Synthesis of Nonnatural Helical Polypeptide via Asymmetric Polymerization and Reductive Cleavage of N–O Bond

Abstract

Herein, we present a novel synthetic strategy, to amino-acid-free peptide synthesis based on postpolymerization conversion, for chiral nonnatural polypeptides. Optically active poly-N-alkoxyamides were prepared by our asymmetric polymerization as precursors of polypeptides, and the reductive cleavage of N–O bonds using a SmI2–THF complex was carried out. The reaction proceeded smoothly with quantitative conversion to afford a nonnatural polypeptide. The resulting polypeptide adopted a one-handed stable helical structure in solution, which was established by circular dichroism (CD) and theoretical calculations using density functional theory (DFT). The simulated spectra by time-dependent (TD) DFT methods clearly indicated the validity of the proposed structure. The synthetic approach is a promising candidate for the synthesis of nonnatural polypeptides.

Periodic introduction of aromatic units in polypeptides via chemoenzymatic polymerization to yield specific secondary structures with high thermal stability

“…Therefore, sequence control of aromatic monomercontaining polypeptides is essential for thermal and mechanical properties. There are few reports that introducing aromatic amino acids into peptide sequences can induce specific secondary structures [14,32,33]. To synthesize the polypeptides containing aromatic units, we designed novel tripeptide esters in which Abz is sandwiched between Gly and Ala units, namely, GlyAbzGly and AlaAbzAla esters.…”

A Planar‐Chiral Rhodium(III) Catalyst with a Sterically Demanding Cyclopentadienyl Ligand and Its Application in the Enantioselective Synthesis of Dihydroisoquinolones

“…[20] Although these approaches are elegant and efficient, they involve rather complex multistep syntheses of chiral cyclopentadienyl ligands (or the preparation of mutant streptavidin peptides). It is noteworthy that despite the success of planar-chiral complexes in other catalytic reactions, [22] they have apparently not been used for enantioselective CÀHa ctivation thus far. [21] Apart from the simple synthesis,t his approach has two strategic advantages:1 )Itp rovides access to complexes with planar chirality,w hich cannot be obtained from free chiral cyclopentadienyl ligands,a nd 2) it simultaneously gives both enantiomers of the catalyst.…”

“…[21] Apart from the simple synthesis,t his approach has two strategic advantages:1 )Itp rovides access to complexes with planar chirality,w hich cannot be obtained from free chiral cyclopentadienyl ligands,a nd 2) it simultaneously gives both enantiomers of the catalyst. It is noteworthy that despite the success of planar-chiral complexes in other catalytic reactions, [22] they have apparently not been used for enantioselective CÀHa ctivation thus far. [12] Driven by our interest in rhodium-catalyzed transformations of alkynes, [23] we chose an on-classical route for the synthesis of our catalyst, namely a[2+ +2+ +1] cyclotrimerization of terminal alkynes in the coordination sphere of am etal.…”

Estimation of the helical twisting power of chiral inducers by time-dependent density functional theory (TD-DFT) for electrochemical polymerization in cholesteric liquid crystals

“…Currently, electronic circular dichroism (ECD) can be predicted using quantum chemical calculations, such as the calculations of the density functional theory (DFT) method and the Hartree-Fock (HF) method, using the time-dependent self-consistent field (TD-SCF) treatment [27]. The aforementioned methods have been applied to predict the Cotton effect and to confirm the chirality of products in asymmetric synthesis [28]. Employing quantum chemical calculations for predicting the optical activity and HTP of the inducer is considered to be a crucial step in the synthesis of optically active polymers.…”