Synthesis and structural characterization of homochiral homo-oligomers of parent cis- and trans-furanoid-β-amino acids

Abstract

The synthesis of homochiral homo‐oligomers of cis‐ and trans‐3‐aminotetrahydrofuran‐2‐carboxylic acids (parent cis‐ and trans‐furanoid‐β‐amino acids, referred to as “cis‐/trans‐FAA”) has been carried out to understand their secondary structures and their dependence on the ring heteroatom. The oligomers of two diastereomers have been shown to have a distinct left‐handed helicity. The cis‐FAA homo‐oligomers show a 14‐helix structure, in contrast to the homo‐oligomers of cis‐ACPC, which adopt a sheet like structure. The trans‐FAA homo‐oligomers were found to adopt a 12‐helix structure, the same trend found in trans‐ACPC homo‐oligomers. With the help of ab initio calculations, the structural features of cis‐ACPC and cis‐FAA hexamers were compared. We believe that the more compact packing of the cis‐FAA hexapeptide should be due to a more favorable interaction between the ring and the backbone amide hydrogen.