Fl-Cyclodextrin

The progress of the reaction can be monitored by TLC by working up a sample of the reaction mixture filter through Celite, cool to 0°C, and acidify to pH 1 with 10% aqueous HCI. The solid that precipitates is isolated by filtration and dissolved in dimethylformamide (DMF) for TLC analysis on Merck precoated-silica gel 60 plates with methyl ethyl ketone-methanol-water (4 1 1) as eluent, developed by dipping in 5% sulfuric acid-ethanol and heated to 450°C (e.g., with a Bunsen burner). Rf values are 0.25 for fl-cyclodextrin, 0.5 for monotosylate and 0.65 for a second product, probably ditosylate. 

Acylation of fl-cyclodextrin. The acylation of /5-cyclodextrin is modestly accelerated by bound m-nitrophenyl acetate, m-N02C6H40C0CH3. Recently acylation of /3-cyclodextrin at a rate comparable to acylation of chymotrypsin has been reported. The acylating reagent is the p-nitrophenyl ester (1) of ferrocinnamic acid. This reagent was chosen because ferrocene is strongly bound within the cavity of /3-cyclodextrin. The acylation is accelerated by > 50,000-fold compared to hydrolysis of 1 in DMSO-HjO alone buffered at pH 6.8. Thus cyclodextrins can behave as artificial enzymes. 

Mielcarek, J. and Daczkowska, S., 1999, Photodegradation of inclusion complexes of israd-ipine with methyl-fl-cyclodextrin, J. Pharm. Biomed. Anal. 21, 393-398. 

Additives Mixed surfactants formed with neutral and ionic surfactants. For example, Brij 35 (polyoxyethylene [23] dodecyl ether) 1-25 mM Organic solvents methanol, 2-propanol, acetonitrile, tetrahydrofuran 1-25 % (v/v) Higher molecular mass solvents of low water solubility 1-5 % (v/v) Complexing additives such as a-, p-, y-cyclodextrins, hydroxypropyl-fl cyclodextrin and heptakis-(2,3,6-tri-0-methyl)-p-cyclodextrin (5-20 mM)... 

Confinement of azobenzene in defined structures changes the quantum yields. In the cavity of fl-cyclodextrine, the < )e. z reduced and become... 

The use of chiral mthenium catalysts can hydrogenate ketones asymmetrically in water. The introduction of surfactants into a water-soluble Ru(II)-catalyzed asymmetric transfer hydrogenation of ketones led to an increase of the catalytic activity and reusability compared to the catalytic systems without surfactants. Water-soluble chiral mthenium complexes with a P-cyclodextrin unit can catalyze the reduction of aliphatic ketones with high enantiomeric excess and in good-to-excellent yields in the presence of sodium formate (Eq. 8.3). The high level of enantioselectivity observed was attributed to the preorganization of the substrates in the hydrophobic cavity of fl-cyclodextrin. 

Uekama, K., Maeda, T., Arima, H. et al. Possible utihty of fl-cyclodextrin complexation in the preparation of biphenylylacetic acid suppository. Yakugaku. Zasshi 1986,106,1126-1130. 

Evaluation of chiral purity of Sulfobutyl ether fl-cyclodextrin FSCE [154]... 

Chiral separations of a range of Sulfated fl-cyclodextrin (fl-CD-(SO. )4 NACE [157]... 

Enantioseparation of nine racemic Highly sulfated fl-cyclodextrin FSCE [159]... 

Piperaki, S. Perakis, A. Parissi-Poulou, M. Liquid chromatographic retention behaviour and separation of promethazine and isopromethazine on fl-cyclodextrin bonded-phase column. J.ChromatognA, 1994, 660, 339-350... 

He described how di- and trimethyl-i(- and fl-cyclodextrins could be used to improve the stability, solubility, dissolution rate and bioavailability of different drugs such as HCFU (6), Prednisolone and Vitamins Kl, K2 and K3. Looking to the future, the applications of hydroxypropylated, ethylated and maltosylated cyclodextrins were described. 

Because the substituted carbon atoms in HBCD are chiral, enantiomeric forms of each diastereomer exist 16 stereoisomers are theoretically possible [128]. Biotransformation of the stereoisomers can potentially alter the enantiomeric ratios [129], and methods for the determination of six individual enantiomers have been developed. Gomara et al. [130] studied the influence of mobile phase modifiers, gradient conditions, column temperature, and flow rates to achieve baseline resolution of the prevalent HBCD enantiomers, using a permethylated fl-cyclodextrin column (see Figure 13.9). In this work, spiked meat, fish, and butter samples were analyzed to assess detection limits and matrix effects. 

Scheme 9.12 Capping acetal and successive regioselective opening gives access to an original pattern of differentiation on the secondary rim of fl-cyclodextrin.

Two CILs [(ethyl and phenyl choline cations with bis (trifluoromethylsul-fonyl)imide) anion] have been evaluated by Francois et al. as chiral selectors for enantiomeric separation of arylpropionic acids by CE [77]. No direct enantioselec-tivity was observed for these two CILs, except in the presence of fi-cyclodextrins, suggesting that a synergistic effect of the two selectors is responsible for increased resolution and separation efficiency. The authors demonstrated an influence of the fl-cyclodextrin on the competition between the analyte and the IL cation with respect to P-cyclodextrin complexation. However, the presence of the phenyl group in the IL cation appeared to be less important in enhancing the synergistic effects. This indicates that specific ion-pairing interactions could be involved [77]. 

---