Asymmetric catalysis acyl transfer

Under almost anhydrous conditions in organic medium, lipases can be used in the reverse mode for direct ester synthesis from carboxylic acids and alcohols, as well as transesterifications (acyl transfer reactions) which can be divided into alcoholysis (ester and alcohol), acidolysis (ester and acid), and interesterification (ester-ester interchange). The direct esterification and alcoholysis in particular have been most frequently used in asymmetric transformations involving lipases. The parameters that influence enzymatic catalysis in organic solvents have been intensively studied and discussed. ... 

Jarvo ER, Copeland GT, Papaioannou N, Bonitatebus PJ, Miller SJ (1999) A biomimetic approach to asymmetric acyl transfer catalysis. J Am Chem Soc 121 11638-11643... 

Building upon these concepts, this chapter firstly gives an insight into the modes of action of a selection of non-covalent chiral organocatalysts, employing chiral Brpnsted acid catalysis, chiral Brpnsted base catalysis, and chiral phase-transfer catalysis (PTC). Further sections of this chapter describe two separate case studies that aim to compare and contrast selected covalent and non-covalent strategies for achieving two distinct processes, acyl transfer reactions and asymmetric pericyclic processes. 

Although the process of direct phosphoryl transfer shares some mechanistic similarities to acyl transfer in so far as it can be catalyzed by some of the same small-molecule nucleophiles (e.g., N-methylimidazole, 4-DMAP, pyridine-N-ox-ides) [77], it presents some distinct challenges with regard to asymmetric catalysis as the result of the tetrahedral nature of the transferred phosphorus(V) center as compared to the trigonal planar carbonyl carbon. Additionally, achiral alcohol... 

The first organocatalytic asymmetric aziridination reactions of electron-deficient olefins made use of either (i) a chiral tertiary amine combined with a 0-phosphinyl or sulfonyl hydroxylamine for the in situ generation of aminimides as aziridination reagents [133, 134], or (ii) a quaternary salt of cinchona alkaloids in phase-transfer catalysis in combination with ethyl nosyloxycarbamate [135], A-acyl A-aryl... 

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