88511-04-0Relevant academic research and scientific papers
Enzyme-catalysed Asymmetric Synthesis, IV. - Synthesis of Homochiral Building Blocks for the Enantioselective Total Synthesis of Cyclopentanoids with an Esterase-catalysed Asymmetric Reaction as Key Step
Gais, Hans-Joachim,Lukas, Karl L.,Ball, Walter A.,Braun, Siegmar,Lindner, Hans J.
, p. 687 - 716 (2007/10/02)
An efficient synthesis of the homochiral building blocks 2a and ent-2a based on the "enantiotopos-enzyme concept" for the total synthesis of cyclopentanoids is described.Key steps thereof are the almost quantitative PLE-catalysed asymmetric hydrolysis of the meso-diester 8 to the homochiral hemiester 9, whose absolute configuration was determined by crystal structure analysis of the (-)-ephedrine salt 12, the preparation of optically pure 9 and ent-9 by a racemate resolution of rac-9 using (+)- and (-)-ephedrine, the enantiodivergent synthesis of the lactones 18 and ent-18 from 9, as well as the enantioconvergent synthesis of 18 or ent-18 from 9 and ent-9 by optional chemoselective reduction of the ester and carboxy group, and finally the regioselective Dieckmann cyclisation of the isomeric diesters 23b/24b and ent-23b/ent-24b, respectively, to give the cyclopentanoid target compounds 2a and ent-2a.The structures of 23b, 24b, rac-2b, and rac-29 were determined by INADEQUATE-13C-NMR experiments.Dieckmann cyclisation of the trans-diester rac-31 also leads to rac-2a and rac-26a.
CHEMICAL REPERCUSSIONS OF ORBITAL INTERACTIONS THROUGH BOND AND THROUGH SPACE. EFFECT OF REMOTE SUBSTITUENTS ON THE ADDITION OF NITRENES TO BICYCLIC OLEFINS
Aitken, R. Alan,Gosney, Ian,Farries, Hugh,Palmer, Michael H.,Simpson, Isobel,et. al.
, p. 1329 - 1346 (2007/10/02)
The reactivity of a series of bicyclic olefins with nitrenes is profoundly influenced by the nature of remote functional groups.There is a marked lack of reactivity for reactions with carboethoxynitrene as compared to phthalimidonitrene which is distinctly nucleophilic in character.An explanation for the reluctance to form aziridines is offered in terms of orbital interactions between the distant groups and the olefinic bond, making the latter remarkably electron deficient as evidenced by UV-photoelectron spectroscopy.Because of the complexity of the spectra, identification of the Ip associated with the reactive ?-centre was made by recourse to ab initio configuration interaction calculations for key members of the series.
