6-Pyruvoyl tetrahydropterin synthase assay in extracts of cultured human cells using high-performance liquid chromatography with fluorescence detection of biopterin.

An assay for 6-pyruvoyl tetrahydropterin synthase, the second enzyme in the conversion of guanosine triphosphate into tetrahydrobiopterin, has been developed. Cell extracts were incubated with enzymatically prepared dihydroneopterin triphosphate (80 microM) in the presence of Mg2+ (12 mM), excess sepiapterin reductase (EC 1.1.1.153) (2 nmol/min) and NADPH (2 mM). 6-Pyruvoyl tetrahydropterin, the product of the reaction, was thus converted into tetrahydrobiopterin. After oxidation of the reduced biopterin derivatives in acidic iodine solution, biopterin was enriched and separated from the abundant neopterin phosphates by solid-phase extraction on a strong cation exchanger. Biopterin was then directly eluted on a reversed-phase liquid chromatographic column and detected fluorimetrically using excitation at 353 nm and emission at 438 nm. The biopterin concentrations formed by the coupled enzyme reaction increased linearly with incubation times up to 90 min. The assay allows the quantification of 6-pyruvoyl tetrahydropterin synthase in cultured human cells.     

Bis(dimethylmetall(III)glyoximato)metallate(II) (metall(III) = Al,Ga, In,metall(II) = Ni,Pd, Pt,Cu)

When the trimethyl derivatives of aluminium, gallium and indium react with glyoximato metallates, (R₂C₂N₂(O)OH)₂Met^II (R = H, CH₃; Met^II = Ni, Pd, Pt, Cu), in a $\text{2}\text{1}$ molar ratio, 2 mol of methane are evolved and monomeric bis(dimethylmetal(III)glyoximato)metallates(II) (metal(III) = Al, Ga, In) are formed in high yields. The vibrational and NMR spectra of the new complexes were measured and were partly resolved. The X-ray structure determinations of two of these compounds show non-planar structures of approximate C_2h and C₂ symmetry, respectively, with weak metal(III)?metal(II) π-interactions.     

β-Lactam Derivatives as Enzyme Inhibitors: Peptidic Derivatives of ( RS )-2-Oxo-4-phenylazetidine-1-alkanoic Acids

4-Phenylazetidine-2-one was transformed into 4-phenylazetidine-1-alkanoic acids, which were reacted in the presence of diphenylphosphoroazidate with amino acid esters and dipeptide esters yielding β-lactam peptides with different spacers between the lactam ring and the peptide moiety. All structures were established by elementary analyses, HPLC, optical rotation, and spectroscopic data and all new compounds were tested as inhibitors of PPE using standard procedures. Four compounds exhibited a weak activity compared with the standard inhibitor trifluoroacetyl-l-val-l-tyr-l-val.     

Synthesis of (-)-2s,3s, 11s,12r-2,3,11,12-tetraphenyl[18]crown-6

The synthesis of ( - ) 2S,3S,11S,12R-2, 3,11,12-tetraphenyl [18]-crown-6 from (-)-1S,2S-hydrobenzoin and meso-hydrobenzoin is described. Chemical shifts and vicinal coupling constants of the benzylic protons in the 2 S, 3 S and 11 S,12 R substructures in the free ligands and in complexes with KSCN and 1-phenylethylammonium bromides and a brief discussion of the related conformational changes are also presented. A detailed procedure for the resolution of racemic hydrobenzoin is given.     

Dialkylindiumacetate R2InOOCCH3 (R = CH3, C2H5) Darstellung,Eigenschaften und Struktur

Dialkylindium Acetates R₂InOOCCH₃ (R = CH₃, C₂H₅). Preparation, Properties, and Structure. Dimethyl- and diethylindium acetate were prepared and the vibrational spectra (IR and RAMAN ) discussed. The X-ray structure determination shows that diethylindium acetate belongs to the orthorhombic space group Pnma. The unit cell with lattice constants a = 8.40, b = 7.41, c = 15.13 Å contains four molecules. Each indium atom forms with an acetate group a planar four-membered ring. The indium-oxygen distance within such a ring is only a little shorter than the distance of this oxygen to the indium of the next neighboured ring. Indium has therefore the coordination number six.     

Diastereoselective cascade synthesis of azabicyclo[3.1.0]hexanes from acyclic precursors

The diastereoselective synthesis of azabicyclo[3.1.0]hexanes bearing different substituents on all positions of the cyclopropane ring has been achieved in moderate to good yields.     

