Electron and Geometry Structure of Hydrogen-Bonded Complexes of Guanine with One Molecule Methanol. A DFT Level Study

The geometries, harmonic vibrational frequencies, and energies of eight hydrogen-bonded complexes of guanine with one molecule methanol are computed using the DFT (B3LYP) method together with the 6-31+G* basis functions. In the investigation two stable tautomers of guanine (oxo-amino N9H and oxo-amino N7H) were chosen. They were included in a variety of H-bonded complexes with one molecule methanol. In order to investigate the nature of the intermolecular bonds, the bonding energies and thermodynamic properties of the complexes were calculated.     

Synthesis of 5,7,11 b,12-tetrahydro-isoindolo[2,1-b]isoquinolinium methiodides and theirStevens rearrangement

The title compounds5 were synthetized in two steps from the corresponding isoindolo[2,1–b]isoquinoline-5(7H)-ones3, obtained in high yields from 3-ethoxy-1H-isoindoles2 and homopthalic anhydrides1. TheStevens rearrangement of5 gave 2-methyl-2,3-dihydro-1H-isoindole-1-spiro-2-indanes6.

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Synthese von 5,7,11 b,12-Tetrahydro-isoindolo[2,1-b]isochinolinium Methiodiden und ihre Stevens-Umlagerung

Zusammenfassung Die Titelverbindungen5 wurden in zwei Stufen aus den entsprechenden Isoindolo[2,1–b]isochinolin-5(7H)-onen (3) dargestellt, die ihrerseits in hohen Ausbeuten aus 3-Ethoxy-1H-isoindolen (2) und Homophthalsäureanhydriden erhältlich sind. DieStevens-Umlagerung von5 führte zu 2-Methyl-2,3-dihydro-1H-isoindol-1-spiro-2-indanen (6).

     

Hypepontine,a new quaternary alkaloid with antimicrobial properties

Abstract

New isoquinoline alkaloid hypepontine (1) together with a five known compounds, were identified in Hypecoum ponticum Velen, the partial synonym of Hypecoum procumbens L. The structure of the new substance was elucidated based on spectroscopic evidence. The tertiary and quaternary alkaloid mixtures as well as the isolated alkaloids were evaluated for their antibacterial and antifungal activity. The result revealed that the crude alkaloid mixture containing quaternary isoquinoline alkaloids showed potent antifungal and antibacterial activity.     

Synthesis of Gossypol Analogues

Two gossypol analogues 2a and 2b were synthesized for biological evaluation as male contraceptive agents. The naphthol 8c was prepared by analogy with a known procedure starling from 3-isopropylcatechol ( 3 ). (t-Bu)₂O₂-Mediated phenolic coupling of 8c furnished the binaphthol 9c which, after pyrane ring closure, deprotection. and selective bisformylation with SnCl₄/Cl₂CHOCH₃, gave the target compound 2a . The corresponding tetrahydroxy analogue 2b was prepared in a similar way.     

Intermediate Jacobians and Chow groups of threefolds with a pencil of del Pezzo surfaces

Summary In this paper we study threefolds with a pencil of del Pezzo surfaces with 1K²5. The curve which parametrises the exceptional curves on the fibers and the incidence correspondence on it determine a Prym-Tjurin variety which is an abelian subvariety of the Jacobian of the curve. Under certain restrictions on the singular fibers of the pencil we prove that there is a polarized isomorphism between the intermediate Jacobian of the threefold and the Prym-Tjurin variety and an isomorphism between the latter and the Chow group of algebraic one-cycles algebraically equivalent to zero.     

Le chlorure de triphényltétrazolium en tant que réactif en chimie analytique — V

Résumé On a élaboré une méthode de dosage de petites quantités de cobalt. La méthode repose sur l'action mutuelle des ions complexes thiocyanate de cobalt-chlorure de triphényltétrazolium. On extrait le composé obtenu par le chloroforme. La solution est d'un bleu intense et présente un maximum d'absorption pour la longueur d'onde =620 nm.On masque les ions secondaires par le thiosulfate de sodium et le fluorure d'ammonium.L'erreur relative moyenne s'élève à 1,88%.La méthode de dosage du cobalt par le chlorure de triphényltétrazolium est spécifique, rapide et facile à exécuter. Elle n'exige pas la séparation des ions secondaires dans le cas de nombreux matériaux.

