A Dodecalanthanide Wheel Supported by p‐tert‐Butylsulfonylcalix[4]arene

A dodecaholmium wheel of [Ho₁₂(L)₆(mal)₄(AcO)₄(H₂O)₁₄] ( 1 ; mal=malonate) was synthesized by using p‐tert‐butylsulfonylcalix[4]arene (H₄L) as a cluster‐forming ligand. The wheel consists of three fragments of mononuclear A^3? ([Ho(L)(mal)(H₂O)]^3?), trinuclear B^3? ([Ho(H₂O)₂(mal)(Ho(L)(AcO))₂]^3?), and C³⁺ ([Ho(H₂O)₂]³⁺), and an alternate arrangement of these fragments (A^3?? C³⁺? B^3?? C³⁺? A^3?? C³⁺? B^3?? C³⁺? ) results in a wheel structure. The longest and shortest diameters of the core were estimated to be 17.7562(16) and 13.6810(13) Å, respectively, and the saddle‐shaped molecule possesses a pocketlike cavity inside.     

An iron reservoir model based on ferrichrome: iron(III)-binding and metal(III)-exchange properties of tripodal monotopic and ditopic hydroxamate ligands with an L-alanyl-L-alanyl-N-hydroxy-beta-alanyl sequence

To gain knowledge about biological iron mobilization, tripodal monotopic and ditopic hydroxamate ligands (1 and 2) are prepared, and their iron-chelating properties are investigated. Ligands 1 and 2 contain three Ala-Ala-beta-(HO)Ala units and three [Ala-Ala-beta-(HO)Ala](2) units connected with tris(alanylaminoethyl)amine, respectively, and form six-coordinate octahedral complexes with iron(III) in aqueous solution. Ligand 1 and 1 equiv of iron give Fe-1, and ligand 2 and 1 or 2 equiv of iron produce Fe(1)-2, or Fe(2)-2. These complexes exhibit absorptions at lambda(max) 425 nm of epsilon 2800-3000/Fe, characteristic of tris(hydroxamato)iron(III) complexes, and preferentially assume the Delta-cis configuration. Loading of Fe(III) on 1, 2, and M(III)-loaded ligands (M-1 and M(1)-2, M = Al, Ga, In) with ammonium ferric oxalate at pH 5.4 is performed, and the second-order rate constants of loading with respect to Fe(III) and the ligand or M(III)-loaded ligands are determined. The rates of loading of Fe(III) on M-1 increase in the order Al-1 < Ga-1 < In-1, and those on M(1)-2 in the order Al(1)-2 < Ga(1)-2 < Fe(1)-2 < In(1)-2, indicating that the dissociation tendency of M(III) ions from the hydroxamate ligand is an important factor. The iron complexes formed with 2 are subjected to an iron removal reaction with excess EDTA in aqueous pH 5.4 solution at 25.0 degrees C, and the collected data are analyzed by curve-fitting using appropriate first-order kinetic equations, providing the rate constants for the upper site and the lower site of 2. Similar analysis for FeM-2 affords removal rate constants for Fe(up)-2, M(up)-2, and Fe(low)-2, and the iron residence probability at each site. The protonation constants of the hydroxamate groups for 1 and 2 (pK(1,) pK(2), pK(3), and pK(1,) pK(2)., pK(6)) are determined, and the proton-independent stability constants for Fe-1, the upper site of Fe(2)-2, and the lower site of Fe(1)-2 are 10(28), 10(29), and 10(28.5), respectively.     

Skeletal diversity by allylation/RCM on Ugi four-component coupling reaction products

Here, we report a diversity-oriented synthetic approach toward skeletally diverse, cyclized peptidomimetics with diverse appendages. Starting from α-(N-acylamino)amides with various appendages, 12 to 16-membered lactams with defined olefin geometry were synthesized by a common synthetic sequence. We also synthesized the macrocycle in a liquid phase directed toward a construction of the peptidomimetics library.     

1-D cobalt(II) spin transition compound with strong interchain interaction: [Co(pyterpy)Cl(2)].X

Cobalt(II) compounds [Co(pyterpy)Cl(2)].MeOH (1.(MeOH)) and [Co(pyterpy)Cl(2)].2H(2)O (1.(2H(2)O)) were synthesized. The compound 1.(MeOH) forms the quasi 3-D networks by making pi-pi stacking between the 1-D chains. The methanol molecules from 1.(MeOH) can be removed by heating, and substituted by absorption of water molecules. The MeOH molecules in 1.(MeOH) are removed by heating at 410 K, and they are substituted by water molecules to form 1.(2H(2)O). 1.(2H(2)O) exhibits a S = (3)/(2) (HS) left arrow over right arrow S = (1)/(2) (LS) spin transition with a thermal hysteresis. We have succeeded in constructing a guest dependent 1-D spin-crossover cobalt(II) compound.     

