Seleno Analogues Research Articles

Synthesis of 2,3,7,8‐tetramethoxydibenzotellurophene and its thio and seleno analogues

AbstractThe title compounds 5 were obtained from the reaction of 3,3′,4,4′‐tetramethoxybiphenyl (6) or its 2,2′‐dilithio derivative 8 with various chalcogen electrophiles (sulfur dichloride, selenium tetrachloride, selenium oxychloride and tellurium tetrachloride).

New Synthesis of ketene thioacetals, vinylsulfides and their seleno analogues

Title compounds have been prepared on reaction of thioacetals, orthothioesters and their seleno analogues with diphosphorus tetraiodide (P 2I 4) or phosphorus triiodide (PI 3).

The Torsional Barrier of the Dimethylamino Group in N,N-Dimethyltellurobenzamide. A Comparison with N,N-Dimethylbenzamide and its Thio and Seleno Analogues.

The Torsional Barrier of the Dimethylamino Group in N,N-Dimethyltellurobenzamide. A Comparison with N,N-Dimethylbenzamide and its Thio and Seleno Analogues.

New synthetic routes to vinyl sulfides, ketene thioacetals and their seleno analogues from carbonyl compounds

Title compounds have been prepared from carbonyl compounds by formal removal of hydroxyl and sulfenyl or hydroxyl and selenyl moieties from the corresponding functionalized β-hydroxysulfides or β-hydroxyselenides.

ChemInform Abstract: MASS SPECTROMETRY OF NUCLEOSIDE DERIVATIVES. SELENO ANALOGS OF PURINE AND PYRIMIDINE BASES AND NUCLEOSIDES

Chemischer InformationsdienstVolume 11, Issue 6 Organoelement Compounds ChemInform Abstract: MASS SPECTROMETRY OF NUCLEOSIDE DERIVATIVES. SELENO ANALOGS OF PURINE AND PYRIMIDINE BASES AND NUCLEOSIDES J. G. LIEHR, J. G. LIEHRSearch for more papers by this authorC. L. WEISE, C. L. WEISESearch for more papers by this authorP. F. CRAIN, P. F. CRAINSearch for more papers by this authorG. H. MILNE, G. H. MILNESearch for more papers by this authorD. S. WISE, D. S. WISESearch for more papers by this authorL. B. TOWNSEND, L. B. TOWNSENDSearch for more papers by this authorJ. A. MCCLOSKEY, J. A. MCCLOSKEYSearch for more papers by this author J. G. LIEHR, J. G. LIEHRSearch for more papers by this authorC. L. WEISE, C. L. WEISESearch for more papers by this authorP. F. CRAIN, P. F. CRAINSearch for more papers by this authorG. H. MILNE, G. H. MILNESearch for more papers by this authorD. S. WISE, D. S. WISESearch for more papers by this authorL. B. TOWNSEND, L. B. TOWNSENDSearch for more papers by this authorJ. A. MCCLOSKEY, J. A. MCCLOSKEYSearch for more papers by this author First published: February 12, 1980 https://doi.org/10.1002/chin.198006310Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume11, Issue6February 12, 1980 RelatedInformation

Mass spectrometry of nucleoside derivatives. Seleno analogs of purine and pyrimidine bases and nucleosides

AbstractMass spectra of certain selenobases and selenonucleosides, and some of their trimethylsilyl and O,N‐permethyl derivatives have been studied from the standpoint of structural characterization, and in order to ascertain the influence of selenium on normal fragmentation patterns. Molecular ion abundances of the selenouracils are intermediate between those of the corresponding oxygen and sulfur analogs. Fragmentation processes are similar to those of the corresponding normal bases and nucleosides but with additional ions resulting from expulsion of Se or SeH in most cases. Trimethylsilylation occurs at approximately the same rate as for normal bases and nucleosides but the products show decreasing stability with prolonged heating. A least squares procedure is demonstrated which generates monoisotopic mass patterns and assists in interpretation of the mass spectra.

