A-cyclodextrin, permethylated

Jung, J.H., Takehisa, C., Sakata, Y., and Kaneda, T. (1996) p-(4-Nitrophenylazo)phenol Dye-bridged Permethylated a-Cyclodextrin Dimer Synthesis and Self-aggregation in Dilute Aqueous Solution, Chem. Lett. 147-148. 

Urethane-forming reaction between isocyanate and hydroxyl group was utilized by Osakada et al. to prepare polyurethane-cyclodextrin pseudoro-taxanes (Scheme 15) [86]. Polyaddition of a diol and MDI in the presence of permethylated a-cyclodextrin or permethylated (5-cyclo dextrin was carried out in DMF for 20 h at 120 °C to yield the pseudopolyrotaxane. The molar... 

Jung JH, Takehisa C, Sakata Y, Kaneda T. 1996. p (4 Nitrophenylazojphenol dye bridged permethylated a cyclodextrin dimer synthesis and self aggregation in dilute aqueous solution. Chem Lett (2) 147 148. 

An example of a chromatogram of a test mixture used by Supelco to demonstrate the chromatographic characteristics of their a-DEX column is shown in figure 6.1. The stationary phase is claimed to have a high shape selectivity for positional isomers (e.g. xylenes, menthols, cresols etc.) and the small internal cavity of the permethylated a-cyclodextrin gives it a rigid character and unique chiral selectivities. 

Chromatogram of a Test Mixture for a Permethylated a-Cyclodextrin Stationary Phase Courtesy of Supelco... 

Table I. Experimental data for a-cyclodextrin-iracemic 1-phenylethanol complex (I), 3 Cyclodextrin—S-flurbiprofen complex (II), 3-cyclodextrinr-racemic flurbiprofen complex (III), permethylated a-cyclodextrin—L-mandelic acid complex (IV), permethylated a-cyclodextrinHD-mandelic acid complex (V), permethylated 3-cyclodextrin—R-flurbiprofen complex (VI), and permethylated 3-cyclodextrin—S-flurbiprofen complex (VII)...

Permethylated a-Cyclodextrin Complexes with Mandelic Acids [6]... 

Fig. 6. Structures of permethylated a-cyclodextrin complexes with L-mandelic acid (A) and D-mandelic acid (B).

Table II shows geometrical data describing the macrocyclic conformation of cyclodextrins and permethylated cyclodextrins. The radius and side length of the 0(4) heptagon of 3-cyclodextrin, 5,0 A and 4,38-4,39 A, respectively, are similar to those (5,00-5,01 A and 4.38-4,39 A, respectively) of permethylated 3-cyclodextrin. The 0(4) hexagon of permethylated a-cyclodextrin is somewhat larger than that of a-cyclodextrin the radius of the 0(4) hexagon is 4,23 A in a-cyclodextrin and 4.30 A in permethylated a-cyclodextrin.

The geometrical structure of the host-guest interaction of the permethylated a-cyclodextrin complex with L-mandelic acid differs from that of the D-mandelic acid complex. The comparison of the two structures suggests that the complex formation with D-mandelic acid induces the conformational change of the host molecule so as to accommodate the guest... 

Octadeca-O-Me Hexakis(2,3,6-tri-O-methyl) cyclomaltohexaose. Permethyl-a-cyclodextrin [68715-56-0]... 

Fujimoto, T, Nakamura, A., Inoue, Y., Sakata, Y., and Kaneda, T, Photoswitching of the association of a permethylated a-cyclodextrin-azobenzene dyad forming a janus[2]pseudorotaxane, Tetrahedron Lett., 42, 7987, 2000. 

Figure 10.2 MDGC-MS differentiation between the enantiomers of theaspiranes in an aglycone fraction from puiple passion fruit DB5 pre-column (25 m X 0.25 mm i.d., 0.25 p.m film thickness canier gas He, 0.66 ml/min oven temperature, 60-300 °C at 10 °C/min with a final hold of 25 min) permethylated /3-cyclodextrin column (25 m X 0.25 mm i.d., 0.25 p.m film thickness canier gas He, 1.96 ml/min 80 °C isothermal for 20 min and then programmed to 220 °C at 2 °C/min). Reprinted from Journal of High Resolution Chromatography, 16, G. Full et al., MDGC- MS a powerful tool for enantioselective flavor analysis , pp. 642-644, 1993, with permission from Wiley-VCH.

