Catenanes topologically chiral sulfonamide

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

Scheme 2 Two enantiomers of a topologically chiral sulfonamide [2]catenane and their CD spectra...

Figure 47. The topological chirality of catenane 79 results from the different amide-sulfonamide succession in the macrocycles.

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],... 

In addition, sulfonamides bear more acidic, compared to carboxamides, protons that can be selectively A-alkylatcd or V-acylatcd. Thus, alkylation of sulfonamide catenane and rotaxane with Frechet-dendrons of 2nd generation led to the first representatives of the dendrocatenane 15 and dendrorotaxane 16 [46], respectively. These compounds were of especial interest, since they allowed for the first time to study chiral induction of topologically chiral cores on appended dendrons and to compare to the analogous centrochiral dendrimers for which phenomenon of the crypto-optical activity was postulated [47],... 

Recently Vogtle and co-workers synthesized the first catenanes (Structure 53) and rotaxanes containing sulfonamide units. The sulfonamide catenanes 53a, 53b have a topologically chiral structure [67]. 

Let us assume that a rotaxane is formed from an axle with two different stoppers and a wheel that bears a directionality defined by the sequence of atoms in the macrocycle. Both of these subunits are achiral, both are identical to their mirror images. Nevertheless, the corresponding rotaxane exists in two enantiomeric forms, although no chiral center is present in the molecule (Fig. 4). It is the molecular topology that makes these species chiral, and consequently, this phenomenon was coined "topological chirality.. It also exists for catenanes, knots, and other mechanically bound molecules. Shown in Fig. 4 is a detailed structure of such a rotaxane. The wheel contains one sulfonamide group that provides the directionality of... 

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