Supramolecular chiral discrimination

Prior to such a sophisticated attempt, a more straightforward strategy was examined in order to evaluate the chiral discrimination ability of the CDx cavity. Thus the direct photoisomerization at 185 nm of a 1 1 complex of (Z)-cyclooctene 30 with P-CDx was carried out in the solid state to give an E-Z mixture of E Z = 0.47 [122]. The ee of the obtained (E)-isomer 31 was low (0.24 %) [123], but this work paved the way for the supramolecular photosensitization of 30 with chromophore-modified 3-CDx derivatives 53-55 in solution [123,124]. 

Foggasy and co-workers. In many cases, the hydrogen-bond chains form a supramolecular sheet. Thus it is strongly suggested that the chiral discrimination of racemic amines by enantiopure 9 mainly occurs through the formation of a supramolecular hydrogen-bond sheet (chain) of (9-H), which interact with the amine to discriminate its chirality. 

On the other hand, two-dimensional networks of the carboxylates involve a more complicated problem to discriminate the configurations of the nitrogen cations and the supramolecular chirality. 

Photochemical asymmetric synthesis with native and modified CDx s is certainly one of the most potentially successful examples of supramolecular photochirogen-esis, which is applicable in principle to most photoreactive substrates of appropriate size and shape. Despite this wide applicability, the enantiodifferentiating ability of CDx and hence the product ee obtained are not sufficiently high in many cases. Furthermore, the elucidation of the chiral discrimination mechanism and the rationalization of the product chirality and ee are generally more difficult in photochemical asymmetric induction. For more simple and well-defined host-guest interactions (in the ground as well as excited states), several approaches to photochemical asymmetric induction with newly designed synthetic chiral hosts have been reported. 

Kinbara, K. Kobayashi, Y. Saigo, K. Chiral discrimination of 2-arylalkanoic acids by (lS,2R)-l-aminoindan-2-ol through the formation of a consistent columnar supramolecular hydrogen-bond network. J. Chem. Soc. Perkin Tran. 2000, 2, 111-119. 

Francotte E, Zhang T. Supramolecular effects in the chiral discrimination of meta-methylbenzoyl cellulose in high-performance liquid chromatography. J. Chromatogr. A 1995 718 257-266. 

In the rivalry between the D- and L-enan-tiomers of protein and nucleic acid pattern constituents as well as in their chiral amplifications into larger supramolecular motifs, the less fortunate enantiomers, energetically discriminated by the chiral instruction of the electroweak force, fought a losing battle from the beginning of the grand evolutionary competition [31]. Ab initio... 

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