Modular asymmetric synthesis of P-chirogenic beta-amino phosphine boranes

A short concise route to beta-aminophosphine boranes is presented via the desymmetrization of prochiral phosphine boranes, forming P-chirogenic aldehydes that are rapidly transformed to the target compounds employing reductive amination under microwave irradiation. This sequence provides a modular route to P-chirogenic P,N ligands, and in addition, the intermediate aldehydes are versatile P-chiral building blocks for ligand design in general. An alternative pathway via the corresponding alpha-carboxyphosphines is also described. The ligands were subsequently evalutated in the asymmetric conjugate addition of diethylzinc to trans-beta-nitrostyrene.     

A biocatalytic route to P-chirogenic compounds by lipase-catalyzed desymmetrization of a prochiral phosphine-borane

[reaction: see text] Available methods for synthesis of P-chirogenic compounds are limited. We set out to find biocatalytical means to introduce asymmetry in a phosphine-borane. After screening different lipases, Candida antarctica lipase B was found to give excellent results in the desymmetrization of prochiral phosphine-boranes. Both enantiomers can be obtained in up to >98% optical purity via acetylation or hydrolysis in processes that allow recycling of the substrates.     

Solid-phase synthesis of a 6-phenylquinolin-2(1H)-one library directed toward nuclear hormone receptors

A library of 6-phenylquinolin-2(1H)-ones with diversity at position 1 and the ortho, meta, and para positions of the pendant phenyl ring has been synthesized using solid-phase parallel synthetic techniques. A key step in the synthesis of the library is a tandem alkylation cleavage in which diversity can be introduced at position 1 simultaneously to the cleavage from the resin. The yields of this step were significantly improved over what has previously been reported by addition of cesium carbonate to scavenge the acid that is formed during the reaction. Furthermore, we have shown that the solid support linkage is tolerant to Suzuki coupling and etherification reaction conditions and that selective cleavage of the linkage can take place in the presence of esters. The resulting 6-phenylquinolin-2(1H)-one library was screened against a panel of nuclear hormone receptors (androgen, estrogen alpha and beta isoforms, glucocorticoid, mineralocorticoid, and progesterone). Certain members of this library display moderate affinity for several of these receptors, and consequently, the 6-phenylquinolin-2(1H)-one core of the library may be considered a privileged structure for nuclear hormone receptors. In contrast, other members of the library display high selectivity for a particular receptor. The highest affinity ligand (9{2,1,1}) possesses an affinity of 330 nM for the androgen receptor, whereas the most selective ligand (9{2,4,1}) displays an affinity of 900 nM for the androgen receptor and a selectivity of 140-fold over the next highest affinity receptor.     

Test of Lorentz invariance in electrodynamics using rotating cryogenic sapphire microwave oscillators

We present the first results from a rotating Michelson-Morley experiment that uses two orthogonally orientated cryogenic sapphire resonator oscillators operating in whispering gallery modes near 10 GHz. The experiment is used to test for violations of Lorentz invariance in the framework of the photon sector of the standard model extension (SME), as well as the isotropy term of the Robertson-Mansouri-Sexl (RMS) framework. In the SME we set a new bound on the previously unmeasured kappa(ZZ)(e-) component of 2.1(5.7) x 10(-14), and set more stringent bounds by up to a factor of 7 on seven other components. In the RMS a more stringent bound of -0.9(2.0) x 10(-10) on the isotropy parameter, P(MM) = delta-beta + 1 / 2 is set, which is more than a factor of 7 improvement.     

Chemical Composition, Antioxidant and Anticancer Effects of the Seeds and Leaves of Indigo (Polygonum tinctorium Ait.) Plant

Seeds and leaves of indigo (Polygonum tinctorium Ait.) plant were investigated and compared with another medicinal plant named prolipid for their properties such as chemical composition, antioxidant, and anticancer effects by Fourier transform infrared, three-dimensional fluorescence spectroscopy, and electrospray ionization-MS in negative mode. It was found that polyphenols, flavonoids, and flavanols were significantly higher in prolipid (P?<?0.05), following by indigo mature leaves, immature leaves, and seeds. Methanol extract of mature indigo leaves in comparison with the ethyl acetate extract showed higher inhibition of proliferation. The interaction between polyphenol extracts of indigo mature leaves and BSA showed that indigo has a strong ability, as other widely used medicinal plants, to quench the intrinsic fluorescence of BSA by forming complexes. In conclusion, indigo mature leaves were compared with prolipid. High content of bioactive compounds, antioxidant, fluorescence, and antiproliferative properties of indigo justifies the use of this plant as a medicinal plant and a new source of antioxidants.     

Sequential one-pot ruthenium-catalyzed azide-alkyne cycloaddition from primary alkyl halides and sodium azide

An experimentally simple sequential one-pot RuAAC reaction, affording 1,5-disubstituted 1H-1,2,3-triazoles in good to excellent yields starting from an alkyl halide, sodium azide, and an alkyne, is reported. The organic azide is formed in situ by treating the primary alkyl halide with sodium azide in DMA under microwave heating. Subsequent addition of [RuClCp*(PPh(3))(2)] and the alkyne yielded the desired cycloaddition product after further microwave irradiation.     

Mixed crystal formation and structural studies in the mullite-type system Bi2Fe4O9–Bi2Mn4O10

The limits of metal cation substitution and distribution in the sequence Bi₂Fe₄O₉–Bi₂Mn₄O₁₀ have been investigated by solid state synthesis, X-ray powder diffraction, and Mössbauer spectroscopy. Rietveld refinements conducted for the entire range along the join indicate the structures are orthorhombic with space group Pbam, with partial transition-metal site disorder confirmed and detailed by Mössbauer spectroscopy. Single-phase regions are found near each end-member and a two-phase region is observed at intermediate compositions, extending from about x=1 to 3, according to the general formula of the mixed crystals Bi₂Fe_4?xMn_xO_10?δ. An incorporation of Mn at octahedral sites replacing Fe is taken into account for the Bi₂Fe₄O₉-related side of the system. Charge compensation is believed to be effected by addition of O, which gives rise to the formation of FeO₅ pyramids. At the Bi₂Mn₄O₁₀-related side of the system, substitution of pyramidal Mn³⁺ by Fe³⁺ is envisaged.     

Iron carbonyl-mediated parallel solution-phase synthesis of cyclohexadienoic acid amides

Iron carbonyl-stabilized cations have been employed to develop methodology for carbon-carbon and carbon-heteroatom formation suitable for the preparation of combinatorial libraries. Different nucleophiles were added to tricarbonyl(cyclohexa-1,3-dienylcarboxylic acid 4-nitro-phenyl ester)iron hexafluorophosphate. Aminolysis, followed by decomplexation, yielded substituted cyclohexadienyl amides of high purity. Carbon, oxygen, and sulfur nucleophiles gave good results, while amine nucleophiles gave products of somewhat lower purity.