Isolation and identification of three urinary metabolites of retinoic acid in the rat.

After the intraperitoneal administration of high doses of ¹⁴C- and ³H-labelled retinoic acid ( 1 ) to rats three major urinary metabolites have been isolated in microgram amounts by use of column, thin-layer and high-pressure liquid chromatography. Their structures were elucidated by mass spectroscopy and Fourier transform ¹H-NMR. spectroscopy as 2 (5-methyl-5-[2-(2,6,6-trimethyl-3-oxo-1-cyclohexen-1-yl)vinyl]-2-tetrahydrofuranone), 3 (5-[2-(6-hydroxymethyl-2,6-dimethyl-3-oxo-1-cyclohexen-1-yl)vinyl]-5-methyl-2-tetrahydrofuranone) and 4 (6-(6-hydroxymethyl-2,6-dimethyl-3-oxo-1-cyclohexen-1-yl)-4-methyl-4-hexenoic acid). In these metabolites the tetraene side chain of 1 is shortened and the cyclohexene ring oxidized. The radioactivity of 2 and 3 accounted for about 10% (0.9% of the dose) each, metabolite 4 for about 6% (0.5% of the dose) of the total urinary radioactivity.     

Ammonothermal Synthesis,X-Ray and Time-of-Flight Neutron Crystal-Structure Determination,and Vibrational Properties of Barium Guanidinate,Ba(CN3H4)2

We report the crystal structure of Ba(CN₃H₄)₂ as synthesized from liquid ammonia. Structure solution based on X-ray diffraction data suffers from a severe pseudo-tetragonal problem due to extreme scattering contrast, so the true monoclinic symmetry is detectable only from neutron powder diffraction patterns, and structure solution and refinement was greatly aided by density-functional theory. The symmetry lowering is due to slight deviations of the guanidinate anion from the mirror plane in space group P b2, a necessity of hydrogen bonding. At 300 K, barium guanidinate crystallizes in P2₁/c with a=6.26439(2) Å, b=16.58527(5) Å, c=6.25960(2) Å, and a monoclinic angle of β=90.000(1)°. To improve the data-to-parameter ratio, anisotropic displacement parameters from first-principles theory were incorporated in the neutron refinement. Given the correct structural model, the positional parameters of the heavy atoms were also refinable from X-ray diffraction of a twinned crystal. The two independent guanidinate anions adopt the all-trans- and the anti-shape. The Ba cation is coordinated by eight imino nitrogens in a square antiprism with Ba−N contacts between 2.81 and 3.04 Å. The IR and Raman spectra of barium guanidinate were compared with DFT-calculated phonon spectra to identify the vibrational modes.     

Gamma-ray production cross section from energetic neutron inelastic scattering for methodical improvements in planetary gamma-ray spectroscopy

Planetary gamma-ray spectroscopy can be used to chemically analyze the top soil from planets in future planetary missions. The production from inelastic neutron interaction plays an effective role in the determination on the C and H at the surface. The gamma-ray production cross section from the strongest lines excited in the neutron bombardment of Fe have been measured by the use of a time analyzed quasi-mono-energetic neutron beam and a high purity germanium detector. The results from En=6.5, 32, 43, and 65 MeV are presented.     

Citrus-Carotinoide. 1. Mitteilung. Synthese von Apocarotinoiden mit einer anders gelagerten Methylgruppe; Strukturaufklärung von Citrus-Carotinoiden

Synthesis of Apocarotenoides with a Shifted Methyl Group; Structure Elucidation of Citrus-Carotenoides With regard to the investigation of the biosynthesis of the C₃₀-carotenoids in citrus fruits apocarotenoids with a methyl group shifted by one position (diapocarotenoids) were synthesized. Characteristical differences, especially in the 270-MHz-¹H-NMR. spectra between the apo- and the diapocarotenoids are reported. The comparison of the natural pigments with the synthetic compounds proves that the natural products belong to the apocarotenoids as has been postulated earlier.     

Mapping of neutron flux gradient at NIST reactor to optimize neutron activation analysis of53Mn

Determination of⁵³Mn in meteorites by neutron activation analysis requires a thermal neutron flux high enough to ensure adequate production of⁵⁴Mn from⁵³Mn with a sufficiently low fast neutron component to minimize its production through fast neutron reactions. Thermal and fast neutron fluxes were mapped as a function of sample position within the NIST research reactor in order to determine the optimum position for irradiation of⁵³Mn.     

Tuning the Photophysical Properties and Solid‐State Organization of Perfluorophenyl‐functionalized Dithieno[3,2‐b:2′,3′‐d]phospholes

A series of perfluorophenyl‐substituted dithienophosphole derivates has been synthesized. Investigation of their photophysical properties, as well as their organization in the solid state reveals that these properties can be manipulated via introduction of bromine substituents in 2,6‐position of the dithienphosphole scaffold, as well as the complexation of the phosphorus center with an electron rich gold(I) fragment. The strongly electron‐withdrawing character of the perfluorophenyl‐group surmounts the effect of the oxidation of the phosphorus center with respect to photophysics, leading to leading to optoelectronic features similar to those of the trivalent phosphole species. The trivalent phosphole species. The solid‐state organization of the members of this perfluorinated dithienophosphole family, on the other hand, strongly depends on the heteroatoms present within the system, as close intermolecular interactions can be observed between varieties of different atoms (Au‐Au, Br‐Br, Br‐O, Br‐C, F‐C, O‐S), next to regular C‐C π‐stacking interactions.     

Synthesis of chromium(0) and molybdenum(0) bis (eta(6)-arene) derivatives and their monoelectronic oxidation to [M(eta(6)-arene)(2)](+) cations

M(eta(6)-arene)(2) species (M = Cr, arene = 1,3,5-Me(3)C(6)H(3); M = Mo, arene = 1,3,5-Me(3)C(6)H(3), 1,3,5-(i)Pr(3)C(6)H(3)), have been prepared by a modified Fischer-Hafner synthesis or by metal vapour techniques. The reaction of Cr(eta(6)-1,3,5-Me(3)C(6)H(3))(2) with the fulvene derivatives pentacarbomethoxycyclopentadiene (pcmcpH), 1-benzoyl-6-hydroxy-6-phenylfulvene (dbcpH), or 1-benzoyl-3-nitro-6-hydroxy-6-phenylfulvene (dbncpH) proceeds with evolution of dihydrogen and formation of the ionic derivatives [Cr(eta(6)-1,3,5-Me(3)C(6)H(3))(2)][E], where E = pcmcp, dbcp, or dbncp. Mo(eta(6)-arene)(2) derivatives (arene = toluene, 1,3,5-Me(3)C(6)H(3), 1,3,5-(i)Pr(3)C(6)H(3)) are oxidized to [Mo(eta(6)-arene)(2)](+) by pcmcpH. The crystal and molecular structures of [M(eta(6)-1,3,5-R(3)C(6)H(3))(2)][pcmcp] (M = Cr, R = Me; M = Mo, R = Me, (i)Pr) have been solved by X-ray single crystal diffraction.