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Native α-cyclodextrin- (α-CD) and permethylated α-CD (PMeCD)-based rotaxanes with various short alkylene chains as axles can be synthesized through a urea end-capping method. Native α-CD tends to form [3]- or [5]pseudorotaxanes and not [2]- or [4]pseudorotaxanes, which indicates that the coupled CDs act as a single fragment. End-capping reactions of the pseudorotaxanes with C18 and C24 axle lengths do not occur because the axle termini are covered by the densely stacked CDs. The number of PMeCDs on the pseudorotaxane is flexible and mainly depends on the axle length. Peracetylated α-CD (PAcCD)-based rotaxanes are synthesized through O-acetylation of the α-CD-based rotaxanes without any decomposition of the rotaxanated structures. The structures of PMeCD-based [3]- and [4]rotaxanes, and the molecular dynamics calculations on [3]pseudorotaxanes, indicate that the tail face of PMeCDs is regularly directed toward the axle termini. On the basis of the results obtained, it can be concluded that the directions and numbers of CDs in rotaxanes containing short alkylene chains depend on 1)the interactions between CDs, 2)the length of the alkylene axle, and 3)the interactions between the axle end and tail face of the CD. Come on in! Native and permethylated α-cyclodextrin (CD)-based rotaxanes with various short alkylene axles are synthesized with a urea end-capping method. The directions and number of the CD wheels depend on the interactions between CDs, the axle length, and the interactions between axle ends and the tail face of the CDs (see figure).

New permethylated mono-6-deoxy-6-pyridin-1-ium and mono-6-deoxy-6-(1-vinyl- 1H-imidazol-3-ium)-α- and -β-cyclodextrin trifluoromethanesulfonate ionic liquids were synthesized from the corresponding permethylated mono-6-hydroxycyclodextrins in a one-pot reaction and solvent-free procedure. Regioselective transformation of native α- and β-cyclodextrins with the use of a bulky tert-butyldiphenylsilyl protecting group afforded the desired 6-monosubstituted permethylated cyclodextrin derivatives in moderate yields. The new ionic liquids were tested as stationary phases in capillary GC columns towards chiral discrimination in enantio-GC analysis of racemic mixtures. The permethylated 6-deoxy-6-pyridin-1-ium-α-cyclodextrin trifluoromethanesulfonate displayed good enantiomeric separations for some racemic esters and lactones, as well as epoxides. In particular, for both the racemic whiskey lactone and the high boiling point menthyl laurate, not successfully separated in a commercial cyclodextrin phase, the enantiomeric separations were achieved isothermally at 140 °C. In phase: Permethylated mono-6-hydroxy-α- and -β-cyclodextrins react with pyridine or 1-vinylimidazole in the presence of triflic anhydride in a solvent-free procedure to yield new roomerature ionic liquids (ILs). These ILs have been used as stationary phases in gas chromatography; enantiomeric separations are achieved (see figure for whiskey lactone) with permethylated mono-6-deoxy-6-(pyridin-1-ium)-α-cyclodextrin trifluoromethanesulfonate. Copyright

Permethylated i-CD-based rotaxanes with short alkylene chains as an axle were synthesized through urea end-capping in one pot: Products were [2]rotaxane and [3]rotaxane. The headto-head structure of [3]rotaxane obtained as a single isomer was confirmed by the characteristic 1HNMR peak shifts and X-ray single-crystal structure analysis.

Novel cyclodextrin derivatives incorporating one (1,4)-glucosidic bond are easily synthesized in three steps from permethylated alpha- and beta-cyclodextrins, and such host molecules show inclusion selectivity for sodium m-nitrobenzoate over the corresponding p-isomer, in contrast to the cases of the parent permethylated alpha- and beta-cyclodextrins.

A cyclodextrin coat dramatically enhances the stability of an azo dye towards reductive bleaching, oxidative bleaching, and photo-bleaching as is demonstrated by the rotaxane 1. This compound is obtained as single isomer in high yield from the amine-substituted dye and trichlorotriazine in water in the presence of the cyclodextrin.

The O-alkyl (C1, C2, n-C3, n-C4, n-C6) groups distribution in per-O-alkylated cyclodextrins has been investigated by GC - MS. The per-O-alkylated cyclodextrins were acid hydrolysed to partially O-alkylated glucose molecules that were treated with hydroxylamine hydrochloride in dimethylacetamide and then with pyridine and acetic anhydride. The mass spectra of O-ethylated glucononitrile acetates obtained from per-O-ethylated alpha-cyclodextrin are presented.