The enantioselective synthesis of 1-(R)-hydroxypolygodial and its epimer at C-9 is described. α-Ionone was the starting material. Key steps of these syntheses included a Corey-Bakshi-Shibata oxazaborolidine-mediated reduction and a stereoselective Diels-Alder reaction. No vanilloid activity was detected for both compounds in assays on VR1 vanilloid receptor in HEK cells transfected with the human VR1. 相似文献
Soluble short single‐walled carbon nanotubes in aerated D2O emit in the near‐infrared (NIR) region (see picture) with a quantum yield of (3.9±0.5) ×10?3 and a half‐life of 7.65 μs. This emission is quenched by electron‐ acceptor molecules.
Ricerche di Matematica - In this paper we aim to compare a popular numerical method with a new, recently proposed meshless approach for Heston PDE resolution. In finance, most famous models can be... 相似文献
In this paper we consider a Walrasian pure exchange economy with utility function which is a particular case of a general
economic equilibrium problem, without production. We assume that each agent is endowed with at least of a commodity, his preferences
are expressed by an utility function and it prevails a competitive behaviour: each agent regards the prices payed and received
as independent of his own choices. The Walrasian equilibrium can be characterized as a solution to a quasi-variational inequality.
By using this variational approach, our goal is to prove an existence result of equilibrium solutions. 相似文献
1-(2′,4′-dichloro)phenylamino-1H-pyrrole-2,5-dione and 1-(2′,4′,6′-trichloro)phenylamino-1H-pyrrole-2,5-dione were prepared via direct chlorination of 2-phenyl-3-oxo-6-hydroxy-2H-pyridazine. Both pmr and mass spectroscopy clearly showed that dichloro substitution occurred in the aromatic moiety and not in the vinylic region of the molecule. The former method showed that pyridiazine- to pyrrole-ring isomerization had occurred already at the level of dichlorination. The identical 2′,4′-dichlorophenyl and 2′,4′,6′-trichlorophenylpyr-rolediones were also prepared by reaction of maleic anhydride with the appropriate arylhydrazine. Similar 2′,4-dichlorophenyl and 2′,4′,6′-trichlorophenyl analogues were prepared using dichloromaleic anhydride. Cmr spectroscopic techniques were used for pyridazine-/pyrrole-ring stereochemical assignment of products derived from dichloromaleic anhydride. 1-(2′,4′-dichloro)phenylamino-1H-pyrrole-2,5-dione and the trichloro-phenyl analogue were shown to exhibit fungicidal activity in both in-vivo and in-vitro assays. 相似文献
Enantioselective preparation of 1(R)-hydroxypolygodial (5) has been achieved starting from α-ionone through a synthetic strategy involving a Corey-Bakshi-Shibata oxazaborolidine-mediated reduction and a stereoselective Diels-Alder reaction as key steps. 相似文献
In alkene-directed, nickel-catalyzed coupling reactions of 1,3-enynes with aldehydes and epoxides, the conjugated alkene dramatically enhances reactivity and uniformly directs regioselectivity, independent of the nature of the other alkyne substituent (aryl, alkyl (1 degrees , 2 degrees , 3 degrees )) or the degree of alkene substitution (mono-, di-, tri-, and tetrasubstituted). These observations are best explained by a temporary interaction between the alkene and the transition metal center during the regioselectivity-determining step. The highly substituted 1,3-diene products are useful in organic synthesis and, in conjunction with a Rh-catalyzed, site-selective hydrogenation, afford allylic and homoallylic alcohols that previously could not be prepared in high regioselectivity (or at all) with related Ni-catalyzed alkyne coupling reactions. 相似文献
The present study summarizes the last ten years of literature on heavy metal distribution in Suspended Particulate Matter (SPM) and dissolved phase in the Po River (Italy). The work compares different methodologies employed to collect, concentrate and fractionate the samples. The importance of metal speciation as a function of particle size is underlined and two approaches to metal speciation in the colloidal fraction of Po River SPM are presented: Sedimentation Field-Flow Fractionation (SdFFF) and pH-dependent extractions. Finally, emphasis is placed on the need for comparison with a reference "natural background level" of the metal load in Po River particulate matter in order to determine the real human contribution to river pollution. The high values of some trace transition elements, such as Cr and Ni, have been compared with clay sediments around Ferrara and with bricks in historic buildings. The highly comparable natural concentration of these metals in Po fine sedimentary rocks and in historic brick buildings of Ferrara (XII-XVI centuries) can provide information on natural geochemical anomalies. 相似文献