A new polymorph of anhydrous sodium alendronate, C4H12NO7P2Na, has been synthesized and characterized by single crystal X-ray diffraction as well as infrared spectroscopy and thermal analysis. The title compound crystallizes in the monoclinic P21/c space group. Asymmetric unit consists of one alendronic anion and one sodium cation. An interplay of classical strong O-H…O, N-H…O and non-classical weak C-H…O hydrogen bonds creates 3D framework in the crystal. Contrary to previously reported sodium alendronate salts, in which Na+ cation is surrounded by six-coordinated sphere, in compound (1), the Na+ cation is five-coordinated in a distorted trigonal-bipyramidal geometry. In order to provide a detailed investigation of the molecular arrangement in view of intermolecular interactions, the title compound was compared with alendronic acid and other known alkali metal alendronate salts, retrieved from the Cambridge Crystal Structure Database. The intercontacts were qualitatively and quantitatively compared using Hirshfeld surface analysis. It highlights that strong O…H/H…O and subtle H…H contacts play an influential role in the total surface area. The Me+…H/H…Me+ and Me+…O/O…Me+ contacts are meaningful as well. These evidently simple systems show a diverse complexity. Moreover, the powder X-ray diffraction, DSC, thermogravimetry/derivative thermogravimetry, and FT-IR results are also reported.
Four new water-soluble derivatives of dibenzotetraaza[14]annulene have been synthesized, bearing meso substituents with different structures and dimensions: 3-(N,N,N-trimethylammonium)propyl, 3-(N-pyridinium-1-yl)propyl, 2-[3-(N,N,N-trimethylammonium)propoxy]benzoyl, and 2-[3-(N-pyridinium-1-yl)propoxy]benzoyl. The crystal structures of 3-(trimethylammonium)propyl and (N,N,N-trimethylammonium)propoxy]benzoyl derivatives were determined by single crystal X-ray analysis. According to the UV-vis titrations, thermal denaturation experiments, and ethidium bromide displacement assays, all compounds presented here interact strongly with double stranded (ct)-DNA. The product equipped with 3-(trimethylammonium)propyl pendant groups and two positive charges interacts with DNA in one dominant binding mode, whereas the other three derivatives revealed more complex mixed-type interactions. The results have been discussed in terms of dimensions, geometry, and electronic properties of the evaluated compounds, on the basis of corresponding crystallographic data. 相似文献
A series of water-soluble dicationic dibenzotetraaza[14]annulenes have been prepared in order to examine their interactions with nucleic acids. Pendant water-solubilizing N-pyridinium, 4,4′-bipyridinium and N-methyl pyridinium moieties have been attached to the central core via linkers generated by direct N-alkylations and ester creating couplings, respectively. The crystal structures of derivatives equipped with 3-(N-pyridinium-1-yl)propyl and 3-(4,4′-bipyridinium-1-yl)propyl substituents have been determined. Interactions with ct-DNA have been studied and evidenced by means of spectrophotometric titrations with Scatchard analysis and thermal denaturation experiments. 相似文献
An efficient, convergent synthesis of the C1'-C11' side chain (3) of leucascandrolide A (1) has been achieved. The key bond connection is made through the use of a palladium(0)-catalyzed Sonogashira cross-coupling between trifloyl oxazole (4) and alkynylmetal species (5). 相似文献
[reaction: see text] The asymmetric synthesis of a C1-C22 fragment (2) of leucascandrolide A is described. Synthetic highlights include the construction of the C9-C22 pyran fragment using a formal [4 + 2]-annulation of a chiral organosilane. A diastereoselctive Mukaiyama aldol was used to introduce the C9 stereocenter and complete the assembly of the macrocycle's carbon skeleton. 相似文献
Finding good cycles in graphs is a problem of great interest in graph theory as well as in locational analysis. We show that the center and median problems are NP-hard in general graphs. This result holds both for the variable cardinality case (i.e., all cycles of the graph are considered) and the fixed cardinality case (i.e., only cycles with a given cardinality p are feasible). Hence it is of interest to investigate special cases where the problem is solvable in polynomial time. In grid graphs, the variable cardinality case is, for instance, trivially solvable if the shape of the cycle can be chosen freely. If the shape is fixed to be a rectangle one can analyze rectangles in grid graphs with, in sequence, fixed dimension, fixed cardinality, and variable cardinality. In all cases a complete characterization of the optimal cycles and closed form expressions of the optimal objective values are given, yielding polynomial time algorithms for all cases of center rectangle problems. Finally, it is shown that center cycles can be chosen as rectangles for bounded cardinalities such that the center cycle problem in grid graphs is in these cases completely solved. 相似文献