Biomedical subjects

Matthias Zeller

Publications and source records attributed to Matthias Zeller.

8 recordsLinked to original sources

PubMed2006

Application of bis(diphenylphosphino)ethane (DPPE) in Staudinger-type N-glycopyranosyl amide synthesis.

Bis(diphenylphosphino)ethane (DPPE) reacts with pyranosyl azides derived from D-glucose and D-glucuronic acid in the presence of acid chlorides to yield the corresponding glycosyl amides. Reaction rates are comparable to those with triphenylphosphine, however, the byproduct phosphine oxide is easily removed from reaction mixtures using column chromatography. The simple and clean workup allows for the formation of collections of related compounds by parallel synthesis, and the method is also applicable to scaled-up reactions. The beta-stereochemistry of the glycosyl azide precursor is retained in all cases, which is supported by X-ray crystallography in several cases.

Amides↗

PubMed2005

Semiconductive coordination networks from bismuth(III) bromide and 1,2-bis(methylthio)phenylacetylene-based ligands.

This paper reports our initial efforts to integrate phenylacetylene-based conjugate pi-electron systems into hybrid semiconductive coordination networks, as part of the larger scheme to fully synergize organic functionalities and electronic properties in crystalline solid-state materials. On the basis of a well-established Pd-catalyzed procedure, ligands of 3,3',4,4'-tetrakis(methylthio)tolan (L1) and 1,3,5-tris[[3,4-bis(methylthio)phenyl]ethynyl]benzene (L2) were efficiently synthesized in relatively simple procedures. Molecule L1 reacts with BiBr3 to form a 2D semiconductive coordination network (L1.2BiBr3), which consists of infinite chains of the BiBr3 component cross-linked by L1 through the chelation between the 1,2-bis(methylthio) groups and the Bi(III) centers. Molecule L2 reacts with BiBr3 to from a 1D semiconductive coordination network (L2.2BiBr3), which features discrete tetrameric Bi4Br12 units linked by the thioether groups from L2 [only two of the three 1,2-bis(methylthio) groups from each L2 molecule are bonded to the Bi(III) centers]. Diffuse reflectance spectra of both L1.2BiBr3 and L2.2BiBr3 feature strong optical absorptions at energy levels significantly lower than those of the corresponding molecular solids (L1 and L2) and BiBr3, indicating significant electronic interaction between the organic pi-electron systems and the BiBr3 components. Both L1.2BiBr3 and L2.2BiBr3 readily form in high yields and are stable to air, providing advantages for further studies as potentially applicable semiconductive materials.

Acetylene↗

PubMed2005

Inhibition of carboxylesterases by benzil (diphenylethane-1,2-dione) and heterocyclic analogues is dependent upon the aromaticity of the ring and the flexibility of the dione moiety.

Benzil has been identified as a potent selective inhibitor of carboxylesterases (CEs). Essential components of the molecule required for inhibitory activity include the dione moiety and the benzene rings, and substitution within the rings affords increased selectivity toward CEs from different species. Replacement of the benzene rings with heterocyclic substituents increased the K(i) values for the compounds toward three mammalian CEs when using o-nitrophenyl acetate as a substrate. Logarithmic plots of the K(i) values versus the empirical resonance energy, the heat of union of formation energy, or the aromatic stabilization energy determined from molecular orbital calculations for the ring structures yielded linear relationships that allowed prediction of the efficacy of the diones toward CE inhibition. Using these data, we predicted that 2,2'-naphthil would be an excellent inhibitor of mammalian CEs. This was demonstrated to be correct with a K(i) value of 1 nM being observed for a rabbit liver CE. In addition, molecular simulations of the movement of the ring structures around the dione dihedral indicated that the ability of the compounds to inhibit CEs was due, in part, to rotational constraints enforced by the dione moiety. Overall, these studies identify subdomains within the aromatic ethane-1,2-diones, that are responsible for CE inhibition.

Animals↗

PubMed2005

beta-Acyloxysulfonyl tethers for intramolecular Diels-Alder cycloaddition reactions.

[reaction: see text]. beta-Hydroxy sulfone-based tethers were employed for the first time to achieve thermally mediated intramolecular Diels-Alder cycloaddition. The reactions proceeded with complete regioselectivity and high (10/1) to complete endo/exo-selectivity and resulted in the preferential formation of one of the two possible endo-cycloadducts. The yields and stereoselectivities were proportional to the bulk of the R(1) substituent on the beta-acyloxysulfonyl tether.

