A- and P-cyclodextrin

Matsui and Mochida24) have determined the thermodynamic stabilities (log 1 /Kd) for a- and P-cyclodextrin complexes with a variety of alcohols (Table 2) and analyzed the results in connection with the physicochemical properties of the guest molecules by the multivariate technique. The log 1/Kd values were plotted against log Pe, where Pe is the partition coefficient of alcohol in a diethyl ether-water system. The plots for the a- and P-cyclodextrin complexes with eight 1-alkanols gave approximately straight lines with slopes of around one. 

Matsui75) has computed energies (Emin) which correspond to the minimal values of Evdw in Eq. 1 for cyclodextrin-alcohol systems (Table 2). Besides normal and branched alkanols, some diols, cellosolves, and haloalkanols were involved in the calculations. The Emi values obtained were adopted as a parameter representing the London dispersion force in place of Es. Regression analysis gave Eqs. 9 and 10 for a- and P-cyclodextrin systems respectively. 

Nishioka and Fujita 78> have determined the Kd values for a- and P-cyclodextrin complexes with m- and p-substituted phenols at pH 7.0. Taking into account the directionality in inclusion of a guest molecule, they assumed three and two probable orientational isomers for the cyclodextrin complexes with m- and p-substituted phenols respectively (Fig. 6). Then the observed Kd values were divided into two or three terms corresponding to the dissociation of the orientational isomers involved (Eqs. 16, 17) ... 

Figure 34 Chemical formula of y-cyclodextrin consisting of eight glucose molecules with adamantane as the guest entrapped within its hydrophobic cavity. Structures of a- and P-cyclodextrins will be similar but made up of six and seven (n = 6, 7) glucoses,...

It has been claimed that complexes of P-cyclodextrin with anionic surfactants, notably higher fatty alcohol ethoxylates, improve scouring efficiency on cotton and wool in laboratory-scale processing [34]. Residual surfactants carried over from preparation can have undesirable effects in subsequent processing. When cyclodextrins complex with surfactants, their surface activity is reduced. Hence cyclodextrins are potentially useful for the removal of residual amounts of surfactants from substrates [35]. The use of a- and P-cyclodextrins has been studied in this context with one cationic, one anionic and four... 

Even less expected, perhaps, are the reactions involving gas-solid addition of HBr, Cl2, and Br2 to a, 3-unsaturated acid guest species in a- and P-cyclodextrin inclusion complexes (242). Although the chemical yields are not high, the optical yields in some cases are extraordinary. Thus, chlorine addition to methacrylic acid in a-cyclodextrin yields (- )-2,3-dichloro-2-methylpropanoic acid in nearly quantitative optical yield. The 3-cyclodextrin methacrylic acid clathrate undergoes chlorine addition to yield preferentially the enantiomeric (+ )-product, with an e.e. of 80%. 

Other compounds smdied as chiral catalysts include a- and p-cyclodextrins that were used in the hydrolysis of oxazolones although the enantioselectivity in the ring-opening reaction was rather low. When a phenyl group is present at C-2 in these systems the enantioselectivity of the reaction is somewhat higher. 

We have recently studied this point by examining the steric effect of metasubstituents of phenyl acetate on the reactivity with a- and P-cyclodextrins (CD) as enzyme model35). Cyclodextrins form an inclusion complex with phenyl acetates (PA) and then catalyze the cleavage of the ester linkage36) as shown in Eq. 37. 

Sybilska, D., Debowski, J., Jurczak, J., and Zukowski, J., The a- and P-cyclodextrin complexation as a tool for the separation of o-, m- and p-nitro-, cis- and trans-cinnamic acids by reversed-phase high-performance liquid chromatography, J. Chromatgr., 286, 163, 1984. 

Head-to-head a- and p-cyclodextrin homodimers, in which the two primary rims are doubly ligated through alkyl chains, have been efficiently synthesized by Sinay and his groups by a CM followed by an RCM reaction sequence [74]. 

Inclusion complexes have also been shown to aid excimer formation provided that the cavity dimensions and polarity are appropriate. Thus Ueno et al. (1980) have shown that the lipophilic cavity of y-cyclodextrin can accommodate two molecules of sodium (l-naphthyl)methyl acetate and that this leads to enhanced excimer emission. Excimer formation by diaryl-methylammonium salts is promoted by y-cyclodextrin but not by a- and P-cyclodextrins (Emert et al., 1981a). The best results were obtained with compounds having fairly large aryl groups e.g. 4-biphenylyl and 1-naphthyl. The hydrophobic character of these groups helped to solubilise the compounds in the interior of the cyclodextrin. 