Interactions of Methionine and Selenomethionine with Methionine Adenosyltransferase and Ethylene-generating Systems

Since selenomethionine appears to be a better precursor of ethylene in senescing flower tissue of Ipomoea tricolor and in indole acetic acid-treated pea stem sections than is methionine (Konze JR, N Schilling, H Kende 1978 Plant Physiol 62: 397-401), we compared the effectiveness of selenomethionine and methionine to participate in reactions which may be connected to ethylene biosynthesis. Evidence is presented that selenomethionine is also a better substrate of methionine adenosyltransferase (ATP: methionine S-adenosyltransferase, EC 2.5.1.6) from I. tricolor, the V(max) for selenomethionine being twice as high as that for methionine. The affinity of the enzyme is higher for methionine than for selenomethionine, however. Methionine added to flower tissue together with selenomethionine inhibits the enhancement of ethylene synthesis by the seleno analog. Likewise, methionine reduces the high, selenomethionine-dependent reaction rates of methionine adenosyltransferase from I. tricolor flower tissue. On the other hand, selenomethionine is less effective as an ethylene precursor than is methionine in model systems involving oxidation by free radicals. It was concluded that activation of methionine by methionine adenosyltransferase and formation of S-adenosylmethionine are more likely to be involved in ethylene biosynthesis than is oxidation of methionine by free radicals.

Carbon-13 N.M.R. Spectra of Some Amides and Lactams and Their Thio and Seleno Analogues

13C N.M.R. spectra were determined, and resonances were assigned, for 27 amides and lactams and their thio and seleno analogues.

Interaction of cholinergic ligands and local anesthetics with plasma membrane fragments from lobster axon.

Isologous local anesthetics containing the ester, thiolester, or selenolester grouping and their quaternary ammonium analogs were studied for their ability to displace [3H]nicotine from plasma membrane fragments of lobster nerve. Tertiary and quaternary analogs were equiactive. The relative ability of oxo, thio, and seleno analogs to displace nicotine was the same as their relative ability to block axonal conduction and synaptic transmission. Among cholinergic ligands, choline and aminocholine, previously shown to be inactive as depolarizing agents, were uniquely unable to displace nicotine. The findings are compatible with the presence of a biopolymer capable of binding cholinergic ligands in axonal membranes and support the postulate that the relative inactivity of quaternary compounds in intact axons is due to permeability barriers.

The gear effect. VII—Conformational analysis of methyl N,N‐diisopropylcarbamate, its thiol and diseleno analogues. An experimental proof for a two‐step conformational interconversion mechanism

AbstractThe conformations of the isopropyl groups and the barriers to conformational interconversion in methyl N,N‐diisopropylcarbamate, its thiol and seleno analogues have been studied by 1H d.n.m.r. In the diselenocarbamate, complete bandshape analysis of the Se‐methyl proton signals proves unequivocally that the conformational interconversion takes place by rotation of one isopropyl group at a time rather than by a concerted rotation of both groups. The populations and barriers observed for the new compounds fit well into the general scheme found previously for other N,N‐diisopropylamides and ‐thioamides.

Comparative studies of the antineoplastic activity of 5-hydroxy-2-formylpyridine thiosemicarbazone and its seleno- semicarbazone, guanylhydrazone and semicarbazone analogs

Several analogs of 5-hydroxy-2-formylpyridine thiosemicarbazone (5-HP) that contain isosteric replacement of sulfur by Se, NH or O have been synthesized. Measurement of the antineoplastic activity of these compounds in mice bearing Sarcoma 180 ascites cells indicated that 5-HP was the most active of these agents; the seleno analog was intermediate in potency, and the guanylhydrazone and semicarbazone were inactive against this tumor. 5-HP and its seleno analog both caused marked inhibition of DNA synthesis in vitro, as measured by the incorporation of thymidine-methyl- 3H, 5- 3H-cytidine or adenine-8- 14C into DNA. The syntheses of RNA and protein were relatively unaffected by these agents under the conditions employed. None of the compounds prevented the incorporation of 5- 3H-cytidine into acid-soluble pyrimidine ribonucleotides, but 5-HP and its selenosemicarbazone markedly depressed the subsequent progression of radioactivity into pyrimidine deoxyribonucleotide pools, suggesting that these two derivatives inhibited the enzyme ribonucleoside diphosphate reductase in situ. Both 5-HP and the seleno analog inhibited the isolated enzyme ribonucleoside diphosphate reductase from the Novikoff rat hepatoma; to achieve 50 per cent inhibition required 3.5 × 10 −6 and 6.8 × 10 −6 M respectively. Metal/ ligand ratios and the association constants for these ligands with cobalt and copper were determined. The cobalt/ligand ratio for 5-HP and its seleno analog was 1:2 and the copper/ ligand ratio for these agents was 1:1. Metal/ligand ratios for the guanylhydrazone and semicarbazone derivatives were 1:3 for cobalt and 1:2 for copper. Association constants for 5-HP and the seleno derivative with cobalt were 56 × 10 9 and 7.6 × 10 9 respectively. The findings demonstrated that 5-HP was the optimum member of this series with respect to antineoplastic potency and that tumor-inhibitory activity correlated with the degree of inhibition of the synthesis of DNA and the capacity for metal binding.

