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111.
The synthesis of methyl (4R, 8R,)-10-bromo-8-methyl-4-(1,3,6-trioxaheptane)-2-deceneoate ( 5 ), a synthon for the construction of the macrocyclic moieties of the cytochalasins A ( 1), B. (2) F (3) and desoxaphomin ( 4 ) is described. (S)-Glutamic acid ( 6 ) was transformed to the C5-epoxide 10 and 3-methylglutaric acid ( 11 ) to the C5-bromide 15 . Coupling of both 10 and 15 by a CuI-catalyzed Grignard reaction gave the decanol 16 in very high yield. The latter was transformed by several steps to synthon 5 . 相似文献
112.
Usama A. R. Al-Timari Lubor Fišera Peter Ertl Igor Goljer Nada Prónayová 《Monatshefte für Chemie / Chemical Monthly》1992,123(11):999-1013
Summary The cycloaddition of 3-hydroxyglycosyl-N-methylnitrone (1) to N-arylmaleimides gave thesyn isoxazolidines6, whereas 3-acetoxyglycosyl-N-methylnitrone (2) afforded theanti isoxazolidines8 and10. The formation of6 was rationalized by anexo attack, stereoelectronically preferred through the hydrogen bond between the pentose hydroxyl group and one of the carbonyl groups of N-arylmaleimide. The sterically preferredendo attack avoiding the repulsions between N-arylmaleimide and sugar moiety was proposed for addition of2. The structure and steric configuration of the products have been assigned on the basis of1H- and13C-NMR spectroscopy, mainly by nuclear Overhauser effect difference spectroscopy. AM1 calculations of the nitrones and MM2 calculations of the adducts were performed.
Darstellung und Stereoselektivität der 1,3-dipolaren Cycloaddition von C-Glycosyl-Nitronen an N-Arylmaleimiden
Zusammenfassung Die Cycloaddition von 3-Hydroxyglycosyl-N-methylnitron (1) an N-Arylmaleimide gab diesyn-Isoxazolidine6, mit 3-Acetoxyglycosyl-N-methylnitron (2) wurden hingegen dieanti-Isoxazolidine8 und10 erhalten. Die Bildung von6 wurde mit einemexo-Angriff erklärt, der stereoelektronisch wegen einer Wasserstoffbrückenbindung zwischen der Hydroxylgruppe der Pentose und einer Carbonylgruppe des N-Arylmaleimides bevorzugt wird. Für die Addition von2 wurde ein sterisch bevorzugterendo-Angriff vorgeschlagen, da dabei ungünstige Wechselwirkungen zwischen der N-Arylmaleimid- und der Zuckereinheit vermieden werden. Die Struktur und Stereochemie der Produkte wurde mittels1H- und13C-NMR unter Verwendung von NOE-Differenzmessungen ermittelt. Es wurden auch AM1-Rechnungen für die Nitrone und MM2-Rechnungen für die Addukte durchgeführt.相似文献
113.
Kundakovic T Fokialakis N Magiatis P Kovacevic N Chinou I 《Chemical & pharmaceutical bulletin》2004,52(12):1462-1465
Investigation of the aerial parts of Achillea alexandri-regis led to the identification of 19 chemical constituents: twelve 3-O-fatty acid esters of triterpene alcohols arnidiol (1-4), maniladiol (5-8) and 16beta-hydroxylupeol (9-12), alpha-amyrin, beta-amyrin, beta-sitosterol, 3,4-O-dicaffeoyl quinic acid, cinnamic acid, pinoresinol-beta-D-glucoside and rutin. Among them, compounds 3, 4, 8, 11 and 12 are new natural products. The structures of all compounds have been elucidated on the basis of their spectral and chemical data. 相似文献
114.
2-Thioxo-1,2-dihydropyridine derivatives 2a, 2b were reacted with methyl iodide to give 2-methylthiopyridines 3a, 3b, which were reacted with hydrazine hydrate to produce 3-aminopyrazolo[5,4-b]pyridines 4a, 4b. Compounds 4a, 4b were diazotized to afford the corresponding diazonium salts 5a, 5b, which were reacted with some active methylene compounds 6a-6h to give the corresponding pyrido[2′,3′ : 3,4]pyrazole[5,1-c][1,2,4]triazines 7-14. 相似文献
115.
Moreau L Camplo M Wathier M Taib N Laguerre M Bestel I Grinstaff MW Barthélémy P 《Journal of the American Chemical Society》2008,130(44):14454-14455
Supramolecular assembly formation resulting from molecular recognition between complementary nucleolipids has been visualized in real time at the micrometer scale. 相似文献
116.
Several 1,3-diaryl-5-(cyano-, aminocarbonyl- and ethoxycarbonyl-)-2-pyrazoline, pyrrolo[3,4-c]pyrazole-4,6-dione and 1,3,4,5-tetraaryl-2-pyrazoline derivatives were prepared by the reaction of nitrilimine with different dipolarophilic reagents. The new compounds were characterized using IR, (1)H-NMR, (13)C-NMR and mass spectra. Biological screening of some compounds is reported. 相似文献
117.
118.
119.
JPC – Journal of Planar Chromatography – Modern TLC - Estimation of retention data by use of correlation equations and physicochemical properties is a useful tool in liquid... 相似文献
120.
Tibur Schmidlin Peter E. Burckhardt Nada Waespe-ar
evic Christoph Tamm 《Helvetica chimica acta》1983,66(2):450-465
A general scheme for the synthesis of the tetrahydroisoindolinone moiety of naturally occurring cytochalasans and unnatural analogs was developed. The key-step consists of the intermolecular [2+4]cycloaddition of 4-methylsorbinol (7) to an alkylidene malonic ester derivative such as 6, 9 or 10 , obtained from the corresponding amino acids. The products obtained, 4a, 17 , and 18 were converted to the desired lactams 5, 21 , and 22. Cycloaddition of the diene alcohol 7 to the optically active alkylidene malonic ester derivative 9b (s. Footnote 5) prepared from L -leucine gave compound 17b with 98% enantiomeric excess. The optical activity was retained during the conversion of 17b to the lactam 21b . The latter is a subunit for the synthesis of the aspochalasins. 相似文献