Synthesis of linear and cyclic homo-β-peptides based on a binaphthylic β-amino acid with only axial chirality

The terminally protected, linear, homo-β-peptides Boc-[(R)-β2,2-HBin]n-OMe (n = 2-6) as well as the cyclic homo-β-peptides c[(R)-β2,2-HBin]3 and c[(S)-β2,2-HBin]4, all derived from the 2′,1′:1,2;1″,2″:3,4-dinaphthcyclohepta-1,3-diene-6-aminomethyl-6-carboxylic acid residue β2,2-HBin possessing only axial chirality, have been synthesized in solution by the EDC/AtOH coupling method for chain elongation, and by cyclization of pentafluorophenyl esters. A conformational analysis suggested the concomitant occurrence of different intramolecularly H-bonded forms for the linear oligomers in solution.