Intramolecular iodoetherification of ene or diene ketals: facile synthesis of spiroketals

A novel and rapid approach to chiral mono- or di-substituted spiroketals based on remote asymmetric induction by intramolecular iodoetherification of ene or diene ketals has been developed. This strategy concisely offers 5,5- and 5,6-spiroketals including the natural insect pheromone of the wasp.     

Triethylborane-induced radical allylation reaction with zirconocene-olefin complex

[reaction: see text] Allylzirconium reagents are effective for radical allylation of alpha-halo carbonyl compounds. The key steps would be homolytic cleavage of the zirconium-carbon bond and halogen abstraction by the resulting Cp(2)ZrCl(III). Zirconocene-olefin complex can be also utilized for the allylation of alpha-halo compounds.     

Copper-catalyzed annulative amination of ortho-alkynylphenols with hydroxylamines: synthesis of 3-aminobenzofurans by umpolung amination strategy

A room temperature copper-catalyzed annulative amination of ortho-alkynylphenols with electrophilic amination reagents, O-acylated hydroxylamines, proceeds efficiently to provide the corresponding 3-aminobenzofurans of biological and pharmaceutical interest.     

Synthetic and structural studies of [6]-, [7]- and [10]metacyclophanes

A new preparative sequence from 2,3-polymethylene-2-cyclopentenone 5 to 2,6-polymethylenebromobenzenes 3 (n = 6, 7, 10) and 2,6-polymethylenephenyllithiums 6 has been found. The reaction of 6 with various electrophiles produces a number of new compounds to disclose the unique reactivity of the aryl C-Li moiety surrounded by the polymethylene chain. Photolysis of 3a and 3b provides transannular products 8, 10 and 11, all arising from the proximity between the aromatic bromine and the aliphatic hydrogen intraannularly opposed to be removed as HBr. Spectrometric study gives quantitative data of the dependence of the molecular geometry upon the chain length and the aromatic substituents. The energy barriers ΔG_c^≠ of the conformational flipping are 17·4 kcal/mol (T_c 76·5°) for [6]metacyclophane (7a), 11·5 kcal/mol (T_c ?28°) for [7]metacyclophane (7b), ·8 kcal/mol for [10]metacyclophane (7c). The lower-energy process of the aliphatic chain in [6]metacyclophane derivatives is the pseudorotation with substituent-dependent barrier ΔG_c^≠ 11·1 kcal/mol (T_c ?31·5°) for 7a, 12·4 kcal/mol (T_c ?4·5°) for 3a and 12·7 kcal/mol (T_c 1·0°) for 12a. The rather large rotational barrier is attributed to the compressed structure of each system. The benzene ring distortion of the cyclophanes is deduced from the bathochromic shift of the B-band and the diamagnetic shift of the benzene proton signals in the PMR.     

Rhodium-catalyzed asymmetric one-pot transesterification and [2 + 2 + 2] cycloaddition leading to enantioenriched 3,3-disubstituted phthalides

[structure: see text]. We have developed a cationic rhodium(I)/Solphos complex-catalyzed asymmetric one-pot transesterification and [2 + 2 + 2] cycloaddition of 1,6-diyne esters with tertiary propargylic alcohols leading to enantioenriched tricyclic 3,3-disubstituted phthalides. The present method represents a versatile new route to the synthesis of enantioenriched tricyclic 3,3-disubstituted phthalides in view of the easy access to both coupling partners.     

The double Renner effect in the X(2)A" and A(2)A' electronic states of HO(2)

A theoretical investigation of the X(2)A" and A(2)A' electronic states of the HO(2) radical is reported. Both electronic states have nonlinear equilibrium geometries and they correlate with a (2)Pi state at linear geometries so that they exhibit the Renner effect. In highly excited bending states, there is tunneling between two equivalent minima (with geometries where the H nucleus is bound to one, or the other, of the two O nuclei), and the two linear geometries H-O-O and O-O-H become accessible to the molecule. Thus, HO(2) affords an example of the so-called double Renner effect. Three-dimensional potential energy surfaces for the X(2)A" and A(2)A' electronic states of HO(2) have been calculated ab initio and the global potential energy surfaces for the states have been constructed. These surfaces have been used, in conjunction with the computer program DR [Odaka et al., J. Mol. Structure 795, 14 (2006); Odaka et al., J. Chem. Phys. 126, 094301 (2007)], for calculating HO(2) rovibronic energies in the "double-Renner"-degenerate electronic states X(2)A" and A(2)A'. The results of the ab initio calculations, the rovibronic energies obtained, and analyses of the wavefunctions for selected states are presented.     

The microenvironment of DNA switches the activity of singlet oxygen generation photosensitized by berberine and palmatine

The effect of the interaction between DNA and the photosensitizer on photosensitized singlet oxygen (1O2) generation was investigated using DNA-binding alkaloids, berberine and palmatine. These photosensitizers were bound to DNA by electrostatic force. Near-infrared luminescence measurement demonstrated that the photoexcited alkaloids can generate 1O2 only when the photosensitizers are bound to DNA. A fluorescence decay study showed significant enhancement of the lifetime of their photoexcited state with the DNA binding. A calculation study suggested that the electrostatic interaction with DNA inhibits the quenching of the photoexcited state of these alkaloids via intramolecular electron transfer, leading to the prolongation of the lifetime of their excited state. This effect should enhance their intersystem crossing and the yield of energy transfer to molecular oxygen. The results show that the electrostatic interaction with DNA significantly affects the 1O2 generation activity of a photosensitizer. In addition, this interaction may be applied to the control and the design of photosensitizers for medical applications such as photodynamic therapy.     

13CNMR-Untersuchung der Taktizit?t von Poly-(RS)tert-butyloxiran, das durch Polymerisation mit tert-C4H9OK erhalten wurde

Ohne Zusammenfassung     

Synthesis and physiological activity of novel tocopheryl glycosides

Vitamin E glycosides were synthesized and enzymatic hydrolysis was examined for use as potential pro-drugs, however, the glycoside bond was found to be stable. On the other hand, among the glycosides synthesized, dl-alpha-tocopherylglucoside (6b) and dl-alpha-tocopherylmannoside (6c) showed strong inhibitory action on histamine release from mast cells. In addition, 6c also showed a suppressive action on IgE antibody formation. Thus, tocopheryl glycoside showed new properties compared to tocopherol (vitamin E). In particular, 6c was shown to be a novel lead compound with excellent manifold anti-allergic activity and anti-inflammatory activity.     

Participation of lipid peroxidation in rat pertussis vaccine pleurisy. III. Thiobarbituric acid (TBA) reactant and lysosomal enzyme

Activity of lysosomal enzymes, such as N-acetyl-beta-D-glucosaminidase (NAG), was assayed in exudate on a rat model of Bordetella pertussis vaccine pleurisy. Thiobarbituric acid (TBA)-reactive substances (TBA.R) and superoxide dismutase (SOD) activity were then monitored in the exudate on the acute phase response in this inflammatory model. Retention of the exudate in the pleural space increased rapidly after the challenge, and the exudate volume at 24 h reached about three times the volume at 6 h. The activity of SOD at 6 h was shown to be higher than that at 24 h after the challenge, thus showing negative correlations with TBA-R levels and exudate volume. The levels of TBA.R rapidly increased and reached maximum values at 24 h. It was concluded that the above three parameters correlated to the acute phase response in this inflammatory model.