Cyclodextrins, adamantane derivatives

Amphiphilic macrocyclic host molecules have been investigated for many years. Among others, it is known that amphiphilic crown ethers, " cryptands, calixarenes, cyclodextrins, and curcubitnrils can form bilayer vesicles in aqueous solution. However, the host-guest chemistry of such host vesicles remained largely unexplored for many years. Darcy and Ravoo prepared bilayer vesicles composed entirely of amphiphilic cyclodextrin host molecules. These vesicles have a membrane that displays a high density of embedded host molecules that bind hydrophobic guest molecules such as f-butylbenzyl and adamantane derivatives. The characteristic size-selective inclusion behavior of the cyclodextrins is maintained, even when the host molecules are embedded in a hydrophobic... 

The condensation reactions described above are unique in yet another sense. The conversion of an amine, a basic residue, to a neutral imide occurs with the simultaneous creation of a carboxylic acid nearby. In one synthetic event, an amine acts as the template and is converted into a structure that is the complement of an amine in size, shape and functionality. In this manner the triacid 15 shows high selectivity toward the parent triamine in binding experiments. Complementarity in binding is self-evident. Cyclodextrins for example, provide a hydrophobic inner surface complementary to structures such as benzenes, adamantanes and ferrocenes having appropriate shapes and sizes 12) (cf. 1). Complementary functionality has been harder to arrange in macrocycles the lone pairs of the oxygens of crown ethers and the 7t-surfaces of the cyclo-phanes are relatively inert13). Catalytically useful functionality such as carboxylic acids and their derivatives are available for the first time within these new molecular clefts. 

Rhodopsin is a seven ot-helix trans-membrane protein and visual pigment of the vertebrate rod photoreceptor cells that mediate dim light vision. In this photoreceptor, retinal is the chromophore bound by opsin protein, covalently linked to Lys296 by a Schiff base linkage. Kpega et al.64 have studied NMR spectra of Schiff bases being derivatives of all-frans retinal and amino-p-cyclodextrins as a model of rhodopsin, where p-cyclodextrin plays a role of a binding pocket. On the basis of analysis of the chemical shift differences for the model compound in the presence and in the absence of adamantane carboxylate, it has been shown that the derivative of 3-amino-p-cyclodextrin forms dimer in water and retinoid is inserted into p-cyclodextrin cavity [31]. 

The one-electron oxidation of iV-benzylphenothiazine by nitric acid occurs in the presence of /i-cyclodextrin, which stabilizes the radical cation by incorporation into its cavity. The reaction is inhibited by adamantane, which preferentially occupies the cavity. Novel Pummerer-type rearrangements of / -sulfinylphenyl derivatives, yielding /7-quinones and protected dihydroquinones, and highly enantioselective Pummerer-type rearrangements of chiral, non-racemic sulfoxides have been reviewed. A comprehensive study has demonstrated that the redox potential for 7- and 8-substituted flavins is linearly correlated with Hammett a values. DFT calculations in [3.3.n]pro-pellanes highlight low ionization potentials that favour SET oxidative cleavage of the strained central C-C bond rather than direct C-H or C-C bond attack. Oxidations and reductions in water have been reviewed. ... 

E-S Kwak, FA Gomez. Determination of the binding of f -cyclodextrin derivatives to adamantane carboxylic acids using capillary electrophoresis. Chromatographia 43 659-662, 1996. 

Nakajima et al. (1) prepared liquid crystalline polyrotaxane derivatives containing the mesogenic group 4-cyano-4 -hydroxybiphenyl attached to the a-cyclodextrin component of linear polyethylene glycol containing an a-cyclodextrin inclusion complex with an adamantane termini. 

Figure 7 Molecular structures of amphiphilic S-cyclodextrin derivative 1, which self-assembles into CDVs, and adamantane-modilied octapeptide 2, which binds to the CDVs by host-guest interaction. Peptide 2 adapts a random coil conformation at pH 7.4 while bound to the vesicles. Upon acidification to pH 5.0, peptide 2 forms a S-sheet which induces a morphological change from a vesicle to a nanotube, with concomitant release of contents.

The formation of a supramolecular inclusion complex by host-guest associations between biomolecules or nanoparticles bearing p-cyclodextrin groups and polymerized adamantane groups was used to develop new biointerfaces. The electropo-lymerizatiOTi of an adamantane-pyrrole derivative... 

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