Recently, it was found that the commercially available heptakis(2,3,6-tri-0-methyl)-/i-cyclodextrin (permethylated /1-cyclodextrin, TRIMEB), induced nonequivalence in the NMR spectra, in CD3OD, of enantiomeric mixtures of trisubstituted allenes devoid of polar functional groups, thus affording a simple and general way to determinations of their enantiomeric purity63. 

Zhu, X., Lin, B., Jakob, A., Wuerthner, S., Koppenhoefer, B. Separation of drugs by capillary electrophoresis, part 10. Permethyl-alpha-cyclodextrin as chiral solvating agent. Electrophoresis 1999, 20,1878-1889. 

Hydrogenation of unsaturated carboxylic acids, such as acrylic, methacryUc, maleic, fumaric, cinnamic etc. acids was studied in aqueous solutions with a RhCU/TPPTS catalyst in the presence of p-CD and permethylated P-cyclodextrin [7]. In general, cyclodextrins caused an acceleration of these reactions. It is hard to make firm conclusions with regard the nature of this effect, since the catalyst itself is rather undefined (probably a phosphine-stabilized colloidal rhodium suspension, see 3.1.2) moreover the interaction of the substrates with the cyclodextrins was not studied separately. 

The stability of the polypyridyl rhenium(I) compounds mentioned above stimulated applications of this coordination chemistry. Thus, new heterotopic bis(calix[4]arene)rhenium(I) bipyridyl receptor molecules have been prepared and shown to bind a variety of anions at the upper rim and alkali metal cations at the lower rim. A cyclodextrin dimer, which was obtained by connecting two permethylated /3-cyclodextrins with a bipy ligand, was used for the preparation of a luminescent rhenium(I) complex. The system is discussed as a model conipound to study the energy transfer between active metal centers and a bound ditopic substrate. The fluorescence behavior of rhenium(I) complexes containing functionalized bipy ligands has been applied for the recognition of glucose. ... 

Ravid U, Putievsky E, Katzir I, Ikan R, Determination of the enantiomeric composition of terpinen-4-ol in essential oils using a permethylated 3-cyclodextrin coated chiral capillary column. Flavour Fragr/7 49—52, 1992. 

The first gas chromatographic enantiomer separation on a cyclodextrin-based stationary phase was that of the apolar, racemic hydrocarbons a- and /i-pinenc and cis- and trans-pinane on packed columns coated with native a-cyclodextrin dissolved in formamide157. Very soon, it was recognized that alkylated cyclodextrins can be employed in capillary columns for high-resolu-tion enantiomer analysis. Thus, molten permethylated /(-cyclodextrin, hcptakis(2,3,6-tri-0-methyl)-/ -cyclodextrin (Table 2), was used158- 160 at elevated temperatures. 

Permethylated /1-cyclodextrin has also been used as a solution in moderately polar polysiloxanes (e.g., OV-1701)161 165. By diluting the chiral selector, the inherent enantioselec-tivity of cyclodextrins is combined with the unique chromatographic properties of polysiloxanes. Even unfunctionalized saturated hydrocarbons, e.g., l-ethyl-2-methylcyclohexane and l-methyl-2-propylcyclohexane, can be resolved (Figure 15). 

Many types of cyclodextrin derivatives coated onto fused silica capillary columns are commercially available, notably, permethyl-/3-cyclodextrin dissolved in OV-1701 (CP-Cyclodextrin-/l-2,3,6-M-19) and Chirasil-Dex from Chrompack International14,3 and Lipodex A-D (Table 2) from Macherey-Nagel182. 

