Other Macrocycles

The properties of natural macrocycles, the cyclodextrins, has stimulated interest in the preparation of synthetic macrocycles. Three basic types have been made macrocyclic amines, cyclophanes, and cyclic peptides. Hersh-field and Bender (33) prepared a bicyclic amine with hydroxamate sub- 

Sunamoto et al. 94) have studied the reaction of (14) with 2,4-dinitro-phenyl sulfate in aqueous organic solvent with 0.1 A sodiiun hydroxide. The rate of esterolysis by (14) was greater than the rate of the reaction catalyzed by -cyclodextrin. Better binding by the paracyclophane cavity and the greater nucleophilicity of the oxime group as compared to the secondary hydroxyl group of jS-cycdextrin were cited to explain the difference in catalytic efficiency. 

In a number of laboratories macrocyclic peptides have been studied as enzyme models 47,63, 70, 72a, 91). A bicyclic peptide (17) with considerable apolar character was made by Murakami et al. (70) in which Hex is 6-amino-hexanoyl Und is co-aminoundecanoyl. The esterolysis of p-nitrophenyl carboxylates by (17) was studied over the pH range 10-12. The rate depends on the ionization of one group (pK 12.3), which is apparently the anionic imidazole group. 

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The Friedlander reaction makes available a wide variety of 1,10-phenanthrolines and other macrocyclic chelators (e.g. 33, 34 and 35). These polyaza-aromatic rings can bind a variety of metals or organic substrates. 

In this section, the corrinoids, the other macrocyclic complexes, and the cyanides are dealt with separately (Sections A-C). The preparative organo-metallic chemist will be primarily interested in Sections B and C, whereas... 

In the polyazamacrocyclic phenols [64], an acidic function, the phenol group, has an intra-annular orientation while the basic units, the nitrogen atoms of the macrocycles, have no defined orientation. In water at 25°C, the pATa values of the phenols were measured and compared with those of other macrocyclic and non-macrocyclic phenols (Kimura et al., 1987a,b). Because the nitrogen atoms and the phenol function both possess acid-base properties, more than one pXg value could be measured. By the use of UV measurements, the values of the phenol group could be distinguished from those of the amines. 

The first structurally characterized example of a platinum(II) derivative containing a saturated tetraamine macrocycle, 6,13-dimethyl-l,4,8,ll-tetraazacyclotetradecane-6,13-diamine has been reported (80).251 The species crystallizes as the colorless tetra-cationic complex from dilute HC104 solution by slow evaporation, where the two pendant primary amines are protonated. Other macrocyclic tetraamine complexes including [Pt([14]aneN4)]Cl2 have also been described.252... 

Reasoning that other macrocyclic materials might also display many of the specific properties of the cycloamyloses, Hershfield and Bender (1972) prepared a macrocyclic amine containing two potentially catalytic hydrox-amic acid groups (16). The aliphatic chains of this material provide a potential binding site similar to the cycloamylose cavity (the diameter of the... 

Other macrocyclic ligands 218 with a single pendant arm have been prepared from l,4,7-triazacyclio[5.2.1.04 10]-decane 40 <1996ICA(246)343> by reacting with appropriate alkyl bromide/alkenyl bromide followed by base hydrolysis (Scheme 34). 

DA reactions with polycyclic hydrocarbon derivatives have also been applied to other macrocycles. Lukyanets and coworkers have explored this methodology by adding the unsubstituted tetraazaporphine 20 to a series of anthracene derivatives (Scheme 6). For instance, the reaction with naphthacene (after 6 h at reflux) afforded the chlorin 21 and a tetraazabacteriochlorin (bisadduct) in small amounts <00JPP525>. 

Macrocyclic lactones [840-850], lactams [842,851], carbamates [852], pyridi-nium salts [853], ethers [811,854-858], peptoids [859-864], and calixarenes [865] can also be prepared by RCM. As in other macrocyclizations, yields can usually be improved by lowering the concentration of the reactants. 

Antamanide, a cyclodecapetide, is the first naturally-occurring antibiotic discovered to be selective for sodium and against potassium. Its constitution was established chemically as (IX) (71), which lacks the repetition characteristic of the other macrocyclic antibiotics, and it also differs from them in consisting entirely of L-residues. 

Pseudopolyrotoxanes and polyrotoxanes are polymers composed of a linear polymer chain threaded through one or more cyclic species [Gihson and Mahan, 2000 Raymo and Stoddart, 1999]. Synthesis of pseudopolyrotoxanes and polyrotoxanes involves polymerization of monomer(s) in the presence of the cyclic species. Cyclodextrins, crown ethers, paraquots, and other macrocyclics are used as the cyclic component. Both step and chain polymerizations have heen successfully used. 

Molina et al. prepared macrocycles containing two, four, or six 1,3,4-thiadiazole moieties by reacting bis[4-methyl-5(methylthio)-l,3,4-thiadiazolium] diperchlorates with diamines. They used multiple reaction conditions, varied the size of the spacer (A) between the thiadiazole units, and increased the chain length (B) of the diamine units. Equation (5) depicts a macrocycle accommodating four thiadiazole moieties other macrocycles containing two or six thiadiazole units were also synthesized <94JOC3665>. 

Other macrocyclic polyket naracvclophanes cylindrocyciophanes (Cylindrospermum licheniforme Kutzing, Nostocales, from American Type Culture Collection, and nostocyclophanes from Nostoc linckia (Roth) Bomet ex Bomet Flahault, from Univ. of Texas Culture Collection, freshwater Cyanobact. Hoye 2000). 

The animals are kept in cages, and the fresh secretion is taken from the pouches at regular (about one-week) intervals. Civet is almost liquid with a light yellow color. It darkens when exposed to light and takes on a consistency like salve. In dilutions (e.g., as an alcoholic tincture), civet has a pleasant, sweetish odor. A resinoid prepared by extraction with acetone is a dark brown-red mass [257]. Civetone (see p. 88) is the main odoriferous constituent of civet (2.5-3.4%). Civet contains other macrocyclic ketones such as cyclohexa- and cycloheptadecanone and 6-cw-cycloheptadecenone. Traces of indole and skatole contribute to the animal note [258]. 

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