Calix[4]arene Amino Acid Derivatives. Intra- and Intermolecular Hydrogen-Bonded Organisation in solution and the Solid State

摘要

Chiral calix[4]arene derivatives with four O-(N-acetyl-PhgOMe), (1). (Phg denotes R-phenylglycine), or O-(N-acetyl-LeuOMe) (2) strands have been synthesised. Both compounds exist in chloroform in stable cone conformations with a noncovalently organised cavity at the lower rim that is formed by circular interstrand amidic hydrogen bonds. Such organisation affects both the selectivity and extraction/transport properties of 1 and 2 toward metal cations. Calix[4]arene derivatives with one OCH_2COPhgOMe strand (3), two OCH_2COPhgOMe strands (5) and with 1,3-OMe-2,4-(O-CH_2COPhgOMe) substituents (4) at the lower rim have also been prepared. For 3, a conformation stabilised by a circular hydrogen-bond arrangement is found in chloroform, while 4 exsts as a time-averaged C_2 conformation with two intramolecular NH... OCH_3 hydrogen bonds. Compound 5 has a unique hydrogen-bonding motif in solution and in the solid state with two three-centred NH...O and two OH...O hydrogne bonds at the lower rim. Tis motif keeps 5 in the flattened cone conformation in chloroform. The X-ray structure analysis of 1 revealed a molecular structure with C_2 symmetry; this structure is organised in infinite chains by intra- and intermolecular H bonds. The solid-state and solution structures of the [1-Na]ClO_4 complex are identical, C_4 symmetric cone conformations.