Classes of Macrocycles

With sp bond angles calculated to be around 162°, macrocycle 131 would be highly strained and was therefore expected to be quite reactive [79]. The octa-cobalt complex 132, on the other hand, should be readily isolable. Indeed, 132 was prepared easily from 133 in five steps, and was isolated as stable, deep maroon crystals (Scheme 30). All spectroscopic data supported formation of the strain-free dimeric structure. Unfortunately, all attempts to liberate 132 from the cobalt units led only to insoluble materials. Diederich et al. observed similar problems when trying to prepare the cyclocarbons [5c]. Whether the failure to prepare these two classes of macrocycles is due to the extreme reactivity of the distorted polyyne moiety or to the lack of a viable synthetic route is not certain. Thus, isolation and characterization of smaller bent hexatriyne- and octatetrayne-containing systems is an important goal that should help answer these questions. 

Many polyazamacrocycles have been alkylated with chloroacetic acid leading to compounds which contain both amine and carboxylic acid functions, e.g. [63] (Stetter et al., 1981). These compounds are similar to EDTA (ethylenediamine tetraacetate). Although the ring size of this class of macrocycles and the number of N—CH2—COOH groups has been modified... 

Studies on the electrocatalytic activity of metal porphyrins are limited in comparison with those on other classes of macrocyclic metal complex. Among the few porphyrin complexes tested, cobalt porphyrins have been demonstrated to be efficient electrocatalysts for the reduction of C02 to CO... 

A Versatile Class of Macrocyclic Compounds, J. Vicens, V. Bohmer, Eds., Kluwer, Dordrecht, 1991, p. 65 G. D. Andreetti, F. Ugozzoli, Inclusion Properties and Host-Guest Interactions of Calixarenes in the Solid State, ibid., p. 87. 

Included in the class of macrocyclic lactones are avermectins and milbemycins, which are fermentation products possessing a 16-member cyclic lactone, a spiroketal moiety, and a disaccharide unit. Abamycin, ivermectin, doramectin, and eprinomycin are the avermectins most often available for anthelminthic treatment of livestock, whereas moxidectin is a milbemycin with worldwide acclaim as a cattle anthelminthic. Other anthelminthics currently used in food-producing animals are clorsulon, which is a benzenesulphonamide derivative praziquantel, which is a racemate derivative of pyrazino-isoquinoline and hygromycin B, which is an aminoglycoside antibiotic that exhibits anthelminthic properties. 

For monographs, see Vicens Bohmer Calixarenes A Versatile Class of Macrocyclic Compounds, Kluwer Dordrecht, 1991 Gutsche Calixarenes Royal Society of Chemistry Cambridge, 1989. For reviews, see Gusche Prog. Macrocycl. Chem. 1987,3, 93-165, Top. Curr. Chem. 1984, 123, 1-47. 

A class of macrocyclic polyethers built on a triazine ring (192) have been proposed in 1981 by Au.291 These compounds are active as phase transfer catalysts in the conversion of C8H,7Br to C8H17OPh. These molecules have chelating arms properly arranged in order to trap cations. 

A.23 Calixarenes a Versatile Class of Macrocyclic Compounds, (Eds. J. Vicens and V. Boh-mer), Kluwer, Dordrecht, 1991. 

Two further miscellaneous classes of macrocyclic metal complexes are included in this section because they have structural features such as aza linkages and a high degree of unsaturation associated with fused aromatic rings. Ogawa and coworkers have shown that when 2,4-di-chloro-l,10-phenanthroline is fused with ammonium tetrachlorozincate, a macrocyclic zinc complex is produced. The metal can be removed subsequently by acidic treatment (Scheme 57).244 The free macrocycle can also be prepared by non-template methods, which however do not appear to be as effective as they require reaction of the dichlorophenanthroline with 2,9-diaminophen-anthroline.245... 

Ansamycins are a class of macrocyclic compounds in which non-adjacent positions on an aromatic ring system are spanned by the long aliphatic bridge (Latin ansa = handle). The aromatic portion may be a substituted naphthalene or naphthaquinone, or alternatively a substituted benzene ring. The macrocycle in the ansamycins is closed by an amide rather than an ester linkage, i.e. ansamycins are lactams. The only ansamycins currently used therapeutically are semi-synthetic naphthalene-based macrocycles produced from rifamycin B. 

