Chiral calixarenes patterns

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. 

A more subtle way to generate a chiral calixarene is to create dissymmetry or asymmetry within the molecule itself One of the means for doing this with a calix[4]arene is to establish a substitution pattern of AABC or ABCD on the upper or lower rim, producing a compound that is inherently chiral in all possible conformations. Tabulations of the cone, partial cone, 1,2-alternate, and... 

The unique feature of calixarenes is their concave structure that clearly distinguishes the upper and lower rims. When the inversion of the concave structure is hindered, an asymmetric/dissymmetric substitution pattern leads to the formation of chiral structures (Fig. 2.14). This type of chirality is known as inherent chirality. Calix[4]arenes were the first scaffolds for which the term inherent chirality was... 

Although chiral calix[4]arenes can be generated by simply attaching chiral residues at the upper [40] or lower [41-43] rim of the calixarene skeleton, recent interest has been focused on the possibility of synthesizing inherently chiral calix[4]arenes, which are build up of nonchiral subunits and consequently owe their chirality to the fact that the calixarene molecule is nonplanar. Molecular asymmetry can arise from the substitution pattern at the lower rim and/or conformation. In this respect, Shinkai has recently reported a systematic classification of all possible chiral isomers derivable from calix[4]arene, and delineated some basic concepts for the design and synthesis of chiral derivatives [44]. 

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