Syntheses and Vero toxin-binding activities of carbosilane dendrimers periphery-functionalized with galabiose

Carbosilane dendrimers bearing galabiose (Galα1-4Gal) with three, four, and six galabiose units at the periphery of the dendrimers were synthesized for use as artificial inhibitors against Shiga toxins (Stxs) produced by Escherichia coli O157:H7. The galabiose unit, prepared from penta-O-acetyl-β-d-galactopyranose, was linked with carbosilane dendrimers of three shapes to afford acetyl-protected glycodendrimers in good yields. De-O-acetylation of the clusters was carried out in the presence of NaOMe and then aq NaOH to give the desired three shapes of galabiose-coated carbosilane dendrimers. Their biological activities toward Stxs were evaluated by kinetic analysis, binding assays, and cytotoxic assays.     

Reaction of 2,5-diisopropyl- and 2,5-di-sec-butylpyrazine 1-oxide. Derivatives with phosphoryl chloride and acetic anhydride

In order to examine the α-substitution of side chains, various derivatives of 2,5-diisopropyl- and 2,5-disec-butylpyrazine 1-oxides were subjected to the reaction with phosphoryl chloride and acetic anhydride. Chlorination and acetoxylation were recognized to take place on the pyrazine ring in almost all cases.     

A facile photoinduced iodoperfluoroalkylation of dienes, diynes, and enynes with perfluoroalkyl iodides via selective radical cyclization

Perfluoroalkyl iodides serve as excellent mediators for the radical cyclization of dienes, diynes, and enynes upon irradiation with near-UV light, providing the corresponding iodoperfluoroalkylated cyclic compounds in moderate to good yields.     

Ethanol vapor-mediated maturing for the enhancement of structural regularity of hexagonal mesoporous silica films

Structural regularity of hexagonal mesoporous silica films is dramatically enhanced when allowed to stand for a few hours in an ethanol vapor-containing closed bottle before dryness.     

A data base of data banks for toxicological information

The procedures necessary to find the appropriate data banks in seeking particular information or data are much less systematic than the way in which the information is stored at some data banks. Based on the information taken from several hundred direct-mailed questionnaires, a conceptual design is proposed for a data base of toxicological data banks relating to other areas such as medicine, pharmacology, biology, chemistry and environmental science. The system (not yet implemented) contains nearly 150 data banks (both computerized and manual) all over the world with data on the type of information, the way to obtain it, its cost, etc.     

Antiallergic agents from natural sources 9. Inhibition of nitric oxide production by novel chalcone derivatives from Mallotus philippinensis (Euphorbiaceae)

Three novel chalcone derivatives, mallotophilippens C (1), D (2) and E (3) were isolated from the fruits of Mallotus philippinensis MUELL. ARG. These compounds were identified, using chemical and spectral data, as 1-[6-(3,7-dimethyl-octa-2,6-dienyl)-5,7-dihydroxy-2,2-dimethyl-2H-chromen-8-yl]-3-(4-hydroxy-phenyl)-propenone, 3-(3,4-dihydroxy-phenyl)-1-[6-(3,7-dimethyl-octa-2,6-dienyl)-5,7-dihydroxy-2,2-dimethyl-2H-chromen-8-yl]-propenone and 1-[5,7-dihydroxy-2-methyl-6-(3-methyl-but-2-enyl)-2-(4-methyl-pent-3-enyl)-2H-chromen-8-yl]-3-(3,4-dihydroxy-phenyl)-propenone, respectively. They inhibited nitric oxide (NO) production and inducible NO synthase (iNOS) gene expression by a murine macrophage-like cell line (RAW 264.7), which was activated by lipopolysaccharide (LPS) and recombinant mouse interferon-gamma (IFN-gamma). Furthermore, they downregulated cyclooxygenase-2 (COX-2) gene, interleukin-6 (IL-6) gene and interleukin-1beta (IL-1beta) gene expression. These results suggest that they have anti-inflammatory and immunoregulatory effects.     

