Cyclodextrin trimer

D. K. Leung, J. H. Atkins, R. Breslow, Synthesis and binding properties of cyclodextrin trimers. Tetrahedron Lett., 2001, 42, 6255-6258. 

The concept of cyclodextrin guest inclusion has been extended to the synthesis of a library of multicavity dimers and trimers of cyclodextrin that can bind specific guest molecules to mimic enzymes (Figure 6) Such supramolecular structures were tested with mono-, di-, and tri-substituted Gd + complexes bearing hydrophobic cyclohexyl moieties for interaction with the cyclodextrin cavities. The relaxivity enhancement increased with the number of cyclohexyl groups on the Gd + chelate. Further, the cyclodextrin trimer host-guest supramolecule with the tri-substituted Gd " " complex exhibited the greatest relaxivity... 

As the reaction proceeds under mild reaction conditions, this original promoter, SnCl2-AgCl04, can also be employed in the synthesis of complex glycosides such as rhynchosporosides [95], cyclodextrin [41,96], trimeric Lex [55,97], globotriaosylcer-amide (Gb3) [98] or Elfamycin [99]. As a representative example, the synthetic route... 

The extent of stereoselectivity in the chiral synthesis can be checked by determining the enantiomeric excess of the optically active olefins in the products. The optical purity was determined by gas chromatographic resolution of enantiomers by means of an optically active column. Thermostable substituted cyclodextrins are well suited as asymmetric phases (206). The trimer, 2,4-dimethyl-l-heptene, was resolved into its enantiomers by capillary gas chromatography with an octakis(6-0-methyl-2,3-r/-0-pentyl-)-7-cyclodextrine phase. 

Fig. 24. Asymmetric oligomerization of propylene at various temperatures gas-chromatographic separation of 2,4-dimethyl-2-heptene (trimer) in a capillary column coated with octakis(6-0-methyl-2,3-di-0-pentyl)cyclodextrin) (204).

Figure J4.12 Supramolecular polymers obtained by Harada and coworkers, (a) Self-inclusion complex (cyclic monomer) formed as a result of the flexibility of the linker between the hydrophobic guest and yS-cyclodextrin (CD) [47] (b) Cyclic dimer and trimer formed when more rigid linkers were applied [48] (c) Supramolecular...

These channels, however, are unique in that they have in one asymmetric unit three cyclodextrin molecules. These are arranged in head-to-head and head-to-tail mode in alternating sequence so that the whole structure is built up of trimers of Y-cyclodextrin. In detail, however, the crystal packing is even more complicated because there are two independent stacks per asymmetric unit which differ only in very slight atomic displacements and disorder. In total, this crystal structure contains therefore six quarter y-cyclodextrin molecules per asymmetric unit (Figure 3). 

Figure 6 Examples of supramolecular multicavity cyclodextrin dimer and trimer scaffolds.

S. Aime, E. Gianolio, F. Arena, A. Barge, K. Martina, G. Heropoulos, and G. Cravotto, New cyclodextrin dimers and trimers capable of forming supramolecular adducts with shape-specific ligands, Org. Biomol Chem., 7 (2), 370-379,2009. 

Sequence-selective binding of peptides and small proteins is of considerable interest. We saw that some cyclodextrin dimers could selectively doubly bind peptides in water with appropriately placed hydrophobic side chains. This built on our earlier collaborative work on the selective binding of peptides by simple cydodextrin. We then showed that we could break up a protein dimer and a protein tetramer with appropriate cydodextrin dimers in water, since such protein aggregation ordinarily involved hydrophobic side chains that our dimers could bind to. In perhaps the most striking example, our cydodextrin dimers and trimers were able to inhibit the protein aggregation involved in the formation of Alzheimer s plaques. ... 

Moore, S., Askew, J.A., Gibson, G.L., Aborgrein, A., El-Agnaf, O., Allsop, D., Leung, D.K. and Breslow, R., Novel cyclodextrin dimers and trimers as inhibitors of amyloid peptide aggregation, Neurohiol Aging, 2002, 23, S105. 

Partial enzymic hydrolyses of substituted P-cyclodextrins using bacterial a-amylase have been described. From the mono-6-tosylate maltotriose carrying the ester group at the nonreducing terminal position was obtained, and from the mono-2,3-anhydro-D-a//o-compound the trimer bearing the anhydride ring in the central position was the product. This work is related to degradative studies with y-cyclodextrin and a different amylase (Vol. 24, p. 60, ref. 20). ... 

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