Conformational Study of Naringenin in the Isolated and Solvated States by Semiempirical and Ab Initio Methods

Naringenin is a natural widespread flavanone occurring in different foodstuffs that presents several important biological activities. Although its properties are well documented, its mechanisms of action are still controversial. The present article reports a conformational analysis of naringenin, using the semiempirical AM1 and ab initio methods, at the Hartree–Fock level of theory. The 3-21G, 3-21G*, 6-31G, and 6-31G** basis sets were used. The electron correlation effects were included through the Møller–Plesset second-order perturbation theory. The solvation of naringenin has been investigated through the standard SCRF, the supermolecule (SM), and the combined SM/SCRF models. The results have shown that there are two degenerate forms of naringenin, differing mainly by the orientation of a hydroxyl group (C4—OH). The energy barrier for the interconversion between them is ca. 6 kcal.mol^–1, suggesting some conjugation between the -system of the aromatic B ring and the hydroxyl group (C4—OH).     

Isolierung von 10′-Apo-β-carotin-10′-ol und (3R)-10′-Apo-β-carotin-3,10′-diol (Galloxanthin) aus Rosenblüten. 5. Mitteilung über Rosenfarbstoffe

Isolation of 10′-Apo-β-carotene-10′-ol and (3R)-10′-Apo-β-carotene-3,10′-diol (Galloxanthin) from Rose Flowers The novel (all-E)-10′-apol-β-carotene-10′-ol ( 2 ) and (all-E,3R)-10′-apo-β-carotene-3,10′-diol ( 5 ) have been isolated from petals of one yellow species and various whitish or yellow blend varieties of rose cultivars. Each (all-E)-compound is accompanied by a (Z)-isomer, probably the (9Z)-isomer. Diol 5 proved to be identical with galloxanthin, an apo-10′-carotenol previously isolated from the retina of chicken.     

Coleone C,D, I,I′ aus einer madegassischen Plectranthus sp. nov. Interkonversion von cis- und trans-A/B-6,7-Diketoditerpenen

Coleons C, D, I, I′, obtained from a Madagascan Plectranthus sp. nov.. Interconversion of cis- and trans-A/B-6,7-Diketoditerpenes. Fairly large amounts of Coleons C and D, as well as Coleons I and I′ (3-O-formyl derivative of Coleon I) can bc isolated from the orange glands of an unclassified North Madagascan Plectranthus sp. A reversible transformation of cis- and trans-A/B-6,7-dioxo-abietane via its diosphenol has been achieved for the first time. CD.-Spectra of these compounds are presented. Hydrogenolysis of Coleon D leads to 6β,16-dihydroxy-royleanone.     

Analysis of chlorine and other halogens by activation with photons and neutrons

The analysis of halogens in various matrices is described. Activation analysis with mainly high energy bremsstrahlung (PAA) and pile neutrons (NAA) was applied. In the case of chlorine, fast procedures were worked out requiring not more than 100 min for one determination. The particular problems of fluorine analysis are discussed. The described techniques were applied for the following cases: Determination of total chlorine resp. bromine in oil samples; determination of chlorine in wood, glasses and TiN powders; determination of iodine in ZnSe single crystals using instrumental photoactivation.The limits of detection are: (interference-free in μg/g) F: 0.03/–; Cl: 0.1/0.05; Br: 0.04/0.003 and I: 0.1/0.01 using PAA/NAA. Activation analysis, being independent upon the chemical status of the analyte and usually less affected by blank problems has been found to be a useful complement to conventional chemical analysis. Received: 28 February 199 / Revised: 14 April 1998 / Accepted: 18 April 1998     

Pheromone, 3.Mitt.: Eine einfache Methode zur Steuerung der Reduktion von α-Alkoxy-carbonylverbindungen

Summary Enantiomerically pure 1,2-diols bearing optionallysyn oranti configurated secondary hydroxylic groups are synthesized from acetal-protected cyanohydrins. After resolution of the diastereomers the cyanohydrins are converted into -alkoxy-ketones by Grignard-reaction followed by reduction using common chelating or non-chelating agents. Among others syntheses of enantiomerically pure pheromones,endo-Brevicomin,exo-Brevicomin and Dispalure are given as examples.

Prof. Dr. Hans Berbalk zum 70. Geburtstag gewidmet     

Signatures andS-discrete lattice-ordered groups

The central theme of this article is the approximation of lattice-ordered groups (l-groups) first by Specker groups and, subsequently, by the so-calledS-discretel-groups. The sense of these approximations is made precise via the notion of a signature, defined below, and by that ofa ^*-subgroups. Sample result: ifG is a projectablel-group then it has anl-subgroupH which is Specker and for which the mapPPH defines a boolean isomorphism between the algebras of polars ofG andH.Presented by L. Fuchs.This article was written while this author was a Stouffer Visiting Professor at the University of Kansas. He wishes to thank the members of the Mathematics Department of that institution for their hospitality.     

Isolation and Absolute Configuration of β,β-Carotene Diepoxide

The 5,6:5′,6′-diepoxy-5,6:5′,6;-tetrahydro-β,β-carotene, isolated from tubers of a white-fleshed variety of sweet potato (Ipomoea batatas LAM .) has been assigned the (5R,6S,5′R,6′S)-chirality on the basis of its HPLC, UV/VIS, and CD data.