Sulfur and selenium isologs related to acetylcholine and choline—IX: Further comparative studies of the pharmacological effects of acetylcholine and its thio and seleno analogs and their hydrolysis products

The pharmacological effects of acetylthiolcholine (ASCh) and acetylselenolcholine have been compared with those of their oxygen analog, acetylcholine, on the guinea pig ileum, innervated rat diaphragm, and rat blood pressure preparations. The close similarity of the affinity constants for the muscarinic antagonist, lachesine, obtained with all three members of the series, is interpreted as evidence that they act primarily on the same receptor system. Further evidence is offered to support the contention that the unusual actions of these thio and seleno analogs of acetylcholine (ACh) on the blood pressure and at the neuromuscular junction, are attributable to the relatively high activity of their hydrolysis products which readily undergo oxidation to bis-onium compounds of lesser activity. This unusual chemical behaviour provides possible explanations for further recently reported anomalies in the pharmacology of ASCh.

Inhibitory action of selenite on Escherichia coli, Proteus vulgaris, and Salmonella thompson.

Weiss, K. F. (Iowa State University, Ames), J. C. Ayres, and A. A. Kraft. Inhibitory action of selenite on Escherichia coli, Proteus vulgaris, and Salmonella thompson. J. Bacteriol. 90:857-862. 1965.-The resistance of three microorganisms, Escherichia coli (ISU-41), Proteus vulgaris (ISU-37c), and Salmonella thompson (ISU-86-2), to increasing concentrations of selenite was determined. E. coli was completely inhibited by 1.25% sodium hydrogen selenite, and 0.25% sodium hydrogen selenite caused a pronounced lag. P. vulgaris survived selenite concentrations of over 3%. S. thompson was inhibited completely by 3% selenite but not by 2.5%, although there was a considerable lag and a decrease in total growth. The relationship of growth, uptake, and reduction of selenite was determined. The susceptible E. coli incorporated up to twice as much selenium as did the other two organisms during the early stages of incubation. Radioautographs of seleno analogues of sulfur-containing amino acids revealed the presence of seleno-cystine in all three organisms, and seleno-methionine in E. coli. Compounds having R(F) values corresponding to possible oxidation products of seleno-methionine were present in the hydrolysates of P. vulgaris and S. thompson. Kinetic aspects of selenite uptake, rather than the ultimate localization of selenite in the cell protein, appear to be the factors that determine the degree of resistance or of susceptibility to selenite.

Analogs of parasympathetic neuroeffectors—II: Comparative pharmacological studies of acetylcholine, its thio and seleno analogs, and their hydrolysis products

Acetylthiocholine and acetylselenocholine exert acetylcholine-like effects on the guinea pig ileum and frog rectus abdominis preparations. With the latter preparation, responses to acetylthiocholine and acetylselenocholine, in contrast to that to acetylcholine, are not enhanced by the addition of an anticholinesterase. This is attributable to the relatively high activity of the hydrolysis products, cholinethiol and cholineselenol; acetylthiocholine and acetylselenocholine undergo enzymatic hydrolysis at approximately the same rate as does acetylcholine. The hydrolysis products of acetylthiocholine and acetylselenocholine, which have effects on the guinea pig ileum comparable to those of the parent esters, are readily oxidized in air to the relatively inactive eholine disulfide and choline diselenide, respectively. These observations are helpful in explaining many of the apparently contradictory statements in the literature regarding the actions of acetylthiocholine.