Lower Rim Amides

Amides of the general structure 266 were first prepared and studied by Ungaro and coworkers and subsequently in considerable detail by McKervey and coworkers and Beer and coworkers. The cyclic tetrameric amides 

Arnaud-Neu, F. Barrett, G. Fanni, S. Marrs, D. McGregor, W. McKervey, M. A. Schwing-Weill, M.-J. Vetrogon, V. Wechsler, S. J. Chem. Soc., Perkin Trans. 2 1995,453. 

Trivalent cations are also effectively bound by the amides. For example, 266a forms 1 1 complexes with Pr (log 8.5), Eu (log 8.7), and Yb (log 8.1). In extraction studies the cyclic tetramers are shown to 

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The XH NMR study of receptors 70a-c revealed [90] that these compounds complex simultaneously sodium cation (lower rim amidic cavity) and anions (upper rim urea/thiourea), which markedly improves the solubility of the cor-... 

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