Chiral separation by a terminal chirality triggered P- helical quinoline oligoamide foldamer

Recent advances of optically active helical polymers as adsorbents and chiral stationary phases for chiral resolution

Chiral resolution is very important and still a big challenge due to different biological activity and same physicochemical property of one pair (R)- and (S)-isomer. There is no doubt that chiral selectors are essentially needed for chiral resolution, which can stereoselectively interact with a pair of isomers. To date, a large amount of optically active helical polymers as chiral selectors have been synthesized via two strategies. First, the target helical polymers are derived from natural polysaccharide such as cellulose and amylose. Second, they can be synthesized by polymerization of chiral monomers. Alternatively, an achiral polymer is prepared first followed by static or dynamic chiral induction. Furthermore, a part of them is harnessed as chiral stationary phases for chromatographic chiral separation and as chiral adsorbents for enantioselective adsorption/crystallization, resulting in good enantioseparation efficiency. In summary, the present review will focus on recent progress of the polymers with optical activity for chiral resolution, especially the literature published in the past 10 years. In addition, development prospects and future challenges of optically active helical polymers will be discussed in detail.

One-Handed Helical Tubular Ladder Polymers for Chromatographic Enantioseparation

Defect-free one-handed contracted helical tubular ladder polymers with a π-electron-rich cylindrical helical cavity were synthesized by alkyne benzannulations of the random-coil precursor polymers containing 6,6'-linked-1,1'-spirobiindane-7,7'-diol-based chiral monomer units. The resulting tightly-twisted helical tubular ladder polymers showed remarkably high enantioseparation abilities toward a variety of chiral hydrophobic aromatics with point, axial, and planar chiralities. The random-coil precursor polymer and analogous rigid-rod extended helical ribbon-like ladder polymer with no internal helical cavity exhibited no resolution abilities. The molecular dynamics simulations suggested that the π-electron-rich cylindrical helical cavity formed in the tightly-twisted tubular helical ladder structures is of key importance for producing the highly-enantioseparation ability, by which chiral aromatics can be enantioselectively encapsulated by specific π-π and/or hydrophobic interactions.

Chiral graphene-based supramolecular hydrogels toward tumor therapy

Drugs with chiral property are playing very important role on precise treatment of diseases (especially antitumor drugs), however, enantioselective delivery of chiral anticancer drugs is still challenge. Herein, a chiral...

Strategies for Preparation of Chiral Stationary Phases: Progress on Coating and Immobilization Methods

Enantioselective chromatography is one of the most used techniques for the separation and purification of enantiomers. The most important issue for a specific successful enantioseparation is the selection of the suitable chiral stationary phase (CSP). Different synthetic approaches have been applied for the preparation of CSPs, which embrace coating and immobilization methods. In addition to the classical and broadly applied coating and immobilization procedures, innovating strategies have been introduced recently. In this review, an overview of different methods for the preparation of coated and immobilized CSPs is described. Updated examples of CSPs associated with the various strategies are presented. Considering that after the preparation of a CSP its characterization is fundamental, the methods used for the characterization of all the described CSPs are emphasized.

Functionalized 1,8-Diazaiptycenes as Monomers for Aromatic Oligoamide Foldamers

Diversification of the structures and the applications possible for foldamers rely on expansion of the building block library available for their synthesis. In this work, we describe the synthesis of a range of three dimensional heteroaromatic monomers, based on iptycene scaffolds, that are suitable for the synthesis of aromatic oligoamide foldamers. These units can be obtained in gram quantities in up to 80 % yield through [4+2] cycloaddition between diester, diamine, and amino acid derivatives of 1,8-diazaanthracenes and a variety of dienophiles. X-ray structural studies of the monomers and an oligomer show that the new motif orients the two heterocyclic rings and attached groups at an angle of approximately 120° to each other, opening new geometric considerations for the design of this class of foldamer.

Fabrication of Carbon-Like, π-Conjugated Organic Layer on a Nano-Porous Silica Surface

This paper presents a new type of black organic material-porous silica composite providing an extremely highly selective adsorption surface. This black composite was prepared by lamination on nano-sized pores with a carbon-like, π-extended structure, which can be converted via the on-site polymerization of 1,5-dihydroxynaphthalene with a triazinane derivative and a thermally induced condensation reaction with denitrification. This bottom-up fabrication method on porous materials had the great advantage of maintaining the pore characteristics of a raw porous material, but also the resultant black surface exhibited an extremely high molecular-shape selectivity; for example, that for trans- and cis-stilbenes reached 14.0 with the black layer-laminated porous silica, whereas it was below 1.2 with simple hydrophobized silica.

Light-responsive vesicles for enantioselective release of chiral drugs prepared from a supra-amphiphilic M-helix

A kind of M-helix based vesicle with enantioselective release abilities towards racemic propranolol (a β-blocker) was presented.

Supramolecular nanochannels self-assembled by helical pyridine–pyridazine oligomers

We present a novel helix-based supramolecular nanochannel, wherein alkali ions could be easily collected, transported and even controllably released.

Stereospecific control of the helical orientation of indolocarbazole–pyridine hybrid foldamers by rational modification of terminal chiral appendages

The helical handedness excess of an indolocarbazole–pyridine hybrid oligomer capable of folding into a stable helical structure was achieved up to 96% by rational modification of terminal chiral residues.

Chiral stationary phases consisting of π-conjugated polymers bearing glucose-linked biphenyl units: reversible switching of resolution abilities based on a coil-to-helix transition

We have succeeded in developing a novel chiral stationary phase that can reversibly switch resolution abilities based on a coil-to-helix transition in a column.

Synthesis and chiroptical properties of a π-conjugated polymer containing glucose-linked biphenyl units in the main chain capable of folding into a helical conformation

Naturally occurring ellagitannins provide us with inspiration for the development of a chiral π-conjugated polymer bearing glucose-linked biphenyl units in the main chain.

Green preparation of d-tryptophan imprinted self-supported membrane for ultrahigh enantioseparation of racemic tryptophan

Green and clean preparation of molecularly imprinted membrane for ultrahigh enantioseparation of racemic tryptophan.