Showing papers in "Tetrahedron in 1970"

TL;DR: In this paper, the 2 S configuration and 3-hydroxy-flavanones of 2 R, 3 R configuration, having equatorial 2-aryl substituents in the former or diequatorial 2,3-substituents of the latter, exhibit a positive Cotton effect due to the n → π * transition (∼ 330 nm) and a negative Cotton effect in the n α π ∆ * region(∼ 280-290 nm).

TL;DR: In this article, a mecanisme aprotique 1-3 dipolaire de la formation d'epoxyde is proposed, which is based on the reaction of the olefiniques.

TL;DR: Glyoxal reacts with primary aliphatic amines such as cyclohexylamine, n-butylamine (n-b), cyclohexhexyl-cyclohexyl-(n)-b) amines to give conjugated diimines whose conformations are shown to be E − E.

TL;DR: Five N-nitroso derivatives of the amino acids sarcosine, azetidine-2-carboxylic acid, proline, hydroxyproline and pipecolic acid have been prepared and characterized and it is shown that four of these nitrosamino acids preferentially crystallize in a conformation in which the C atom bearing the carboxyl group is syn to the nitroso O atom.

TL;DR: Studies are described which have led to the structure and absolute configuration of secalonic acid D as shown in Ia.

TL;DR: In this article, ein geschlossenes, sehr allgemein anwendbares and vergleichsweise einfaches and berschaubares Nomenklatursystem fur alle Phane wird entwickelt.

TL;DR: In this paper, the CD curves of a large number of sesquiterpene lactones together with a limited number of ORD curves have been measured and a simple correlation between the sign of the Cotton effect (CE) and the stereochemistry of the α-methylene-γ-lactone chromophore can be deduced from the resulting data.

TL;DR: In this article, the authors have shown that α-15-(2-furyl)-1,2,4-triazol-3-ylthiol acethydrazide has significant activity against Myco tuberculosis.

TL;DR: In this paper, the structure of trimethylsilyl derivatives of aldonic and deoxyaldonic acids is investigated using mass spectrometric methods, and the most prominent fragmentations are α-cleavages of the carbon chain, frequently followed by rearrangement loss of the trimethylsilanol.

TL;DR: Withania somnifera Dun (Solanaceae) growing in the southern coastal plane of Israel constitutes a new chemotype and is designated as chemotype III as mentioned in this paper, and the following structures have been assigned to seven of the above compounds: Withanolide G, 20α,27dihydroxy-1-oxo-20R,22R-witha-2,5,8(14),24-tetraenolide (2,2,14)

TL;DR: A new sesquiterpenoid containing bromine and its debromo analog, laurinterol (I) and debromolaurinterols (II), as well as an isomeric bromo compound, isolaurinteroll (III), have been isolated from Laurencia intermedia Yamada (Rhodomelaceae) and their structures determined as mentioned in this paper.

TL;DR: A new common method of synthesis of 3′(2′)-O-aminoacyl esters of nucleoside-5′-mono-and triphosphates with subsequent removal of the N-protecting group from the amino acid part is elaborated.

TL;DR: The structure of a new antibiotic, aquayamycin, has been established as derivative of benze[ a ]-anthracene by spectroscopic and degradative experiments.

TL;DR: In this article, photosensitized oxygenation of 3-hydroxyflavones was investigated in the presence of rose, bengal, gave corresponding depsides 2a, 2b, and 2c, carbon monoxide, and carbon dioxide.

TL;DR: In this paper, the first step in gas-phase pyrolysis is azide-tautomerization with subsequent nitrene formation, and the electron donating groups in positions 5 and 7 stabilize the azido-form (VI-VII), while in position 8 they favour the tetrazole form (III-IX).

TL;DR: In this article, the rate constants for attack of various ketones from the axial and from the equatorial side were computed by reducing the ketones in pairs and analyzing the alcohol mixtures thus obtained.

TL;DR: In this article, a general carbonyl olefination scheme taking into account the majority of known reactions of this kind is proposed, and a stable solution of methylene magnesium halide which easily olefinates aldehydes and ketones affording the corresponding methylenic ole fins in good yields.

TL;DR: In this article, it was shown that if more than one cyclization is possible the photoconversion follows the pathway for which ΣF* is maximal; if ΔΣF*) for various cyclizations is smaller than 0·1, a second product is sometimes formed.

TL;DR: In this article, a quantitative description of the conformation of seven substituted cyclohexanes in terms of bond distances, bond angles and torsional angles is given, and the geometrical details of the molecules from X-ray structure determinations are compared with those obtained by computer calculations.

TL;DR: In this article, optically active stationary phases for the separation of α-amino acid enantiomers were presented, which are derivatives of the di- and the tripeptide of l -valine.

TL;DR: In this paper, the authors derived the magnetic anisotropy screening and the electric field screening effect of the CO group in a complete series of monoketo-androstanes, including the values of the anisotropies of the CO double bond and of K, a parameter descriptive of the electric screening effect.

TL;DR: In this paper, it was shown that the sign of the Cotton effect of the principal (πx → πx*) transition of chiral olefins near 200 nm predicts the absolute configuration of the molecule through the olefin octant rule.

TL;DR: In this paper, the relative configuration of optically active dimethyl methylenecyclopropane- trans -2,3-dicarboxylate and its two products of thermal rearrangement, methyl syn - and anti -2-carbomethoxycyclopropylideneacetate, has been established.

TL;DR: A qualitative study of the influence of the reaction medium on pyrrole oxidation with hydrogen peroxide is reported in this paper, where a simple oxidation product was obtained of which the isolation, structure, and some aspects of the chemical reactivity are reported.

TL;DR: Laureatin and isolaureatin, new bromo compounds isolated from Laurencia nipponica Yamada, were shown to possess structures I and II, respectively as mentioned in this paper.

TL;DR: The present series of reactions affords a convenient and novel method for the synthesis of purine cyclonucleoside through sulfonylation using sodium hydride and triisopropyl-benzenesulfonyl chloride in N,N-dimethylformamide solution.

TL;DR: In this paper, 20 optisch active Derivate and Folge-produckte dargestellt und untereinander chemisch korreliert were found, and the absoluten Konfigurationen wurden durch kinetische Racematspaltung des Anhydrids von 1 with (−)-α-Phenathylamin and durch Anwendung der Methode von Horeau auf zwei epimere Carbinole (18 and 19) ermittelt.

TL;DR: Zusammenfassung Der Einfluss der Substituenten X and Z auf die syn-anti-Isomerisierung in den Iminen X2C = NZ wird am Breispiel der Guanidine [X = N(CH3)2] untersucht.

TL;DR: In this paper, the semi-empirical SCF MO Π approximation was used for several benzo derivatives of furan and indole, including isoindole and isobenzofuran.