solid-in-)oil-in-water extraction/evaporation techniques. Particular attention was paid to minimize spontaneous oxidation of the labile drug and to optimize the key features of the microparticles, including encapsulation efficiency, initial burst release and particle size. Various formulation and processing parameters were adjusted in this respect. The systems were thoroughly characterized using SEM, EDX, DSC, laser diffraction, headspace-GC as well as in vitro drug release measurements in agitated flasks and flow-through cells. Importantly, apomorphine could effectively be protected against degradation during microparticle preparation and within the delivery systems upon exposure to phosphate buffer pH 7.4 (containing 0.2% ascorbic acid) at 37 °C: 90% intact drug was released at a constant rate during about 10d.
Assuntos
Antiparkinsonianos/administração & dosagem , Apomorfina/administração & dosagem , Portadores de Fármacos/química , Ácido Láctico/química , Ácido Poliglicólico/química , Antiparkinsonianos/química , Apomorfina/química , Varredura Diferencial de Calorimetria , Composição de Medicamentos , Estabilidade de Medicamentos , Liofilização , Concentração de Íons de Hidrogênio , Microscopia Eletrônica de Varredura , Tamanho da Partícula , Copolímero de Ácido Poliláctico e Ácido Poliglicólico , Solubilidade , Propriedades de Superfície , Difração de Raios XRESUMO
Novel PLGA derivatives bearing carboxylated side chains have been synthesized and used to encapsulate the fragile drug apomorphine HCl with a solid-in-oil-in-water solvent extraction/evaporation method. Blends of d,l-lactide and l-3-(2-Benzyloxycarbonyl)Ethyl-1,4-Dioxane-2,5-dione (BED) were co-polymerized at different ratios via ring-opening using benzyl alcohol as initiator. Optionally, the ester groups in the side chains as well as the terminal ester groups were hydrogenolyzed (leading to free COOH groups). For reasons of comparison, different types of "conventional" PLGAs were also synthesized and used for apomorphine HCl encapsulation. The polymers and microparticles were thoroughly characterized using SEC, (1)H NMR, DSC, SEM, X-ray and laser diffraction, Headspace-GC as well as in vitro drug release measurements in flow-through cells and agitated flasks. Importantly, microparticles based on the new polymers bearing carboxylic groups in the polymeric side chains: (i) allowed a significant reduction of the amount of residual solvent (dichloromethane), and (ii) provided different types of drug release patterns compared to microparticles based on "conventional" PLGAs (at least partially due to altered polymer degradation kinetics). Thus, they offer an interesting potential as novel matrix formers in controlled drug delivery systems, overcoming potential shortcomings of standard PLGAs.
Assuntos
Apomorfina/administração & dosagem , Ácidos Carboxílicos/química , Portadores de Fármacos/química , Ácido Láctico/química , Ácido Poliglicólico/química , Varredura Diferencial de Calorimetria , Cromatografia em Gel , Preparações de Ação Retardada , Portadores de Fármacos/síntese química , Composição de Medicamentos , Ácido Láctico/síntese química , Microscopia Eletrônica de Varredura , Estrutura Molecular , Tamanho da Partícula , Ácido Poliglicólico/síntese química , Copolímero de Ácido Poliláctico e Ácido Poliglicólico , Extração em Fase Sólida , Solubilidade , Solventes/química , Propriedades de Superfície , Difração de Raios XRESUMO
A tetraphosphabenzene analog of the postulated anti-tricyclohexylene, a singlet biradical valence isomer of benzene, has been isolated. The tricyclic derivative features one-electron phosphorus-phosphorus bonds, which result from the pi*-pi* interaction between two diphosphirenyl radicals. Such one-electron bonds may play a wider role in phosphorus chemistry.