Showing papers in "Tetrahedron in 1967"

TL;DR: In this paper, the effect of bending of the C-C-C angle and twisting of the CH2-CH2 torsional angle has been examined through their effect on calculations of stable conformations and excess enthalpies of all the cycloalkane molecules from C6H12 to C12H24.

TL;DR: In this paper, a method of glycosylation using 1,2-O-alkyl orthoesters of sugars as glycolyating agents and a new convenient synthesis of these orthoeppers is described.

TL;DR: In this paper, the order of reactivity of secondary OH groups has been deduced from the results and is different for each glycoside, being 2-OH > 3-OH> 4-OH for the glucoside, 3-H > 2-HO > 4-HO for the mannoside, and 2-H, 3H, 4H > 4H for the galactoside.

TL;DR: The acid dissociation constants on the H− and H= indicator acidity scales of 25 substituted indoles give a fairly linear correlation with the proper substituent constants, yielding a value of ρ = 1·75 for indole dissociation.

TL;DR: In this article, photooxidation in methanol of 2-methyl-, 2,5-dimethyl-, dicyclohexano- and menthofuran, sensitized by Rose Bengal, produces crystalline 2-methoxy-5-hydroxyperoxy-2,5dihydrofuran derivatives by addition of solvent to intermediate ozonide-like peroxides.

TL;DR: In this article, aldehyde and ketone oxime O methyl ethers were assigned to conformations and configurations from analysis of their 60-Mc NMR spectra, based on the data from the cis-isomers (methoxy cis-to hydrogen) of the derivatives in terms of rotamers I and II.

TL;DR: A rational synthesis of bullvalene (I) proceeds in seven steps from cycloheptatriene-7-carboxylic acid by way of cycloencathonyl chloride, cyclohetatrien-7]-diazomethyl ketone (B-1), barbaralone (VI), bullvalone (V), 9-hydroxytricyclo [3.3.2.0.

TL;DR: In this article, an acid-catalysed exchange with trimethyl orthoacetate and orthobenzoate was applied to the preparation of 3′,5′-di-O-acyl-ribonucleoside derivs, which are required as intermediates in oligoribonucleotide synthesis.

TL;DR: In this paper, the Guerbert reaction between an alcohol and an alkanolate in presence of excess potassium hydroxide has been studied, mainly with benzyl alcohol and potassium lactate as reactants, α-hydroxy-γ-phenylbutyric acid being formed in the reaction.

TL;DR: Piperlongumine and piperlonguminine are shown to be N-(3,4,5-trimethoxycinnamoyl)-Δ5-piperidin-2-one and isobutylamide of piperic acid respectively.

TL;DR: In this article, it was shown that acryl radicals combine with nitroso compounds to give acyl-alkyl-nitroxides, which are identified by their ESR spectra.

TL;DR: A convenient synthesis of α-amino-β-lactams has been devised with the aim of preparing derivatives and analogs of penicillin and cephalosporin C and 1-Cholestanyl-3,3-dimethylazetidine-2-one has been prepared as an analog of the β- lactam-substituted steroid alkaloids reported recently.

TL;DR: A summary of proton-proton coupling constant data for cyclobutanes, cyclobutanones and cyclobutenes can be found in this article, where the authors show that the coupling constants of cyclobuttanes and cyclogenes resonate at slightly lower field than those in the larger cycloalkanes.

TL;DR: In this paper, the PMR spectra of four 6a,11a-dihydro-6H-benzofuro derivatives have been analyzed and the conformation of the heterocyclic rings has been derived from the vicinal coupling constants.

TL;DR: In this article, the interaction of electronic and steric factors in aromatic azomethine molecules has been investigated and theoretical calculations predict and the experimental data confirm that the azogenine molecule exists as a stable non-planar conformation in which the dihedrical angle between the amino nucleus and the rest of the molecule plane is 40-60° and that substituents in the aryl nucleus have little effect.

TL;DR: In this article, two new gibberellins, namely, Gibbler A7 and Gibbler 9, were isolated from culture filtrates of the fungus Gibberella fujikuroi, and they were shown by degration and interrelation with gibbererellic acid via gibbererllin A4, to have structured I and III respectively.

TL;DR: Ritonucleosides undergo acid-catalysed orthoester exchange with trimethyl orthoformate to give their 2′,3′-O-methoxymethylidene derivatives, which are required as intermediates in oligoribonucleotide synthesis, have been prepared.

TL;DR: In this article, the main products of 1,1-dibromo-2-vinylcyclopropane derivatives with MeLi were identified as cyclopentadienes and diallenes.

TL;DR: The racemization and ring-opening reactions of the oxazolone from benzyloxycarbonylaminoisobutyryl- l -phenylalanine with a number of amino acid esters were studied in several commonly used peptide solvents to show that oxzolone racemized tripeptide is a pseudo first-order reaction when the rate of Racemization is much larger than the rate-opening.

TL;DR: In this paper, the authors modified the McDonnel equation to include those cases where the distance between the shielding group and the proton observed is small compared to the length of the induced dipole.

TL;DR: In this article, the Extended Huckel Theory (EHT) has been applied to a series of nitrogen heterocyclic molecules, and their anions and mono-and di-protonated derivatives.

TL;DR: Alkaline solutions of "humic acid" (HA) isolated from some eighty different soils and peats give ESR spectra indicative of the presence of remarkably stable semiquinone ion radicals as mentioned in this paper.

TL;DR: In this article, a 4-flavanylflavene is first formed and then oxidized by a second molecule of the flavylium salt, which is reduced to a monomeric flav-2-ene.

TL;DR: In this paper, a 3,6-substituted bis-s-triazolo-(4,3-b,3′,4′-f)-pyridazine (VIII) was proposed.

TL;DR: In this article, the seeds of Millettia dura (Dunn) have yielded durlettone, durmillone, mildurone, and 6 ω 12 ω -dehydrodeguelin, and the relation of these observations to the question of the natural occurrence of 12 a -hydroxyrotenoids and 6 a,12 a-dehydrorotenoids is discussed.

TL;DR: In this article, the preparations of cis-and trans-1-benzylisatylidene-3-acetaldehyde, cis- and trans -1-bensylisatisatylidsene- 3-acetic acid and some derivatives are described.

TL;DR: An unusual rearrangement involving solid state X-irradiation has been discovered and evaluated in hirsutic acid C from Stereum hirsutum.

TL;DR: In this article, a gute Linearitat wird bei Anwendung der Taft'schen Kombination 0·40 σI + 0·70 σM*) erreicht.

TL;DR: In view of the anticancer activity of thiophene-2,5-dicar-ylic acid, a series of derivatives of this acid were prepared as discussed by the authors.

TL;DR: In this paper, the structure of ochratoxin A, the main toxic metabolite of Aspergillus ochraceus Wilh, was proved by an unambiguous synthesis.