Phosphoramidites of Chiral (Rp)-and (Sp)-Configurated d(T[P-18O]-A): Synthesis,Configurational Assignment,and Use as Dimer Blocks in Oligonucleotide Synthesis

The N,N-diisopropylphosphoramidites 10a and 10b of appropriately protected chiral diastereoisomers of d(T[P-¹⁸O]-A) ( 8a and 8b , resp.), chiral by virtue of the isotope ¹⁸O at the P-atom, have been synthesized. The ¹⁸O-isotope was incorporated by oxidation of the phosphite triester 3 with H₂[¹⁸O]/I₂. Separation of the diastereoisomers was accomplished by flash chromatography of the O-3′-deprotected phosphate triesters 5a/b . The absolute configuration at the chiral P-atom was deduced from the methylation products of the fully deprotected diastereoisomers 8a and 8b . Phosphinylation of 5a and 5b yielded the configurationally pure phosphoramidites 10a and 10b , respectively, which were then employed in solid-phase synthesis to yield the self-complementary oligomers d(G-A-G-T-(R_p)-[P-¹⁸O]-A-C-T-C) ( 13 ) and d(G-A-G-T-(S_P)-[P-¹⁸O]-A-C-T-C) ( 14 ), respectively.     

MS-Express: data-extracting and -processing software for high-throughput experimentation with mass spectrometry

High-throughput experiments (HTE) result in large amounts of raw data that have to be evaluated for sample classification. Especially mass spectrometry, a widely used detection method in catalytic HTE applications, produces enormous amounts of data. In the past few years, in catalysts research, several test rigs based on mass spectrometric detection have been independently reported by different groups. In a typical HTE, the catalysts are tested sequentially; the recording of the scans, however, occurs continuously. For this reason, the scans of interest have to be extracted from the raw data, and scans belonging to the same sample have to be averaged in a tedious procedure before further processing. In this publication, we present our custom-designed software MS-Express (mass spectrometry data-extracting and -processing software), an efficient tool for HTE MS data evaluation. MS-Express not only sorts the data, it also establishes statistical significance with the help of reference and blank data and provides concise information about abundance and intensity distributions of expected peaks. A special feature is that the program also reports unexpected MS signals, which potentially lead to unexpected discoveries.     

Schwefeldioxid als Ligand und Synthon. XIII. Reaktionen von Isocyanid-tris(triphenylphosphan)nickel(0)-Komplexen mit Schwefeldioxid und N-p-Tolylsulfinylamin

Sulfur Dioxide as Ligand and Synthon. XIII. Reactions of Isocyanide-tris(triphenylphosphane)nickel(0) Complexes with Sulfur Dioxide and N-p-tolylsulfinylamine Reactions of the isocyanide-tris(triphenylphosphane)-nickel(0) complexes [(RNC)Ni(PPh₃)₃] (R = ^tBu, Cy, PhCH₂, p-TosCH₂) with SO₂ and p-TolNSO are described. The sulfur dioxide and N-p-tolylsulfinylamine complexes obtained by PPh₃ ligand substitution have been characterized by means of i.r. and ³¹P n.m.r. spectra. The X-ray crystal structure of [(Ph₃P)₂(CyNC)Ni(SO₂)] · 0.5 PhMe and (Ph₃P)(^tBuNC)Ni(η²-p-TolNSO) have been determined.     

Bis(diphenylphosphano)alkan- und 1-(Diphenylphosphano)-2-(2-pyridino)ethan-N-Arylsulfinylamin-Nickel(0)-Komplexe

Bis(diphenylphosphano)alkane- and 1-Diphenylphosphano-2-(2-pyridino)ethane-N-arylsulfinylamine Nickel(0) Complexes Synthesis and properties of the bis(diphenylphosphano)alkane-N-phenyl-sulfinylamine-nickel(0) complexes [Ni{Ph₂P(CH₂)_nPPh₂}(PhNSO)] (n = 2 dppe, n = 3 dppp, n = 4 dppb) as well as of the 1-(diphenylphosphano)-2-(2-pyridino)ethane nickel(0) complexes [Ni(dpppe)₂], [Ni(dpppe)(p-TolNSO)] and [Ni(dpppe)(PPh₃)₂] are described. These compounds have been characterized by i. r. and ³¹P n.m.r. spectroscopy. The N-arylsulfinylamine ligands are η²-(N, S)-side on coordinated.     

Biosynthesis of anthecotuloide,an irregular sesquiterpene lactone from Anthemis cotula L. (Asteraceae) via a non-farnesyl diphosphate route

Retrobiosynthetic analysis of the allergenic sesquiterpene lactone, anthecotuloide, suggested that this natural product could be formed either by head to head condensation of geranyl diphosphate with dimethylallyl diphosphate, or from farnesyl diphosphate (FPP), the accepted regular sesquiterpene precursor via the rearrangement of a germacranolide precursor. Isotopic labelling of anthecotuloide has now been achieved by feeding [1-(13)C]-glucose, [U-13C6]-glucose and [6,6-(2)H2]-glucose to aseptically grown plantlets of Anthemis cotula(family Asteraceae). Analysis of labelling patterns and absolute 13C abundances using quantitative 13C NMR spectroscopy showed that the isoprene building blocks of this sesquiterpene are formed exclusively via the MEP terpene biosynthetic pathway. This was supported by results from an experiment using [U-13C6]-glucose. A deuterium labelling experiment using [6,6-(2)H2]-glucose supported the original proposal and showed that anthecotuloide is formed from a non FPP precursor. Isotope ratio mass spectrometry suggested that there were two pathways for sesquiterpene biosynthesis in A. cotula.     

Stereoisomeric flavor compounds,part LVIII: The use of heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin as a chiral stationary phase in flavor analysis

The characteristics of the new chiral stationary phase heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin are outlined and compared with permethyl- and perethyl-β-cyclodextrins.     

Synthesis and characterization of a magnetic semiconductor Na(2)RuO(4) containing one-dimensional chains of Ru(6+)

A new ternary ruthenium oxide Na(2)RuO(4) was prepared and shown to crystallize with a new structure type. Single crystal X-ray diffraction measurements reveal that Na(2)RuO(4) consists of RuO(4) chains made up of RuO(5) trigonal bipyramids by sharing axial corners. Na(2)RuO(4) is a magnetic semiconductor with a variable range hopping behavior, and its molar magnetic susceptibility chi(mol) has a broad maximum at approximately 74 K. The derivative d(chi(mol).T)/dT exhibits a peak at 37.7 K which has been confirmed by heat capacity measurement to be due to long-range antiferromagnetic ordering.