Inherently Chiral Resorcin[4]arenes

In this contribution we especially focus on the structural features and the synthesis of inherently chiral resorcin[4]arenes which offer a high potential as enantiodiscriminating artificial receptors. In special, we will discuss selected examples from the literature as well as some results from our own studies. Following a detailed discussion of Sumna we are using the term “inherently chiral” rather than “cyclochiral” since the latter term originally introduced by Prelog and Gerlach has some restrictions in calixarene chemistry. Moreover, concepts to extend the cavity (“deep cavity”) of resorcin[4]arenes as well as to increase the functionality and reactivity of these macrocycles at the upper rim are emphasized. Chiral resorcin[4]arenes have occasionally been used in chromatography, mass spectrometry, NMR, and fluorescence spectroscopy to differentiate between enantiomers.