Abstract
Abstract As the third-generation supramolecular main structure, calixarenes, especially chiral calixarenes, have been applied to various fields. In this study, the bridging chiral de-tert-butylcalix[4]arene derivatives with an amide group attached to a chiral point was synthesized for the first time, which provided a new group for its structural derivation at the bridging chiral position. The racemic compound 2 was optically resolved by column chromatography on silica gel with the aid of the chiral auxiliary (1S)-(+)-10-camphorsulfonyl chloride, and finally a pair of optically pure bridging chiral de-tert-butylcalix[4]arene derivatives 4a and 4b were obtained. The results of experimental and calculated ECD showed that compounds 4a and 4b were a pair of enantiomers, and their absolute configurations were designated S and R, respectively. This study provides new idea for the derivatization of specific chiral groups based on bridging chiral calix[4]arenes and their chiral resolution.
Highlights
With its unique three-dimensional cavity structure, calixarene has become the third-generation supramolecular host molecule after crown ether and cyclodextrin
(1S)-(+)-10-camphorsulfonyl chloride was used as a chiral auxiliary, and under the action of Cs2CO3 in CH3CN at room temperature, a nucleophilic substitution reaction occurred with the phenolic hydroxyl group on compound 2 to obtain a pair of diastereomeric mixtures 3a and 3b
This study focused on the structure of bridging chiral de-tert-butylcalix[4]arene and obtained the first bridging chiral de-tert-butylcalix[4]arene with an amide group attached to the chiral point
Summary
With its unique three-dimensional cavity structure, calixarene has become the third-generation supramolecular host molecule after crown ether and cyclodextrin. Chiral calixarenes are derived from asymmetric substitution only on the phenyl rings and (or) oxygen atom. The bridging chiral calixarenes exhibit asymmetric substitution on the bridged methylene group. Inherently chiral calixarenes have been studied for decades and applied to many fields, its chiral recognition ability and asymmetric catalytic efficiency are often not satisfactory. Lack of further derivable groups on the chiral structure, such as amide, amino, or carboxyl groups. We introduced an amide group on the chiral group of the chiral calixarenes for the first time and used chiral auxiliary (1S)-(+)-10-camphorsulfonyl chloride to perform optical resolution on it by column chromatography. This study provides a new method for the structure derivation and chiral resolution of bridging chiral calix[4]arenes
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