Studies of Unusual Amino Acids and Their Peptides. XI. The Resolution of β-(2-Furyl)-β-alanine and β-(2-Thienyl)-β-alanine and Their Absolute Configurations

Abstract (+)-β-(2-Furyl)-β-alanine and (+)-β-(2-thienyl)-β-alanine were obtained by resolving the N-benzyloxycarbonyl-Dl-amino acids with quinine and by removing the protecting group from them. It was concluded, from the changes in their ORD curves depending on the pH, and also from the sign of the Cotton effects of their DCHA salts of the N-ethylthiocarbonothioyl derivatives, that both the compounds belong to the l-series. This conclusion was supported by the fact that the aspartic acid obtained by the oxidation of these amino acids belongs to the d-series.