Cucurbituril (CB[6]) is a hexameric macropolycyclic compound self-assembled from an acid-catalyzed condensation reaction of glycoluril and formaldehyde. 1,2 Its easy synthesis and rigid structure with a hollow core make CB[6] one of the attractive synthetic receptors. Its inclusion properties have been investigated extensively by Mock and co-workers. 3 Enzyme-like behavior of CB[6] effecting a large rate acceleration in a cycloaddition reaction has also been observed. 4 Its ability to bind alkali metal ions at the portals of the cavity allowed us to study molecular container systems capable of reversible encapsulation and release of guest molecules. 5 We also have demonstrated that CB [6] can be used as a molecular "bead" in self-assembly of interlocked structures such as polyrotaxanes and molecular necklaces. 6 CB- [6] is also known to be effective for removal of dyes from waste waters. 7 Although several homologues are available in calixarenes, which are obtained from a base-catalyzed condensation of phenol and formaldehyde, cucurbituril homologues with greater or fewer glycoluril units have not been reported. 8 Here we report the new family of cucurbituril, cucurbit[n]uril (CB[n]) (n ) 5, 7, and 8) containing five, seven, and eight glycoluril units, respectively.Reaction of glycoluril with formaldehyde in 9 M sulfuric acid at ∼75°C for 24 h and then at ∼100°C for 12 h yielded a mixture of CB[n] (n ) 5-11) as evidenced by electrospray ionization mass spectrometry. 9 Although its contents vary from batch to batch, the mixture typically contains ∼60% of CB[6], ∼10% of CB [5], ∼20% of CB [7], and ∼10% of other higher CB homologues. Apparently, the reaction of glycoluril and formaldehyde first generates linear oligomeric products which then cyclize to produce a library of cucurbituril. The cyclization at the lower temperature compared to that employed in the conventional synthesis 2 of CB[6] allows formation of significant amounts of other CB homologues besides CB [6]. The major product CB [6] was separated from the mixture by fractional dissolution of other CB homologues with acetone/water. From the acetone/water soluble portion, CB[5] and CB[7] were isolated by fractional crystallization/precipitation. 9 The homologue CB[8] was isolated from a CB[n] mixture that had been prepared by a modified procedure. Reaction of glycoluril and formaldehyde in the presence of HCl in a high-pressure reactor at 115°C for 24 h produced a white powder which, when treated with dilute sulfuric acid in a way similar to the one described above, yielded a mixture of CB[n] having a similar composition with slightly higher CB[7] and CB[8] contents. Upon standing, crystals of CB[8] were produced from a solution of the CB[n] mixture in 6 M sulfuric acid. 9 The new CB homologues CB[5], CB[7], and CB [8] have been characterized by various spectroscopic methods and X-ray crystallography. In the 1 H NMR spectra, CB homologues show the same peak pattern as that of CB[6], but their chemical shift values are slightly and yet distinctivel...

Two different molecules are selectively included in cucurbit[8]uril to form a stable 1:1:1 ternary complex, which has been characterized by X‐ray crystallography (see picture). The inclusion of a hetero‐guest pair (a pyridinium derivative (blue) and 2,6‐dihydroxynaphthalene (magenta)) in the molecular host is driven and stabilized by a charge‐transfer interaction between the electron‐rich and electron‐deficient guests.

We investigated a case of hepatitis E acquired after persons ate wild boar meat. Genotype 3 hepatitis E virus (HEV) RNA was detected in both patient serum and wild boar meat. These findings provided direct evidence of zoonotic foodborne transmission of HEV from a wild boar to a human.

No abstract

Highly symmetric structures often appear in nature as revealed by, for example, the capsids of spherical viruses that have icosahedral symmetry consisting of 60n identical protein subunits.[1] The reason for the high symmetry lies behind the principle that increasing the number of elements with the same symmetry reduces the amount of independent structural information, which is directly related to the length of DNA. Thus, the self-organization of tiny subunits into a giant biological molecule can be regarded as the process of not only structural growth but of the amplification of molecular information. We show herein that, through metal-ligand interactions, [2,3] simple banana-shaped organic molecules self-organize into finite, spherical coordination networks with a diameter of up to 7 nm, which is in contrast to the formation of two-dimensional (2D) infinite networks that occurs with linear organic ligands. The spherical coordination networks consist of 36 components, 12 equivalent metal centers (M) and 24 equivalent ligands (L), and have cuboctahedron symmetry. By attaching a functional group (e.g., C 60 or porphyrin) to each ligand, 24 functional groups are aligned equivalently at the periphery of the sphere.Over the last decade, extensive studies have been made on infinite coordination networks that are formed by the complexation of exo-multidentate ligands with transitionmetal ions. A typical and simple example is given by a 2D grid complex that forms from a rodlike ligand and a metal (Figure 1 a). [4] We expect that, if the ligand framework is slightly bent, the coordination network will develop with a[*] Dr.

Supramolecular interaction of fullerenes with cyclic dimers of metalloporphyrins (1‐M, M=central metal ions) showed a pronounced dependence on the nature of the metal ions, whereby 1‐RhMe/fullerene systems displayed extremely high association constants (ca. 108 M−1) and low dissociation activities. Crystal‐structure analysis and NMR data suggested a charge‐transfer interaction and van der Waals interactions between the host and guest.

No abstract

No abstract