Induced Axial Chirality in the Biphenyl Core of the C-alpha-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 Cα,α-disubstituted glycine, was observed by electronic CD and 1H 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 310-helical -(Bip)n-L-Val (n = 2−6) oligopeptides by CD and vibrational CD techniques.