Chirality catenanes

In the topologically chiral catenane 79 the succession of amide and sulfonamide units defines sequence information for each macrocycle (Figure 47). Consequently one wheel gives an orientation to space and the other defines the configuration [60 b], Remarkably, the enantioseparation performed by Okamoto and Vogtle et al. by HPLC on chiral column materials resulted in baseline separation with a very large separation factor a = 6.95 [61, 62],... 

Yamamoto, C., Okamoto, Y., Schmidt. T., Jager, R., Vogtle, F. Enantiomeric resolution of cycloenantiomeric rotaxane, topologically chiral catenane, and pretzel-shaped molecules observation of pronounced circular dichroism, J. Am. Chem. Soc. 119 (1997), 10547-10548. 

Keywords Dynamics Chirality Catenane Rotaxane Molecular shuttle ... 

Fig. 20. Two topologically chiral catenanes 71 and 72 with oriented rings m and n are the numbers of atoms in-between the substituents of the constitutive macrocycles. Note that these catenanes lose their chirality when m = n...

Chiral catenanes can be obtained by the use of an unsynunetrically substituted 1,10-phenanthroline derivative such as LI 123 in the Cu+-template method. Thus the catenate [Cu(L1124)2] , generated in 12% yield as shown in Scheme 4-26 [247J, is topologically chiral. 

Template synthesis and chirality of catenanes, rotaxanes, and pretzelanes including N-macroheterocyclic lactams and related compounds as structure components 99PAC247. 

This molecule has no chiral carbons, nor does it have a rigid shape, but it too has neither a plane nor an alternating axis of symmetry. Compound 32 has been synthesized and has, in fact, been shown to be chiral. Rings containing 50 or more members should be able to exist as knots (33, and see 37 on p. 114 in Chapter 3). Such a knot would be nonsuperimposable on its mirror image. Calixarenes, ° crown ethers, catenanes, and rotaxanes (see p. 113) can also be chiral if suitably substituted. For example, A and B are nonsuperimposable mirror images. 

For a review of chirality in Mobius-strip molecules catenanes, and knots, see Walba, D.M. Tetrahedron, 1985, 41, 3161. 

Other supramolecular structures such as catenanes and rotaxanes can be formed using zinc as a template ion for example, a benzylic imine catenate formed by Leigh et a/.288 The reversible five-component assembly of a [2]catenane from a chiral metallomacrocycle and a dinaphtho-crown ether has been achieved. Zinc is used as the metal component and drives assembly via the coordination to a bipyridyl unit 7r interactions between the aromatic components are also... 

A chiral [4]pseudocatenane 16 was synthesized from chiral triptycene-based /m( crown ether) and three equivalents of hw[p-(but-3-enyloxy)benzyl]ammonium salt in CH2CI2 in the presence of Grubbs II catalyst, followed by reduction <06CEJ5603>. Several novel calix[4]arenocrowns were prepared by a simple one-pot reaction of calix[4]monohydroquinone diacetate with bw-tosylates, e.g. l,4-bw[2-(2-(2-(2-tosyloxy-ethoxy)ethoxy)ethoxy)ethoxy)benzene, in dry MeCN in the presence of NaOH the self-assembly into calix[4]areno[2]catenanes with a dicationic salt and />-bfr(bromomethyl)-benzene was also demonstrated <06TL6012>. 

Some racemates (Figure 3.23) are more efficiently resolved on the bonded-type CSP than the coated-type CSP by using chloroform as a component of the eluent. On the bonded-type CSP of 24n, topologically interesting catenanes and molecular knots are successfully resolved using a hexane-chloroform-2-propanol mixture.185 The first direct HPLC resolution of the smallest chiral... 

Out of many exciting recently obtained topologically distinct structures combined rotaxanes 41,400 [23], pretzel-molecule 35 [24a] and bis(pretzelane) 401 [24b], a topologically chiral [2]catenane [25] and an interestiig catenated... 

We can use this same approach to prove that other molecular knots and links are topologically chiral. For example, consider the molecular link illustrated in Figure 18. This catenane was synthesized by Nierengarten et al. [12]. For this molecule the set T(G) consists of many unlinks together with many copies of the (4,2)-torus link, illustrated as L in Figure 12. However we saw earlier that this unoriented link is topologically chiral. Therefore, the molecular (4,2)-torus link is topologically chiral as well. 

Catenane 7 exists in a well defined conformation in which two identical macro-cycles are interlocked and held together by six hydrogen-bonds. The crystal structure also revealed the chirality of the ground state conformation. 

Figure 29. Synthesis of macrocycle 65 and the corresponding, topologically chiral sulfonamide catenane 79.

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