Cyclodextrin chemical structure

Fig. 12 Cyclodextrin chemical structure and geometrical arrangement of the glucose units.

Figure 7 /3-cyclodextrin, chemical structure (left), and repre-... 

Fig. 1. Chemical structure of a-cyclodextrin. Six glucopyranose units are numbered G1 to G6. The numbers on the G1 glucopyranose refer to those of the carbon atoms...

In an attempt to change and broaden the capabilities of the vancomycin CSP, the glycopeptide was derivatized with (R)- and (S )-(l-naphthylethyl) isocyanate (NEIC) and then bonded to a silica-gel support [48]. A variety of chiral compounds was tested on the two composite stationary phases and the results were compared with the ones obtained using the underivatized vancomycin CSP. The advantages of the NEIC derivatization were not as obvious or substantial as they were in the case of cyclodextrin phases [49]. Moreover, the exact chemical structures of the synthesized NEIC derivatives of vancomycin were not reported. 

Additives are often used to increase selectivity. They are paramount in chiral separations, but they are also frequently used in non-chiral separations, e.g., cyclodextrins (CDs). In our lab, BGEs with and without a cyclodextrin are part of our generic protocol. Figure 8 demonstrates that although one can more or less predict interaction with the additive from the chemical structures, it is still difficult to predict separation.Batch-to-batch variability and variability between suppliers can be a problem of (chiral) additives and a check of different batches has to be part of the robustness test (e.g., reference 56). If the additive is charged and has one or more pK s around the pH of the BGE, extra care should be taken to control the pH. Alternatively, better robustness might be obtained with another uncharged additive, even if this results in lower resolution. 

Fig. 1.—Chemical Structure and Numbering of the Atoms of Beta Cyclodextrin.

Programmed temperature (120 -200°C) chiral separation on a 0.25-mm x 25-m open tubular column with a 0.25-nm-thick stationary phase containing 10 wt% fully methylated p-cyclodextrin chemically bonded to dimethyl polysiloxane. [From W. Vetter and W. Jun, Elucidation of a Polychlorinated Bipyrrole Structure Using Enantioselective GC," Anal. Chem. 3002, 74,4287.]... 

FIGURE 1 The chemical structures of cyclodextrins and their derivatives. 

FIGURE 3 The chemical structures of some cyclodextrin-based CSPs. 

FIGURE 15 The chemical structures of some CSP-based a- and /1-cyclodextrin derivatives. (From Ref. 49.)... 

FIGURE 16 The chemical structures of some drugs resolved on different CSPs based on a- and /1-cyclodextrin derivatives (Fig. 15) Troger s base (I), tra .s-2,.1-diphenyloxirane (II), l-(9-anthryl)-2,2,2-trifluoroethanol (III), 1,2,2,2-tetraphenylethanol (IV), 2,2 -dihy-droxy-6,6-dimethylbiphenyl (V), 2-phenylcyclohexanone (VI), flavanone (VII), benzoin (VIII), and tnms -cyclopropanedicarboxylic acid anilide (IX). (From Ref. 49.)... 

Summary The analysis of supramolecular structures containing polymers, and the discussion about the effect of polymeric materials with different chemical structures that form inclusion complexes is extensively studied. The effect of the inclusion complexes at the air-water interface is discussed in terms on the nature of the interaction. The entropic or enthalpic nature of the interaction is analyzed. The description of these inclusion complexes with different cyclodextrines with several polymers is an interesting way to understand some non-covalent interaction in these systems. The discussion about the generation and effect of supramolecular structures on molecular assembly and auto-organization processes is also presented in a single form. The use of block copolymers and dendronized polymers at interfaces is a new aspect to be taken into account from both basic and technological interest. The effect of the chemical structure on the self-assembled systems is discussed. 

