Expanding the structural repertoire of β/α Ant-Pro (anthranilic acid-proline) oligomers into γ/α 2-Amb-Pro (2-aminomethyl benzoic acid-proline) oligomers

In this article, we report a novel class of heterogeneous synthetic oligomers featuring the conformationally constrained amino acid residues – 2-aminomethyl benzoic acid (2-Amb) and proline (Pro) in repeating sequences. Oligomers as large as hexadecamers featuring the conformationally restricted γ/α 2-Amb-Pro motif have been assembled using solution-phase Boc strategy, following multi-step synthetic sequences starting from the commercially available O-toluic acid. EDC-mediated peptide coupling has been found to be optimum for the assembly of the relatively non-polar oligomers, which could be readily purified by the standard column chromatographic purification procedures. This study offers considerable prospects of expanding the structural repertoire of β/α Ant-Pro motif, which has been described earlier to assume right-handed helical architecture displaying robust nine-membered-ring closed network of hydrogen-bonding interactions, into γ/α 2-Amb-Pro motif.