Linear synthesis of the tumor-associated carbohydrate antigens Globo-H,SSEA-3, and Gb3

The tumor-associated carbohydrate antigens Globo-H, SSEA-3, and Gb3 were synthesized in a linear fashion using glycosyl phosphate monosaccharide building blocks. All of the building blocks were prepared from readily available common precursors. The difficult alpha-(1-->4-cis)-galactosidic linkage was installed using a galactosyl phosphate donor with high selectivity. Introduction of the beta-galactosamine unit required the screening a variety of amine protecting groups to ensure good donor reactivity and protecting group compatibility. An N-trichloroacetyl-protected galactosamine donor performed best for the installation of the beta-glycosidic linkage. Conversion of the trichloroacetyl group to the N-acetyl group was achieved under mild conditions, fully compatible with the presence of multiple glycosidic bonds. This synthetic strategy is expected to be amenable to the synthesis of the globo-series of tumor antigens on solid-support.     

Recent advances in micellar electrokinetic chromatography

This review contains nearly 200 reference citations, and covers advances in electrokinetic capillary chromatography based on micelles, including stabilized micelle complexes, polymeric and mixed micelles from 2003-2004. Detection strategies, analyte determinations, and applications in micellar electrokinetic capillary chromatography (MEKC) are discussed. Information regarding methods of analyte concentration, analyte specific analyses, and nonstandard micelles has been summarized in tabular form to provide a means of rapid access to information pertinent to the reader.     

The synthesis of some 4,4′-disubstituted-2,2′-biquinolines

2,2′-Biquinoline dioxide and 4,4′-dichloro-2,2′-biquinoline have been used for the preparation of the following 4,4′-disubstituted-2,2′-biquinolines: dimethoxy, diethoxy, dihydroxy, dipiperidino, dipyrrolidino, dibromo, diphenoxy, dithiophenoxy, di(p-chloro-phenoxy), di(p-bromophenoxy), di(p-fluorophenoxy), di(β-naphthoxy) and the dinitro dioxide. Molar extinction coefficients have been determined for several of the copper (I) complexes of these compounds.     

Multi-step polymer-assisted solution-phase (PASP) library synthesis of functionalized diaminobenzamides

A parallel solution-phase library synthesis of functionalized diaminobenzamides is described. The four-step library synthesis is accomplished using polymer-assisted solution-phase (PASP) synthesis techniques. This high-yielding, multi-step sequence utilizes sequestering resins for the removal of reactants, reactant by-products, and employs a resin capture/release strategy as a key library synthesis step. Step one of the sequence relies on the displacement of an activated fluoro-group from the aromatic ring of 1a, b with a variety of primary amines to introduce the first diversity position. Step two is hydrolysis of the benzoate ester to a benzoic acid which is subsequently captured on a polyamine resin, washed, and released to give 4a, b in pure form. Step three utilizes PASP resins to mediate the amide coupling of a benzoic acid with a variety of primary amines to give the aminonitrobenzamides 5a, b and introduces the second diversity position. Step four is the parallel reduction of the aminonitrobenzamides 5a, b to the functionalized diaminobenzamides 6a, b. This library synthesis proceeds with high overall purities which average 80 % over the 4-step sequence.     

Characterization of single- and double-stranded DNA on gold surfaces

Single- and double-stranded deoxy ribonucleic acid (DNA) molecules attached to self-assembled monolayers (SAMs) on gold surfaces were characterized by a number of optical and electronic spectroscopic techniques. The DNA-modified gold surfaces were prepared through the self-assembly of 6-mercapto-1-hexanol and 5'-C(6)H(12)SH -modified single-stranded DNA (ssDNA). Upon hybridization of the surface-bound probe ssDNA with its complimentary target, formation of double-stranded DNA (dsDNA) on the gold surface is observed and in a competing process, probe ssDNA is desorbed from the gold surface. The competition between hybridization of ssDNA with its complimentary target and ssDNA probe desorption from the gold surface has been investigated in this paper using X-ray photoelectron spectroscopy, chronocoulometry, fluorescence, and polarization modulation-infrared reflection absorption spectroscopy (PM-IRRAS). The formation of dsDNA on the surface was identified by PM-IRRAS by a dsDNA IR signature at approximately 1678 cm(-)(1) that was confirmed by density functional theory calculations of the nucleotides and the nucleotides' base pairs. The presence of dsDNA through the specific DNA hybridization was additionally confirmed by atomic force microscopy through colloidal gold nanoparticle labeling of the target ssDNA. Using these methods, strand loss was observed even for DNA hybridization performed at 25 degrees C for the DNA monolayers studied here consisting of attachment to the gold surfaces by single Au-S bonds. This finding has significant consequence for the application of SAM technology in the detection of oligonucleotide hybridization on gold surfaces.     