Journal Article↗

PubMed2005

Chromatographic separation and identification of products from the reaction of dimethylarsinic acid with hydrogen sulfide.

The reaction of dimethylarsinic acid (DMAV) with hydrogen sulfide (H2S) is of biological significance and may be implicated in the overall toxicity and carcinogenicity of arsenic. The course of the reaction in aqueous phase was monitored, and an initial product, dimethylthioarsinic acid, was observed by using LC-ICP-MS and LC-ESI-MS. Dimethylarsinous acid was observed as a minor product. A second slower-forming product was identified, and the electrospray mass chromatograms for this species produced ions at m/z 275, 171, and 137 in positive mode. To aid in the identification of this slower-forming product, crystalline standards of sodium dimethyldithioarsinate and dimethylarsino dimethyldithioarsinate were prepared and re-characterized by using improved spectroscopic and structural analysis techniques. An aqueous solution of sodium dimethyldithioarsinate produced a single major chromatographic peak that matched the retention time (7.6 min) of the slower-forming product and contained similar molecular ions at m/z 275, 171, and 137 via LC-ESI-MS. The dimethylarsino dimethyldithioarsinate standard produced four aqueous phase species one of which coeluted with the slower forming product. This coeluting peak also produced the identical ESI-MS ions as the slower-forming product of DMAV + H2S. ESI-MS/MS experiments conducted on sodium dimethyldithioarsinate in deuterated water produced molecular ions at m/z 276, 173, and 137. Subsequent collisionally activated dissociation (CAD) experiments on m/z 276 did not produce a product ion at m/z 173. These data indicate that two different species are present in solution, while NMR data indicate that only dimethyldithioarsinic acid exists in aqueous solutions. This discrepancy was investigated by conducting NMR studies on the acidic solution of sodium dimethyldithioarsinate after taking this solution to dryness. The resolubilized solution produced a proton NMR signal characteristic of dimethylarsino dimethyldithioarsinate. Therefore, it was concluded that the ESI-MS ion at m/z 275 associated with the slowly forming second reaction product and the sodium dimethyldithioarsinate compound is a product of the ESI desolvation process.

Cacodylic Acid↗

PubMed2004

Doubled-cubic Ca2NF.

Crystals of dicalcium nitride fluoride, Ca2NF, grown from the melt have been characterized by X-ray diffraction and were found to have a cubic (Fd-3m) structure. Owing to ordering of N and F atoms along all three cell axes, the cell edge is doubled relative to the rocksalt-type structure reported previously. Residual electron density at an interstitial tetrahedral site was refined as a Frenkel defect of F atoms, giving a final composition of Ca2N(F0.913)oct(F0.087)tet.

Journal Article↗

PubMed2004

p-Nitrophenyl isocyanide.

Achiral p-nitrophenyl isocyanide, C(7)H(4)N(2)O(2), crystallizes in the orthorhombic chiral space group P2(1)2(1)2(1). Attractive intermolecular interactions between the nitro O atoms and both aromatic H and nitro N atoms of neighbouring molecules are observed. The O.N interaction is surprisingly strong [N.O = 2.869 (2) A] compared with other aromatic nitro compounds.

Journal Article↗

PubMed2002

Hexaphosphapentaprismane: a new gateway to organophosphorus cage compound chemistry.

Several independent synthetic routes are described leading to the formation of a novel unsaturated tetracyclic phosphorus carbon cage compound tBu4C4P6 (1), which undergoes a light-induced valence isomerization to produce the first hexaphosphapentaprismane cage tBu4C4P6 (2). A second unsaturated isomer tBu4C4P6 (9) of 1 and the bis-[W(CO)5] complex 13 of 1 are stable towards similar isomerization reactions. Another starting material for the synthesis of the hexaphosphapentaprismane cage tBu4C4P6 (2) is the trimeric mercury complex [(tBu4C4P6)Hg]3 (11), which undergoes elimination of mercury to afford the title compound 2. Single-crystal X-ray structural determinations have been carried out on compounds 1, 2, 9, 11, and 13.

Journal Article↗