Zwei neue Alkylimido-methylgallane mit Käfigstruktur

Two New Alkylimido-Methylgallanes with Cage Structure The tetrameric alkylimido-methylgallanes (MeGa? NR)₄ (R = CH(CH₃)₂ ( ⁱPr), C(CH₃)₃ ( ^tBu) and Me = CH₃) have been prepared by pyrolyses of the dimeric amido compounds (Me₂Ga? N(H)R)₂ at 250–260°C. The mass, NMR and vibrational spectra are discussed, they prove almost identical structures of the skeletons. The X-Ray structure determination of (MeGa? N^tBu)₄ shows four heterocubane molecules in the trigonal unit cell (space group P3 c1, a = b = 1061.7(1), c = 3191.8(5) pm) and two disordered benzene solvate molecules. The Ga? N bonds range between 198.4 to 199.9 pm, the Ga? N? Ga and N? Ga? N bond angles lie between 90.6 to 91.4 and 88.6 to 89.2°, respectively. The structure was refined to an R₁(R₂)-value of 0.049 (0.057).     

Total synthesis of the ramoplanin A2 and ramoplanose aglycon

A convergent total synthesis of the ramoplanin A2 and ramoplanose aglycon is disclosed. Three key subunits composed of residues 3-9 (heptapeptide 15), pentadepsipeptide 26, and pentapeptide 34 (residues 10-14) were prepared, sequentially coupled, and cyclized to provide the 49-membered depsipeptide core of the aglycon. Key to the preparation of the pentadepsipeptide 26 incorporating the backbone ester was the asymmetric synthesis of an orthogonally protected L-threo-beta-hydroxyasparagine and the development of effective and near-racemization free conditions for esterification of its hindered alcohol (EDCI, DMAP, 0 degrees C). The coupling sites were chosen to maximize the convergency of the synthesis including that of the three subunits, to prevent late stage racemization of carboxylate-activated phenylglycine-derived residues, and to enlist beta-sheet preorganization of an acyclic macrocyclization substrate for 49-membered ring closure. As such, macrocyclization at the chosen Phe(9)-D-Orn(10) site may benefit from both beta-sheet preorganization as well as closure at a D-amine terminus. Deliberate late stage incorporation of the subunit bearing the labile depsipeptide ester and a final stage Asn(1) side chain introduction provides future access to analogues of the aglycons which themselves are reported to be equally potent or more potent than the natural products in antimicrobial assays.     

Synthese der Stannatetraphospholane (tBuP)4SnR2 (R = tBu,nBu, C6H5) und (tBuP)4Sn(Cl)nBu Molekül- und Kristallstruktur von (tBuP)4Sn(tBu)2

Synthesis of the Stannatetraphospholanes (tBuP)₄SnR₂ (R = tBu, nBu, C₆H₅) and (tBuP)₄Sn(Cl)nBu Molecular and Crystal Structure of (tBuP)₄Sn(tBu)₂ The reaction of the diphosphide K₂[tBuP-(tBuP)₂-PtBu] 4 with the halogenostannanes (tBu)₂SnCl₂, (nBu)₂SnCl₂, (C₆H₅)₂SnCl₂ or nBuSnCl₃ in a molar ratio of 1 : 1 leads via a [4 + 1]-cyclocondensation reaction to the stannatetraphospholanes (tBuP)₄SnR₂ 3 b–3 d and (tBuP)₄Sn(Cl)nBu 3 e , respectively, with the binary 5-membered P₄Sn ring system. 3 b was characterized by a single crystal structure analysis; the 5-membered ring exists in a planar conformation. The compounds 3 b–3 e were identified by NMR and also by mass spectroscopy; the ³¹P{¹H}-NMR spectra of 3 b–3 d showed an AA′MM′ (AA′MM′X), 3 e on the other hand an ABCD (ABCDX) spin system.     

Numerische Ermittlung quasikonformer Abbildungen mit finiten Elementen

Summary In this note we consider so called p-analytic mappings of simply or doubly connected domains on rectangles or circular rings. Real and imaginary parts of the mappings can be described by minimal-principles. By minimizing the corresponding functionals in a class of linear or bilinear finite elements we obtain an approximation of the mapping and also upper and lower bounds for the p-module of a domain with polygonal boundary. Error bounds are given for smooth and for piecewise constant functionsp. We present numerical experiments.