Synthesis of phenyl furyl sulfides and phenyl furyl ethers by nucleophilic substitution of nitrofurans

Phenyl furyl sulfides ( 3a‐j ) and phenyl furyl ethers ( 3k‐n ), which are useful in synthesizing furocondensed 3‐ring compounds, can be synthesized by nucleophilic substitution of nitrofurans having electron withdrawal groups. In our experiments using 5‐nitrofurans having electron withdrawal groups ( 2a‐i ), nucleophilic substitution readily occurred with the benzenethiolate anion of thiosalicylic acid ( 1a ), the benzenethiolate anion of thiosalicylate ester ( 1b ), and the phenylate anions of salicylate esters ( 1c‐d ) to yield phenyl furyl sulfides ( 3a‐j ) and phenyl furyl ethers ( 3k‐n ).     

Ab initio MO study of the chlorophyll dimer in the photosynthetic reaction center. I. A theoretical treatment of the electrostatic field created by the surrounding proteins

The charge separation occurring in the photosynthetic reaction center is the primary subject in order to understand the whole photosynthetic process. In this article, the electronic structures of the chlorophyll dimer, in which photoexcitation occurs, are investigated by using the ab initio molecular orbital scheme and pseudocharges and dipoles method which takes into account the electrostatic effect of the surrounding proteins, pigments, and aqueous solvent. As a first step, the ionization potentials of BCmp, BCIp, and the dimer of Rhodopseudomonas viridis are computed to study the characteristic of each molecule toward the elucidation of the primary charge separation. It has been found, from the present calculations, that BCmp and BClp constituting the dimer are not equivalent in their electronic ground states, since the electron could be removed more easily from BCmp than from BClp for two reasons: (1) the distorted molecular plane of Cmp, and (2) the effects of the surrounding electrostatic potentials to BCmp and BCIp. This tendency is further strengthened by the polarization of the environment, when, to the ab initio MO calculation, the contribution from the induced dipoles of the neighboring atoms in the proteins and other chromophores is included. From the present application, induced electric dipoles are found to be important to describe the molecular electronic structures affected by proteins. © 1997 John Wiley & Sons, Inc.     

A counterexample to the bold conjecture

A pair of vertices (x,y) of a graph G is an o-critical pair if o(G + xy) > o(G), where G + xy denotes the graph obtained by adding the edge xy to G and o(H) is the clique number of H. The o-critical pairs are never edges in G. A maximal stable set S of G is called a forced color class of G if S meets every o-clique of G, and o-critical pairs within S form a connected graph. In 1993, G. Bacsó raised the following conjecture which implies the famous Strong Perfect Graph Conjecture: If G is a uniquely o-colorable perfect graph, then G has at least one forced color class. This conjecture is called the Bold Conjecture. Here we show a simple counterexample to it. © 1997 John Wiley & Sons, Inc. J Graph Theory 25: 165–168, 1997     

Rhodium(I)-catalyzed asymmetric 1,4-addition of arylboronic acids to alpha,beta-unsaturated amides.

The conjugate addition of arylboronic acids to alpha,beta-unsaturated amides was carried out in the presence of a chiral rhodium catalyst and an aqueous base. The catalyst prepared in situ from Rh(acac)(CH(2)=CH(2))(2) and (S)-binap provided (R)-N-benzyl-3-phenylbutanamide with 93% ee in the addition of phenylboronic acid to N-benzyl crotonamide. The reaction suffered from incomplete conversion resulting in moderate yields, but addition of an aqueous base, such as K(2)CO(3) (10-50 mol%) was found to be highly effective to improve the chemical yields. The role of the base giving a RhOH species active for transmetalation with arylboronic acids was discussed.     

Immersed

We give two congruence formulas concerning the number of non-trivial double point circles and arcs of a smooth map with generic singularities --- the Whitney umbrellas --- of an -manifold into , which generalize the formulas by Szücs for an immersion with normal crossings. Then they are applied to give a new geometric proof of the congruence formula due to Mahowald and Lannes concerning the normal Euler number of an immersed -manifold in . We also study generic projections of an embedded -manifold in into and prove an elimination theorem of Whitney umbrella points of opposite signs, which is a direct generalization of a recent result of Carter and Saito concerning embedded surfaces in . The problem of lifting a map into to an embedding into is also studied.

     

Facile preparation of cyclopropanes from 2-iodoethyl-substituted olefins and 1,3-dihalopropanes with zinc powder

Two efficient, simple, cheap, and environmentally benign preparations of cyclopropanes were achieved. One is the formation via 3-exo-trig manner from various electron-deficient 2-iodoethyl-substituted olefins with zinc powder in a mixture of t-butyl alcohol and water, and the other is the formation via 3-exo-tet manner from various 1,3-dihalopropanes with zinc powder in ethanol.     

Stereoselective iodine atom transfer [3 + 2] cycloaddition reaction with alkenes using unsymmetrical allylated active methine radicals

Treatment of 1-diethylphosphonyl- or 1-phenylsulfonyl-2-(iodomethyl)cyclopropane-1-carboxylate with Et(3)B leads to an unsymmetrical allylated active methine radical species that gives functionalized cyclopentane derivatives with high stereoselectivity through iodine atom transfer [3 + 2] cycloaddition reaction with alkenes.     

Phosphorylcholine (PC)-bonded protein A affinity chromatographic medium for high-throughput purification with reduced non-specific protein adsorption

A protein A affinity chromatographic medium based on porous silica modified with phosphorylcholine (PC) groups and amino groups (PNSP) was synthesized. The PC groups functioned as suppressors of non-specific protein adsorption. Recombinant protein A was bound to the amino groups on PNSP with a glutaraldehyde used as a spacer (PNSP-PA). The PC groups and amino groups were immobilized on porous-silica particles using two silane coupling reagents, PC-bound silane, and 3-aminopropyltrimethoxysilane. After optimizing various factors in the synthetic process, the resultant protein A medium showed improvements in non-specific protein adsorption, dynamic binding capacity, and chemical stability under basic conditions compared with conventional protein A affinity media.     

Development of a novel two-dimensional gel electrophoresis protocol with agarose native gel electrophoresis

A new protocol for conducting two-dimensional (2D) electrophoresis was developed by combining the recently developed agarose native gel electrophoresis with either vertical sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) or flat SDS agarose gel electrophoresis. Our innovative technique utilizes His/MES buffer (pH 6.1) during the first-dimensional (1D) agarose native gel electrophoresis, which allows for the simultaneous and clear visualization of basic and acidic proteins in their native states or complex structures. Our agarose gel electrophoresis is a true native electrophoresis, unlike blue native–PAGE, which relies on the intrinsic charged states of the proteins and their complexes without the need for dye binding. In the 2D, the gel strip from the 1D agarose gel electrophoresis is soaked in SDS and placed on top of the vertical SDS–PAGE gels or the edge of the flat SDS–MetaPhor high-resolution agarose gels. This allows for customized operation using a single electrophoresis device at a low cost. This technique has been successfully applied to analyze various proteins, including five model proteins (BSA, factor Xa, ovotransferrin, IgG, and lysozyme), monoclonal antibodies with slightly different isoelectric points, polyclonal antibodies, and antigen–antibody complexes, as well as complex proteins such as IgM pentamer and β-galactosidase tetramer. Our protocol can be completed within a day, taking approximately 5–6 h, and can be expanded further into Western blot analysis, mass spectrometry analysis, and other analytical methods.