Asymmetric synthesis of α-amino-β-hydroxy acids using a chiral pyridoxal-like pyridinophane-zinc complex as an enzyme mimic; scope and limitation

Article abstract of DOI:10.1246/bcsj.63.88

A chelate complex (4) with high homogeneity was precipitated upon stirring a mixture of zinc(II) ion and a Schiff base produced from glycine and (R)- or (S)-15-formyl-14-hydroxy-2,8-dithia[9](2,5)pyridinophane, chiral pyridoxal-like pyridinophane. A four-coordinated zinc chelate complex was newly proposed as the structure of 4. Aldol condensations between 4 and several aldehydes were attempted at pH 10.0. Only small linear chain aldehydes, such as acetaldehyde and propionaldehyde, could react with 4 under these conditions to give the corresponding α-amino-β-hydroxy acid in the range of 27-77% enantiomeric excess.