An Approach to the Imine Ring System of Pinnatoxins
摘要:
A concise stereoselective approach to the spirobicyclic imine fragment of pinnatoxins and pteriatoxins is described. The approach relies on a tandem reaction sequence involving consecutive sigmatropic rearrangements to build the quaternary chiral center at the core of the spirobicyclic ring system.
[EN] STEREOSELECTIVE SYNTHESIS OF 3,4-DISUBSTITUTED CYCLOPENTANONES AND RELATED COMPOUNDS [FR] SYNTHESE STEREOSELECTIVE DE CYCLOPENTANONES 3,4-DISUBSTITUES ET COMPOSES CORRESPONDANTS
A two-step sequence for the asymmetric vicinal acylation of olefins by a [2+2+1] strategy is reported. The key reaction is a [2+2] cycloaddition of an olefin to a chiral keteniminium salt derived from N-tosylsarcosinamide. This is followed by a regioselective Baeyer-Villigeroxidation of the resulting cyclobutanone to yield a lactol derivative that is equivalent to the product of addition of a carboxyl
The asymmetric hydrolysis of five-membered cyclic diesters was carried out by using pig liver esterase (PLE) as a catalyst. The absolute configurations of the resulting half esters and recovered diesters were established and the stereospecificity of PLE action in such systems was revealed.
Enantioselective Diene Cyclization/Hydrosilylation Catalyzed by Optically Active Palladium Bisoxazoline and Pyridine−Oxazoline Complexes
作者:Nicholas S. Perch、Tao Pei、Ross A. Widenhoefer
DOI:10.1021/jo0003192
日期:2000.6.1
palladium pyridine-oxazoline complex (N-N)Pd(Me)Cl ¿N-N = (R)-(+)-4-isopropyl-2-(2-pyridinyl)-2-oxazoline (R-5b) and NaBAr(4) (5 mol %) catalyzed the asymmetric cyclization/hydrosilylation of 2 and triethylsilane at -32 degrees C for 24 h to form carbocycle S,S-3 in 82% yield (>95% de, 87% ee) as the exclusive product. Asymmetric diene cyclization catalyzed by complex R-5b was compatible with a range
An optical laminate comprising, laminated in the order mentioned, a support substrate, adhesive layer, cholesteric liquid crystal layer and protection layer, characterized in that the cholesteric liquid crystal layer has in at least part thereof an area indicating a diffraction power. The optical laminate is used for a polarization diffraction element, liquid crystal display device compensation element, decorative member, and forgery prevention element.