Amide-linked catenanes

Nonionic template synthesis of amide-linked catenanes and rotaxanes with macroheterocyclic fragments 97AG(E)930. 

R. Jager, F. Vogtle, A New Synthetic Strategy towards Molecules with Mechanical Bonds Nonionic Template Synthesis of Amide-Linked Catenanes and Rotaxanes , Angew. Chem Int. Ed. Engl. 1997,36,930-944. 

The spectroscopic data of the amide-linked catenanes revealed that the cir-cumrotation [6 a] of the two interlocked cycles is hindered, i.e. the steric demand... 

Recently Vogtle et al. in cooperation with Sessler et al. synthesized a Leigh-type amide-linked catenane 29 which coordinates anions (Figure 14) [26]. 

Amide-linked catenanes and rotaxanes, readily accessible via nonionic template synthesis, are molecules with fascinating topology, but their final breakthrough was only achieved when they became substrates for further chemical derivatiza-tion. A potential reaction site in the catenanes and rotaxanes presented so far is the sulfonamide group, because the proton can be selectively abstracted in the presence of carbon amide groups. Subsequent alkylation offers numerous possibilities of catenane and rotaxane chemistry. 

When macrocycle 65 is synthesized, the in/out isomer of [2]catenane 79 is also formed in 11% yield (Figure 29) [46]. A first attempt to methylate both sulfonamide groups by treatment of the DMF solution of 79 with iodomethane and potassium carbonate was successful. By bridging the two sulfonamide units with a bifunctional alkylating reagent, we were able to synthesize the first pretzel-shaped molecule [54]. Considerations of the X-ray structure analysis of amide-linked catenanes [16] and CPK models led to the diiodo compound 95 as a suitable brid-... 

Amide-linked catenanes and rotaxanes can play a major role in the study of rare forms of chirality, e.g. topological chirality and cycloenantiomerism [60]. Resolution of enantiomeric catenanes, rotaxanes, and pretzelanes has been achieved by HPLC on chiral column materials, but further work must be performed to determine absolute configurations and to realize new chiral skeletons composed of achiral building blocks. Topological asymmetric synthesis still belongs to dreams of the future yet should be kept in mind. 

Jager. R. Vogtle, F. A new synthetic strategy towards molecules with mechanical bonds Nonionic template synthesis of amide-linked catenanes and rotaxanes. 26. Angew. Chem. Int. Ed. 1997, 36, 930. 

Figure 8. Synthesis of the first amide-linked [2]catenane consisting of two different macrocycles.

After the synthesis of the first amide-linked [2]rotaxanes, Vogtle et al. set out to study the limits of molecular recognition, which in terms of Emil Fischer means to discover if the lock (macrocycle) is specific to a certain key, or if several keys (monoamide threads) fit. It turned out that - in contrast to catenane formation - rotaxane synthesis is very tolerant towards the variation of the building... 

Finally catenane 79 and rotaxane 80e were covalently bound to form the first amide-linked catrotane 108 (Figure 44) [41]. 

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