Lahandeira, J.J. (2001) Combination of 2D-, 3D-connectivity and quantum chemical descriptors in QSPR. Complexation of a- and p-cyclodextrin with benzene derivatives./. Chem. Inf. Comput. Sci., 41, 1561-1568. 

Hadaruga NG, Hadaruga Dl, Paunescu V, Tatu C, Ordodi VL, Bandur G, Lupea AX. 2006. Thermal stability of the hnoleic acid/a- and p-cyclodextrin complexes. Food Chemistry 99(3) 500-508. 

Lezcano M, Al-Soufi W, Novo M, Rodrfguez-Nunez E, Tato TV. 2002. Complexation of several benzimidazole-type fungicides with a- and P-cyclodextrins. Journal of Agricultural and Food Chemistry 50(1) 108-112. 

Antenucci, R. and Palmer, J. K. (1984) Enzymatic degradation of a-and p-cyclodextrins by bacteroides of the human colon. J. Agric. Food Chem. 32 1316-1321. 

It is interesting to note that unmodified a-and p-cyclodextrins were investigated as earners of organic molecules into water before the concept of IPTC was rationalized. For instance, Trifonov and Nikiforov reported... 

Regiospecific bifunctionalization onto the A, B C-2 hydroxyl moieties of a-and p-cyclodextrins has been achieved using benzophenone 3,3-disul-fonylimidazole and molecular sieves (Scheme 10). Diepoxidation and amination products were subsequently formed from the sulfonate 42. ... 

The only example recorded is the gas-solid phase reaction of hydrogen bromide with a- and P-cyclodextrin complexes of ethyl trans-cinnamate to give (R)-(+)-3-bromo-3-phenyl propanoate (46% ee) and (S)-(-)-3-bromo-3-phenyl propanoate (31% ee) (Scheme 5). 

Nxumalo EN, Msomi PF, Mhlanga SD, Mamba BB (2013) Production of N-doped carbon nanombes using a- and p-cyclodextrins the effect of solubility. Mater Lett 100 66-69 Ogasawara T, Ishida Y, Ishikawa T, Yokota R (2004) Characterization of multi-walled carbon nanombe/phenylethynyl terminated polyimide composites. Compos A Appl Sci Manuf 35 (l) 67-74... 

Similar spectral changes have been observed for Fecp2 in its inclusion complexes with cyclodextrins. Of particular interest is a comparison of the motional behaviour of ferrocene included in a-, p- and y-cyclodextrins, which have 6,7, and 8 rings respectively in the cyclic structures. The spectra of the Fecp2 inclusion complexes of a- and p-cyclodextrins are closely similar, but marked differences are observed for the complex with y-cyclodextrin. These differences are broadly consistent with proposals from CD studies of the inclusion complexes in solution which indicate that in both or and p-cyclodextrins the Fecp2 molecular axis is parallel to the cavity axis, but in y-cyclodextrin it is perpendicular to it [ ]. The different motional averaging experienced in the different complexes therefore relates closely to the... 

Enantiomeric RP-TLC separations of amino acids and derivatives were obtained with a- and P-cyclodextrins (171), hydroxypropyl-P-cyclodextrin (172), and bovine serum albumin (173-176)... 

Scheme 9.30 Selective debenzylation on the prirrary rirr of a- and p-cyclodextrins.

Cyclodextrins Persilylated on the Primary Rim When cydodextrins bearing tert-butyldimethylsilyl ethers on their primary rim were subjected to the action of DIBAL-H, the same selective de-Osilylation happened on one or two positions [68]. The regioselectivity is the same as for the de-O-benzylation, and deprotections occurred selectively on the farthest positions, leading to 6A,6D-dihydroxy a- and P-cyclodextrins. Application of this methodology to Y[Pg.268]

Monoazide a- and p-cyclodextrins 77a-b were easily obtained from the corresponding monohydroxy cyclodextrins 63a-b. When submitted to DIBAL-H, the azide is reduced first. Aluminum derivatives complexed on the formed amide create steric hindrance, which directs the following de-O-benzylation toward the farthest position [74] (Scheme 9.36) as in the case of monohydroxy cyclodextrin 63a (Scheme 9.30 and Scheme 9.31). For a-cyclodextrin, the farthest position is 6D, which leads to the 6A-amino,6D-hydroxyl regioisomer 78a in 74% yield. For P-cyclodextrin, a molecular model study revealed that the farthest position is 6E, leading to the formation of the 6A-amino,6E-hydroxyl regioisomer 78b in 89% yield. It has to be noted that this pattern of differentiation is the same as for 6A-hydroxyl,6D-azido cyclodextrins 43a-b (Scheme 9.18). 

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