Synthesis of N-Phtaloyl Amino Acid p-tert-butylcalix[4]arene Esters

The chemistry of calixarenes has received increasing attention in the field of Supramolecular Chemistry, as this class of molecules offers a suitable platform for the synthesis of receptors for anions, cations and neutral molecules. Their structures allow acylation and alkylaton reactions of the phenolic groups. The conformation and degree of substitution of acylated products are related to the reagent used to promote the reaction; the substituent at para position of the calixarene and the acid chloride. For example, Gutsche reported tetrasubstitution in the reaction of p-tert-butylcalix[4]arene with p-substituted benzoyl chlorides, using AlCl3 or NaH as catalyst. In this case the products had 1,3 alternate, partial cone and cone conformations4a while when pyridine was used as catalyst, only trisubstituted calix[4]arene in partial cone was obtained6. The complexation and transport of racemic mixtures with chiral receptors has been pointed out as a smooth method for enantiomeric resolution, because it requires low concentrations of the receptor, which can be recovered at the end of the process. Chiral receptors based on calix[4]arene structures are obtained by three approaches: reaction of calixarenes with chiral compounds7, use of four different phenols as building blocks for cyclization in the synthesis of calixarenes8, and from functionalization of achiral calixarenes on meta-positions of the aromatic rings, leading to an inherently chiral conformation9. In this work, we report the synthesis of calixarene amino acid esters and their structures have been elucidated by 1H NMR spectroscopy. Results and Discussion