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[14C]Quincetone was prepared from Ba14CO3 with a radiochemical yield of 21.3%. Ba14CO3, as starting material, was acidified to release 14CO2, which reacted with PhMgBr to [14C]benzoic acid. [14C]Benzoic acid was reduced with LiAlH4 to [14C]benzyl alcohol, and oxidized with CrO3 to [14C]benzaldehyde. In the last reaction, [14C]benzaldehyde was condensed with 3-methyl-2-acetyl-quinoxaline-1,4-dioxide to [14C]quincetone. The specific radioactivity of the labeled product was 7.76 mCi/mmol and its radiochemical purity was >97%. [ABSTRACT FROM AUTHOR]

Abstract In order to study the relationship between biological and pharmacological activities with their structures, a series of tri-, tetra-oxygenated xanthones including 1-hydroxyl-2,3,4,7-tetramethoxy xanthone 1, 1-hydroxyl-2,3,4,5-tetramethoxyl xanthone 2, 1-hydroxyl-3,5-dimethoxy xanthone 3, 1,8-dihydroxyl-3,5-dimethoxyl xanthone 4, 1,5,8-trihydroxyl-3-methoxy xanthone 5 has been isolated from Swertia chirayita. Their structures were established on the basis of spectral and chemical evidence. The crystal structure of 5 was also investigated by single crystal X-ray diffraction analysis. It crystallizes in the triclinic system, space group P $$\bar{1}$$, with a = 7.1540(10) Å, b = 7.520(2) Å, c = 10.671(2) Å, V = 562.7(2) Å3, a = 86.50(3)°, ß = 80.06(3)°, ? = 85.00(3)°, Z = 2, Dc = 1.618 g m-3, Rint = 0.0230, wR(F2) = 0.1028, F(000) = 284. The molecular structure is nearly plane and four substituents are much closer to the plane of the molecule. Compound 5 also shows three intermolecular hydrogen bonds. A recent study shows that phenolic hydroxyls in xanthones are the main active groups capable of scavenging •OH and O2•. [ABSTRACT FROM AUTHOR]

PM3 calculations in vacuum were performed on the inclusion complexation of β-cyclodextrin (β-CD), heptakis-(2-O-methyl)-β-cyclodextrin (2-Me-β-CD) and heptakis-(6-O-methyl)-β-cyclodextrin (6-Me-β-CD) with ibuprofen (IB) enantiomers. Inclusion process pathways are described and the most probable structure of the 1:1 complex are sought through a potential energy scan. The energy differences between the inclusion complexes and the hosts (native and modified CDs) by calculation show that modified CDs have much more interaction sites with IB and enhance van der Waals interaction and hydrophobic interaction between them, form more stable complexes than native CD does. Stabilization energies of S-IB complexes are higher than that of R-IB complexes both for native and modified CDs. [ABSTRACT FROM AUTHOR]

Inclusion reactions of α- and β-CD with Orange II were measured by means of a stopped-flow method and UV-spectra. The forward rate constants (k+), backward rate constants (k-) and the equilibrium constants (K) for the inclusion reactions were determined. The inclusion processes of CD with Orange II follow a one-step reaction mechanism. The value of the forward rate constant at neutral and alkaline conditions for Orange II binding to α-CD cavity was large. This suggests that the naphthalene side is partially included in the final complex form. In the case of β-CD, only marginal difference is shown. It is probable that inclusion covers the whole naphthalene group and part of the azo group as well, resulting in a small effect from the pH variation. The results show that the equilibrium constant at pH 7 for the binding of Orange II to α-CD is the largest because the included part of Orange II matches the cavity of α-CD well. [ABSTRACT FROM AUTHOR]

Enantiodifferentiating photoisomerization of (Z)-cyclooctene included and sensitized by m-methoxybenzoyl-β-cyclodextrin gave chiral (E)-isomers in up to 46% enantiomeric excess, which is the highest value ever reported for supramolecular photochirogenesis with analogous hosts, thus demonstrating the crucial role of the sensitizer-spacer moiety in supramolecular photochirogenic systems. [ABSTRACT FROM AUTHOR]