JS-cyclodextrin

A different non-classical approach to the resolution of sulphoxides was reported by Mikolajczyk and Drabowicz It is based on the fact that sulphinyl compounds very easily form inclusion complexes with -cyclodextrin. Since jS-cyclodextrin as the host molecule is chiral, its inclusion complexes with racemic guest substances used in an excess are mixtures of diastereoisomers that should be formed in unequal amounts. In this way a series of alkyl phenyl, alkyl p-tolyl and alkyl benzyl sulphoxides has been resolved. However, the optical purities of the partially resolved sulphoxides do not exceed 22% after... 

Carbonates of jS-cyclodextrin are prepared with imidazole carboxylates ... 

Matsue et al. [43] attempted to study the molecular rocket reaction in a ruthenocene-/ -cyclodextrin inclusion compound using the I00Ru y, p) "raTc reaction. They noticed a parallel relationship between chemical processes and nuclear-recoil-induced processes in the non-included ruthenocene compound, as shown in Fig. 9. In the nuclear-recoil-induced processes no dimerization can be observed because of the extremely low concentration of the product, whereas in the chemical processes dimerization is possible, as demonstrated by Apostolidis et al. [48]. When ruthenocene included in /J-cyclodextrin is irradiated with y-rays, a part of the ruthenocene molecule is converted to [TcCp2-] which escapes from the jS-cyclodextrin cavity. The [TcCp2] rocket thus produced can attack neighboring inclusion compounds so as to extract the enclosed ruthenocene molecules and abstract H or Cp (Cp cyclopentadienyl radical). This process is shown schematically in Fig. 10. 

Lin et al. [95] used capillary electrophoresis with dual cyclodextrin systems for the enantiomer separation of miconazole. A cyclodextrin-modified micellar capillary electrophoretic method was developed using mixture of /i-cyclodextrins and mono-3-0-phenylcarbamoyl-/j-cyclodextrin as chiral additives for the chiral separation of miconazole with the dual cyclodextrins systems. The enantiomers were resolved using a running buffer of 50 mmol/L borate pH 9.5 containing 15 mmol/L jS-cyclodextrin and 15 mmol/L mono-3-<9-phcnylcarbamoyl-/j-cyclodextrin containing 50 mmol/L sodium dodecyl sulfate and 1 mol/L urea. A study of the respective influence of the /i-cyclodcxtrin and the mono-3-(9-phenylcarbamoyl-/i-cyclodextrin concentration was performed to determine the optical conditions with respect to the resolution. Good repeatability of the method was obtained. 

The transformation of famotidine from form B to form A was found to be controlled by pressure, temperature, and the interaction between those factors [252]. A subsequent study focused on identifying appropriate milling conditions to avoid conversion [253]. A study of milled Ti and C powders to form TiC found that Raman spectroscopy provided insights not available from XRD studies alone [254]. The successful complexation, or process-induced transformation, of nimodipine (NMD) and hydroxylpropyl-jS-cyclodextrin... 

J and Yabe et al. [155J have formed LB films of amphiphilic derivatives of jS-cyclodextrin and have incorporated azobenzene derivatives into them in such a way as to form a host-guest complex. Many workers have used the cis to trans change of structure referred to above and brought about by ultraviolet irradiation to change some measurable physical parameter of LB films formed from azobenzene derivatives [156-62J. 

The influence of jS-cyclodextrin on the reduction of acetophenone by aqueous NaBH4 is to induce a small ee of (stoichiometric amounts of triethylamine has been found to invert the absolute configuration of the main product, and substantially higher ee values (up to 56%) are then observed.241 In a separate study, the stereoselectivity of the same reaction has been reversed through use of 6-dcoxy-6-(cthylcnediamine)-/j-cyclodextrin.242... 

Fig. 6.21 POPAM dendrimers with terminal adamantyl guest units for inclusion in the host cavities of jS-cyclodextrin (according to Meijer and Reinhoudt et ai.)...

Another method used in the diastereoselective synthesis of isoxazo-lines involved reactions of the iron complexed trienes (115) with nitrile oxides to give the cycloadducts (116) and (117) in a ratio of ca. 9 1 (Scheme 53) (89TL6517). There have been reports on the use of baker s yeast in the enantioselective synthesis of isoxazolines from 4-vinyIpyridine and arylnitrile oxides, and of the enhancement of that selectivity using jS-cyclodextrin (90TL3201 92PACI141). 

Crystal Structure of 6-0-(Phenylthio)-jS-Cyclodextrin and 6-0-(Phenylsulphinyl)-jS-Cyclodextrin... 

Recently, Komiyama and co-workers have reported the preparation of novel cyclodextrin derived imprinted carbohydrates for the efficient recognition of cholesterol [34]. jS-Cyclodextrin was cross-linked in the presence of cholesterol using different diisocyanates as the cross-linking agents. These cyclodextrin matrices, after removal of the template, exhibited selective preference towards cholesterol compared to the non-templated cross-linked cyclodextrin. 

Epidemiological observations are beginning to be confirmed in vitro. For example, in APP751-transfected HEK 293 cells the elevated, by various means, level of cholesterol caused a dramatic reduction in secretion of the soluble APP fragment sAPPa (84). At the cellular level it is by now proved that cholesterol depletion (by 70%) in cultured neurons by combination of lovastatin treatment and methyl-jS-cyclodextrin extraction reduces production of Aj8 below detectable levels (85) by shifting the APP processing to a-secretase (86). 

