N-Alkyl salts derived from ephedrine do not promote enantioselective Corey–Chaykovsky reactions involving sulfonium methylides under phase-transfer conditions
摘要:
N-Alkyl salts derived from ephedrine have twice been reported to act as chiral phase-transfer catalysts in Corey-Chaykovsky reactions between sulfonium ylides and benzaldehyde; reportedly furnishing the terminal epoxide product in moderate-excel lent enantiomeric excess. This study unequivocally demonstrates that these reactions proceed without measurable stereoinduction and explains how previous studies mistakenly attributed product optical activity to asymmetric catalysis. (C) 2008 Elsevier Ltd. All rights reserved.
Deracemization of bilirubin as the marker of the chirality of micellar aggregates
作者:Alessandro Sorrenti、Barbara Altieri、Francesca Ceccacci、Pietro Di Profio、Raimondo Germani、Luisa Giansanti、Gianfranco Savelli、Giovanna Mancini
DOI:10.1002/chir.21026
日期:2012.1
The deracemization of bilirubin in micellaraggregates of structurally correlated chiral surfactants was studied by circular dichroism experiments and exploited as the marker of the expression of chirality of the aggregates. The obtained results suggest that the hydrophobic interactions control the transfer of chirality from the monomers to the aggregates, and that different regions of the same aggregate
carried out on the heteroaggregates formed in water upon the interaction of Chicago Sky Blue with four different cationic surfactants derived from ephedrine and pseudoephedrine and featuring hydrophobic tails of different length. The chirooptical features of the heteroaggregates indicate that hydrophobic interactions control the transcription of the chiral information from the surfactant to the supramolecular