Cyclodextrins and calixarenes are members of a general class of macrocycles commonly referred to as cyclophanes, although the naturally occurring CDs are usually considered separately from the synthetic members of the cyclophane family of compounds. The properties and guest-host complexes of cyclophanes... 

Yang, X. G., Knobler, C. B., Zheng, Z. P., Hawthorne, M. F., Host-guest chemistry of a new class of macrocyclic multidentate lewis-acids comprised of carborane-supported electrophilic mercury centers. J. Am. Chem. Soc. 1994,116, 7142-7159. 

A convenient and efficient synthetic route to a new class of macrocyclic aryl ether ether sulfide oligomers was reported. The process is shown in Fig. 28. This new class of cyclic oligomers is prepared in excellent yield by quantitative chemical reduction of macrocyclic aryl ether ether sulfoxide oligomers with oxalyl chloride and tetrabutylammonium iodide. The cyclic sulfoxide oligomeric precursors are prepared in high yields by an aromatic nucleophilic substitution reaction from bis(4-fluorophenyl) sulfoxide with potassium salts of bisphenols under high-dilution conditions [99]. 

Calixarenes provided the main inspiration for the artifidal receptors studied in my group. We wanted to develop a new class of macrocyclic host with binding properties and structural variability similar to calixarenes but a closer relationship to natural systems. The obvious choice was, of course, to base such receptors on cyclopeptides, macrocydic compounds that are composed of the same subunits as the natural systems. 

This class of macrocycles has recently been expanded to include the 2,2 -dipyridine subunit within the macrocyclic framework. Vogtle et al. have synthesized 175 (59%) and 176 (24%). Thus far, no complexes of these two ligands have been reported 119). 

Andreetti, Ugazzoli, in Calixarenes A Versatile Class of Macrocyclic Compounds. 

Vicens, J. Bohmer, V. (eds), Calixarenes A Versatile Class of Macrocyclic Compounds, Kluwer Academic Publisher Dordrecht, 1991. 

One of the most studied class of macrocyclic ligands in lanthanide coordination chemistry is without any doubt the molecules derived from cyclen, a 12-membered ring bearing four amino functions. In particular, its tetracarboxylic derivative H4DOTA (see Fig. 4.40) was synthesized in 1976 by a German chemist, H. Stetter from the University of Aachen,... 

In this chapter we present an overview of chiral structures realized on the basis of calixarenes and resorcarenes.8 Clearly this cannot be an exhaustive survey, due to the enormous development calixarene chemistry has experienced during the last decade (mainly the last 5 years). Rather, it is a survey of the potential possibilities that are offered by this class of macrocyclic molecules—illustrated by selected examples of what has been done and indicating what might be done in the future. 

Most of the theoretical works dealing with this class of macrocycles is devoted to the calculation of the structure and properties of their complexes. 

A very large class of macrocyclic thiophene derivatives is the thiophene-modified porphyrins. Several compounds (153-157) with ter- or quaterthiophene subunits <2006OL2325, 2006OL4847, 2007CC43> have been reported. All of them have been synthesized by the classical acid-catalyzed porphyrin synthesis. Solution and solid-state structures have been investigated using nuclear magnetic resonance (NMR) and ultraviolet (UV) spectroscopy, calculations, and X-ray structures. 

The present volume is intended to provide this knowledge, showing synthetic principles and creative strategies for the above-mentioned classes of macrocycles with stress on crowns, strained and cavityshaped cyclophanes, expanded porphyrins and macrolide antibiotics. 

Another class of macrocyclic molecules for binding with alkali metal cations is cahx[n]arene (n = 4,6,8) and its derivatives. They are made up of phenol and methylene units which provide a rigid arrangement of various number of oxygen donor atoms for metal complexation. Some of them are proved to display exceptional selectivity for K+ and Cs+ 131 Further details of this developing field will be found in Macrocyclic Ligands. 

Finally, both upper and lower rim substitution have been used to produce a class of macrocycles referred to as calixarene-crown ethers, or calixcrowns. One simple example is shown here (103). These receptors combine characteristics of the crown ethers and calixarenes, and have been intensively studied for metal ion extraction, in particular, for the removal of cesium from nuclear waste. ... 

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