Cyclotriveratrylene-BINOL-Based Host Compounds: Synthesis, Absolute Configuration Assignment, and Recognition Properties

Abstract

New host compounds combining a cyclotriveratrylene (CTV) unit and three binaphthol moieties have been synthesized enantiomerically and diastereomerically pure. The use of a chemical correlation allows for the assignment of their absolute configuration. The energy barrier of epimerization was measured, suggesting that no intramolecular hydrogen bonding occurs between the hydroxyl groups of the binaphthols. These open-shell host compounds were then tested in the recognition of carbohydrates; a preferential binding of mannose toward glucose was observed, and good diastereoselectivities were reached (up to 1:10). This recognition of sugar derivatives by open-shell CTV-based host compounds is unprecedented and opens up the way for a wider use of this easily accessible class of molecules as chiral sensors.

Efficient resolution of racemic crown-shaped cyclotriveratrylene derivatives and isolation and characterization of the intermediate saddle isomer

“…At that time, they converted the racemic triol into diastereomeric triesters upon reaction with ( R )-(+)-2-phenoxypropionic acid, separated those via column chromatography, and received the desired enantiomers upon reductive cleavage of the esters. Similar synthetic approaches through the formation of diastereomeric esters were also used for other chiral CTV derivatives [63–67]. However, performing the separation on the stage of a monomeric CTV always bears the risk of racemization because of the flexibility of these molecules and kinetic studies for several CTVs demonstrate that the energy barrier for the racemization in each case is around 110 kJ mol −1 [62,68–69].…”

Closed vs Open‐Shell CTV Based Host Compounds: A Direct Comparison

“…Several trends can be drawn from table 1. Firstly, for a given carbohydrate guest molecule, host 2 exhibits association constants that depend on the configuration of its different components, as also observed for its related open‐shell host 1 . For instance, P‐RRR ‐ 2 and M‐RRR ‐ 2 display higher binding constants than their stereoisomer counterparts for mannose and glucose derivatives respectively.…”

“…Firstly, for a given carbohydrate guest molecule, host 2 exhibits association constants that depend on the configuration of its different components, as also observed for its related open-shell host 1. [38] For instance, P-RRR-2 and M-RRR-2 display higher binding constants than their stereoisomer counterparts for mannose and glucose derivatives respectively. As a consequence, excellent enantioselectivities can be reached: M-RRR-2 and P-RRR-2 present a binding constant of 287 M À1 and 182 M À1 toward OctbGlc and OctaMan respectively, whereas no affinity was evidence with the enantiomer hosts.…”

“…The related hemicryptophanes, which are built from the association of a CTV with another C 3 symmetrical unit, are heteroditopic hosts able to recognize chiral molecules of biological interest such as neurotransmitters and carbohydrates . Recently, we reported the synthesis and the enantioselective recognition properties of the “open‐shell” enantiopure CTV stereoisomers 1 (Figure ), which combine both the axial chirality of the binaphthol units with the inherent chirality of the CTV . These enantiomerically and diastereomerically pure compounds exhibit selective recognition properties toward carbohydrates with diastereoselectivities up to 1:10.…”

Attempted Resolution and Racemization of Beckmann‐Derived CTV‐Lactam and the Use of Chirabite‐AR® to Determine the Optical Purity of the Supramolecular Scaffold

“…Some of the fascinating supramolecular structures of self‐assembled cages derived from CTV‐type scaffolds have recently been reviewed, such as a racemic C3‐symmetric bipyridyl‐bearing CTV ligand with zinc shown to self‐assemble into triply interlocked chiral catenanes within an overall chiral crystal . CTV‐based host compounds bearing three binaphthol moieties have been reported as chiral sensors with recognition of sugar derivatives …”