Rh-catalyzed one-pot and practical transformation of aldoximes to amides.

Wilkinson's complex has been found to catalyze the one-pot transformation of aldoximes to the corresponding amides with high selectivity and efficiency under essentially neutral conditions.

Conjugated enynes as a new type of substrates for olefin metathesis.

[reaction: see text] It has been demonstrated for the first time that conjugated enynes can be employed as a facile substrate in olefin metathesis with the use of a bispyridine-substituted ruthenium benzylidene catalyst. Cross-metathesis of the enynes with alkenes turns out to proceed with preferential formation of (Z)-isomers over (E)-isomers up to >25:1 in moderate to good yields. The intramolecular version of conjugated enynes affords novel butadienyl cycloalkenes, which are a highly useful synthetic building blocks, in acceptable yields.

Beta-elimination of a phosphonate group from an alkoxy radical: an intramolecular acylation approach using an acylphosphonate as a carbonyl group acceptor.

On the basis of facile beta-elimination of a phosphonate group from an alkoxy radical, intramolecular acylation reaction has been developed, in which an acylphosphonate is used as an excellent carbonyl group radical acceptor.

Ru-catalyzed hydroamidation of alkenes and cooperative aminocarboxylation procedure with chelating formamide.

[reaction: see text] A strategy of chelation-assisted activation of formamide was employed to achieve hydroamidation of alkenes to generate one-carbon-elongated amides in moderate to good selectivity and yields. Also reported is the two-metal-catalyzed cooperative aminocarboxylation of aryl iodides, in which Ru is presumed to catalyze decarbonylation of formamide to release carbon monoxide and amine for the subsequent Pd-catalyzed aminocarboxylation routes, thus enabling the net transformation to be performed in the absence of external CO pressure.

Cyano-bridged homometallic 1-D and bimetallic 2-D assemblies: synthesis, structures, and magnetic properties of [Ni(baepn)(CN)]n(ClO4)n and [Ni(baepn)]2n[Fe(CN)(6)]n(H2O)8n.

Cyano-bridged homometallic complex [Ni(baepn)(CN)](n)(ClO(4))(n)(1) and bimetallic complex [Ni(baepn)](2)(n)[Fe(CN)(6)](n)(H(2)O)(8)(n)(2) [baepn = N,N'-bis(2-aminoethyl)-1,3-propanediamine] were synthesized and characterized. 1 crystallizes in the monoclinic space group P2(1)/n with a = 9.560(3) A, b = 10.

Enantioselective mercuriocyclization of gamma-hydroxy-cis-alkenes.

Asymmetric mercuriocyclization of gamma-hydroxy-(Z)-alkenes has been achieved using Hg(II) complexed with tartrate-derived 4-(2-naphthyl)bisoxazoline as chiral ligand to give rise to 2-monosubstituted tetrahydrofurans in 86-95% ee. Not only the linker connecting two oxazolines but also their 4-substituents were found crucial for high enantioselectivity. In addition, tuning the ketal protecting group of tartrate as well as adding MeOH and K(2)CO(3) worked beneficially.

Highly regioselective cleavages and iodinations of cyclic ethers utilizing SmI2.

Various functionalized cyclic ethers such as oxiranes, oxetanes, and tetrahydrofurans have been prepared, and the regiochemistry of their ring opening with samarium diiodide and acyl chloride or anhydride has been investigated. Alkyl-substituted oxetane 5 and tetrahydrofurans 1 and 2 show almost no regioselectivity. However, high regioselectivities from the branched cyclic ethers (3, 8, 9, and 10) containing ethereal or hydroxyl moieties have been observed.

Interaction of C5 protein with RNA aptamers selected by SELEX.

RNA aptamers binding to C5 protein, the protein component of Escherichia coli RNase P, were selected and characterized as an initial step in elucidating the mechanism of action of C5 protein as an RNA-binding protein. Sequence analyses of the RNA aptamers suggest that C5 protein binds various RNA molecules with dissociation constants comparable to that of M1 RNA, the RNA component of RNase P. The dominant sequence, W2, was chosen for further study.

3'-end processing of precursor M1 RNA by the N-terminal half of RNase E.

M1 RNA, the catalytic component of Escherichia coli RNase P, is derived from the 3'-end processing of precursor M1 RNA, a major transcript of the rnpB gene. In this study, we investigated the mechanism of 3'-end processing of M1 RNA using the recombinant N-terminal half RNase E. The cleavage site preference of RNase E differed from that of the 40% ammonium sulfate precipitate (ASP-40), a partially purified cell extract containing processing activity.

Diastereoselectivity control in photosensitized addition of methanol to (R)-(+)-limonene.

Highly diastereodifferentiating bimolecular asymmetric photoreaction was achieved in the photosensitized polar addition of methanol to (R)-(+)-limonene. The diastereomeric excess (de) of the photoadduct could be controlled and fine-tuned by changing the internal/external factors such as solvent polarity, reaction temperature, and structure of the sensitizers. The de increased from 23% obtained upon xylene photosensitization in pure methanol at room temperature to >96% upon singlet sensitization with methyl benzoate at -75 degrees C in 0.

Development of tripeptidyl farnesyltransferase inhibitors.

The first example of tripeptide inhibitors of farnesyltransferase with sub-micromolar inhibition activity was developed based on the fact that CVFM is not a substrate for farnesyltransferase.

