Calixarene analogues

Calixarene analogues having L-cysteine 52,105 (/ ,/ )-cystine 53/54,106 and other amino acid residues 55107 incorporated into one or two bridges of the macrocyclic skeleton have been synthesized by condensation of a bis(chloromethylated) dimer, trimer, or tetramer with the corresponding amino acid ester under basic conditions (Figure 10). 

Figure 10. Calixarene analogues with chiral bridges.

The binding of N,N V-trimethyl- 1-phenylethylammonium iodide by 55 was studied in chloroform, where 1 1 complexes having association constants in the range (Afa =) 10 - 15 M 1 were found. The signals of the racemic salt were split into two patterns in the presence of the chiral calixarene analogues. 

The etherification of calixarene analogues containing methylene and 1,3-propylene bridges leads in good yield and regioselectively to 1,3-di-O-substituted derivatives 90.175 To prevent enantiomerization the ether residues must be at least propyl... 

SCHEME 6. One-pot synthesis of calixarene analogues by condensation of bisphenols with formaldehyde... 

A new method has been developed for the preparation of calixarene analogues from macrocyclic polyethers via intramolecular successive carbon-carbon bond formation in a tandem Claisen rearrangement, and a similar tandem Claisen rearrangement promoted by Et2AlCl and 2-methylbut-2-ene, has been used ° to synthesize macrocycles containing phenolic moieties from the corresponding macrocyclic polyether compounds (see Scheme 28). A number of furo[3,2-c 5,4-/]bis[l]benzopyran-3-ones have been synthesized regioselectively by the sequential... 

Yamato, T. Haraguchi, M. Nishikawa, J. Ide. S. Synthesis, conforniational studies and inclusion properties of 0-ben-zylated calixarene analogues of trihydroxy[3.3.3]-metacyclophanes. J. Chem. Soc., Perkin Trans. 1 1998. (3), 609-614. 

Calixarene analogues containing indole rings have been synthesized recently by Black and coworkers. In initial studies, 4,6-dimethoxy-3-methylindole 24 was condensed with a range of aryl aldehydes in the presence of phosphoryl chloride to produce the calix[3]indoles 25 in moderate to high yields (Scheme 3). - The same calix[3]indoles were also produced from the intermediate hydroxymethyl compounds. 

A new class of nitrogen heterocyclic ring based calixarene analogues, the calix[4] imidazolium 47a and calix[5]imidazolium 47b salts has been reported by Chun et al. [71]. When an aqueous solution of the pentabromide salt of 47b was boiled with Cso for 2 h the NMR signal at 167.8 ppm in the resulting solution showed the presence of Cgo- The fluorescence emission spectrum of the Ceo in an aqueous solution of 47b showed enhancement due to the calix [5] imidazolium n to the Ceo tt system. The protons of 47b except for the imidazolium (C-H) are shifted down-field. Therefore, the authors concluded, the interaction with the fullerene occurs at the double bond of the imidazolium ring, as shown from the resolution identity DFT calculated optimized structure shown in Fig. 33.32. 

The highest reported binding constant to date for a mono-macrocyclic calixarene or calixarene analogue receptor and Cgo is 3.48 x 10 which was ascribed to the Ag(I) A-heterocyclic carbene-bridged calixarene 48 synthesized by Quin et al. [72]. This binding constant for the 1 1 complexation was determined by fluorescence quenching titration study of in acetonitrile at 298 K (Fig. 33.33). 

---