Cucurbit[7]uril‐Dimethyllysine Recognition in a Model Protein

Here, we provide the first structural characterization of host–guest complexation between cucurbit[7]uril ( Q7 ) and dimethyllysine (KMe₂) in a model protein. Binding was dominated by complete encapsulation of the dimethylammonium functional group. While selectivity for the most sterically accessible dimethyllysine was observed both in solution and in the solid state, three different modes of Q7 ‐KMe₂ complexation were revealed by X‐ray crystallography. The crystal structures revealed also entrapped water molecules that solvated the ammonium group within the Q7 cavity. Remarkable Q7 ‐protein assemblies, including inter‐locked octahedral cages that comprise 24 protein trimers, occurred in the solid state. Cucurbituril clusters appear to be responsible for these assemblies, suggesting a strategy to generate controlled protein architectures.     

Blurring the Lines between Host and Guest: A Chimeric Receptor Derived from Cucurbituril and Triptycene

We report the synthesis and X‐ray crystal structure of a cucurbituril–triptycene chimeric receptor ( 1 ). Host 1 binds to guests typical of CB[6]–CB[8], but also binds to larger guests such as blue box ( 20 ) and the Fujita square ( 22 ). Intriguingly, the geometries of the 1 ? 20 and 1 ? 22 complexes blur the lines between host and guest in that both components fulfill both roles within each complex. The fluorescence output of 1 is fully quenched by the formation of complexes with pyridinium‐derived guests.     

The cucurbit[n]uril family

In 1981, the macrocyclic methylene-bridged glycoluril hexamer (CB[6]) was dubbed "cucurbituril" by Mock and co-workers because of its resemblance to the most prominent member of the cucurbitaceae family of plants--the pumpkin. In the intervening years, the fundamental binding properties of CB[6]-high affinity, highly selective, and constrictive binding interactions--have been delineated by the pioneering work of the research groups of Mock, Kim, and Buschmann, and has led to their applications in waste-water remediation, as artificial enzymes, and as molecular switches. More recently, the cucurbit[n]uril family has grown to include homologues (CB[5]-CB[10]), derivatives, congeners, and analogues whose sizes span and exceed the range available with the alpha-, beta-, and gamma-cyclodextrins. Their shapes, solubility, and chemical functionality may now be tailored by synthetic chemistry to play a central role in molecular recognition, self-assembly, and nanotechnology. This Review focuses on the synthesis, recognition properties, and applications of these unique macrocycles.     

Preparation of Novel Side-chain Pseudopolyrotaxanes Consisting of Cucurbituril[6] and Polyamine Salts

Pseudorotaxane monomer （VBCB） containing cucurbitutil[6] （CB[6]） and N^1-（4-vinylbenzyl）-1,4-diaminobutane dihydrochloride （VBDADC） is obtained by self-assembly of cucurbituril[6] with VBDADC in water and then polymerized using potassium persulfate （KPS） as initiator to give novel water-soluble side-chain cucurbituril[6]-based pseudopolyrotaxane（PVBCB）. The chemical structures of PVBCB, VBCB and VBDADC are confirmed by ^1H NMR,^13C NMR spectra and elemental analysis. In VBCB, CB[6] is localized aliphatic group of the side chain and the molar ratio of CB[6] to VBDAC is 1：1 .     

新型准轮烷的合成及性质研究——丁烷基紫精与葫芦[6]脲的超分子自组装

通过葫芦[6]脲(CB[6])与丁烷基紫精(BV)在水溶液中于室温下进行超分子自组装, 得到一种新型的准轮烷(BVCB), 并通过¹H NMR, IR, 质谱, 元素分析对其结构进行了表征, 证实CB[6]位于BV的脂肪链上通过非共价键与BV结合, 并且 CB[6]与BV的结合摩尔比为2∶1; 通过热重分析(TGA)、紫外-可见吸收(UV-vis)和化学还原等方法对其性质进行了研究, 证实了BVCB比BV有更高的热稳定性、UV-vis吸收和更强的氧化能力; 盐效应表明 NaI是BVCB优良的沉淀剂; 环境扫描电镜(ESEM)证实BVCB比BV具有较强的刚性和较差的结晶能力.     

Synthesis and guest exchange reactions of inclusion compounds of cucurbit[8]uril with nickel(II) and copper(II) complexes

Inclusion compounds of the macrocyclic cavitand cucurbit[8]uril (CB[8]) with the nickel(II) complex, {trans-[Ni(en)₂(H₂O)₂]@CB[8]}Cl₂ · 23.5H₂O, the copper(II) complex, {2[Cu(dien)(bipy)(H₂O)]@CB[8]}(ClO₄)₄ · 11H₂O, and the organic molecules, 2(pyCN)@CB[8]} · 16H₂O and {2(bpe)@CB[8]} · 17H₂O, where bipy is 4,4′-bipyridyl, pyCN is 4-cyanopyridine, and bpe is trans-1,2-bis(4-pyridyl)ethylene, were synthesized. The inclusion compounds with organic molecules were synthesized starting from inclusion compounds of cucurbit[8]uril with cyclam and ethylenediamine complexes of copper(II) and nickel(II) by the guest exchange method, which is based on the replacement of one guest with another in the cavity of the cavitand The resulting compounds were characterized by X-ray diffraction, ESR, ¹H NMR, IR, and electronic absorption spectroscopy, and electrospray mass spectrometry. Photochemically induced [2+2]-cycloaddition of two 1,2-bis(4-pyridyl)ethylene molecules included in cucurbit[8]uril was studied. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 25–34, January, 2006.     

Cucurbituril and α- and β-Cyclodextrins as Ligands for the Complexation of Nonionic Surfactants and Polyethyleneglycols in Aqueous Solutions

The complexation of nonionicsurfactants and polyethylene glycols by the ligandscucurbituril, - and -cyclodextrin wasstudied in aqueous solution. All the examined guestmolecules form complexes with these ligands.Calorimetric titrations were performed to determinedirectly the stability constants and reactionenthalpies. The presence of an aromatic part innonionic surfactants leads to more stable complexeswith -cyclodextrin than with the other ligands.If the surfactants contain no benzene group, theinteractions with -cyclodextrin are strongercompared to other ligands. The chain length of thepolyethylene glycols has only an influence upon thevalues of the reaction enthalpy in the case of-cyclodextrin.