Your web browser is out of date. Update your browser for more security, speed and the best experience on this site

Shu Kobayashi

23 September 2008
IOCB Prague
Prof. Shu Kobayashi (University of Tokyo, Japan)
Toward Truly Efficient and Powerful Organic Synthesis - New Dimension of Acid and Base Catalysis


Recent advances in acid and base catalysis will be discussed. Catalytic asymmetric 1,4-addition and [3+2] cycloaddition reactions using chiral calcium complexes prepared from calcium isopropoxide and chiral bisoxazoline ligands have been developed. Glycine Schiff bases reacted with acrylic esters to afford 1,4-addition products, glutamic acid derivatives, in high yields with high enantioselectivities. During the investigation of the 1,4-addition reactions, we unexpectedly found that a [3+2] cycloaddition occurred in the reactions with crotonate derivatives affording substituted pyrrolidine derivatives in high yields with high enantioselectivities. Based on this finding, we investigated asymmetric [3+2] cycloadditions, and it was revealed that several kinds of optically active substituted pyrrolidine derivatives containing contiguous stereogenic tertiary and quaternary carbon centers were obtained with high diastereo- and enantioselectivities. NMR spectroscopic analysis and observation of non-amplification of enantioselectivity in non-linear effect experiments suggested that a monomeric calcium complex with an anionic ligand was formed. A stepwise mechanism of the [3+2] cycloaddition, consisting of 1,4-addition and successive intramolecular Mannich-type reaction was suggested. Furthermore, modification of the Schiff base structure resulted in a modification of the reaction course from a [3+2] cycloaddition to a 1,4-addition affording 3-substituted glutamic acid derivatives with high diasterero- and enantioselectivities.
Share this article