Total Synthesis of Sialylated Glycans Related to Avian and Human Influenza Virus Infection

Human and avian influenza type A viruses bind sialylated pentasaccharides. Herein, the total synthesis of four of these glycans is reported. Efficient sialylations relied on two N‐Troc‐protected (Troc=2,2,2‐trichloroethoxycarbonyl) sialic acid building blocks. The first, a thiophenyl glycoside, readily produced the sialyl‐α(2‐6)galactose disaccharide. Combination of the second building block, a novel glycosyl phosphite, and a benzylidene‐protected galactoside produced the best results for the formation of the sialyl‐α(2‐3)galactose. Two common trisaccharides were assembled by the introduction of glucose, galactose, and glucosamine building blocks followed by selective deprotection. Two sets of pentasaccharides were obtained by the union of two sialylgalactose N‐phenyl trifluoroacetimidate building blocks with the two trisaccharides above. Global deprotection furnished the desired pentasaccharides. The products of these total syntheses are currently employed on the surface of carbohydrate microarrays to detect and type different strains of the influenza virus.     

Structural assignment of isomeric 2-aminopyridine-derivatized oligosaccharides using negative-ion MSn spectral matching

To investigate the possibility of structural assignment based on negative-ion MS2 spectral matching, three isomeric pairs of 2-aminopyridine (PA)-derivatized non-fucosylated, fucosylated, and sialylated oligosaccharides (complex type N-glycans) were analyzed using high-performance liquid chromatography/ion trap mass spectrometry (HPLC/ITMS) with a sonic-spray ionization (SSI) source. In the SSI negative-ion mode the deprotonated molecule [M-2H]2- becomes prominent. Negative-ion MS2 spectra derived from such ions contain many fragment types (B and Y, C and Z, A, and D) and therefore are more informative than the positive-ion MS2 spectra derived from [M+H+Na]2+ ions, which usually consist mainly of B and Y fragment ions. In particular the internal ions (D- and E-type ions) provided useful information about the alpha1-6 branching patterns and the bisecting GlcNAc residue. Spectral matching based on the correlation coefficients between negative-ion MS2 spectra was performed in a manner similar to the positive-ion MS2 spectral matching previously reported. It was demonstrated that negative-ion MS2 spectral matching is as useful and applicable to the structural assignment of relatively large non-fucosylated, fucosylated, and sialylated PA-oligosaccharide isomers as its positive-ion counterpart.     

A new synthesis of pyrroles by the condensation of cyclopropenes and nitriles mediated by gallium(III) and indium(III) salts

Gallium(III) and indium(III) halides were found to mediate the condensation of cyclopropenes and nitriles to give pyrrole derivatives in moderate yields. When excess nitrile was present, diazepine was also formed.     

Profiling and comprehensive expression analysis of ABC transporter solute-binding proteins of Bacillus subtilis membrane based on a proteomic approach

We analyzed ABC transporter solute-binding proteins (SBPs) of the Bacillus subtilis membrane using a proteomic approach. We prepared a washed cell membrane fraction that was insoluble in 134 mM nondetergent sulfobetaine and then extracted proteins using mixtures of detergents in a stepwise manner. The membrane proteins were resolved by three two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) or two one-dimensional (1-D) PAGE procedures, electroblotted, and digested in the presence of 5% or 80% acetonitrile. Thereafter, matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF MS) identified 637 proteins corresponding to 15.9% of the total cellular proteins. We predicted that among these, 256 were membrane proteins, 101 were lipoproteins or secretory proteins and 280 were soluble proteins containing peripheral proteins that function in both the cytoplasm and the cell membrane such as SecA and FtsY. Among the 637 proteins, we identified 30 SBPs among 38 importers predicted by a bioinformatic search of the genome. We confirmed expression of the genes for the 30 SBPs using DNA microarray analysis. We compared the 2-D gel separation profiles of submembrane fractions solubilized by 1% n-dodecyl-beta-D-maltoside from cells cultured on Luria Bertani (LB), S7, and S7 medium without glutamate as well as DNA microarray data on LB and S7. The results suggested that YcdH, YtmK and YurO are binding proteins for Mn(++), glutamate and glucose, respectively, and that YqiX and YxeM are binding proteins for amino acids (tryptophan in S7 medium).     

Synthesis of pyrimidine derivatives by the reaction of ketene dithioacetals with amides

Reactions of methyl 2-cyano-3,3-bis(methylthio)acrylate ( 1a ) with carboxamides 2a-g in the presence of sodium hydride in a mixture of benzene and N,N-dimethylacetamide took place displacement with the methylthio group to give the corresponding methyl 3-N-acylamino-2-cyano-3-(methylthio)acrylates 3a-g which were readily converted to the corresponding pyrimidine derivatives at reflux in methanol in good yields. Reactions of 2-cyano-3,3-bis(methylthio)acrylonitrile ( 1b ) with the carboxamides 2a-f gave directly pyrimidine-5-carbonitrile derivatives 7a-f . Ketene dithioacetals 1a,b smoothly reacted with thioamide 2g or urea 2h,i to give the expected pyrimidine derivatives 9,10a,b . Polyfunctionalized pyrimidines, thus obtained, were also used for the synthesis of fused pyrimidine derivatives.