Radical alkenylation of alpha-halo carbonyl compounds with alkenylindiums

Alkenylation reaction of alpha-halo carbonyl compounds with alkenylindiums proceeded via a radical process in the presence of triethylborane. Unactivated alkene moieties as well as a styryl group could be introduced by this method. The geometry of the carbon-carbon double bonds of the alkenylindiums was retained. Preparation of an alkenylindium via a hydroindation of 1-alkyne followed by radical alkenylation established an efficient one-pot strategy. [reaction: see text]     

Wedderburnzerlegung für Jordan-Paare

In the first section we summarize some properties of Jordan pairs. Then we state some results about some groups defined by Jordan pairs.In the next section we construct a Lie algebra to a Jordan pair. This construction is a generalization of the wellknown Koecher-Tits-construction. We calculate the radical of this Lie algebra in terms of the given Jordan pair.In the last section we prove a Wedderburn decomposition theorem for Jordan pairs in the characteristic zero case. Some special cases in arbitrary characteristic have been shown by R. Carlson (see [5]). Also we show that any two such decompositions are conjugate under a certain group of automorphism. Analogous theorems will be shown for Jordan Triples.     

Triethylborane-mediated hydrogallation and hydroindation: novel access to organogalliums and organoindiums

Hydrogallation of carbon[bond]carbon multiple bonds proceeds in the presence of triethylborane as a radical initiator. Several functionalities do not interfere with this reaction. Resulting alkenyl- and alkylgallium species can be trapped by several electrophiles. Highly regioselective radical addition of an indium hydride reagent to alkynes is also achieved. Various functionalities are tolerant under the reaction conditions. The reaction proceeds with complete anti stereoselectivity. Alkenylindiums obtained via hydroindation can be employed for the following cross-coupling reaction with aryl halides in one pot.     

Effect of boron non-stoichiometry on B-site in perovskite type structure ScBxRh3 and CeBxRh3 on charges of atoms on A-site: study by X-ray photoelectron and nuclear magnetic resonance spectroscopies

The solid solutions of ScBRh₃-ScRh₃ and CeBRh₃-CeRh₃ are synthesized by the arc melting method, where RBRh₃ and RRh₃ (R=rare earth element) have perovskite and AuCu₃ type structures, respectively. The binding energy of Sc 2p_3/2 for ScB_xRh₃ increases with the boron concentration. The Knight shift of ⁴⁵Sc observed by nuclear magnetic resonance spectroscopy decreases with increase of boron concentration. The decrement of the Knight shift corresponds the Sc 4s electron density at the Fermi level. The intensity ratio of f²: f¹: f⁰ of Ce 3d XPS spectrum changes with boron concentration of CeB_xRh₃. It is concluded that in both cases of ScB_xRh₃ and CeB_xRh₃ the charge on the atoms on A-site changes with the concentration of the atoms on B-site, where the atoms are not directly bound.     

Improvement of in-gel digestion protocol for peptide mass fingerprinting by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

High-sensitivity, high-throughput analysis of proteins for proteomics studies is usually performed by polyacrylamide gel electrophoresis in combination with mass spectrometry. However, the quality of the data obtained depends on the in-gel digestion procedure employed. This work describes an improvement in the in-gel digestion efficiency for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) analysis. A dramatic improvement in the coverage of tryptic peptides was observed when n-octyl glucoside was added to the buffer. Whole cell extracted proteins from S. cerevisiae were separated by two-dimensional gel electrophoresis and stained with silver. Protein spots were identified using our improved in-gel digestion method and MALDI-TOFMS. In addition, the mass spectra obtained by using the matrix alpha-cyano-4-hydroxycinnamic acid (CHCA) were compared with those obtained using 2,5-dihydroxybenzoic acid (DHB). The DHB matrix usually gave more peaks, which led to higher sequence coverage and, consequently, to higher confidence in protein identification. This improved in-gel digestion protocol is simple and useful for protein identification by MALDI-TOFMS.     

