In recent years, it has become increasingly clear that the planar aromatic ring plays a vital three-dimensional role in chemical and biological recognition by virtue of its ability to participate in noncovalent interactions.[1] Since a detailed understanding of protein-ligand interactions involving aromatic rings is essential for drug design and lead optimization, considerable research effort has been devoted to studies involving such phenomena as aryl-aryl interactions, [2] the behavior of aromatic rings as hydrogen-bond acceptors, [3] and their marked affinity for cationic species.[4] In qualitative terms, the quadrupolar model of aromatic systems [5] has proven to be the most popular in terms of providing a simple unifying theoretical basis upon which these different types of interaction can be considered. In this model, an aromatic ring is viewed as a quadrupole with the positive charge distributed around the edges and the negative charge located above and below the plane of the ring. A variety of elegant approaches, including structural database mining, [6] measurements of gasphase complexes, [7] and computational modeling, [8] all provide corroboration for this simple picture.Nevertheless, in terms of an even more rational approach for the design of new drugs, asymmetric ligands, and sensors, there is a clear need for a much more quantifiable estimation of the strength, distance, and angular dependence of the intermolecular forces acting between individual functional groups and aromatic rings. The vitally important but often neglected influence of the solvent on such noncovalent interactions should also be taken into account. Since the interaction energies are small, such data are relatively difficult to obtain and special care must accordingly be taken in the design of suitable model systems which allow their observation and evaluation. The pioneering work on the molecular torsion balance by Wilcox and co-workers [1a, 2d] provides an exemplary approach to the problem of quantifying such weak interactions, and recent studies by Diederich and co-workers [9a] and by Hunter and Cockroft [9b] confirm the power of this method.Consideration of the above requirements suggested to us that a detailed study of the conformational equilibria in suitably functionalized dibenzobicyclo[3,2,2]nonane (BCN) derivatives would provide a useful probe as shown in Figure 1.Both the aromatic rings and the functional groups of the BCN derivatives are spatially confined but do not suffer from any further undesirable conformational flexibility which often impedes evaluation of measured results. Moreover, the substituents on the central carbon atom of the bridge are brought into close proximity with the centers of the aromatic rings and hence interaction energies are large enough to measure. In essence, so many of the structural features are the same on both sides of the equilibrium between conformers D and U, that the dibenzopropanoanthracene skeleton can function as a highly sensitive balance for comparison of the relative ...

This report is the outcome of an EFSA procurement aiming at investigating and summarising the state of knowledge on (I) the mode-of-action of dsRNA and miRNA pathways, (II) the potential for nontarget gene regulation by dsRNA-derived siRNAs or miRNAs, (III) the determination of siRNA pools in plant tissues and the importance of individual siRNAs for silencing. The report is based on a comprehensive and systematic literature search, starting with the identification and retrieval of~190,000 publications related to the research area and further filtered down with keywords to produce focused collections used for subsequent screening of titles and abstracts. The report is comprised of an (I) Introduction to the field of small RNAs, (II) a Data and Methodologies section containing strategies used for literature search and study selection, and (III) the Results of the literature review organized according to the three main procurement tasks. The outcome of the first task reviews dsRNA and miRNA pathways in mammals (including humans), birds, fish, arthropods, annelids, molluscs, nematodes, and plants. Eight taxon-dedicated chapters are based on~1,400 cumulative references chosen from~10,000 inspected titles and abstracts. We review conserved and divergent aspects of small RNA pathways and dsRNA responses in animals and plants including structure and function of key proteins as well as four basic mechanisms: genome-encoded posttranscriptional regulations (miRNA), degradation of RNAs by short interfering RNA pools generated from long dsRNA (RNAi), transcriptional silencing, and sequence-independent responses to dsRNA. The outcome of the second task focuses on base pairing between small RNAs and their target RNAs and predictability of biological effects of small RNAs in animals and plants. The outcome of the last task reviews methodology, siRNA pools, and movement of small RNAs in plants. Potential transfer of small RNAs between species and circulating miRNAs in mammals is described in the final chapter.

Selective examples of OH...arene, NH2...arene and C-HN[triple bond, length as m-dash]C weak interactions are presented using a flexible dibenzobicyclo[3.2.2]nonane scaffold for detection and comparative characterisation of non-covalent interactions in solution and solid states.

A new heterocyclic compound has been prepared by four step synthesis. The reaction of methyl thiosalicylate I with excess methyl chloroacetate in the presence of potassium carbonate gives methyl 3-[(methoxycarbonyl)methoxy]benzo[b]thiofen-2-carboxylate (II) which on cyclization by action of potassium tert-butoxide gives methyl 3-hydroxy[1]benzothieno[3,2-b]furan-2-carboxylate (III). Its base catalyzed hydrolysis and decarboxylation forms [1]benzothieno[3,2-b]furan-3(2H)-one (IV) whose reduction with NaBH4 gives the title compound.

In recent years, it has become increasingly clear that the planar aromatic ring plays a vital three-dimensional role in chemical and biological recognition by virtue of its ability to participate in noncovalent interactions.[1] Since a detailed understanding of protein-ligand interactions involving aromatic rings is essential for drug design and lead optimization, considerable research effort has been devoted to studies involving such phenomena as aryl-aryl interactions, [2] the behavior of aromatic rings as hydrogen-bond acceptors, [3] and their marked affinity for cationic species.[4] In qualitative terms, the quadrupolar model of aromatic systems [5] has proven to be the most popular in terms of providing a simple unifying theoretical basis upon which these different types of interaction can be considered. In this model, an aromatic ring is viewed as a quadrupole with the positive charge distributed around the edges and the negative charge located above and below the plane of the ring. A variety of elegant approaches, including structural database mining, [6] measurements of gasphase complexes, [7] and computational modeling, [8] all provide corroboration for this simple picture.Nevertheless, in terms of an even more rational approach for the design of new drugs, asymmetric ligands, and sensors, there is a clear need for a much more quantifiable estimation of the strength, distance, and angular dependence of the intermolecular forces acting between individual functional groups and aromatic rings. The vitally important but often neglected influence of the solvent on such noncovalent interactions should also be taken into account. Since the interaction energies are small, such data are relatively difficult to obtain and special care must accordingly be taken in the design of suitable model systems which allow their observation and evaluation. The pioneering work on the molecular torsion balance by Wilcox and co-workers [1a, 2d] provides an exemplary approach to the problem of quantifying such weak interactions, and recent studies by Diederich and co-workers [9a] and by Hunter and Cockroft [9b] confirm the power of this method.Consideration of the above requirements suggested to us that a detailed study of the conformational equilibria in suitably functionalized dibenzobicyclo[3,2,2]nonane (BCN) derivatives would provide a useful probe as shown in Figure 1.Both the aromatic rings and the functional groups of the BCN derivatives are spatially confined but do not suffer from any further undesirable conformational flexibility which often impedes evaluation of measured results. Moreover, the substituents on the central carbon atom of the bridge are brought into close proximity with the centers of the aromatic rings and hence interaction energies are large enough to measure. In essence, so many of the structural features are the same on both sides of the equilibrium between conformers D and U, that the dibenzopropanoanthracene skeleton can function as a highly sensitive balance for comparison of the relative ...