共查询到20条相似文献,搜索用时 15 毫秒
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The first calculation of a molecule, N2, by the SCF -Xα-SW method using the theoretically derived parameter αta is reported. 相似文献
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Richard Buchecker Robert Egli Helen Regel-Wild Christoph Tscharner Conrad Hans Eugster Gerald Uhde Günther Ohloff 《Helvetica chimica acta》1973,56(7):2548-2563
By chemical correlation with manool and ambrein the absolute configurations of the enantiomeric α-cyclogeranic acids, α-cyclogeranials, α-ionones and α- and ?-carotenes have been elucidated. 相似文献
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K. Dehnicke 《无机化学与普通化学杂志》1974,409(3):311-319
IR- and RAMAN Spectra of CuN3, AgN3, TlN3, BiON3, Cu(N3)2, and α-Pb(N3)2 The vibrational spectra of the title compounds were recorded and assigned with respect to their crystal structure. The RAMAN spectra mere obtained in aqueus sus-pension. 相似文献
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Five rare hexoses, which are components of antibiotics or cardiac glycosides, have been synthesized as methyl glycosides through a common intermediate methyl 2,3-dehydro-2,3,6-trideoxy-α-dl glucopyranoside (7). Epoxidation and subsequent treatment with dimethylamine of7 afforded methyl α-dl-mycaminoside (9). The addition reaction of MeOH to12 gave methyl α-dl-oleandroside (15) and methyl β-dl-cymaroside (17). The hydroxymercuration and subsequent reduction of12 afforded methyl α-dl-chromoside C (19) and methyl β-dl-tyveloside (25). 相似文献
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Ronda M. Sandifer Luther W. Dasher Wayne M. Hollinger C. Wayne Thomas David C. Reames Charles F. Beam Robert S. Foote Charles R. Hauser 《Journal of heterocyclic chemistry》1975,12(6):1159-1163
Several C(α), O-dilithiooximes were condensed with diethyl oxalate and acid-cyclized to give biisoxazoles. Only dilithio p-fluoroacetophenone phenylhydrazone gave the bipyrazole when condensed with this diester. Other C(α), N-dilithiophenylhydrazones and several C(α), N,N-trilithio-hydrazones were condensed with diethyl oxalate and acid-cyclized to give the intramolecular 4-hydroxy-3-pyridazones. Several non-cyclized intermediates were isolated and a reaction mechanism is presented. 相似文献
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1H NMR chemical shifts for some α-hetero-substituted N,N-diethylacetamides were recorded. The resonance assignments for the syn- and anti-methylene and -methyl protons have been made unambiguously through their aromatic solvent induced shifts and are opposed to the literture assignments for the N-methylene protons. An empirical relationship between the Charton polar (σL) and steric (V) parameters and the α-methylene proton resonances was found. The N-methylene proton chemical shifts also showed a qualitative dependence on the α-substituent electronegativity, while the N-ethyl methyl proton chemical shifts were related to the α-substituent steric effects. The Paulsen and Todt anisotropic model and the more populated rotamers proposed seem to explain the results very well. 相似文献
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Transformations of N'-heteroaryl-N,N-dimethylformamidines 1 as a general method for the preparation of β-heteroarylamino-α,β-dehydro-α-amino acids, β-heteroarylamino-α-amino acid derivatives 5–9 , and dipeptides 10 , are described. 相似文献
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Claudio Palomo Jesus M. Aizpurua Ana Benito Regina Galarza Uttam K. Khamrai Jordi Vazquez Beatriz de Pascual-Teresa Pedro M. Nieto Anthony Linden 《Angewandte Chemie (International ed. in English)》1999,38(20):3056-3058
Remarkable asymmetric induction is achieved in the alkylation of the lithium enolate of the β-lactam 1 . This allows the first time access to a new family of peptidomimetics 2 with predictable conformational constraints. 相似文献