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Synthesis and Properties of Upper Rim C ‐Linked Peptidocalix[4]arenes
Author(s) -
Lazzarotto Marcio,
Sansone Francesco,
Baldini Laura,
Casnati Alessandro,
Cozzini Pietro,
Ungaro Rocco
Publication year - 2001
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200102)2001:3<595::aid-ejoc595>3.0.co;2-#
Subject(s) - chemistry , stereochemistry
Abstract Cone calix[4]arenes, functionalized with two or four L ‐alanine or L ‐phenylalanine units at the upper rim , have been synthesized. These compounds, in which the amino acids are attached to the calix[4]arene macrocycle through their carboxy groups, have been named C ‐linked peptidocalix[4]arenes. The solubility, conformational, and recognition properties of this novel class of chiral receptors are quite different from those previously reported for N ‐linked peptidocalix[4]arenes. The tetrafunctionalized phthaloyl derivatives 2 are soluble in low polarity media, whereas the corresponding acetyl and benzoyl derivatives 4 and 5 are completely insoluble in CDCl 3 , suggesting a high degree of aggregation of the latter compounds. Protonation of the terminal amino groups of 3 results in positively charged water‐soluble receptors, which represent the cationic counterparts of negatively charged, water‐soluble, N ‐linked peptidocalix[4]arenes. The difunctionalized acetyl derivatives 9 are soluble in CDCl 3 and show a pinched cone conformation, which is mainly determined by intramolecular hydrogen bonding, as revealed by solvent‐dependent 1 H NMR spectra and molecular modelling. In contrast to the N ‐linked analogues, which complex ammonium cations and carboxylic acids, the newly synthesized C ‐linked peptidocalix[4]arenes interact preferentially with anionic species.