1 research outputs found
“Backdoor Induction” of Chirality: Asymmetric Hydrogenation with Rhodium(I) Complexes of Triphenylphosphane-Substituted β‑Turn Mimetics
Bioconjugate
bidentate ligands <b>2</b>–<b>10</b> were obtained
by tethering triphenylphosphanecarboxylic acid to
amino acid substituted spacers with different flexibility, ranging
from a rigid enediyne-based β-turn inducer to flexible linear
aliphatic chains with up to eight carbon atoms. The 21 synthesized
ligands revealed up to 81% ee selectivity in rhodium-catalyzed asymmetric
hydrogenation of α,β-unsaturated amino acids. The key
feature of the catalysts is the prochiral coordination sphere of the
catalytic metal while the chirality is transmitted by “backdoor
induction” from distant hydrogen-bonded amino acids. DFT calculations
were applied to study the structure and relative stability of the
precatalytic organometallic Rh(I) complexes, with particular emphasis
on hydrogen-bonded secondary structures