Imidoylketene-alpha-oxoketenimine and alpha-oxoketene-alpha-oxoketene rearrangements. 1,3-shifts of substituted phenyl groups

1,3-phenyl shifts interconvert imidoylketenes 1 and alpha-oxoketenimines 2 and, likewise, alpha-oxoketenes 3 automerize by this 1,3-shift. These rearrangements usually take place in the gas phase under conditions of flash vacuum thermolysis. Energy profiles calculated at the B3LYP/6-31G(d,p) and B3LYP/6311 + G(3df,2p)//B3LYP/6-31G(d,p) levels demonstrate that electron donating substituents (D) in the migrating phenyl group and electron withdrawing ones (W) in the non-migrating phenyl group, can stabilise the transition states TS1 and TS2 to the extent that activation barriers of ca. 100 kJ mol(-1) or less are obtained; i.e. enough to make these reactions potentially observable in solution at ordinary temperatures. The calculated transition state energies DeltaG(TS1) show an excellent correlation with the Hammett constants sigma(p)(W) and sigma(p+)(D).     

Directed evolution of the dioxygenase complex for the synthesis of furanone flavor compounds

Herein we report a new preparation of 4-hydroxy-2,5-dimethyl-2,3-dihydrofuran-3-one, the flavor compound strawberry furanone, based on a ‘green’ approach with a minimum number of steps. The first step is an enzymatic dioxygenation of p-xylene to form cyclohexadiene-cis-diol, followed by ring opening via ozonolysis, and ring closure to form the furanone. In efforts to improve the efficiency of the enzymatic step, a directed evolution approach was taken to increase the substrate specificity and selectivity of the toluene dioxygenase enzyme system.     

Vierdimensionale quadratische Divisionsalgebren über Hilbert-Körpern

Zusammenfassung Inhalt der vorliegenden Untersuchung ist eine Klassifizierung der vierdimensionalen quadratischen Divsionsalgebren über einem Hilbert-Körper. Die Anregung dazu entstammt einer Arbeit von Kuz'min [6], in der endlichdimensionale reelle Divisionsalgebren durch Aussagen über ihre Multiplikationskonstanten charakterisiert werden. Der Schwerpunkt liegt dort auf den quadratischen Divisionsalgebren. Deren Struktur wird wesentlich durch quadratische Formen bestimmt. Deshalb ist es naheliegend, diese Algebren für eine allgemeinere Klasse von Körpern mit einer überschaubaren Theorie der quadratischen Formen zu betrachten. A Fröhlich [5] hat eine axiomatische Beschreibung für eine Klasse von Körpern, die sogenannten Hilbert-Körper, gegeben, die eine Theorie der quadratischen Formen wie die -adischen Zahlen oder die reellen Zahlen haben. Diese Körper legen wir in der Untersuchung zugrunde. Eine genauere Motivation für das Vorgehen und einen Ausblick auf die Ergebnisse gibt die folgende Einleitung.Die Verfasserin dankt Herrn Prof. Dr. K. Strambach, Erlangen, für die Anregung und Begleitung dieser Arbeit und Herrn Prof. Dr. L. Bröcker, Münster, für die konstruktiven Vorschläge zur Überarbeitung des ursprünglichen Manuskiptes.     

Eine Topologie auf der Menge der endlichdimensionalen nichtassoziativen Algebren über einem lokalen Körper

Motivated by an investigation ofKuz'min [2], in this note we introduce a topology on the set of nonassociative algebras of a fixed dimensionr< over a local fieldF. We obtain a space, which is notT ₁. If the trivial algebra is removed, the remaining subspace is quasicompact. The space is homeomoprhic to the group of square classes ofF ^*; forr3 the space is notT ₁. The set of division algebras is open in.     

Modeling Pb sorption to microporous amorphous oxides as discrete particles and coatings

Hydrous amorphous Al (HAO), Fe (HFO), and Mn (HMO) oxides are ubiquitous in the subsurface as both discrete particles and coatings and exhibit a high affinity for heavy metal contaminants. To assess risks associated with heavy metals, such as Pb, to the surrounding environment and manage remedial activities requires accurate mechanistic models with well-defined transport parameters that represent sorption processes. Experiments were conducted to evaluate Pb sorption to microporous Al, Fe, and Mn oxides, as well as to montmorillonite and HAO-coated montmorillonite. Intraparticle diffusion, a natural attenuating process, was observed to be the rate-limiting mechanism in the sorption process, where best-fit surface diffusivities ranged from 10(-18) to 10(-15) cm(2) s(-1). Specifically, diffusivities of Pb sorption to discrete aluminum oxide, aluminum oxide-coated montmorillonite, and montmorillonite indicated substrate surface characteristics influence metal mobility where diffusivity increased as affinity decreased. Furthermore, the diffusivity for aluminum oxide-coated montmorillonite was consistent with the concentrations of the individual minerals present and their associated particle size distributions. These results suggest that diffusivities for other coated systems can be predicted, and that oxide coatings and montmorillonite are effective sinks for heavy metal ions.