Chiral diaza crown ethers

Tricyclic derivatives, such as (96), of diaza-12-crown-4 form inclusion complexes with suitable guest ammoniimi salts. Some structural selectivity is shown for example diamine salts H3N(CH2) NH3 with n = 5 or 6 give the strongest complexes with (96), presumably by host recognition of a best fit in its cavity. In a study of complexes of chiral diaza-crown ethers such as (97) with chiral... 

Pietraszkiewicz, M., Kozbial, M., Pietraszkiewicz, O. (1997). Chiral recognition of amino acids by diaza crown ethers and crowns incorporating a mannopyranoside unit, immobilized in a supported liquid membrane. Enantiomer, 2, 319-25. 

Chirality derived from the readily accessible a-amino acids has been incorporated into the side chains of aza and diaza macrocyclic polyethers. A number of procedures suitable for peptide synthesis have proved (178) to be unsuitable for acylating the relatively unreactive secondary amine groups of aza crown ethers. Eventually, it was discovered that mixed anhydrides of diphenylphos-phinic acid and alkoxycarbonyl-L-alanine derivatives do yield amides, which can be reduced to the corresponding amines, e.g., l-172. By contrast, the corresponding bisamides of diaza-15-crown-S derivatives could not be reduced and so an alternative approach, involving the use of chiral A-chloroacetamido alcohols derived from a-amino acids, has been employed (178) in the synthesis of chiral receptors, such as ll-173 to ll-175, based on this constitution. 

CyDs were coupled with calixarene or crown ether to improve their binding affinity. j8-CyD functionalized with diaza-18-crown-6 at the primary face 68 showed 7-10-fold greater affinities for aromatic ammonium ions [178] and the introduction of a benzo-18-crown-6 moiety at the secondary-hydroxy side 69 improved chiral recognition for tryptophan (Trp), whereas its introduction at the primary-hydroxy side 70 was not effective for the Trp recognition [179]. 

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