ja301430h_si_001.pdf (3.61 MB)
Diastereoselective Imine-Bond Formation through Complementary Double-Helix Formation
journal contribution
posted on 2016-02-21, 13:08 authored by Hidekazu Yamada, Yoshio Furusho, Eiji YashimaOptically active amidine dimer strands having a variety
of chiral
and achiral linkers with different stereostructures are synthesized
and used as templates for diastereoselective imine-bond formations
between two achiral carboxylic acid monomers bearing a terminal aldehyde
group and racemic 1,2-cyclohexanediamine, resulting in a preferred-handed
double helix stabilized by complementary salt bridges. The diastereoselectivity
of the racemic amine is significantly affected by the chirality of
the amidine residues along with the rigidity and/or chirality of the
linkers in the templates. NMR and kinetic studies reveal that the
present imine-bond formation involves a two-step reversible reaction.
The second step involves formation of a preferred-handed complementary
double helix assisted by the chiral amidine templates and determines
the overall reaction rate and diastereoselectivity of the amine.