Host-guest interactions between xanthones and water: the role of O-H center dot center dot center dot O, C-H center dot center dot center dot O, and pi center dot center dot center dot pi contacts in the channel- and cage-type frameworks

In this article were studied two xanthone derivatives known as 1,5-dihydroxy-8-methoxyxanthone (I) and 1,3,7-trihydroxy-8-methoxyxanthone (II), which show one water molecule into their crystal structures. In xanthone I, there are water wires contributing to build up channel-like cavities along the c axis, whereas in xanthone II the water is surrounded by three xanthone molecules forming a cage-type structure. The geometries of I and II were optimized using the density functional theory method with B3LYP functional, and the results were compared with crystal structure. Both theoretical and experimental investigations reveal a concordance between structural parameters, with the xanthone core presenting an almost flat conformation and substituents adopting the more stable orientations. In the two compounds, the hydroxyl group linked at position 1 is involved in a resonance-assisted hydrogen bond with the carbonyl group. Besides, the supramolecular arrangement of the host/guest systems are stabilized mainly by classical intermolecular hydrogen bonds (O-H center dot center dot center dot O) involving xanthone-to-water and xanthone-to-xanthone. In addition, C-H center dot center dot center dot O weak hydrogen bonds, as well as pi-pi interactions play an important role to stabilize the crystal self-assembly of xanthones I and II. The results reported here underline the role of inclusion of water molecules and their different arrangement into the crystal structure of two xanthone host/guest systems.

Cytogenetic findings in pediatric radiation-induced atypical meningioma after treatment of medulloblastoma: case report and review of the literature

Ionizing radiation is the most recognized risk factor for meningioma in pediatric long-term cancer survivors. Information in this rare setting is exceptional. We report the clinical and cytogenetic findings in a radiation-induced atypical meningioma following treatment for desmoplastic medulloblastoma in a child. This is the second study to describe the cytogenetic aspects on radiation-induced meningiomas in children. Chromosome banding analysis revealed a 46, XX, t(1;3)(p22;q12), del(1)(p?)[8]/46, XX[12]. Loss of chromosome 1p as a consequence of irradiation has been proposed to be more important in the development of secondary meningiomas in adults. Deletions in the short arm of chromosome 1 also appear to be a shared feature in both pediatric cases so far analyzed.