Photomodulated chiral induction in helical azobenzene oligomers

Appending L-alanine to the terminal positions of a helical azobenzene oligomer produced a P helical bias, which increased with oligomer length. Irradiation gave rise to E --> Z isomerization of the terminal azo linkages, which displaced the stereogenic center Of L-Ala from the helix backbone and suppressed chiral induction. Theoretical simulations of the CD spectrum of the P helical conformation are in qualitative agreement with the experimental spectra.