Calixarene phosphates

For a review on calixarene phosphates see J. Gloede, Phosphorous, Sulfur, Silicon, 127, 97 (1997). 

Diethyl phosphate esters of the sterically congested phenols of calixarenes have been prepared in acceptable yields (>55%) and used in the preparation of meta-cyclophanes [8]. The corresponding reaction using diethyl phosphite, with triethylamine in place of the quaternary ammonium catalyst, results in only partial phosphorylation of the hydroxyl groups. 

Pattern recognition using cahxarene receptors that bind to proteins via surface electrostatic interaction has been used to identify a variety of proteins (Kolusheva et al. 2006). Amphiphilic calixarenes terminated with either amino or phosphate groups were incorporated into mixed PDA/phospholipid vesicles, which were incubated with various proteins that differed in their isoelectric points (pi). As expected, proteins with low pi values resulted in a large CR with liposomes containing cationic calixarene receptors. Each protein was characterized by a unique ACR value, where... 

Log Kex Lanthanides Ln3+ 6 Alkyl phosphates, calixarenes Toluene LR Ligand s strain energy e 86... 

This review groups the information published on degradation of the main families of extractants studied in the frame of long-lived minor-actinide and fission-product recovery (1-4) (see Chapter 1) alkyl-phosphorus compounds (phosphates, phosphonic acids, bifunctional compounds like CMPO), amide compounds (dialkyl-amides, malonamides, and diglycolamides), N-donor compounds, and macrocycles like crown ethers and calixarenes (Table 8.1). The multicomponent systems based on the chlorinated cobalt dicarbollide process have not been considered. 

The extractant s stability can be improved if the selected diluent has a lower ionization potential than the extractant, like aromatic compounds (183). This protective effect has been observed for numerous extractants alkyl phosphates, alkyl phosphonates, amides, and calixarenes (25, 39, 68, 84,... 

Many artificial systems have been designed recently to imitate the function and behaviour of native enzymes - biomimetic chemistry [27]. Among them, calixarene-based receptors bearing one, two or three Zn(II) complexes on the upper rim were prepared as a model for phosphoesterases [28-31]. Dinuclear receptor 25 was reported to enhance the rate of transesterification of the RNA model substrate 2-hydroxypropyl-p-nitrophenyl phosphate more than 20,000 times compared with the non-catalysed reaction. The complexation mode for the phosphate anion can be described as cascade complexation where the anion is coordinated within the cavity formed by two zinc cations. 

If the phosphorotropic rearrangement is combined with selective electrophilic substitution of free phenolic units (e.g. bromination) and hydrolysis of ester or phosphate groups a variety of inherently chiral calixarenes becomes available,130 as demonstrated by the examples in Figure 15. 

Phosphine Chalcogenides as Ligands. - The complexation of lanthanide and actinide ions by phosphine oxide ligands remains an active area, and a theoretical assessment of the coordination of phosphine oxides (and phosphate esters) by trivalent lanthanide ions has appeared." Trivalent lanthanide complexes of the functionalised enol phosphine oxide (265), (and a related phosphonate), have been describedComplexes of thorium(iv) with bis(di-phenylphosphino) ethane dioxide and bis(diphenylphosphinoyl)amide have also been characterised." Calixarene systems which bear phosphine oxide... 

Interest in phosphorus-containing calixarenes continues. Structures reported include hexa(diethoxyphosphoryloxy)calix[6]arene (8), inherently chiral 1,2-bridged calix[4]arene diphosphates, and a calixarene like C3 symmetric receptor with a phosphate function at the cavity bottom. " The purification of phosphate substituted calixarenes has been studied by chiral HPLC and by normal reverse phase HPLC. Mono(6-0-diphenoxyphosphoryl)-P-cyclodextrin (9) and mono(6-0-ethoxyhydroxyphosphoryl)-p-cyclodextrin (10) have been synthesised and show enantioselective inclusion of D and L amino acids e.g. 3.6 for D/L serine in the case of 9). ... 

Miscellaneous Reactions. Wittig technology has been used to prepare ylide-, phosphate-, phosphite- and phosphinate-terminated dendrimers, and calixarenes bearing pyridyl podands on their upper rim 7°... 

Reports which have clear applications in DNA hydrolysis include one of a dinuclear lanthanum(III) complex that catalyses phosphate diester hydrolysis to give unprecidented rates of reaction and one describing the preparation of two new dinuclear bisimidazolyl-Cu(II) calixarenes and an investigation of these complexes as metalloenzyme models for phosphate diester cleavage. The importance of tuning microenvironments when designing synthetic nucleases is illustrated by a report that intramolecular trans-esterification of 2-hydroxy-propyl-4-nitrophenyl phosphate (84) is up to 5000 times faster in organic solvents than in water/ ... 

Another calixarene, with long alkyl side chains and eight phosphate groups, has been used to recover uranium from seawater in 68-94% yields.71 Seawater contains 3 ppb of uranium. The resin could be recycled several times. 

A number of other types of calixarene esters are known, including the aryl-sulfonates (often used to establish the calix[4]arenes in the cone conforma-tion ), phosphates (often used as intermediates in the replacement of the OH groups with and phosphonates. ... 

The ability of the calix[4]arene system to form cyclic phosphates has been demonstrated. When acted upon by PCI5, calixarene (8) (n = 0, R — = OH)... 

In the phosphorus(V) acids area, there has been continued interest in the preparation of phosphates from elemental phosphorus, and also of compounds derived from the calixarenes. Apart from these, there has been little of real significance in the phosphate field. A much greater interest has been shown in enantio- or diastereo-selectivity in synthesis and reactivity of phosphonates and... 

Figure 8.7 Catalysis by a dinuclear Cu -calixarene complex in the cleavage of an ollgorlbonucleotide labelled at the 5 -terminus with a phosphate dianion...

On the basis of the catalytic roles of calix[4]arene derived model 18-[Zn"]2 (99JOC3896) and cis-diaqua Cu complexes for cleavage of phosphate diesters, Reinhoudt designed a calix[4]arene derivative 66-[Cu ]2 functionalized with two ds-diaqua Cu° centers at the distal positions of the upper rim as a model for dinuclear metalloenzymes that catalyze chemical transformations of phosphate esters. It was synthesized from Cu(C104)2 and 5,17-bis(bis(l-methylimidazol-2-yl)hydroxy-methyl)-25,26,27,28-tetrakis(2-ethoxyethoxy)calix[4]arene which was conveniently obtained from the precursor diester and lithiated 1-methyl-imidazole. In this model, the two Cu° centers are well organized on the calixarene scaffold for performing S5mergistic action. 

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