A chiral selector can also be dissolved in the IL solvent and be subsequently coated on the capillary wall [38]. In this approach, the achiral [C4CiIm]Cl was used to dissolve permethylated p-cyclodextrin (p-PM) and dimethylated P-cyclodextrin (p-DM). The chromatographic separations obtained from these two columns were compared to two commercially available CSPs based on p-PM and p-DM dissolved in polydimethylsiloxane. From a set of 64 chiral molecules separafed by fhe commercial p-PM column, only 21 of the molecules were enantioresolved by the IL-based p-PM column. Likewise, from a collecfion of 80 analytes separated by the p-DM column, only 16 analytes could be separated on the IL-based p-DM column. The authors also noted a considerable enhancement in the separation efficiency of fhe IL-based CSPs. This resulf, coupled to fhe loss of enantioselecfivify for mosf separations, suggests that the imidazolium cation may occupy the cavity of the cyclodextrin preventing the analyte-cyclodextrin inclusion complex-ation that is crucial for chiral recognition. The ability for ILs to form inclusion complexes wifh cyclodextrin molecules has been recently studied by Tran and coworkers using near-infrared spectromefry [39]. 

Another beautiful example of multiple recognition by the use of multi-functionalized cyclodextrin is symmetrical triamino-O-permethyl-a-cyclo-dextrin (16), which is designed for the specific recognition for the phosphate group (Fig. 23) (55). As is expected, 16 shows a higher affinity toward benzyl phosphate (Kass = 3.2 x 104) than does the corresponding monoammonium derivative (Kaas = 3.3 x 101). 

Figure 10.1 Analysis of racemic 2,5-dimethyl-4-hydroxy-3[2H]-furanone (1) obtained from a strawberry tea, flavoured with the synthetic racemate of 1 (natural component), using an MDGC procedure (a) dichloromethane extract of the flavoured strawberry tea, analysed on a Carbowax 20M pre-column (60 m, 0.32 mm i.d., 0.25 pan film thickness carrier gas H2, 1.95 bar 170 °C isothermal) (b) chirospecific analysis of (1) from the strawberry tea extract, transferred for stereoanalysis by using a permethylated /1-cyclodextrin column (47 m X 0.23 mm i.d. carrier gas H2, 1.70 bar 110°C isothermal). Reprinted from Journal of High Resolution Chromatography, 13, A. Mosandl et al., Stereoisomeric flavor compounds. XLIV enantioselective analysis of some important flavor molecules , pp. 660-662, 1990, with permission from Wiley-VCH.

Permethylated tosylated a-cyclodextrin was coupled with aminohydroxyazo-benzene. The product was dimerized to Janus [2]pseudorotaxane, which in turn was bis-azo coupled with 2-naphthol-3,6-disulfonic acid. The product undergoes selfassociation as shown in Figure 14 [44], Note that the final product has o-quinone hydrazone structure. 

Jung et al. [58] obtained permethylated a-CD bridged with (nitrophenylazo)-phenol dye (Figure 21). This compound exhibits time-dependend UV-Vis and NMR spectra in aqueous solutions at room temperature in the dark. This phenomenon was interpreted in terms of self-aggregation involving intermolecular inclusion of the p-nitrophenylazophenol group with one of the two permethylated cyclodextrin residues of the original compound. 

Fig. 4.9. (A) Structure of permethyl-p-cyclodextrin linked to silica support by means of a sulfide spacer and (B) a CEC separation of hexobarbital in a column packed with the the material shown in A. Adapted from ref. [81] with permission. Copyright Elsevier 1998.

Enantiomer separation of various compounds such as barbituric acids, benzoin, MTH-proline, glutethimide, a-methyl-oc-phenyl-succinimide, y-phenyl-y-butyrolac-tone, methyl-mandelate, l-(2-naphthyl)ethanol, mecoprop methyl, diclofop methyl and fenoxaprop methyl by pressure supported CEC on a permethyl-P-cyclodextrin modified stationary phase was described by Wistuba and Schurig [42-44]. Three different separation beds were used (i) permethyl-P-cyclodextrin was covalently attached via a thioether to silica (Chira-Dex-silica) [42], permethyl-P-cyclodextrin was linked to a dimethylpolysiloxane and thermally immobilized (ii) on silica (Chirasil-Dex-silica) [43] or (iii) on a silica monolith (Chirasil-Dex-monolith) [44], respectively. 

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