Amino-, carboxy-, and sulfonato-calixarenes and the 1,8-naphthol-derived 12 form moderately strong complexes with polycyclic aromatic compounds in aqueous solution (see ref. 1, pp. 180-185), with Xassoc values approaching 10 M" The aminocalixarenes have been shown to be capable of being transported through a liquid membrane. The water soluble j -cyclodextrin-calix[4]arene 281 (for attachment-of jS-cyclodextrin at the lower rim, see ref. 728) forms a complex with 2-p-toluidino-6-naphthalenesulfonate with assoc = 1-53 X 10 M" . The cysteine-substituted calixarenes 282 (n = 4 and... 

C. Ortiz Mellet. J. M. Garcfa Fernandez. S. Madejewski. and J. Defaye. Synthesis, water-solubility and inclusion properties of thioureido jS-cyclodextrins. in Proceedings of the Eight International Symposium on Cyclodexlrins. J. Szejtli and L. Szente (Eds.), Kluwer, Dordrecht, 1996.141-144. 

Irradiation of the tropolone (334a) as a complex with jS-cyclodextrin gave the isomer (335a, 64%) as the main product, accompanied by a small amount of (336a). A similar result was obtained from the photolysis of (334b) as a complex which yielded the two products (335b) and (336b). The photoisomers obtained from these reactions were optically active. ... 

Fig. 7. l/(ife b5 — A ) for p-nitrophenyl acetate decomposition is plotted vs. the reciprocal of the jS-cyclodextrin concentration (data from Fig. 6). From VanEtten, R.L., Sebastian, J.F., Clowes, G.A. and Bender, M.L. (1967) J. Am. Chem. Soc. 89, 3242, reprinted by permission.

Karakhanov s group has also been exploring poly(ethylene oxide)- and poly(alkene oxide)-copolymer-bound catalysts [99-102]. A notable aspect of this work is the design of polyethers like 39 that contain jS-cyclodextrins and calyx[4]- and calyx[6]arenes. Such polyethers couple the molecular recognition associated with these macrocycles with the catalytic activity of acac, phosphine, dipyridyl, and catechol ligands. Metals complexed to such ligands have been used in reactions like hydroformylation, Wacker oxidations, and arene hy-droxylation. 

The influence on the photochromism in dithienylethene systems of replacing the favoured perfluorocylopentene moiety by other cyclic ethene units has attracted the attention of a number of research groups. Dutch workers have shown that the use of the perhydrocyclopentene unit as in (91) has little effect on the photochromic behaviour of (92) but note that in situations where fatigue resistance and thermal stability are critical, the fluorinated moiety would be preferable. The cyclization quantum yield of (93) is reported to increase in the presence of metal ions, and more detailed accounts have been published of the interesting application of the dithienylcyclopentene-tethered jS-cyclodextrins (94) as photoswitchable hosts for meso tetrakis(4-sulfonatophenyl)porphyrin. ... 

Ficarra R, Tommasini S, Raneri D, Caiabro ml, Di Bella MR, Rustichelli C, Gamberini MC, Ficarra P, Study of flavonoids/jS-cyclodextrins inclusion complexes by NMR, FT-IR, DSC, X-ray investigation, J. Pharm. Biomed. Anal. 2002 29 1005-1014. 

Myron Bender had reported that a meta-f-butylphenyl acetate (4) acetylated 8-cyclodextrin in water with a rate 250 times as fast as that for hydrolysis of that same substrate at the same pH. We had shown that the same reaction was even faster in a mixed DMSO/ water solvent, but still the acceleration was not what one would have hoped for. Model-building suggested that in the acylation reaction the tetrahedral intermediate is partly pulled out of the cavity, so cyclodextrin binding is to some extent fighting against the reaction rate. Thus we made a new substrate, the p-nitrophenyl ester of ferrocene-acrylic acid (5), and saw that it acylated jS-cyclodextrin with a rate acceleration of 51,000 compared with the hydrolysis rate in free solution. With this substrate there... 

In a later study we examined Diels-Alder reactions in non-aqueous polar solvents, both in the solvents alone and in the solvents with jS-cyclodextrin. We found that DMSO did not promote j8-cyclodextrin binding, but that it was promoted by both ethylene glycol and... 

In our first study we attached a pyridoxamine unit to a primary carbon of jS-cyclodextrin (structure 12). We saw that pyridoxamine alone is able to transaminate pyruvic acid to form alanine, phenylpyruvic acid to form phenylalanine, and indolepyruvic acid to form tryptophan, all with equal reactivity by competition experiments. However, when the cyclodextrin was attached to the pyridoxamine there was a 200-fold preference for the indolepyruvate over pyruvate in one-to-one competition, forming greater than 98% of tryptophan, and in the competition with phenylpynivate and pyruvate the phenyManine was formed in greater than 98% as well. Thus the ability of the substrates to bind into the cyclodextrin cavity led to striking selectivities. In addition there was some chiral induction in these processes, since )3-cyclodextrin is itself chiral, but the magnitudes of the induction were quite modest. 

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