Induced axial chirality in the biphenyl core of the Calpha-tetrasubstituted alpha-amino acid residue Bip and subsequent propagation of chirality in (Bip)n/Val oligopeptides

In the dipeptides Boc-Bip-L-Val-OMe and Boc-Bip-D-Val-OMe, an induced axial chirality in the biphenyl core of the Bip residue, a conformationally labile, proatropoisomeric C(alpha,alpha)-disubstituted glycine, was observed by electronic CD and (1)H NMR. Chiral induction is significantly higher when the Val residue is located at the C-terminal position of Bip. An outstanding phenomenon of propagation of chirality was demonstrated to occur in the related 3(10)-helical -(Bip)n-L-Val (n = 2-6) oligopeptides by CD and vibrational CD techniques.