Catenanes applications

Guest Chemistry of Rotaxanes and Catenanes Application of a Polarizable All-Atom Force Field to Cyclobis(paraquat-p-phenylene) Complexes with Disubstituted Benzenes and Biphenyls. 

As expected, the yields of catenanes by this approach are low, which is why improved methods for the preparation of such compounds have been developed. The acyloins are often only intermediate products in a multistep synthesis. For example they can be further transformed into olefins by application of the Corey-Winter fragmentation. 

Although the number of applications of olefin metathesis to transition metal complexes is small compared to the number of applications in organic synthesis, this field is becoming increasingly important. Spectacular examples are the double RCM reactions of copper phenanthroline complexes as a synthetic route to catenanes [113] or a recently reported approach to steric shielding of rhenium complex terminated sp-carbon chains [114]. 

The examples summarized in Table 5 and in Sect. 5 of this review illustrate the applicability of RCM to the preparation of various macrocyclic perfume ingredients [30], pheromones [30], antibiotics [31-35], crown ethers [36], cyclic peptides [37],catenanes [38] and capped calixarenes [39]. 

Other applications of the polymer substrate technique include the synthesis of threaded macrocyclic systems (hooplanes, catenanes, knots), the retrieval of a minor component from a reaction system, and the trapping of reaction intermediates [Frechet, 1980a,b Hodge, 1988 Hodge and Sherrington, 1980 Mathur et al., 1980],... 

A spectacular application of the acyloin ester condensation was the preparation of catenanes like ll7 These were prepared by a statistical synthesis which means that an acyloin reaction of the diester 10 has been carried out in the presence of an excess of a large ring compound such as 9, with the hope that some diester molecules would be threaded through a ring, and would then undergo ring closure to give the catena compound ... 

Are there any other possible uses for the construction of complex topological species One possible application is in the mass production of DNA polyhedral catenanes by biological means, such as the polymerase chain reaction (PCR) (Saiki et al. 1986) or by production in vivo. Figure 21 illustrates that semi-conservative replication (the mechanism used by DNA polymerases) cannot reproduce a stable branch. The DNA with different sequences in the two arms of the branch (cartooned as dashed and solid lines) leads to two heterologous duplex DNA molecules, rather than a second branched molecule. 

Mechanically interlocked molecular compounds, including catenanes, rotax-anes, and carceplex, are constituted of molecules composed of two or more components that cannot be separated from each other [95-98]. The development of strategy for achieving controlled self-assembling systems by non-covalent interaction enables one to prepare such attractive compounds for applications in nanoscale molecular devices. The dithiafulvene derivatives are effective electron donors, which are good candidates to form those supramolecular systems with appropriate acceptors by virtue of intermolec-ular CT interactions. In this chapter, dithiafulvene polymers forming rotax-ane structures are especially described. 

So far we discussed the application of the graph theory in studies of electronic structure of molecules. In this chapter we shall describe some topological concepts that appeared in stereochemistry in connection with the investigations of a new remarkable type of chemical compounds, catenanes, rotaxanes, knots. 

In a further study, a solid support has been employed to assemble a closed [14]-catenane (again from DNA) whose double helical edges show the connectivity of a truncated octahedron. The structure is composed of 14 cyclic DNA molecules and contains 2550 nucleotides it has a molecular weight of about 790 000 Daltons. The successful assembly of structures such as these owes much to the use of biochemical techniques and, in particular, the application of restriction enzymes to cleave DNA strands at appropriate places and a DNA ligase to join the sticky ends where required. Overall, studies of this latter type represent a remarkable achievement and suggest that DNA is a tractable medium for nanoscale construction. However, the challenge remains to make like structures from more robust materials than DNA. 

Knot theoretical techniques are easily applicable to polymer chains that do form actual knots or links, such as some DNA fragments or various catenanes [59-72,204-213]. By appropriate modifications, the knot theoretical polynomials are also applicable to the analysis of chirality properties of general molecules that may not form knots by themselves, but the space around them can be represented by a knot. This approach has led to the concept of chirogenicity, and to a nonvisual, algorithmic, computer-based analysis of molecular chirality [62]. 

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