Improvement of a stereoselective biocatalytic synthesis by substrate and enzyme engineering: 2-hydroxy-(4'-oxocyclohexyl)acetonitrile as the model.

Even if biocatalysis is finding increasing application, it still has to gain widespread use in synthetic chemistry. Reasons for this are limitations that enzymes have with regard to substrate range, reaction scope, and insufficient selectivity with unnatural compounds. These shortcomings can be challenged by enzyme and/or substrate engineering, which are employed to alter substrate specificity and enhance the enzyme selectivity toward unnatural substrates.

Ortho-lithiation of free ferrocenyl alcohols: a new method for the synthesis of planar chiral ferrocene derivatives.

An ortho-metalation method for free ferrocenyl alcohols has been developed, which allows preparation of planar chiral ferrocene derivatives with high yields and diastereoselectivities.

De-racemization of enantiomers versus de-epimerization of diastereomers--classification of dynamic kinetic asymmetric transformations (DYKAT).

The isolation of single stereoisomers from a racemic (or diastereomeric) mixture by enzymatic or chemical resolution techniques goes in hand with the disposal of 50% (racemate) or more (diastereomeric mixtures) of the "undesired" substrate isomer(s). In order to circumvent this drawback, dynamic systems have been developed for the de-racemization of enantiomers and the de-epimerizations of diastereomers. Key strategies within this area are discussed and are classified according to their underlying kinetics, that is, dynamic kinetic resolution (DKR), dynamic kinetic asymmetric transformations (DYKAT), and hybrids between both of them.