Preparation from cyclodextrins

Compound 38 can be prepared from cyclodextrin dialdehyde via cyanohydrin synthesis according to Ref. [35a], This reaction affords a single diastereomer as product. 

Even smaller, nanometer size particles, can be prepared from cyclodextrin. These particles are useful as a carrier for pharmaceuticals and cosmetics. First, a solution of cyclodextrin in an organic solvent mixture is prepared, followed by the preparation of a water dispersion of siufactant. When the two components are mixed together a colloidal dispersion of microspheres is produced." Particles sizes range from 90 to 900 run. Typical solvents are methanol, ethanol, isopropanol, and acetone. Solvents are used in the pmifica-tion of xanthan gum to lower ash and to obtain a product with no traces of solvents."" Lower alcohol is used as the solvent. Solvents have also been used to decolor fatty acid esters." Crude oils extracted by pressing or with solvents cannot be used in cosmetic products. Re-... 

Vesicles directly prepared from cyclodextrin-ftorafur supramolecular amphiphiles were reported. Ftorafur can be efficiently encapsulated in the cyclodextrin cavities embedded in the vesicle membrane. The morphologies and diameters of the vesicles were identified in detail by TEM, SEM, AFM and DLS. X-ray diffraction (XRD), FT-IR, UV-vis spectrum, NMR and 2D NMR ROESY were further employed to study the formation mechanism of the vesicles. Various morphologies were detected when different host molecules were employed as the hydrophilic moieties of the vesicles building blocks. ... 

Optical properties of cyanines can be usefiil for both chiral substituents/environments and also third-order nonlinear optical properties in polymer films. Methine-chain substituted die arbo cyanines have been prepared from a chiral dialdehyde (S)-(+)-2-j -butylmalonaldehyde [127473-57-8] (79), where the chiral properties are introduced via the chiral j -butyl group on the central methine carbon of the pentamethine (die arbo cyanine) chromophore. For a nonchiral oxadicarbocyanine, the dimeric aggregate form of the dye shows circular dichroism when trapped in y-cyclodextrin (80). Attempts to prepare polymers with carbocyanine repeat units (linked by flexible chains) gave oligomers with only two or three repeat units (81). However, these materials... 

Prior to 1939, however, it was not known whether the cyclodextrins were products of the synthetic metabolism of Bacillus macerans, and therefore, perhaps, quite different from the components of starch, or whether they were formed by a single enzyme and therefore closely related to the starch structure. Then, Tilden and Hudson announced the discovery of a cell-free enzyme preparation from cultures of Bacillus macerans which had the ability to convert starch into the Schardinger dextrins without the production of maltose, glucose, or any other reducing sugars. They thus concluded that the Schardinger dextrins were either the true components of starch or closely related to such true components. 

A more attractive chemo-enrymatic approach for the production of he-mithiocyclodextrins has been developed. More than ten years ago, cyclodextrin glucosyltransferase (CGTase) was shown to use a-maltosyl fluoride for the synthesis of a-, p-, and y-cyclodextrins [47] and has been used for the chemoenzymatic synthesis of regioselectively substituted cyclodextrins [48]. For this purpose, 4-thio-a-maltosyl fluoride (58) was easily prepared from (45). Incubation of (58) in the presence of pure CGTases afforded hemithiocyclodex-trins (57a), (57b) and (57c) isolated in 14,16 and 15% yields respectively [49]. 

Specific (or selective) polyfunctionalization of cyclodextrin is, in principle, possible based upon stepwise regiospecific flamingo-type capping as is shown schematically in Scheme 5. Simple tetrasubstitution (or hexasubstitu-tion) is more easily attained through double (or triple) capping. A typical example is the successful preparation of tetrasubstituted /J-cyclodextrin (8), prepared from 7 by the authors as a channel-forming compound for metal ion transport (77). 

When supramolecular polymers are treated with bulky stopper groups, they may form poly[2]rotaxane daisy chains [32,60-68]. Cyclic tri[2]rotaxanes (daisy chain necklace) containing cyclodextrins have been prepared from the mixture of 6-(4-aminocinnamoyl)-Q -CD and 2,4,6-trinitrobenzene sulfonic acid sodium salt [50,59] in an agueous solution (Fig. 21). If the molecule changes its conformation (or co-conformation), the ring may expand or shrink by external conditions (temperature, solvents, photochemically, elec-trochemically). These compounds are important because the cycle can be used as a chemical valve as seen in ion channels in biological membranes. 

Enantiomeric Stationary Phases. Chiral nonracemic chromatographic stationary phases prepared from p-cyclodextrin, derivatized with (R)- and (S)-NEI, and covalently bonded to a silica support are useful for the direct separation of enantiomers of a wide variety of compounds in both normal-phase and reversed-phase HPLC. ... 

Surface tension 62 mN/m (62 dynes/cm) at 25°C Method of manufacture dimethyl-P-cyclodextrin is prepared from P-cyclodextrin by the selective methylation of all C2 secondary hydroxyl groups and all C6 primary hydroxyl groups (C3 secondary hydroxyl groups remain unsubstituted). 

Fig. 20 a The polyrotaxane formed by a-CD and PEO with 2,4-dinitro-phenyl end caps, b The figure-of-eight cross-link covalently cross-linked cyclodextrins. c Schematic diagram of the polyrotaxane gel prepared from the sparse polyrotaxane by covalently cross-linking cyclodextrins using cyanuric chloride as crosslinking agent [89]... 

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