Absolute control of helicity at the C-termini in quinoline oligoamide foldamers by chiral oxazolylaniline moieties

Abstract

Absolute one-handed chiral quinoline tetramers andoctamers containing different oxazolylanilines at the C-terminus have been synthesized. The absolute one-handed sense and diastereomeric excess values were valued by 1H NMR. X-ray crystal diffractionand CD studies reveal that the S-oxazolylaniline always induces a P-handed helicity and the absolute helicity is driven by the stable three-center hydrogen bonding between protons in the amide and N atoms in oxazolylaniline and adjacent quinoline ring. CPL investigations demonstrated that S-CQn-a⿼d are CPL active and its glum values are dependent on its length. Interestingly, the sizes of the substituents in the chiral centers are different, however, they exert no effect on the dissymmetric factors gabs and glum of quinoline oligoamide foldamers.