Consecutive carbon-carbon bond formation approach in tandem cyclization reactions.

The conventional tandem cyclization reactions involve the formation of alternating carbon-carbon bonds, whereas the newly developed cyclization reactions involve the formation of consecutive carbon-carbon bonds, in which N-aziridinylimines have been utilized as geminal radical acceptor and donor equivalents in a single operation. This unprecedented tandem cyclization approach becomes feasible by the successful generation of 5- and 6-membered ring radicals by radical cyclizations of N-aziridinylimines. The same notion can be applied to the anionic cyclizations of N-aziridinylimines, thereby allowing anionic consecutive carbon-carbon bond formation.

Alteration of stringent response of the Escherichia coli rnpB promoter by mutations in the -35 region.

It is well known that the GC-rich discriminator region between the -10 region and the transcription start site is important for the stringent control of the transcription. However, the discriminator activity is influenced by flanking regions, in particular in conjunction with the promoter -35 and -10 sequences. In this study, we changed the sequence in the -35 region of the rnpB P-1 promoter to see how such changes affect the stringent control.

Dual enantioselective control in asymmetric synthesis.

It is desirable and practical to produce both enantiomers of a target from the same chiral starting material by stereodifferentiation of prochiral compounds, for instance utilizing a chiral ligand derived from a natural (L) amino acid. During the past 7 years, excellent results have been achieved in several cases by multiple stereodifferentiation of chiral ligands derived from (S)-indoline-2-carboxylic acid: highly diastereo- and enantioselective pinacol coupling reactions of chiral alpha-ketoamides gave both (S,S)- and (R,R)-quaternary tartaric acid for the first time; asymmetric Diels-Alder cyclization of chiral acrylamides in the presence of Lewis acid afforded extremely high diastereoselectivities of both opposite configurations of the cyclized diastereomers depending upon the structures of chiral ligands and Lewis acids; and asymmetric alkylation of aldehydes to both enantiomers of secondary alcohols and asymmetric hydrogenation of ketones to both enantiomers of chiral secondary alcohols have been achieved using catalysts derived from (S)-indoline-2-carboxylic acid.

Identification of a structural motif of 23S rRNA interacting with 5S rRNA.

To identify RNA motifs interacting with 5S rRNA, a systematic evolution of ligands by exponential enrichment experiment was applied. Some of the resulting RNA aptamers contained a consensus sequence similar to the sequence in the loop region of helix 89 of 23S rRNA. We show that the synthetic helix 89 RNA motif indeed interacted with 5S rRNA and that the region around loop B of 5S rRNA was involved in this interaction.

Unusual ferromagnetic couplings in single end-to-end azide-bridged cobalt(II) and nickel(II) chain systems.

Two new one-dimensional single azide-bridged metal(II) compounds [[M(5-methylpyrazole)4(N3)]n](ClO4)n(H2O)n [M = Co (1a), Ni (2a)] were prepared by treating an M(II) ion with stoichiometric amount of sodium azide in the presence of four equivalents of the 3(5)-methylpyrazole ligand. The isostructural compounds 1a and 2a crystallize in the monoclinic space group P2(1)/n. The azide bridging ligands have a unique end-to-end coordination mode that brings two neighboring metal centers into a cis-position with respect to the azide unit to form single end-to-end azide-bridged cobalt(II) and nickel(II) chains.

Role of the sequence of the rne-dependent site in 3' processing of M1 RNA, the catalytic component of Escherichia coli RNase P.

The 3' processing of M1 RNA, the catalytic component of Escherichia coli RNase P, occurs by two pathways involving multiple steps. The precursor of M1 RNA has an rne-dependent site downstream of the processing site, whose sequence variation affects the processing efficiency. In this study, we showed that the sequence itself of the rne-dependent site possessed the ability to determine the processing pathways and that it also affected the cleavage specificity with the generation of the processing products at one nucleotide upstream or downstream of the normal cleavage sites.

Internalization of tenecin 3 by a fungal cellular process is essential for its fungicidal effect on Candida albicans.

Tenecin 3 is a glycine-rich, antifungal protein of 78 residues isolated from the insect Tenebrio molitor larva. As an initial step towards understanding the antifungal mechanism of tenecin 3, we examined how this protein interacts with the pathogenic fungus Candida albicans to exert its antifungal action. Tenecin 3 did not induce the release of a fluorescent dye trapped in the artificial membrane vesicles and it did not perturb the membrane potential of C.

Testis-specific expression of an intronless gene encoding a human poly(A) polymerase.

A mouse intronless gene, encoding a testis-specific poly(A) polymerase (mPAPT), was previously identified. mPAPT may play a role as a putative enzyme that is responsible for polyadenylation regulation during mouse spermatogenesis. In order to understand how PAPT genes are conserved in mammals, we isolated a human cDNA homolog encoding a human PAPT (hPAPT), which was specifically expressed in the testis.

Tin-Free Radical Acylation Reactions with Methanesulfonyl Oxime Ether.

A simple strategy involving thermal decomposition of the methanesulfonyl radical into the methyl radical and the subsequent transfer of an iodine atom or phenyl telluride group was used to develop a tin-free radical acylation reaction (see scheme; V-40=1,1'-azobis(cyclohexane-1-carbonitrile). The key was finding reaction conditions under which the I or PhTe transfer is faster than the direct addition of the alkyl radical to the methanesulfonyl oxime ether.