Cyclodextrins analogues

A similar type of macrocycle stacking leading to the nanotube formation was recently reported by the Stoddart group [44b]. The latter authors synthesized cyclodextrins analogues 96 built of alternating D- and L- sugar units. The... 

Carboranes are particular cyclic spacers that have been introduced for boron neutron capture therapy to be taken up by tumor cells [295,296,297]. Aromatic spacers have been integrated in cyclodextrin analogues to modify the guest binding properties [298,299,300]. Also amide-linked polymeric open chain sugars with aromatic spacers were prepared [257,264,301]. Sugars with cyclic spacers are also found in Nature [302], well known examples are antibiotics such as calicheamicin [303,304] or vancomicin [305]. 

General Matters. - Oligomerization of carbamate 52 in the presence of sodium hydride gave only cyclic products which are cyclodextrin analogues. ... 

Cyclodextrin analogues based on 2-acetamido-2-deo3 -D-glucose have been prepared and their complexing abilities have been studied, and a S-(l- 3) linked... 

Calixarenes (from the Latin ca/ x) may be understood as artificial receptor analogues of the natural cyclodextrins (96,97). In its prototypical form they feature a macrocycHc metacyclophane framework bearing protonizable hydroxy groups made from condensation of -substituted phenols with formaldehyde (Fig. 15b). Dependent on the ring size, benzene derivatives are the substrates most commonly included into the calix cavity (98), but other interesting substrates such as C q have also been accommodated (Fig. 8c) (45). 

Tabushi et al. (1979) have shown that p-cyclodextrin in aqueous alkaline solution allows highly selective one-step synthesis of vitamin Kj (or K2) analogues here the key step is alkylation of 2-methyl hydronaphthoquinone with allyl, crotyl, methallyl, or prenyl bromide. 

W Saenger, J Jacob, K Gessler, T Steiner, D Hoffmenn, H Sanabe, K Koizumi, SM Smith, T Takaha. Structure of the common cyclodextrins and their larged analogues—beyond the doughnut. Chem Rev 98 1787-1802, 1998. 

The branched cyclodextrins (CDs, 17 a, 17 b) and their analogues with D-galactosyl and a-D-mannosyl residues (17c, 17d) have also been prepared under mild conditions by the approach depicted in Scheme 6 [24,25]. Selective in situ S-deacetylation and activation was obtained by treatment of peracetylated 1-thioglycoses (10a, 8e, 8g) by cysteamine in the presence of diAioerythritol in HMPA [26]. This method was very efficient for ffie synthesis of branched CDs (17a) (80%), (17b) (60%), and (17c) (85%) when the acceptor molecule (15b) bearing primary iodide was used. However, peracetylated 1-thioa-D-mannose (8f) failed as a donor under these conditions, but tetra-O-acetyl-l-thio-a-mannose (8 b) afforded the expected CD (17d) in high yield (83%). 

We saw in Section 12.3.1 the use of the cyclodextrins as mimics for transacylases, a well-understood class of enzymes that perform the task of transferring an acyl group from one substrate to another (e.g. from an ester to water). Transacylase chemistry has also been addressed by Cram,5 who used chiral corands, such as 12.11, related to 3.106 bearing thiolate nucleophiles situated above and below the plane of the macrocycle. An acyclic analogue 12.12 was also prepared for comparison. The salient features of 12.11 are shown diagrammatically in Figure 12.4. 

Subsequently, Purdie and coworkers studied the CD induced in phencyclidine (and its pyrrolidine and morpholine analogues), 6-phenethylamine, phenobarbital, meperidine HC1, diazepam, and dilantin by 6-cyclodextrin [59], In this work, a method was described for the assay of meperidine in commercially available Demerol tablets. The complexation between 6-cyclodextrin and eight 5,5-disubstituted derivatives of barbituric acid was characterized on the basis of the... 

An obvious limitation of the application of a-cyclodextrin for a wider variety of compounds is its narrow cavity diameter. Larger molecules do not fit the cavity. Due to its low aqueous solubility, 6-cyclodextrin is not adequate for similar purposes. However its highly soluble polymer (a low molecular crosslinked product) proved to be very useful for the TCL separation of larger molecules. The wider cavity diameter, and probably some cooperativeness between the vicinally fixed cyclodextrin-moieties, render such soluble polymers adequate in the mobile phase for a great variety of compounds. The reversed phase TLC-behaviour of antibiotics polymixine (48), 17 substituted s-triazine derivatives (49), 25 triphenyl-methane derivatives and analogues (50) 33 nitrostyrene derivatives (51) and 21 barbiturates (52) were studied on silica or cellulose plates. 

FIGURE 4 Molecular structure of (3-cyclodextrin covalently functionalized with the thiamine analogue (top). Schematic representation of its covalent anionic complexes formed with included benzaldehyde (bottom) (27-23). 

A clean conversion of 9.118 to 9.119 was obtained, with moderate stereoselection (15-20% enantiomeric excess e.e.) for the RJi (9.123,9.124) or the SJS enantiomer (9.125). Resynthesis of the unbound analogues of 9.120-9.125 was planned to test their effectiveness in the same reaction and to evaluate the influence of the soM support on the reaction outcome. The deconvolution-prone, pooled format for catalyst discovery has been used by Venton (175) for the synthesis of a >28,000-member p-cyclodextrin library (13 pools) as a source of Zn-based catalytic systems with phosphatase-like activity. 

Benzoquinones such as (227) have been prepared by regiospecific oxidative prenylation of the corresponding methylhydroquinone with Me2C=CHCH2Br in the presence of /3-cyclodextrin. Detailed descriptions are available of methods for the preparation of ubiquinone analogues,and the synthesis of some new ubiquinone analogues, e.g. (228), has been reported. ... 

Further details have been presented of the one-step preparation of vitamin K analogues through the use of -cyclodextrin extrusion catalysts. A paper has appeared dealing with the photoreduction of vitamin K [phylloquinone (229)]. ... 

W. Saenger, J. Jacob, K. Gessler, T. Steiner, D. Hoffman, H. Sanbe, K. Koizumi, S. M. Smith, and T. Takaha, Structure of the common cyclodextrins and their larger analogues—Beyond the doughnut, Chem. Rev. 98 (1998), 1787. 

J. I. Seeman and H. V. Secor, Enantiomeric resolution and chiral recognition of racemic nicotine and nicotine analogues by P-cyclodextrins complexation. Structure-enantiomeric resolution relationship in host guest interaction, Anal. Chem. 60 (1988), 2120. 

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