Phosphinoselenothioic acids and their salts: synthesis, characterization, and reaction with electrophiles

[reaction: see text] Phosphinoselenothioic acid ammonium salts were synthesized in good yields by reacting phosphinoselenothioic acid S-[2-(trimethylsilyl)ethyl] esters with ammonium fluorides. Phosphinoselenothioic acid alkali metal salts were obtained as 18-crown-6 ether complexes with high efficiency by treating the esters with alkali metal fluorides and 18-crown-6 ether. The salts were stable under air and soluble in water. The structures of the phosphinoselenothioic acid tetramethylammonium salt and P-methylseleno-P-methylthiophosphonium triflate were determined by X-ray molecular structure analyses. These salts exhibited monomeric structures, and the central phosphorus atoms adopted tetrahedral structures. Alkylation of the ammonium salts selectively gave phosphinoselenothioic acid Se-alkyl esters, whereas acylation of the salts preferentially gave S-acyl products. Protonation of the salts selectively gave the phosphinoselenothioic S-acid. The S-acid generated in situ was reacted with alpha,beta-unsaturated carbonyl compounds and cyclohexene oxide to give the adducts. Molecular orbital calculations were carried out for the model compound H2P(Se)S- to elucidate the electronic structure.     

Asymmetric synthesis catalyzed by chiral ferrocenylphosphine-transition metal complexes VII. New chiral ferrocenylphosphines with C2 symmetry

A new chiral ferrocenylphosphine ligand, 2,2′-bis[1-N,N-dimethylamino)ethyl]-1,1′-bis(diphenylphosphino)ferrocene (2), which has C₂ symmetry and a functional group on the side chain, was prepared by ortho-lithiation and phosphination of 1,1′-bis[1-N,N-dimethylamino)ethyl]ferrocene followed by optical resolution; recrystallization of the diammonium salt with tartaric acid. An X-ray diffraction study of PdCl₂[(+)-2] showed that the complex has square-planar geometry with two cis chlorine and two phosphorus atoms and ligand (+)-2 has an (S) configuration on the 1-dimethylaminoethyl side chain and (R) ferrocene planar chirality.     

Dual substrate recognition of aminotransferases

Pyridoxal 5'-phosphate-dependent aminotransferases reversibly catalyzes the transamination reaction in which the alpha-amino group of amino acid 1 is transferred to the 2-oxo acid of amino acid 2 (usually 2-oxoglutarate) to produce the 2-oxo acid of amino acid 1 and amino acid 2 (glutamate). An aminotransferase must thus be able to recognize and bind two kinds of amino acids (amino acids 1 and 2), the side chains of which are different in shape and properties, from among many other small molecules. The dual substrate recognition mechanism has been discovered based on three-dimensional structures of aromatic amino acids, histidinol phosphate, glutamine:phenylpyruvate, acetylornithine, and branched-chain amino acid aminotransferases. There are two representative strategies for dual substrate recognition. An aromatic amino acid aminotransferase prepares charged and neutral pockets for acidic and aromatic side chains, respectively, at the same place by a large-scale rearrangement of the hydrogen-bond network caused by the induced fit. In a branched-chain aminotransferase, the same hydrophobic cavity implanted with hydrophilic sites accommodates both hydrophobic and acidic side chains without side-chain rearrangements of the active-site residues, which is reminiscent of the lock and key mechanism. Dual substrate recognition in other aminotransferases is attained by combining the two representative methods.     

Neolignans from Piper futokadsura and their inhibition of nitric oxide production

From a MeOH extract of the aerial part of Piper futokadsura, the tetrahydrofuran lignans, futokadsurin A [(7S,8S,7'S,8'R)-3,4,3'-trimethoxy-4'-hydroxy-7,7'-epoxylignan], futokadsurin B [(7R,8R,7'R,8'S)-3,4-dimethoxy-3',4'-methylenedioxy-7,7'-epoxylignan], and futokadsurin C [(7R,8R,7'S,8'S)-3,4-methylenedioxy-3',4'-dimethoxy-7,7'-epoxylignan] were isolated, together with nine known neolignans. In addition, L-tryptophan, pellitorine, phytol, elemicin, and 1,2,4-trimethoxyphenyl-5-aldehyde were isolated. The structures of the new compounds were elucidated using spectroscopic methods. These lignans inhibited nitric oxide production by a murine macrophage-like cell line (RAW 264.7), which was activated by lipopolysaccharide and interferon-gamma.