Three-dimensional cyclodextrin: A new class of hosts by trehalose capping of �-cyclodextrin (original) (raw)
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Journal of Inclusion Phenomena and …, 1998
A new capped derivative of cyclomaltoheptaose (CDTHCM) was synthesized by the reaction of 6,6 0 -dideoxy-6,6 0 -di(S-cysteamine)-, 0 -trehalose with 6A,6D-dideoxy-6A,6D-diiodocyclomaltoheptaose. The CDTHCM obtained was characterized, together with its behaviour towards protonation. The CDTHCM/ACS (anthraquinone-2-sulfonic acid sodium salt) system was investigated by 1 H NMR spectroscopy and by i.c.d. (induced circular dichroism) at two different pHs. The deep inclusion of ACS within the CDTHCM cavity, with an association constant about six times larger compared to the -CD/ACS system was found at pH 6.
Cyclodextrins and their applications in biotechnology
Cyclodextrins and their derivatives enhance the solubility of cornplexed substrates in aqueous media, but do not damage the microbial cells or the enzymes. Therefore the enzymatic conversion of lipophilic substrates can be intensified (accelerated, or performed at higher substrate concentrations). Examples are the hydrolysis of triglycerides and lanatoside glycosides or the conversion of hydrocortisone to prednisolon and of cholesterol to androstenedione. In the presence of an appropriate cyclodextrin-derivative (e.g. 2,6-dimethyl-fl-cyclodextrin). The lipid-like inhibitor substances are complexed, therefore the propagation of Bordatella pertussis and the production of pertussis toxin increases up to lO0-fold. Cyclodextrins or their fatty acid complexes can substitute mammalian serum in tissue cultures. A highly soluble 7-cyclodextrin-nystatin complex can protect tissue cultures from fungal infections. The tolerance level to toxic compounds during biological detoxication of organic chemical industries sewage can be elevated by admixing small amounts of 13cyclodextrin to the system, because the complexed toxic substances do not kill the detoxicating microbes.
Molecular recognition by cyclodextrin dimers
Tetrahedron, 1995
Cyclodextrin dimers strongly bind substrates with the correct geometry in water solution. Studies with antihydrophobic agents help clarify the factors involved.
Fluid Phase Equilibria, 2016
Molecular inclusion of two natural amino acids, viz., L-asparagine and L-aspartic acid as guest into the host cavity of a and b-cylodextrins in aqueous solution have been studied which have various applications in the field of present bio-medical science for controlled delivery of necessary amount of the guest at the targeted site for a period of time efficiently and precisely. Surface tension and conductivity studies establish the formation of inclusion complexes with 1:1 stoichiometry. The inclusion complexes have been characterized by various thermodynamic factors basing upon density and viscosity studies. Contributions of various groups of the guest amino acid molecules toward the limiting apparent molar volume and viscosity B-coefficient have been calculated, as well as the solvation and hydration numbers are determined to support the inclusion phenomenon. Formations of the inclusion complexes have been explained with the help of hydrophobic effect, H-bonding, electrostatic forces and structural effects.
Synthesis and properties of a new family of cyclodextrin analogues
Journal of Inclusion Phenomena and Molecular Recognition in Chemistry, 1996
The chemical synthesis of a series of cyclic oligosaccharides built up from (1 ---~4)-linked alternating D-and L-pyranosidic units is described for the first time. Key intermediates employed were disaccharides representing minimal repeating units. These disaccharides ('monomers') have been prepared in specifically modified forms so that they bear both 'glycosyl donor' (cyanoethylidene group) and 'glycosyl acceptor' (trityloxy group) functions. Polycondensation-cyclisation of these disaccharide monomers, catalysed by TrC10 4 under normal conditions of dilution, has led to series of homologous cyclic oligosaccharides with an even number of sugar residues (6, 8, 10, 12, etc.) in each case. Cyclic hexa-and octa-saccharides, based on L-rhamnose and D-mannose as the alternating monosaccharides units, have been deprotected to produce analogues of ~-and y-cyclodextrins (CDs) and the X-ray crystal structure of the cyclic octasaccharide has been determined.
