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Alexopoulos T Allen C Anderson EW Areti H Banerjee S Beery PD Biswas NN Bujak A Carmony DD Carter T Cole P Choi Y De Bonte RJ Erwin AR Findeisen C Goshaw AT Gutay LJ Hirsch AS Hojvat C Kenney VP Lindsey CS LoSecco JM McMahon T McManus AP Morgan N Nelson KS Oh SH Piekarz J Porile NT Reeves D Scharenberg RP Stampke SR Stringfellow BC Thompson MA Turkot F Walker WD Wang CH Wesson DK 《Physical review letters》1990,64(9):991-994
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Lazarus EA Navratil GA Greenfield CM Strait EJ Austin ME Burrell KH Casper TA Baker DR DeBoo JC Doyle EJ Durst R Ferron JR Forest CB Gohil P Groebner RJ Heidbrink WW Hong R Houlberg WA Howald AW Hsieh C Hyatt AW Jackson GL Kim J Lao LL Lasnier CJ Leonard AW Lohr J La Haye RJ Maingi R Miller RL Murakami M Osborne TH Perkins LJ Petty CC Rettig CL Rhodes TL Rice BW Sabbagh SA Schissel DP Scoville JT Snider RT Staebler GM Stallard BW Stambaugh RD St John HE Stockdale RE Taylor PL Thomas DM 《Physical review letters》1996,77(13):2714-2717
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[reaction: see text] Stereoselective aminohydroxylation and dihydroxylation using osmium(VIII) oxidants enabled the short and efficient synthesis of the aminocyclitol core of hygromycin A. In addition to allowing the selective introduction of the heteroatoms N and O, the use of osmium (via an osmate ester) as a protecting group for a 1,2-glycol is also reported. This tactic allowed efficient differentiation of otherwise equivalent hydroxyl groups and allowed us to complete the synthesis in short order (14 steps) and excellent overall yield (12%). 相似文献
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[reaction: see text] A short synthesis of (+/-)-secosyrin 1 is presented that starts from an electron-deficient furan; reductive alkylation under Birch conditions gives rapid access to the natural product skeleton. Two aspects of stereoselectivity are explored, the first being directed dihydroxylation of a homoallylic alcohol. Second, the facial selectivity obtained during reduction of a highly substituted cyclic ketone was examined. Finally, our synthesis was rendered enantioselective by the reduction of a furan bearing a chiral auxiliary. 相似文献
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[reaction: see text] The partial reduction of electron-deficient 2,5-disubstituted pyrroles has been developed into a flexible procedure that gives control of relative stereochemistry by variation of the reduction conditions. After the reaction, the pyrroline products were dihydroxylated at C-3,4 to give either the cis or trans isomers; this flexibility means that a variety of polyhydroxylated pyrrolidines can be prepared in a short sequence. Finally, this method was applied to a synthesis of the naturally occurring glycosidase inhibitor DMDP. 相似文献
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The synthesis and structural characterization of a rare example of a uranyl complex possessing three equatorial ligands, [M(THF)2][UO2(N(SiMe3)2)3] (3a, M = Na; 3b, M = K), are described. The sodium salt 3a is prepared by protonolysis of [Na(THF)2]2[UO2(N(SiMe3)2)4], whereas the potassium salt 3b is obtained via a metathesis reaction of uranyl chloride UO2Cl2(THF)2 (4) with 3 equiv of K[N(SiMe3)2]. A single-crystal X-ray diffraction study of 3a revealed a trigonal-bipyramidal geometry about uranium, formed by two axial oxo and three equatorial amido ligands, with average U=O and U-N bond distances of 1.796(5) and 2.310(4) A, respectively. One of the oxo ligands is also coordinated to the sodium counterion. 1H NMR spectroscopic studies indicate that THF adds reversibly as a ligand to 3 to expand the trigonal bipyramidal geometry. The degree to which the coordination sphere in 3 is electronically satisfied with only three amido donors is suggested by (1) the reversible THF coordination, (2) a modest elongation in the bond distances for a five-coordinate U(VI) complex, and (3) the basicity of the oxo ligands as evidenced in the contact to Na. The vibrational spectra of the series of uranyl amido complexes [UO2(N(SiMe3)2)n]2-n (n = 2-4) are compared, to evaluate the effects on the axial U=O bonding as a function of increased electron density donated from the equatorial region. Raman spectroscopic measurements of the nu 1 symmetric O=U=O stretch show progressive axial bond weakening as the number of amido donors is increased. Crystal data for [Na(THF)2][UO2(N(SiMe3)2)3]: orthorhombic space group Pna2(1), a = 22.945(1) A, b = 15.2830(7) A, c = 12.6787(6) A, z = 4, R1 = 0.0309, wR2 = 0.0524. 相似文献
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