Cucurbit[n]uril Analogues

Abstract

Molecular recognition and self-assembly in aqueous solution have experienced rapid growth in recent years. The use of -, -, and -cyclodextrins, calixarenes, and cyclophanes have served as the platforms for molecular recognition in aqueous solution. Recently, the investigation of an alternative platform based on cucurbituril has become the focus of several research groups. The rigid structure and capability of forming complexes with molecules and ions through hydrophobic, iondipole and hydrogen-bonding interactions make cucurbituril an attractive candidate as a synthetic receptor as well as a building block for the construction of supramolecular architectures.However, before cucurbituril can be used to supplant the more common platforms as the molecule of choice for molecular recognition and self-assembly in aqueous solution, several advances must be made: 1) cucurbiturils must become available in a variety of sizes, 2) their solubility must be improved, and 3) synthetic procedures must be advanced to include the ability to selectively generate specific cucurbituril homologues, derivatives, and analogues. To help rationalize the high yields obtained in these macrocyclization reactions, we performed mechanistic studies of model methylene bridged glycoluril dimers.The molecular recognition properties of a water soluble cucurbit[6]uril analogue in aqueous buffer toward a variety of guests including alkanediamines, aromatics, amino acids, and nucleobases were studied by fluorescence spectroscopy.For the alkanediamines studied, as the length of the alkane is increased between the amines, the association constants also increase. The CB [6] analogue is capable of forming strong complexes with guests containing aromatic rings with association constants (K a ) ranging from 10 2 to 10 6 M -1 due to the favorable -interactions that occur between the host and the aromatic portion of the guest while encapsulated in its hydrophobic cavity. CUCURBIT[N]URIL ANALOGUES

Chlorine Anion Encapsulation by Molecular Capsules Based on Cucurbit[5]uril and Decamethylcucurbit[5]uril

“…Figure 1) [14][15][16][17]. Recently some efforts have been made to introduce substitution in order to achieve ready solubility in both aqueous systems and common organic solvents, and a number of fully and partially substituted Q[n]s have been reported [18][19][20][21][22][23]. Decamethylcucurbit [5]uril (Me 10 Q [5]) was the first fully substituted Q[n] discovered in 1992 by Stoddart and co-workers [19].…”

Cucurbiturilas

“…A basicidade destes compostos é bastante baixa sendo verificados pKa's do ácido conjugado do CB [6] da ordem de 3, sendo desconhecida para os outros cucurbitandos. Uma das estratégias para contornar o problema de solubilidade é a utilização de meios salinos ou ácidos para aumentar a solubilidade destes compostos pela formação de complexos com ácidos duros ou, ainda, pela protonação das carbonilas dos opérculos destas estruturas 12 4,7,[16][17][18][19][20][21][22][23][24][25][26][27] . A reação de CB [6], por exemplo com K 2 S 2 O 8 , dá origem a 12 grupos OH radiais nos carbonos terciários em meio aquoso 22,28 , enquanto que a utilização de dimetil glicolurila como monômero precursor dá origem à decametil-CB [5] …”

Synthesis and X-ray Structure of the Inclusion Complex of Dodecamethylcucurbit[6]uril with 1,4-Dihydroxybenzene

“…The chemistry of cucurbit[n]uril (Q[n]s) has expanded dramatically with the discovery of cucurbituril(Q [6]) and its homologues (Q [5], Q [7], Q [8], and Q [10]) [1][2][3]. Recently, the direct functionalization of CB[n] [4][5][6] and introduction of building blocks for the preparation of Q[n] derivatives [7][8][9] and analogues [10][11] providing CB[n]s with solubility in both organic and aqueous solution has further expanded the range of the research and applications, which have been summarized in related reviews [12][13][14][15][16][17][18][19].…”

“…Recently, the direct functionalization of CB[n] [4][5][6] and introduction of building blocks for the preparation of Q[n] derivatives [7][8][9] and analogues [10][11] providing CB[n]s with solubility in both organic and aqueous solution has further expanded the range of the research and applications, which have been summarized in related reviews [12][13][14][15][16][17][18][19]. More recently, we have found that the solubilities of substituted cucurbit[n]urils (SQ[n]s) are dependent upon the kind, position and number of substituent groups on the substituted cucurbit[n]urils Q[n]s [20].…”