The cyclodextrins (cycloamyloses) are torus-shaped molecules that can form crystalline inclusion compounds, recently attracting much attention as enzyme-site models. Their history has been seen in three phases. From 1891 to 1935 they were known as natural products, but with no recognition of their exact chemical structure. This recognition emerged in the second period, to about 1970, when most of their characteristics were also elucidated. The period from 1970 to the present has seen considerable research into their industrial use and production.239 Their inclusion compounds or complexes have found employment in such diverse fields as explosives, insecticides, pharmaceutical products, rust-prevention agents, and even baking powder. 

Figure 1. Chemical structure and molecular dimensions of a-, 6-and Y-cyclodextrins.

Figure 3. Computer imaging of the inclusion complexes of d- A) and 1-(B) propranolol with B-cyclodextrin. The chemical structures are illustrated with van der Waals radii shown for only the secondary amine of propranolol and the 2- and 3- hydroxyl groups of the B-cyclodextrin.

The monoallyl derivative of P-cyclodextrin in its peracetylated form, namely mono-(6-N-allylamino)-6-deoxy)-peracetylated-P-cyclodextrin, was synthesized in 3 steps from native P-cyclodextrin. The synthesis of this derivative is reported in ref [20], The NMR and IR analyses were consistent with the expected chemical structure. 

Fig. 6.26 Chemical structure and conical shape of cyclodextrins (from ref [1161)...

Fig. 7.14 (A) The chemical structure of a-, (1, and y-cyclodextrin. (B) Schematic representation of the cone-like conformation of cyclodextrins, with the upper rim presenting the secondary 2,3-hydroxy and the lower rim the primary 6-hydroxy groups.

Figure 11 Chemical structures and molecular dimensions of the most common cyclodextrins, abbreviated oc, P, and y-CDX.

Methods development for chiral analyses has been one of the most challenging separation problems for the analytical chemist in the pharmaceutical industry. Racemic drug substances have a variety of chemical structures and several chiral selectors are available for the analyst to choose in order to obtain the enan-tioselectivity needed for chiral resolution. To alleviate this problem, a fast capillary electrophoresis procedure for the enantiomeric separation of acidic and basic compounds using native and modified cyclodextrins has been described (200). The technique is called cyclodextrin array chiral analysis. A generalized optimi-... 

As the native cyclodextrins (CDs) exhibit some limitations in application, they need to be modified to improve the properties. All the modification methods could be divided into two kinds, chemical modification and enzymatic modification. Based on the stable cyclic structure, CDs could be modified via etherification, esterification, oxidation and crosslinking reactions. The chemical modification has a special purpose of introducing novel functional group. CDs modified by chemical means were named as cyclodextrin chemical derivatives (CCDs). 

Figure 21 (a) Chemical structures and schematic representations of photoswitchable stilbene bi-p-cyclodextrin derivative 37 and bi-Ad guest 38. 

Its solubilizing power was tested by solubility studies involving a lot of poorly water soluble substrates of different chemical structure The enhancement of water solubility of these substances in 10 aqueous dimethyl- -cyclodextrin solution was found to be 3-800 fold See table IV ... 

Cyclodextrins are another category of substances that are used for complex formation. Cyclodextrins are ring-shaped oligosaccharides consisting of six, seven or eight glucose units referred to as alpha-, beta-, and gammacyclodextrin, respectively (see Fig. 18.2 for the chemical structure of betacyclodextrin) [15]. 

Figure 4A.42 Cyclodextrin, (a) The helical structure of the starch yields mainly cyclodextrins with six to eight glucose units. fhttp //www.chemiedidaktik.uni-wuppertal.de/disido cy/cyen/info/01 manufacture cy.htmj (b) Chemical structure of the three main types of cyclodextrins, Stanisfaw Skowron, shape of single monomers. From work of Bartosz Marcin Kojak, for Wikimedia commons, GNU Free Documentation License, Version 1.2) c) Host-Guest complex of 3-cyclodextrin and phenolphthalein hydrogen bonds between the p-cyclodextrin molecule and the phenolphthalein dianion. fhttp //www.chemiedidaktik.uni-wuppertal.de/disido cy/cyde/exp/06 cy phenol.htm (aj 7ndfc,)ProfessorDr. Simone Krees, Westfdlische Wiihelms-University Munster, with kind permission)...

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