Design of a Novel Inherently Chiral Calix[4]arene for Chiral Molecular Recognition

Abstract

A newly designed inherently chiral calix[4]arene was synthesized and resolved to an optically pure form. Enantiomeric recognition ability of the chiral calix[4]arene was examined using 1H NMR experiments with mandelic acid. In addition, the chiral calix[4]arene was applied to asymmetric reactions, as an organocatalyst.

Synthesis of N,O-Type Inherently Chiral Calix[4]arenes Substituted on the Lower Rim and their Organocatalysis Properties

“…So many heavy efforts have been made to structurally modify inherently chiral calix [4]arenes substituted at the meta position and the upper rim in Chen and Huang group 1,2 and Shimizu group. [3][4][5][6][7] However, the enantioselectivities in their asymmetric catalysis processes are always poor. Therefore, the asymmetric catalysis prospects of inherently chiral calix [4]arenes seem somewhat gloomy.…”

“…To mimic enzymatic catalysis process and develop efficient chiral catalysts, a variety of inherently chiral calix [4]arenes substituted at the meta position and the upper rim have been applied as chiral organocatalysts in aldol reaction, 1 addition of diethylzinc to benzaldehyde, 2 Michael addition [3][4][5][6][7] and alkylation of a glycine derivative. 7 And the highest ee in these catalytic reactions is up to 31%.…”

Synthesis of an Inherently Chiral Calix[4]arene Amino Acid and Its Derivatives: Their Application to Asymmetric Reactions as Organocatalysts

“…[7] In spite of these efforts, only a few examples of enantiomeric recognition [8] and asymmetric catalysis [9][10][11] with inherently chiral calixarenes have been reported. These limited results might arise from difficulties associated with both the design of a synthetic route to func-moiety were easily transformed to novel inherently chiral calix [4]arenes containing an amino alcohol structure or a quaternary ammonium moiety.…”

“…[10,11] Chiral calix [4]arenes have traditionally been synthesised as racemates and each of the calixarenes was then resolved into optically pure enantiomers. In the course of these studies we became interested in the design and synthesis of an inherently chiral calix [4]arene amino acid [12,13] as a chiral building block for subsequent transformation to various types of inherently chiral calix[4]-arenes.…”

Can Hetero‐Polysubstituted Cyclodextrins be Considered as Inherently Chiral Concave Molecules?

“…To date, asymmetrically substituted cavitands have been synthesized 1) as racemic mixtures, [4] which were resolved by HPLC on a chiral stationary phase, [5] 2) by introduction of a chiral auxiliary and resolution [6] or separation of the diastereoisomers, [7,8] or more recently 3) through crystallization of the inclusion complex between a racemic host and an enantiomerically pure guest. [9] Only very few reports of enantioselective syntheses of hetero-polysubstituted inherently chiral concave cycles have been reported, all of which present modest selectivities and/or yields. [10,11] Within the general class of concave molecules, cyclodextrins (CDs) are an exception because they are rendered intrinsically chiral by their chiral sugar subunits.…”