Induced axial chirality in the biphenyl core of linear and cyclic Bip and beta~(2,2)-Bip short peptides

摘要

Bip and beta~(2,2)-Bip are atropoisomeric,conformationally labile amino acid residues with interconverting,non isolable(R)and(S)enantiomers.We have previously reported that in linear dipeptides with Ala,Val,Leu,Phe,(alpha Me)Val and(alpha Me)Leu residues at the C-and/or N-terminal positions of Bip,the onset of an equilibrium between two diastereoisomeric conformers with unequal populations could be observed by CD and 1H NMR.We have now expanded the study of the Bip linear dipeptides to a larger series of Bip/Ala,Bip/beta~3-Ala,beta~(2,2)-Bip/Ala and beta~(2,2)-Bip/beta~3-Ala linear and cyclic dipeptides(Fig.1).