Tetrahedron Letters, 1990
A new member of capped$cyclodextrin, phenanthridinone-2,9-disulfonate cap a, has been prepared. The amide NH proton of the capping moiety was found to dissociate into amide-N-anion with pKa=l 1.2 based on the results of UV-VIS titration, providing for the first time an anionic charged cap above pH 12 to bind cationic guests effectively. Some. of chemically modified cyclodextrins (CD) form inclusion complexes with various hydrophobic guest molecules much more strongly than the parent CD.le9) However, inclusion of a charged guest into a CD cavity having the counter ion, especially anion, has not been investigated we117-9) in spite of the fact that recognition of ionic charged substrates is very common and important in enzymes, such as trypsin, acetylcholine esterase, or ATPase,lO* 1 l) and also in the recognition of neurotransmitter substances, acetylcholine, etc., by receptors.12) Capped cyclodextrins are most appropriate for studies along the lines, since capped cyclodextrins can provide expanded or stronger hydrophobic domain than the parent CD.3-5v 13-16) Now the authors wish to report the first successful example of an anion cap made from phenanthridinone-2,9-disulfonate capped P-CD a) in an alkaline solution(pH>12, Scheme 2). 5,5'-Disulfamoyldiphenamic acid a), which was prepared from o-toluidine-S-sulfonic acid in 8 steps (Scheme 1), was converted to phenantluidinone-2,9-disulfonamide (&) by Hofmann rearrangement (84%). After hydrolysis of 4 with concentrated H2SO4 followed by reaction with PC15, the corresponding disulfonyl chloride (.& capping reagent) was obtained, and the structure was ascertained by IR, NMR, MS and elemental analysis.17) Dry P-CD (10.4g, 9.2 mmol) was treated with 3.62 g (9.2 mmol) of 2 in dry pyridine at room temperature, and new capped CD 0 thus formed was purified successfully by reprecipitation from CHsCN-Hz0 (5:1, V/V) followed by silica gel column chromatography (CH$N-Hz0 = 5 : 1, V/V), affording pure 1 (TLC, SiO2, PrOH-AcOEt-HzO-NH3 aq = 5 : 3 : 3 : 1, V/V, Rf=O.5) in 3% yield. Moreover the cap was converted to CD(N3)2, and CD(S-Ph-p-tBu)zl@ by the treatment with NaN3 and NaSPh-p-tBu, respectively, and this fact also supports the structure of 1 strongly. The pKa value of 1 was determined as 11.2-11.25 (2O"C, Table) by UV titration of the t Deceased March 22,1987.
Cyclodextrins: An Overview of Fundamentals, Types, and Applications
Cyclodextrins - New Perspectives [Working Title]
Cyclodextrins are one of the most interesting pharmaceutical excipients with substantial theoretical and applied impacts in pharmaceutical industry. Even though the chemical foundation of these macrocyclic molecules was laid more than 100 years ago by Villiers and Schardinger, it was not until recently that cyclodextrins have been regarded as a subject of numerous potential pharmaceutical applications including inclusion complexation. This particular chapter discusses the fundamental concepts of cyclodextrin chemistry, structure, properties, and host-guest interaction with a special focus on molecular dynamics. Further in this regard, applications of cyclodextrins and numerous drug delivery approaches including novel lipid-based nanosystems are also highlighted.
The Journal of Organic Chemistry, 2008
Concise and efficient strategies toward the synthesis of D 2h -and D 3h -symmetric cyclodextrin analogues alternating R,R′-trehalose disaccharide subunits and pseudoamide segments (cyclotrehalans, CTs) are reported. The conformational properties of these cyclooligosaccharides are governed by the rigidity of the R,R′-trehalose disaccharide repeating unit and the partial double-bond character of the N-(CdX) linkages. In contrast to the typical concave-shaped cavity of cyclodextrins (CDs), CTs feature a convexshaped hydrophobic cavity in which the -face of the monosaccharide subunits is oriented toward the inner side, as supported by NMR and modeling (molecular mechanics and dynamics) studies. In the case of cyclodimeric CTs (CT2s), the existence of intramolecular hydrogen bonds results in collapsed cavities, too small to allow the formation of inclusion complexes with organic molecules. Cyclotrimeric CTs (CT3s) display cavity sizes that are intermediate between those of RCD and CD, ideally suited for the complexation of complementary guests with ternary symmetry such as adamantane 1-carboxylate (AC). The higher flexibility of the pseudoamide bridges as compared with classical glycosidic linkages endow these glyconanocavities with some conformational adaptability properties, making them better suited than CDs for complexation of angular guests, as seen from comparative inclusion capability experiments against the fluorescent probes 6-p-toluidinonaphthalene-2-sulfonate (TNS; linear) and 8-anilinonaphthalene-1-sulfonate (ANS; angular).
European Journal of Organic Chemistry, 2008
Amphiphilic cyclodextrins represent a new generation of these oligosaccharides, which are well known previously as host molecules in water. Cyclodextrins are now being modified with polar groups, lipophilic groups and conjugates which elaborate further their amphiphilicity and molecular recognition. The resulting amphiphiles are host molecules capable of forming all the assemblies expected of amphiphiles, but showing additional supramolecular properties. Examples of these macrocyclic amphiphiles are by now known that form thermotropic liquid crystals, while lyotropic assemblies include micelles, unimolecular micelles, nanoparticles, monolayers and bilayer vesicles. The assembly proper-