Chiral lithium binaphtholate aqua complex as a highly effective asymmetric catalyst for cyanohydrin synthesis

A highly enantioselective cyanohydrin synthesis with aromatic aldehydes using chiral lithium binaphtholate aqua or alcohol complexes has been developed and is a simple and inexpensive catalyst suitable for process chemistry to give gram-scale cyanohydrins successfully. Dramatic improvements in enantiomeric excess have been realized along with an interesting changeover in absolute stereochemistry of cyanohydrin product against the thoroughly "dry" catalytic systems.     

Photochemical study of [3(3)](1,3,5)cyclophane and emission spectral properties of [3n]cyclophanes (n = 2-6)

Thephotochemical reaction of [3(3)](1,3,5)cyclophane 2, which is a photoprecursor for the formation of propella[3(3)]prismane 18, was studied using a sterilizing lamp (254 nm). Upon photolysis in dry and wet CH2Cl2 or MeOH in the presence of 2 mol/L aqueous HCl solution, the cyclophane 2 afforded novel cage compounds comprised of new skeletons, tetracyclo[6.3.1.0.(2,7)0(4,11)]dodeca-5,9-diene 43, hexacyclo[6.4.0.0.(2,6)0.(4,11)0.(5,10)0(9,12)]dodecane 44, and pentacyclo[6.4.0.0.(2,6)0.(4,11)0(5,10)]dodecane 45. All of these products were confirmed by the X-ray structural analyses. A possible mechanism for the formation of these photoproducts via the hexaprismane derivative 18 is proposed. The photophysical properties in the excited state of the [3n]cyclophanes ([3n]CP, n = 2-6) were investigated by measuring the emission spectra and determining the quantum yields and lifetimes of the fluorescence. All [3n]CPs show excimeric fluorescence without a monomeric one. The lifetime of the excimer fluorescence becomes gradually longer with the increasing number of the trimethylene bridges. The [3n]CPs also shows excimeric phosphorescence spectra without vibrational structures for n = 2, 4, and 5, while phosphorescence is absent for n = 3 and 6. With an increase in symmetry of the benzene skeleton in the [3(3)]- and [3(6)]CPs, the probability of the radiation (phosphorescence) process from the lowest triplet state may drastically decrease.     

Periodate oxidation analysis of carbohydrates: Part IV. Simultaneous determination of aldehydes in di-aldehyde fragments as 2,4-dinitrophenylhydrazones by thin-layer or liquid chromatography

A method for the simultaneous determination of aldehydes in dialdehyde fragments, obtained from carbohydrate samples by periodate oxidation, is proposed. Reaction mixtures obtained from the periodate oxidation of carbohydrate samples are deionized by resins, and evaporated to dryness. The syrupy residues are treated with 2,4-dinitrophenylhydrazine hydrochloride in 1.2-dimethoxyethane at 25°C for 3 h. The resultant mixtures of hydrazones are separated by t.l.c. or l.c., and individual hydrazones are determined by spectrophotometric measurement. Reliable analyses of carbohydrate linkages are possible with 50–250-μg samples.     

Diastereoselective Iodocarbocyclization Reaction of 2- or 3-Oxy-4-pentenylmalonate Derivatives

1,2- Or 1,3-asymmetric induction in the iodocarbocyclization reaction of 4-pentenylmalonate derivatives having a stereogenic center at an allylic or a homoallylic position has been investigated. The iodocarbocyclization reactions of 3-oxy-4-pentenylmalonate derivatives proceeded with high cis-selectivity through stereoelectronic control of the oxygenated substituent at an allylic position. In the reaction of (S)-2-siloxy-4-pentenylmalonate, an excellent diastereoselectivity was achieved through the utilization of double stereodifferentiation with a chiral titanium catalyst. Furthermore, as an application of the present reaction, the asymmetric syntheses of cyclosarkomycin and a synthetic intermediate of brefeldin A from optically pure 2- and 3-oxy-4-pentenylmalonate derivatives are also described.