Betaine Heterocalixarenes

The increasing interest in anionic recognition has focused attention towards synthetic receptors possessing positively charged moieties which could induce non-covalent 

In the formation of 113, an anion template effect was not visible because of the diminished ability of the 1,2,4-triazole nucleus to form H-bonds, but the enhanced 

115b-(Cl )2-(H20)3.g-(CH3CN)o.s. (Reprinted with permission from 99JCS(CC)295, Copyright 1999, Royal Society of Chemistry.) 

The above investigations on charged heterocalixarenes were conveniently extended to hexameric and octameric systems with enlarged cavities, employing (5 +1) and 

For investigating diastereoselectivity, Mannich reactions of calix[4]resorcinarene with chiral primary amines were studied (95TL4905, 95TL6221). In a representative case of the reaction of R-(+)-l-phenethylamine, formation of two diastereomers 131 and 132 is possible but only one of these is formed with high stereoselectivity as shown by H- and C-NMR spectra and X-ray confirmed structure 131 with 

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