Other Synthetic Macrocyclic Compounds

A new discovery attracting interest in the field of maerocyelic ehemistry is the cyanostar (1.34), which was introduced by Flood et cyanostars 

34 are pentagonal star-shaped macrocyelie eompounds with a one-pot synthesis in high yields that involves the cyelization of cyanostilbene repeat units. Their eleetropositive eentral cavity stabilizes anions because the CH hydrogen-bonding units are aetivated by the eleetron-withdrawing cyano groups. 

Another interesting class of macrocyclic compounds are 7i-conjugated macrocycles. ° Cyclic phenylenes are classified into o-, m-, and p-bridged phenylenes. Cyclic o-tetra- and hexaphenylenes have been investigated as 

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Several of these patterns have also been found with cryptands or other synthetic macrocyclic compounds (such as polyethers and polyamines), antibiotics as well as proteins (cf. below). 

Together with CDs, other chiral selectors such as non-cyclic oligosaccharides and polysaccharides [118, 119], chiral surfactants [120-123], macrocyclic antibiotics [124, 125], proteins, peptides [126, 127], peptide libraries [128, 129], ligand exchange materials [130], and synthetic macrocyclic compound [131] can be used as chiral selectors in EKC. 

Nitrenium ions have been applied to the synthesis of macrocycles and other medicinally interesting compounds. The most successful reactions have been in cases where the nitrenium ion is covalently tethered to its intended target. Further efforts aimed at modulating the selectivity of these intermediates would increase their synthetic utility. 

While the aforementioned ionophores are microbial metabolites, the crown polyethers, the depicted prototype of which is dicyclohexyl-18-crown-6 (Fig. 2D) are synthetic macrocyclic ethers. The first crown ether synthesized, dibenzo-18-crown-6, is the first multidentate synthetic macrocycle with the ability to form stable complexes with alkali and alkaline earth compounds. The complexing abilities of this crown ether led to the preparation of many others in rapid succession. Different size crown rings have been synthesized containing benzyl, cyclohexyl and naphthyl moieties Optically pure dinaphthyl crown ethers have been used to resolve asymmetric amine salts by enantioselective extraction from an aqueous solution into chloroform... 

A review of recent developments in synthetic organic sulphur chemistry included much valuable material pertinent to cyclic sulphur compounds, and another review covered photocycloaddition reactions of thiocarbonyl compounds with olefins to give 1,4-dithians and cycloadditions with dienes to give thian derivatives. Macrocyclic polythioethers and their complexes have been reviewed, and in other articles the conformational aspects of multisulphur heterocycles, sulphur-containing [2,2]metacyclophanes, and other cyclic sulphur compounds have been discussed. Other reviews mention configurational aspects of cyclic sulphur compounds. ... 

In addition to the classes and groups of macrocyclic compounds discussed in previous chapters there exist a number of other macrocycles and groups of macrocycles that are also produced by template synthesis. Some of these have the same donor atom sets as considered previously, but incorporated in different cyclic backbones. Information on these compounds may provide a useful basis for the development of further synthetic activity with which to further develop matrix reaction chemistry. 

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