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The convergent synthesis of N-Boc-(2R,3R,8R,9R,4E,6E)-3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldecadenoic acid (enantio-N-Boc-ADDA) is reported. Our flexible approach takes advantage of highly efficient non-aldol aldol and cross-metathesis methodologies. 相似文献
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Total Synthesis of (6R,10R,13R,14R,16R,17R,19S,20R,21R,24S, 25S,28S,30S,32R,33R,34R,36S,37S,39R)‐Azaspiracid‐3 Reveals Non‐Identity with the Natural Product
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Nathaniel T. Kenton Dr. Daniel Adu‐Ampratwum Dr. Antony A. Okumu Dr. Zhigao Zhang Dr. Yong Chen Dr. Son Nguyen Dr. Jianyan Xu Dr. Yue Ding Dr. Pearse McCarron Dr. Jane Kilcoyne Prof. Dr. Frode Rise Prof. Dr. Alistair L. Wilkins Dr. Christopher O. Miles Prof. Dr. Craig J. Forsyth 《Angewandte Chemie (International ed. in English)》2018,57(3):805-809
A convergent and stereoselective total synthesis of the previously assigned structure of azaspiracid‐3 has been achieved by a late‐stage Nozaki–Hiyama–Kishi coupling to form the C21?C22 bond with the C20 configuration unambiguously established from l ‐(+)‐tartaric acid. Postcoupling steps involved oxidation to an ynone, modified Stryker reduction of the alkyne, global deprotection, and oxidation of the resulting C1 primary alcohol to the carboxylic acid. The synthetic product matched naturally occurring azaspiracid‐3 by mass spectrometry, but differed both chromatographically and spectroscopically. 相似文献
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Zusammenfassung Für verschiedene Zelluloseproben wurden mittels Röntgenweitwinkelstreuung die mittleren lateralen Kristallitgrößen und ihre Gestaltellipse in der Ebene senkrecht zur Kettenrichtung bestimmt. Die Gaußanalyse der Weitwinkelreflexe zeigt teilweise eine Aufspaltung in Vielfache einer kleinsten Kristallitgröße. Dies wird auf teilweise Rekristallisation zurückgeführt. Die Gaußanalyse der kontinuierlichen Kleinwinkelstreuung liefert in allen Fällen gleichfalls Vielfache einer kleinsten Einheit. Zeigt der Weitwinkelreflex keine Aufspaltung, kann das Kleinwinkelergebnis nicht durch Rekristallisation, sondern durch einfache Clusterbildung erklärt werden.Weitwinkel- und Kleinwinkelergebnisse stimmen sehr gut miteinander überein.
Mit 4 Abbildungen und 4 Tabellen 相似文献
Summary The mean lateral crystallite sizes and the shape ellipse in the plane perpendicular to the chain direction have been estimated for different cellulose samples by wide angle X-ray diffraction. Gaussian analysis of the wide angle reflexions partly shows a splitting into multiples of a smallest crystallite size. This is explained by partly recrystallization. Gaussian analysis of the continuous small angle diffraction in all cases yields multiples of a smallest unit, too. If the wide angle reflexion does not show any splitting, the small angle result cannot be explained by recrystallization, but simply by clustering of the fibrils.There is an excellent agreement between the wide angle and the small angle results.
Mit 4 Abbildungen und 4 Tabellen 相似文献
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In the present work, vapour-liquid equilibria of four binary systems refrigerant-lubricant oil have been investigated, CF3CHF2 (R125), CF3CH2F (R134a), CF3CH3 (R143a) and CH2F2 (R32) as refrigerants and a commercial perfluoropolyether (PFPE), Fluorolink D10H, as lubricant. Vapour-liquid equilibrium data, consisting of isothermal measurement of equilibrium pressure at a fixed composition, have been correlated with an extended Flory-Huggins equation and the corresponding parameters have been determined. Good agreement has been found between experimental data and the model predictions. 相似文献
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Amalia M. Estévez Raquel G. Soengas José M. Otero Juan C. Estévez Robert J. Nash Ramón J. Estévez 《Tetrahedron: Asymmetry》2010,21(1):21-26
A divergent synthesis of the two novel polyhydroxylated azepanes (2R,3R,4R,5R,6R)-2-(hydroxymethyl)azepane-3,4,5,6-tetraol and (2R,3R,4R,5R,6S)-2-(hydroxymethyl)azepane-3,4,5,6-tetraol from d-mannose is described. The method involves a Henry reaction between dimethyl-tert-butylsilyl 2,3-O-isopropylidene-α-d-lyxo-pentodialdo-1,4-furanoside and 2-nitroethanol followed by a reductive ring closure of the resulting epimeric nitro aldols. Glycosidase inhibition tests showed that (2R,3R,4R,5R,6S)-2-(hydroxymethyl)azepane-3,4,5,6-tetraol exhibits a weak but selective inhibition against α-l-fucosides. 相似文献
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Anastasy О. Kolodiazhna Аleksei I. Skliarov Alena A. Slastennikova 《Phosphorus, sulfur, and silicon and the related elements》2020,195(9):713-717
AbstractAn asymmetric synthesis of (+)- and (–)-methiine (S-methyl-(R)-cysteine sulfoxide) diastereomers has been developed. These natural sulfur compounds were isolated from a variety of Brassica vegetables. As the starting compound, (R)-cysteine was used, which was methylated to form (R)-S-methylcysteine. Then the oxidation of S-methylcysteine with tert-butyl hydroperoxide catalyzed by the chiral tetra(isopropylate)titanium/(S)- or (R)-Binol complex led to the formation of (1?R,2S)-(+)- or (1?R,2R)-(–)-methiin stereomers. 相似文献
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A. Niemann und W. Schmidt 《Fresenius' Journal of Analytical Chemistry》1966,219(5):453-454
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F. Schärtl 《Analytical and bioanalytical chemistry》1967,231(4):277-277
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W. Bögershausen und W. Schmidt 《Fresenius' Journal of Analytical Chemistry》1967,226(2):204-205
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P. Günther H. Stintzing U. Dehlinger R. Glocker E. Kaupp G. von Hevesy J. Böhm W. Traub A. J. H. Busé A. Bouwers I. N. Stranski V. M. Goldschmidt L. Thomassen V. Thal Jantzen J. Nishina Ida Noddack W. Noddack E. Schwarz von Bergkampf C. E. Eddy und T. H. Laby 《Fresenius' Journal of Analytical Chemistry》1935,101(1-2):42-46
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P. Günther H. Stintzing U. Dehlinger R. Glocker E. Kaupp G. von Hevesy J. Böhm W. Traub A. J. H. Busé A. Bouwers I. N. Stranski V. M. Goldschmidt L. Thomassen V. Thal Jantzen J. Nishina Ida Noddack W. Noddack E. Schwarz von Bergkampf C. E. Eddy T. H. Laby 《Analytical and bioanalytical chemistry》1935,101(1-2):42-46
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Zeit R. Berthold 《Analytical and bioanalytical chemistry》1933,94(9-10):344-347
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