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

The terminally protected, linear, homo-b-peptides Boc-[(R)-b2,2-HBin]n-OMe (n = 2–6) as well as the cyclic homo-b-peptides c[(R)-b2,2-HBin]3 and c[(S)-b2,2-HBin]4, all derived from the 20,10:1,2;100,200:3,4-dinaphthcyclohepta-1,3-diene-6-aminomethyl-6- carboxylic acid residue b2,2-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