In the wide area of supramolecular chemistry, cucurbit[n]urils (CBn) present themselves as a young family of molecular containers, able to form stable complexes with various guests, including drug molecules, amino acids and peptides, saccharides, dyes, hydrocarbons, perfluorinated hydrocarbons, and even high molecular weight guests such as proteins (e.g., human insulin). Since the discovery of the first CBn, CB6, the field has seen tremendous growth with respect to the synthesis of new homologues and derivatives, the discovery of record binding affinities of guest molecules in their hydrophobic cavity, and associated applications ranging from sensing to drug delivery. In this review, we discuss in detail the fundamental properties of CBn homologues and their cyclic derivatives with a focus on their synthesis and their applications in catalysis.

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Cucurbiturils: from synthesis to high-affinity binding and catalysis

Cucurbit[n]uril chemistry has become an important part of contemporary supramolecular chemistry since cucurbit[n]urils (Q[n]s) are not only able to encapsulate various guests, but are also capable of coordinating to a wide range of metal ions, leading to the establishment of Q[n]-based host–guest chemistry and coordination chemistry. Each of these impressive developments can be attributed to the growth of protocols for obtaining Q[n]s. In this review, we survey synthetic procedures for obtaining cucurbit[n]urils and their substituted derivatives together with the separation and purification of these remarkable compounds. The coverage is aimed at both existing workers in the field as well as at those requiring an “entry” into Q[n]-based research.

Synthesis and separation of cucurbit[n]urils and their derivatives

Development of hydroxylated cucurbit[n]urils, their derivatives and potential applications

The synthesis of the first family of fully substituted cucurbit[n]uril is discussed, and the structural features of precursor glycolurils are highlighted in their importance to achieving higher homologues. The members of the family, where n = 5–7, have been fully characterized, and increased binding affinities have been identified for dioxane in CyP6Q[6] and adamantyl NH3+ in CyP7Q[7]. A higher homologue is indicated but not conclusively identified.

Locating the Cyclopentano Cousins of the Cucurbit[n]uril Family

Diversity, pharmacology and synthesis of bergenin and its derivatives: potential materials for therapeutic usages.

The symmetrical dicyclohexanocucurbit[6]uril has been synthesised by the controlled condensation of the diether of cyclohexanoglycoluril (1) and the dimer of glycoluril (2). The symmetrical dicyclohexanocucurbit[6]uril, (CyH)2Q[6], characterised by the 1H NMR spectroscopy, ESMS and further confirmed by single crystal X-ray diffraction of a cobalt aqua exclusion complex, which demonstrates an ellipsoid cavity. Within a cucurbit[6]uril ellipsoid cavity, an inclusion complex of 5,5′-dimethyl-2,2′-bipyridine adopts a preferred orientation, aligning with the longest axis. The ellipsoid cavity is further supported by semiempirical AM1 gas phase calculations. Preferential orientation of a guest within the ellipsoid cavity of the symmetrical dicyclohexanocucurbit[6]uril

Opposing substitution in cucurbit 6 urils forms ellipsoid cavities: the symmetrical dicyclohexanocucurbit 6 uril is no exception highlighted by inclusion and exclusion complexes

Objective:To analyze components of volatile oil from Hedychium coronarium. Methods:The components of volatile oil were investigated by SPME/GC/MS. Results:48 Compounds were identified,which accounted for 92.65% of total volatile oil. Conclusion:The main constituents in the essential oil were β-Pinene(21.73%),1,8-Cineole(11.8%),Sabinene(11.32%),α-Terpineol acetate(6.69%),α-Pinene(4.67%),Limonene(3.78%) et al.

Analysis of volatile oil in Hedychium coronarium from Guizhou by SPME/GC/MS.

Eight compounds were isolated from Saxifraga stolonifera(L.) Meerb.The compounds were identified by spectral analysis(MS、IR、1H NMR and13C NMR) as 3,4-dihydroxy benzoic acid(1),amber acid(2),betulinic acid(3),3,4-Dihydroxybenzoic acid methyl ester(4),5,7-Dthydroxychromone(5),Quercetin 3-O-β-L-rhamnopyranoside(6),Quercetin 5-O-β-D-glucopyranoside(7),1-O-β-D-glucopyranosyl-(2S,3S,4R,8E/Z)-2-[(2'R)-2'-hydroxytetracosanoylamino) ]-8-octadecene-1,3,4-triol(8).In addition to compounds 1,2,7,other compounds were first isolated from Saxifraga stolonifera(L.) Meerb.Testing the compounds on PC-3 prostate cancer cells in vitro inhibition by MTT showed that compounds 6 and 7 had the certain inhibition to the PC-3 prostate anceer,the extracts and compounds were tested by plate diffusion method for the inhibitory effect of different strains.compound 2 on Bacillus subtilis had potential inhibition.

Chemical Constituents of Saxifraga stolonifera (L.) Meerb.and Biological Activity

Nine compounds were isolated from the Periploca forrestii Schltr.by chromatographic techniques.On the basis of physico-chemical properties and spectral data,they were identified as αamyrin(Ⅰ),α-amyrin acetate(Ⅱ),27hydroxy-α-amyrin(Ⅲ),β-amyrin(Ⅳ),β-amyrin acetate(Ⅴ),ursolic acid(Ⅵ),β-sitosterol(Ⅶ),dauricine(Ⅷ),emodin(Ⅸ).Compounds Ⅰ,Ⅲ,Ⅳ,Ⅴ were isolated from this plant for the first time.

Chemical Constituents of Periploca forrestii Schltr.

Objective:To study the chemical constituents of volatile oil from Indian kalimeris herb.Methods:The volatile oil from Indian kalimeris herb was extracted through steam distillation.The chemical constituents were analyzed by gas chromatography-mass spectrometry(GC-MS).Results:Thirty compounds were identified from stem of Indian kalimeris herb,which accounted for 92.32%of total volatile oil.Thirty-four compounds were identified from root of Indian kalimeris herb,which accounted for 91.32%of total volatile oil.The main constituents in the essential oil from stem of Indian kalimeris herb were β-elemene(6.79%),α-humulene(14.28%),germacrene-D(19.16%),delta.-cadinene(5.58%),germacrene B(11.42%),phytol (5.59%).The main constituents in the essential oil from root of Indian kalimeris herb were beta.-pinene(12.34%),m-Methoxy-β- Cyclopropylstyrene(8.34%),p-Methoxy-β-Cyclopropylstyrene(18.70%),2-(1-E-propenyl)-4-methoxyphenyl 2-methylbutanoate (9.96%),2-(1-E-propenyl)-4-methoxyphenyl 2-methyl-butanoate(7.84%).Conclusion:The compositions of volatile oils from stem and root of Indian kalimeris herb were studied for the first time by GC/MS.

Zhou Xin

Papers

Opposing substitution in cucurbit 6 urils forms ellipsoid cavities: the symmetrical dicyclohexanocucurbit 6 uril is no exception highlighted by inclusion and exclusion complexes

Analysis of volatile oil in Hedychium coronarium from Guizhou by SPME/GC/MS.

Chemical Constituents of Saxifraga stolonifera (L.) Meerb.and Biological Activity

Chemical Constituents of Periploca forrestii Schltr.

Study on volatile oil from stem and root of Indian kalimeris herb.