Amide-type macrocycle

A second experiment should prove that macromonocycles are actually the intermediate supramolecular templates in the course of catenane formation. Therefore macromonocycle 17 was reacted with 5 and 3, and the first [2]catenane 18 of the amide type consisting of two different macromonocycles was isolated (Figure 8). Unsymmetric catenanes like 18 can be identified unambiguously by mass spectrometry, because the corresponding tetrameric macromonocycle can not be formed in this reaction sequence. This confirms the presumption that catenation here proceeds via a macrocycle rather than via intertwining open chain units. 

Figure 7. Mechanism of catenane formation (amide type) the guest is orthogonally embedded in an intermediate macrocycle, the concave template. Depending on the substitution pattern of the reactants (pathways A and B) isomeric catenanes are obtained. For the sake of clarity the diacid dichloride is drawn here to be the nesting guest even though there is clear indication that the effective interactions take place between the corresponding monoamide and the macrocycle.

The unsubstituted, saturated aza macrocycles, the family of cyclic secondary amines, [n]aneN , are generally prepared by the method shown in Scheme 1. Some other types of aza macrocycle, particularly cyclic amides and macrocycles with N=CRCR=CRNH functions (see below), are also prepared conventionally. The preformed ligands are then reacted with the desired metal ion under appropriate conditions. 

In 2000. Vogtle et al. found another route toward [ ]catenanes—new tetralactarn and octalactam macrocycles were used to obtain [njcatenanes (Scheme 5) with up to five rings. The largest of these is the first amide-type olympiadane, which, however, could not be isolated. The octalactam macrocycle served as a ditopic host permitting the threading of two other macrocycles. 

Fig. 2 Template syntheses of rotaxanes the Cu(I) ion binds a phenanthroline ligand inside a macrocycle (top left). A l f5-paraquat macrocycle is clipped around an axle bearing a hydroquinone center piece (top right). Hydrogen bonding permits the use of nonionic template effects for the preparation of amide-type rotaxanes (bottom left). Phenolate anions bound to the macrocycle react as a supramolecular nucleophile (bottom right).

The most popular and commonly used chiral stationary phases (CSPs) are polysaccharides, cyclodextrins, macrocyclic glycopeptide antibiotics, Pirkle types, proteins, ligand exchangers, and crown ether based. The art of the chiral resolution on these CSPs has been discussed in detail in Chapters 2-8, respectively. Apart from these CSPs, the chiral resolutions of some racemic compounds have also been reported on other CSPs containing different chiral molecules and polymers. These other types of CSP are based on the use of chiral molecules such as alkaloids, amides, amines, acids, and synthetic polymers. These CSPs have proved to be very useful for the chiral resolutions due to some specific requirements. Moreover, the chiral resolution can be predicted on the CSPs obtained by the molecular imprinted techniques. The chiral resolution on these miscellaneous CSPs using liquid chromatography is discussed in this chapter. 

A successful synthesis of a rotaxane of this type is shown in Figure 5. First, one tiityl aniline stopper is reacted with the terephthaloyl chloride to from semiaxle 9. This semiaxle threads into the tetralactam macrocycle 3 and is held by the amide template. Then, the preorganized complex is reacted with the second stopper 11 to yield rotaxane 12. Figure 5 shows three hydrogen bonds to form, which is in accord with AMI calculations on this system [19] and X-Ray crystal structure analysis [22],... 

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