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Summary A method has been developed for the determination of small amounts of cobalt. The method is based on the mutual action of the complex thiocyanate ions of cobalt and the chloride of triphenyltetrazolium. The resulting compound is extracted with chloroform. The solution has an intense blue color and shows an absorption maximum for the wave length =620 nm. The secondary ions are masked by sodium thiosulfate and ammonium fluoride. The mean relative error may reach 1.88%. The method of determining cobalt by means of the triphenyltetrazolium is specific, rapid and easily conducted. It does not require the removal of the secondary ions in the case of numerous materials.

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Zusammenfassung Eine Methode zur Bestimmung kleiner Mengen Kobalt wurde ausgearbeitet. Sie beruht auf der Reaktion zwischen Kobaltrhodankomplex und Triphenyltetrazoliumchlorid. Das Reaktionsprodukt wird mit Chloroform extrahiert. Der Extrakt ist intensiv blau gefärbt und hat ein Absorptions-maximum bei 620 nm. Fremdionen werden mit Thiosulfat und mit Ammonium-fluorid maskiert. Der mittlere Fehler beträgt 1,88%. Das Verfahren ist spezifisch, rasch und einfach. In den meisten Fällen ist keine Abtrennung der Fremdionen nötig.

     

Hydrogen Bonded Complexes of Acetylacetone and Methanol: HF and DFT level Study

Summary. Several possible hydrogen-bonded complexes between the tautomeric forms of acetylacetone and methanol were studied by ab initio methods using 6-311G** and D95** basis functions at the HF and DFT (B3LYP) levels of theory. The calculations were carried out for isolated molecules and solvent assisted complexes by means of the isodensity polarized model (IPCM). The theoretical frequencies were compared with the experimental IR spectrum of an equimolar mixture of acetylacetone and methanol. It was proved that the most stable H-bonded complex acetylacetone–methanol is formed between O-bonded methanol- and the enol molecule.     

2-substituted 2,3-dihydro-5H-thiazolo[2,3-b]quinazoline derivatives

The synthesis of a series of 2-substituted 2,3-dihydro-5H-thiazolo[2,3-b]quinazoline derivatives is described. Some of the title compounds exerted antiinflammatory and immunomodulating activities in laboratory animal models.     

Ab initio Study of the Keto-Enol Equilibriumof Malonaldehyde

Summary.  The mechanism of the keto-enol tautomerism of malonaldehyde was studied by ab initio methods using 6-21G^** and 6-311G^** basis functions at the HF level. Two separate mechanisms were examined: through-space proton transfer in the ω-shaped form and through-space proton transfer in a sickle-shaped form obtained from the ω form by rotation. The transition state structure of the ω form is non-planar, whereas that of the sickle form is planar. The sickle form is connected with a 2^nd order saddle, indicating that there should exist a lower energy barrier, i.e. that the through-bond mechanism may be preferred. The calculated energy barriers of keto-enol tautomerism for the sickle form is twice as high as those for the omega form. Received January 18, 1999. Accepted (revised) August 4, 1999     

Excited‐state deactivation channels via internal conversions in two position isomers of hydroxy‐methyl‐pyridine: a theoretical study

Two position isomers of hydroxy‐methyl‐pyridine (3‐hydroxy‐2‐methyl‐pyridine and 2‐hydroxy‐3‐methyl‐pyridine) were studied theoretically at the BLYP level of theory in order to find mechanisms explaining the excited‐state deactivations of isomers through ring puckering and “ethylene‐like” conical intersections. The study aims also to clarify the mechanisms of the ground‐state proton transfers. Three conical intersections S₀/S₁ for each isomer were found, which are accessible through the ¹ππ* excited states. In both isomers, there is a ¹ππ* excited‐state reaction path, which leads, in a completely barrierless manner, to the one of the conical intersections S₀/S₁. Copyright © 2015 John Wiley & Sons, Ltd.