Optical Resolution of Pyridoxal-like Pyridinophanes

Abstract

Abstract Racemic modifications of the pyridoxal-like ansa compounds such as 15-formyl-14-hydroxy-2,8-dithia[9](2,5)pyridinophanes prepared as a pontential catalyst for stereospecific nonenzymatic reactions were optically resolved through formation of Schiff bases by treatment with amino sugar derivatives or amino acids. Resolutions with the amino sugar derivatives were ascribable to the difference of the solubilities of the diastereomeric Schiff bases, whereas those with the amino acids resulted from the difference of the reaction rates for the formation of the diastereomeric Schiff bases. As the amino sugar resolving agents, 3-amino-3-deoxy-1,2:5,6-di-O-isopropylidene-β-d-idofuranose and the corresponding α-d-glucofuranose isomer were employed and gave (R)- and (S)-pyridoxal-like pyridinophanes, respectively. On the other hand, chiral valine was the most efficient resolving agent among the amino acid tested and the presence of half equimolar Fe3+ markedly increased the optical purities of the products. Employment of (S)-valine gave (R)-pyridinophanes in excess and vice versa.