Poly(arylisocyanides) as Versatile, Enantiodiscriminating Alignment Media for Small Molecules

Abstract

Lyotropic liquid crystalline (LLC) phases of amino acid derived polyarylisocyanides were employed as chiral alignment media for the measurement of residual dipolar couplings (RDCs) of small chiral organic molecules. Anisotropic samples in CDCl3 displayed quadrupolar splittings of the deuterium signal in the range of several hundreds of Hertz. The LLC phases showed excellent orienting properties for a broad range of analytes bearing various functional groups. The precise extraction of RDCs in the range of up to ±40 Hertz from F2‐coupled HSQC spectra was possible. Additionally, the chiral environment offers the opportunity for diastereomorphous interactions with the enantiomers of chiral analytes leading to two different sets of RDCs. This differential order effect was particularly pronounced with ketones and alcohols.

Self‐Assembly of Helical Polymers and Oligomers to Create Liquid Crystalline Alignment for Anisotropic NMR Parameters

“…Moreover, both chiral LC phases offer the opportunity for diastereomorphous interactions with the enantiomers of chiral analytes, including carboxylic acids, ketones, aldehydes, alcohols, amines, and unsaturated hydrocarbons. [ 28 ]…”

“…Moreover, both chiral LC phases offer the opportunity for diastereomorphous interactions with the enantiomers of chiral analytes, including carboxylic acids, ketones, aldehydes, alcohols, amines, and unsaturated hydrocarbons. [28] The amino-acid-stabilized polyisocyanides usually possess peptide sidechains that form well-defined hydrogen-bonded networks, which are arranged in the form of helical conformation with twist-type arrays along the main-chain backbone. Inspired by helical polyisocyanopeptides (PIP) bearing alanine and alanine peptide residues of Nolte and co-workers, [29] optically active novel alkyl PIP has been prepared via nickel(II)-catalyzed polymerization, and it can serve as an ideal weak alignment media.…”

Synthesis of poly(3-hexylthiophene)-block-poly(phenylisocyanide) copolymers and their self-assembly in solution

“…Herein, a concise and highly efficient procedure for the synthesis of Val-based isocyanide monomer 5 is presented (Scheme 1a). According to the reported literature, 38,43,44 the traditional preparation process of amino acid-based intermediate 3 (so-called dipeptidyl amide) is often cumbersome and expensive. For example, dipeptidyl amide 3 has been generally prepared by the condensation reaction between nitrobenzoyl acid/nitrobenzoyl chloride and ester derivative 2, and then hydrogenation for reducing the nitro group (-NO 2 ) of the aromatic moiety in palladium catalyst/activated carbon systems.…”

“…[31][32][33][34] Moreover, the Val-derived PPA and PPI homopolymers formed rigid, rod-like structures that aggregate into ordered liquid crystals for acquiring residual dipolar couplings. [35][36][37][38] Yam's group reported the self-assembly properties of a Pt(terpy) complex with Val-modified units appended with supramolecular gelators. 39 The copolymers with dissimilar blocks based on a functional PEG and chiral L-valine isocyanide monomer have the tendency to exhibit various types of self-assemblies.…”

Residual‐Chemical‐Shift‐Anisotropy‐Based Enantiodifferentiation in Lyotropic Liquid Crystalline Phases Based on Helically Chiral Polyacetylenes

“…In the last decade, several groups reported a good number of chiral alignment media that satisfy this criterion [10d–f,12c–e,13b,15] . These media are chiral LLC phases derived from various polymers such as poly‐γ‐benzyl‐ l / d ‐glutamate (PBLG/PBDG), [10d,11,16] poly‐γ‐ethyl‐ l / d ‐glutamate (PELG/PEDG), [17] polyguanidines, [18] polyisocyanides, [13a–b,15b,19] and polyphenylacetylenes (PPAs) [12,20] . Except for PBLG, most of the alignment media induce sufficiently weak alignment to deliver simple extraction of RDCs.…”