Permethyl-P-cyclodextrin

Schurig, V., and Mayer, S. (2001). Separation of enantiomers by open capillary electrochromatography on polysiloxane-bonded permethyl-P-cyclodextrin. J. Biochem. Biophys. Methods 48, 117-141. 

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. 

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]. 

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. 

Ravid, U., Putievsky, E., Katzir, I. and Ikan, R. (1992) Determination of the enantiomeric composition of terpinen-4-ol in essential oils using a permethylated P-cyclodextrin coated chiral capillary column. Flavour and Fragrance Journal 7, 49-52. 

The mechanism of chiral recognition in permethyl-p-cyclodextrin has been thoroughly studied by Lipkowitz et al. [269] employing a molecular modelling approach. Not surprisingly, the host s most enantiodiscriminating domain was found to be inside the macrocyclic cavity. 

An advanced HPLC system has been developed to separate cisltrans isomers of tocotrienols using a chiral permethylated P-cyclodextrin column and an acetonitrile/ water eluent mixture (Drotleff and Temes, 1999). 

The essential oils of the Mentha species are known to be valuable ingredients of pharmaceutical and cosmetic preparations. Menthone, isomenthone, menthol and menthyl acetate, the most important Mentha oil constituents, are defined by their amounts as substantial parameters of mentha oil quality. Even off-line HPTLC/enan-tio-GC coupling has proved to be a valuable method in authenticity control of mint and peppermint oils. After preseparating by HPTLC (silica gel dichloromethane) the menthyl acetate fraction is isolated and directly injected for stereodifferentiation with permethyl p-cyclodextrin. Racemic menthyl acetate was detected by Kreis et al. as a frequently used adulteration of Mentha oils [20]. 

Two-dimensional GC in the direct enantiomer separation of menthone, isomenthone and menthol with Ni(HFC)2 as the chiral main column has been reported by Bicchi et al. [92]. Werkhoff et al. [68] isolated these compounds from peppermint oils before stereoanalysis with permethylated p-cyclodextrin. 

G. Takeoka, R.A. Hath, TR. Mon, R.G. Buttery, R. Teranishi, M. Guntert, R. Lautamo and J. SzejtU. Further Applications of Permethylated p-Cyclodextrin Capillary Gas Chromatographic Columns. J. High Resolut. Chromatogr., 12, 202-206 (1990). 

Vetter and Jun have elucidated the structure of an hexachlorinated by-product obtained during the S5uithesis of the heptachloro 1 -methyl-1,2 -bipyrrole 337. Among the three possible structures, 341 may give atropenantiomers, whereas 339 and 340 are achiral. The GC analysis on 10% permethyl-p-cyclodextrin (Chirasil-Dex, Chrompack) chemically bonded to a dimethyl polysiloxane backbone (CB-p-PMCD) coupled with EI-MS revealed two peaks that confirm the chirality of the product (02AC4287). 

The permethylated P-cyclodextrin has been shown to have broad chiral selectivity based largely on polar (hydrophilic) interactions and in some cases inclusion/size selectivity. This material is thermally stable up to temperatures of 230°-250°C and appears to have the potential to separate over 30% of the GC chiral separations published to date. 

Chiral stationary GC phases based on IL coating have been reported in which either a chiral IL was applied or a chiral molecule was dissolved within the IL film. Berthod et al. were the first to dissolve two chiral selector molecules, namely, permethylated-P-cyclodextrin (BPM) and dimethylated-p-cyclodextrin (BDM), in [BMIM]C1 and tested the as-prepared GC columns in the separation of 64 chiral compounds [41], Comparison with two commercial chiral columns, Chiraldex B-PM (20 m length, 250 pm inner diameter) and Chiraldex B-DM (20m length, 250 pm iruier diameter) was also made. The BDM-[BMIM]Cl-coated column produced efficiencies commonly 700% higher than the corresponding values obtained with the commercial BDM Chiraldex column. The difference was lower for the BPM-[BMIM]Cl-coated column, but stiU this column showed twice the efficiency compared to the BPM Chiraldex column. 

Schurig, V. and H. P. Nowotny. 1988. Separation of enantiomers on diluted permethylated P-cyclodextrin by high resolution gas chromatography. j22i2Ji2 2 C- 441 155-163. 

To obtain HBCD diastereoisomer-specific data, it is essential to use LC, since, using GC, the diastereoisomers interconvert at temperatures above 160°C. Therefore, LC—MS/MS using ESI or APCI are versatile tools for the isomer-specific determination of trace levels of HBCDs, monitoring the specific transitions m/z 640.6 to m/z 78.9 and 80.9. An example of separation using permethylated P-cyclodextrin column is shown in Figure 14.1. 

Three chiral compounds in the cherries (limonene, linalool and a-terpineol) were present at sufficiently high concentrations for further separation into their enantiomers using MDGC. Each component in turn was heart-cut onto the second "analytical chiral column coated with permethyl-p-cyclodextrin where separation of the enantiomers was achieved. All chiral compounds showed an enantiomeric excess of the R- enantiomer (Table I). Small differences in the ratios of the enantiomer pairs between the four varieties were observed. 

Poly(2,7-(9,9-dioetylfluorene)-a/f-(5,5 -bithiophene/permethylated p-cyclodextrin)) H Composition, molecular weight 70... 

In the area of ethers of cyclodextrins, 2,2-dipyridyl has been linked to 0-6 by way of a 3-methylene group in otherwise permethylated P-cyclodextrin. Metal ions can be trapped by the product, and the complexes produced were studied. A chiral phosphinyl ferrocene compound has been tethered by way of a C-2 bridge to 0-3 of heptakis-2,3-di-0-methyl-P-cyclodextrin. Commercially available hydroxypropyl P-cyclodextrin of molecular weight about 1500 has been described, and therefore approximately six of the primary hydroxyl groups are substituted. The four regioisomeric 6, 6"-di-0-trityl-y-cyclodextrins have been synthesized and separated by HPLC. For characterization purposes alkenes were produced at the 5,6-positions previously carrying trityl groups. The molecules were fi- mented at that point and product analysis was done by FAB mass spectrometry. ... 

UcceUo-Barretta G, Balzano F, Caporusso AM, lodice A, Salvadori P. Permethylated p-cyclodextrin as chiral solvating agent for the NMR assignment of the absolute configuration of chiral trisubstituted allenes. J. Org. Chem. 1995 60 2227-2231. 

Most recently, Fernandez-Mayoralas and coworkers [30] designed and synthesized a water-soluble linear copolymer bearing both pendant proHne and permethylated P-cyclodextrin ( 3-CD) (Figure 4.9). The idea originated from the fact that the presence of the hydrophobic cavity of p-CD could bring aromatic substrates into close proximity to the surrounding catalytic proline residues through... 

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