Asymmetric Catalytic Michael Reaction by Means of Natural Proteins

Nanocrystalline MgO for Asymmetric Henry and Michael Reactions

Nanomaterials with their three-dimensional structure and defined size and shape are considered to be suitable candidates for proper alignment with prochiral substrates for unidirectional introduction of reacting species to induce an asymmetric center. We herein report the design and development of a truly recyclable heterogeneous catalyst, nanocrystalline magnesium oxide, for the asymmetric Henry reaction (AH) to afford chiral nitro alcohols with excellent yields and good to excellent enantioselectivities (ee's) for the first time. Bronsted hydroxyls are the sole contributors for the ee, while they add on to the activity in AH. It is demonstrated that the hydrogen bond interactions between the -OH groups of (S)-(-)-binol and the -OH groups of MgO are essential for the induction of enantioselectivity. Further, to prove the above hypothesis, we have successfully carried out another reaction, asymmetric Michael reaction (AM) with nanocrystalline MgO. The reusable and suitably aligned nanocrystalline MgO-catalyzed AH and AM reactions afforded chiral products with comparable ee's to that of the homogeneous system.

Chiral recognition by biological macromolecules. Partial resolution of racemic enones by albumin

A novel approach to the optical resolution of racemic enones has been introduced by using the binding properties of the transport protein albumin, which chemically binds preferentially one antipode of some alpha, beta-unsaturated cyclic enones in a reversible manner. Simple separation of the macromolecules by ultrafiltration leads to partial resolution of racemates.