Optimized double kinetic resolution for the preparation of (S)-solketal

Novel Asymmetric Formylation of Aromatic Compounds: Enantioselective Synthesis of Formyl 7,8‐Dipropyltetrathia[7]helicenes

“…Double kinetic resolution (double‐KR) is a much underused synthetic strategy but with C 2 ‐symmetric substrates such as helicenes, a novel and convenient one‐pot variant is possible. The first examples of double‐KR were reported many years ago,21 but even after the development of the method by Vänttinen and Kanerva in 1997,22 the advantages have been largely ignored by synthetic chemists. With suitable chiral formamides in hand we had an ideal opportunity to test the double‐KR principle in this important practical situation 23.…”

Selection of Pure Enantiomers of 1-Phenyl Alcohols by Sequenced Processes of Ester Hydrolysis and Transesterification in Enzyme Membrane Reactors

“…As already mentioned, tandem reactions can be used for the preparation of substances with enhanced enantiomeric purity (1)(2)(3)(4). This possibility has been proved in the following tandem reactions: hydrolysis of 1-phenylethyl propionate in a biphasic system and transesterification of vinyl acetate with the 1-phenylethanol formed.…”

“…In the enzymatic kinetic resolution of a racemic mixture, the optical purity of the product depends on an enzyme enantioselectivity in the system. It was shown recently that kinetic resolution can be improved by carrying out two enzymatic reactions simultaneously or sequentially (1)(2)(3)(4), and the enantiomeric excess of the product in double kinetic resolution exceeds that gained in one step. The benefits of that strategy in overall yield and enantiomeric purity of the enantiomers produced are especially clear in processes of low or moderate enantioselectivity.…”

A two-step enzymatic resolution of glycidyl butyrate

“…1), while a further increase in the pH to 9.0 resulted in a sharp decrease in both. The activity and enantioselectivity might be significantly affected by the breaking of weak ionic or hydrogen bonds on enzyme caused by the increase of pH [21]. And 7.4 was selected as the optimum pH for further study.…”

“…Contrary to the transformations based on the classic kinetic resolution (KR) catalyzed by enzymes, where one enantiomer can be obtained with high enantiomeric excess [20], two-step enzymatic resolution is a method to obtain both enantionmers with high enantiomeric excess by subjecting the isolated enantiomerically enriched product of the first enzymatic resolution to the second [21], which results in the increase of the enantiomeric excess of the product in the second step. A good example has been proposed by Fishman et al [22], who use CALB as catalyst for a two-step enzymatic resolution of (R,S)-ethyl-3-hydroxybutyrate (HEB) and both enantiomers of (R)-and (S)-HEB are obtained at over 96% enantiomeric excess, with a total process yield of 73%.…”