Sugar Derived Oxazolone Pseudotetrapeptide as γ-Turn Inducer and Anion-Selective Transporter

The C3-tetrasubstituted furanoid sugar amino acid derived linear amino acid dipeptide 8 and tetrapeptide 9 on intra-molecular cyclization afforded oxazolone pseudo-peptides 1 and 2a, respectively, with formation of oxazole ring at the C-terminus. Conformational study of 2a showed seven membered intramolecular C=O×××HN (II) hydrogen bonding leading to the γ-turn conformation which is absent in the precursor tetrapeptide 9 thus indicating the role of oxazolone ring in γ-turn formation in 2a. This fact was supported by the molecular modeling studies. The oxazolone ring containing pseudo-tetrapeptide 2a was found to be better ion transporter than pseudodi-peptide1.The ion selectivity of 2a indicated Cl-anion-selective transport via the antiport mechanism.