Cyclodextrins dimethyl

Name (3-Cyclodextrin, dimethylated bonded phase Structure ... 

Calcium Lignosulfonate beta-Cyclodextrin Dimethyl Dicarbonate Glyceryl Palmitostearate 4-Hexylresorcinol Magnesium Phosphate, Dibasic, Mixed Hydrates Manganese Citrate Olestra... 

Key words Nitrosation reactions 0(-, B-, Y-cyclodextrin, dimethyl-6-cyclodextrin piperazine ethaiributol cim idine 1-etdiedrine fencamfamine. 

ABSTRACT. Second harmonic generation(S.H.G.) in inclusion complexes between dimethyl-cyclodextrin(dimethyl -CD) and nitroaniline derivatives occurs. This is due to the destruction of the centrosyimntric crystal structure in nitroaniline derivatives caused by forming inclusion complexes. S.H.G. intensity of dimethyl /-CD complex with N-methyl-nitroaniline is 5 5 times as large as that of urea. 

In this experiment, three nitroaniline derivatives, i.e. p-nitro -aniline (p-NA), 2-hydroxy-i -nitroaniline(HNA) and N-methyl-i -nitroaniline (NMNA), were chosen as guest molecules because of their large optical nonlinearity. As a host molecule, dimethyl /-cyclodextrin (dimethyl f -CD) was used. It is well known that dimethyl /-CD forms an inclusion complex with many kinds of aromatic derivatives. 

Figure 10.1 Analysis of racemic 2,5-dimethyl-4-hydroxy-3[2H]-furanone (1) obtained from a strawbeny tea, flavoured with the synthetic racemate of 1 (natural component), using an MDGC procedure (a) dichloromethane extract of the flavoured strawbeny tea, analysed on a Carbowax 20M pre-column (60 m, 0.32 mm i.d., 0.25 p.m film thickness earner gas H2, 1.95 bar 170 °C isothermal) (b) chirospecific analysis of (1) from the sti awbeny tea exti act, ti ansfened foi stereoanalysis by using a pemiethylated /3-cyclodextrin column (47 m X 0.23 mm i.d. canier gas H2, 1.70 bar 110 °C isothemial). 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.

Water plays a crucial role in the inclusion process. Although cyclodextrin does form inclusion complexes in such nonaqueous solvents as dimethyl sulfoxide, the binding is very weak compared with that in water 13 Recently, it has been shown that the thermodynamic stabilities of some inclusion complexes in aqueous solutions decrease markedly with the addition of dimethyl sulfoxide to the solutions 14,15>. Kinetic parameters determined for inclusion reactions also revealed that the rate-determining step of the reactions is the breakdown of the water structure around a substrate molecule and/or within the cyclodextrin cavity 16,17). 

Monflier et al. (1995) have intensified the rate of the oxo reaction of sparingly soluble olefins like 1-decene using dimethyl p-cyclodextrine, which seems to form inclusion complexes with the olefin and deliver it in the aqueous phase. 

Monflier et al. (1997) have suggested Pd catalysed hydrocarboxylation of higher alpha olefins in which chemically modified P-cyclodextrin (especially dimethyl P-cyclodextrin) is u.sed in water in preference to a co-solvent like methanol, acetone, acetic acid, acetonitrile, etc. Here, quantitative recycling of the aqueous phase is possible due to easy phase separation without emulsions. A similar strategy has been adopted by Monflier et al. (1998) for biphasic hydrogenations for water-in.soluble aldehydes like undecenal using a water-soluble Ru/triphenylphosphine trisulphonate complex with a. suitably modified p-cyclodextrin. 

A 1996 work deposited four different catalytic metals on a p-cyclodextrin— epichlorohydrin copolymer to prepare Pd(Pt, Rh, Ru)-P-cyclodextrin copolymer catalysts.8 These were used to catalyze the asymmetric hydrogenations of the C=C bonds of trans-2-methyl-2-pentenoic acid, and dimethyl itaconate. 

Ventura CA, Giannone I, Musumeci T, Pignatello R, Ragni L, Landolfi C, Milanese C, Paolino D, Puglisi G (2006) Physico-chemical characterization of disoxaril-dimethyl-beta-cyclodextrin inclusion complex and in vitro permeation studies. Eur J Med Chem 41 233-240. 

The syntheses of the receptors 10 and 12 were carried out by the treatment of bisphenol porphyrin 13 and its Zn complex 14, respectively, with portionwise addition of a large excess of P-cyclodextrin-6-O-monotosylate (CD-Tos) 15 using caesium carbonate as base in N,N dimethyl formamide (DMF) (Fig. 6) (13). 

Acetyl esterase from oranges P04 -buffer, pH 6, 37 °C Dimethyl-/ -cyclodextrin, 35%... 

Cyclodextrins slow the rate of hydrolysis of benzaldehyde dimethyl acetal, PhCH(OMe)2, in aqueous acid as the substrate binds in the cyclodextrin s cavity, producing a less reactive complex. Added alternative guests compete for the binding site, displacing the acetal and boosting hydrolysis. 

Bicchi C, Artuffo G, D Amato A, Manzin V, Galfl A, GaUi M, Cyclodextrin derivatives in the GC separation of racemic mixtures of volatile compounds, Part V Heptakis 2,6-dimethyl-3-pentyl- 3-cyclodextrins,Chromatogr 15 710-714, 1992. 

Separation of the enantiomers of a series of local anaesthetics through their interaction with dimethyl p-cyclodextrin included In the running buffer. Redrawn from Reference 6. 

Table 14.3 Association constants of some enantiomers of some local anaesthetics with dimethyl P-cyclodextrin and their mobilities in free solution...

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]. 

The extracts contained almost pure pheromone, with only minor amounts of other components. By comparison with synthetic samples, derivatization, and gas chromatography on a chiral cyclodextrin phase, the pheromone was identified as a 95 5 mixture of (5)- and (/ )-enantiomers of dimethyl citrate (cupilure (3), Fig. 4.2). Only the (5)-enantiomer was active (Tichy et al., 2001). Cupilure is probably present in ionized form on the silk (pK 3.5), because solvent extracts were neutral. The ionized carboxyl group may be conjugated to basic amino acids of the silk proteins. This would also explain why the pheromone is not volatile, despite its relatively low molecular weight, and is easily washed from the silk by water, including rain. In the tropical habitat of C. salei this would ensure the presence of cupilure only on freshly laid silk. 

P-Cyclodextrin hydrate p-Cyclodextrin, hydrate (10) (68168-23-0) p-Toluenesulfonyl chloride (8) Benzenesulfonyl chloride, 4-methyl- (9) (98-59-9) N,N-Dimethylformamide cancer suspect agent Formamide, N,N-dimethyl-(8,9) (68-12-2)... 

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