Stereoselective Rearrangement of β-Hydroxy-<i>N</i>-acyloxazolidin-2-ones to Afford<i>N</i>-2-Hydroxyethyl-1,3-oxazinane-2,4-diones
作者:Steven D. Bull、Fred J. Feuillet、D. Gangani Niyadurupola、Rachel Green、Matt Cheeseman
DOI:10.1055/s-2005-865212
日期:——
Zinc alkoxides of syn- or anti-β-hydroxy-N-acyloxazolidin-2-ones undergo stereoselective rearrangement to afford their corresponding syn- or anti-N-2-hydroxyethyl-1,3-oxazinane-2,4-diones in good yield.
Lithium Amino Alkoxide–Evans Enolate Mixed Aggregates: Aldol Addition with Matched and Mismatched Stereocontrol
作者:Janis Jermaks、Evan H. Tallmadge、Ivan Keresztes、David B. Collum
DOI:10.1021/jacs.7b13776
日期:2018.2.28
Building on structural and mechanistic studies of lithiated enolates derived from acylated oxazolidinones (Evans enolates) and chiral lithiated amino alkoxides, we found that amino alkoxides amplify the enantioselectivity of aldol additions. The pairing of enantiomeric series affords matched and mismatched stereoselectivities. The structures of mixed tetramers showing 2:2 and 3:1 (alkoxide-rich) stoichiometries
Addition of kinetic boron enolates generated from β-alkoxy methyl ketones to aldehydes. Density functional theory calculations on the transition structures
作者:Luiz C. Dias、Sávio M. Pinheiro、Vanda M. de Oliveira、Marco A.B. Ferreira、Cláudio F. Tormena、Andrea M. Aguilar、Julio Zukerman-Schpector、Edward R.T. Tiekink
DOI:10.1016/j.tet.2009.08.042
日期:2009.10
of 1,5-anti stereoinduction are obtained in boron enolate aldol reactions of 1,2-syn β-alkoxy methyl ketones with achiral aldehydes, when the β-alkoxy protecting group is part of a benzylidene acetal. We have also investigated the effects of the ligands on boron, the α-, β-, and γ-substituents and the β-alkoxy protecting group on the boron enolates, using density functional theory (B3LYP) and Møller–Plesset
Asymmetric Aldol Additions: Use of Titanium Tetrachloride and (−)-Sparteine for the Soft Enolization of <i>N-</i>Acyl Oxazolidinones, Oxazolidinethiones, and Thiazolidinethiones
作者:Michael T. Crimmins、Bryan W. King、Elie A. Tabet、Kleem Chaudhary
DOI:10.1021/jo001387r
日期:2001.2.1
N-methyl-2-pyrrolidinone, selectivities of 97:3 to > 99:1 were obtained for the Evans syn aldol products using N-propionyl oxazolidinones, oxazolidinethiones, and thiazolidinethiones. The non-Evans syn aldol adducts are available with the oxazolidinethione and thiazolidinethiones by altering the Lewisacid/aminebase ratios. The change in facial selectivity in the aldoladditions is proposed to be a result of
α‐ and β‐Lipomycin: Total Syntheses by Sequential Stille Couplings and Assignment of the Absolute Configuration of All Stereogenic Centers
作者:Max L. Hofferberth、Reinhard Brückner
DOI:10.1002/anie.201402255
日期:2014.7.7
structures of α‐lipomycin and its aglycon β‐lipomycin except for the configurations of their side‐chain stereocenters. We synthesized all relevant β‐lipomycin candidates: the (12R,13S) isomer has the same specific rotational value as the natural product. By the same criterion the (12R,13S)‐configured D‐digitoxide is identical to α‐lipomycin. We double‐checked our assignments by degrading α‐ and β‐lipomycin