Calix arenes nucleosides

Among more complex macrocycles, Li et al. [47-52] reported the preparation and characterization of stationary phases incorporating calixarenes or calix-crowns bonded to silica. With individual columns, high selectivity was observed in the separation of alkylated aromatics, aromatic carboxylic acids, sulfonamides, nucleosides, and water-soluble vitamins. In other work, Sokoliess et al. [53] have characterized calixarene- and resorcinarene-bonded stationary phases similar to those described in the previous section of this chapter. And Huai et al. [54] used an end-capped p-tert-butyl-calix[4]arene-bonded silica phase for HPLC separation of a number of organic compounds. Resorcinarenes have also found application in GC. [55-57] Recently, exotic macrocycles have been used in capillary electrochromatography, as reported by Gong et al. [58]... 

Li, L., Liu, M., Da, S., and Feng, Y. (2004) Studies on the Chromatographic Behavior of Nucleosides and Bases on P-tert-butyl-calix[8]arene-bonded Silica Gel Stationary Phase by HPLC, Talanta 63, 433-441. 

For dynamic processes involving hydrogen-bonded entities, see (a) Calama MC et al (1998) Libraries of non-covalent hydrogen-bonded assemblies combinatorial synthesis of supramolecular systems. Chem Commun 1021-1022. (b) Timmerman P et al. (1997) Noncovalent assembly of functional groups on Calix[4]arene molecular boxes. Chem Eur J 3 1823-1832. (c) Cai MM et al. (2002) Cation-directed self-assembly of lipophilic nucleosides the cation s central role in the structure and dynamics of a hydrogen-honded assembly. Tetrahedron 58 661-671... 

Relatively few molecular separations have been studied from the utilitarian standpoint. One of these, the purification of fullerenes via 8 , is discussed on p. 170. In a reciprocal experiment the separation of 4 " , 6 , and 8 with a column using a chemically-bonded C o silica stationary phase has been re-ported. Chromatographic selectivity has been achieved for amino acid esters and alkali metal cations on silica-bonded calix[4]arene tetraesters, the structure of which has been explored by and Si-CP-MAS NMR. Silica-bonded calixarenes have also been used as packing materials for HPLC columns that are capable of separating disubstituted aromatics, peptides, and nucleosides. The HPLC separation of phenols using 6 ° as a constituent of the eluent has been described. ... 

The conjugates of various nucleosides and calix[4]arene 113 and 114, in which one or two 3 -phosphorylated nucleoside moieties were anchored... 

Fig. 24.30 (a) Synthetic steps towards a paira-ter/-butyl-calix[4]arene-bonded silica stationary phase [94]. (b) Chemical structure of para-tert-butyl-calix[8]arene-bonded silica gel stationary phase [95]. (c) Isocratic separation of nucleosides cytidine, uridine, guanosine and adenosine on an Aren Si 60 column with 0.02 M NaH2P04 (pH 3.5) as mobile phase (x-axis time in min y-axis absorbance at 254 nm) [93]. (Reprinted from Ref [93])... 

When ferf-butyl calix[8]arenes were immobilized on silica gel from a 3-glycidoxypropyl-bonded stationary phase (GBS) precursor, nucleosides and bases were strongly retained inside the mobile calixarene cavity and led to much better separation on the advanced stationary phases, especially in mobile phases with a large water content [95]. 

Contrary to probe 22, triazole-linked anthracene bearing calix[4]arene in the cone conformation 23a [50] (Fig. 28.6) showed selectivity for Co " ions, with a detection limit of 55 ppb (0.92 pM). The selectivity is favored by the hexa-coordination of Co " by two ether oxygens, two phenolate oxygens, and two triazole nitrogen atoms of probe 23a. Alkylation of 23a results in the triazolium-anthracenyl calix[4]arene probe 23b (Fig. 28.6) [51]. The fluorescence titrations with various nucleosides showed high selectivity for nucleoside triphosphates... 

Lu et al. investigated the interaction of Langmuir monolayers of amphiphilic calix[4]arenes bearing two adenine units at the lower rim with the nucleosides uridine and thymidine at the air-water interface [46]. Surface pressure-area compression isotherms revealed that the monomolecular films interact specifically with uridine and thymidine at the interface. 

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