DFT survey of monoboron and diboron corroles: regio- and stereochemical preferences for a constrained, low-symmetry macrocycle

The structures of a number of mono- and diboron corrole complexes have been optimized using DFT methods in order to establish regio- and stereochemical preferences for bonding of one or two boron atoms to the corrole macrocycle. The formulations of the complexes were suggested either from preliminary experimental results (to be reported elsewhere) or by analogy with related diboron porphyrin compounds. The computational results suggest for the monoboron corroles BF(2)(H(2)corrole) and BPhH(H(2)corrole) that the regioisomer in which the boron is bound to a dipyrromethene site adjacent to the bipyrrole is preferred over the other possible regioisomers in which boron coordinates either in the bipyrrole or in the dipyrromethene site opposite the bipyrrole. In the N-substituted corrole complexes there are only two possiblities and, for each complex, the regioisomer with boron in the dipyrromethene site adjacent to the bipyrrole is lower in energy. For all four monoboron complexes the stereoisomers in which boron and both its substituents are displaced out of the mean N(4) plane are more stable than the boron in-plane stereoisomers. These regio- and stereochemical preferences are rationalised by an analysis of the deformations to the corrole macrocycle and the geometry at the boron atoms. The lowest energy structures in all cases correspond to the least strained configurations. In addition, all four complexes show significant BFHN hydrogen bonding and BHHN dihydrogen bonding interactions, which are maximised in the lowest energy configurations for each structure, indicating that these are important additional stabilising interactions. Three different regioisomers, each with cisoid or transoid stereochemistry were optimised for the diboron complex PhBOB(corrole) which contains a bridging BOB group. The dipyrromethene/dipyrromethene isomer is more stable than either of the dipyrromethene/bipyrrole isomers and cisoid stereochemistry is preferred over transoid. This contrasts with porphyrin complexes containing BOB groups for which both stereochemical possibilities are observed, and reflects the contracted size of the corrole macrocycle. Three further diboron corroles were investigated, the diboranyl cation [B(2)(corrole)](+) and its one- and two-electron reduced derivatives B(2)(corrole) and [B(2)(corrole)](-). These calculations were undertaken to determine whether the site of reduction of [B(2)(corrole)](+) is likely to be the diboron moiety or the macrocycle. The B-B bond lengths do not shorten upon reduction and an analysis of the molecular orbitals of each species indicates that reduction will be most likely to occur at the macrocycle, offering a potential route to an example of the two-electron reduced corrole ligand, an analogue of the 20-electron isophlorin ligand observed in the corresponding reduced porphyrin complex B(2)(porphine).     

Conformational analogues of Oxamflatin as histone deacetylase inhibitors

Conformational analogues of the hydroxamic acid Oxamflatin compounds, have been synthesised to enable evaluation of the impact of varying the linking section on histone deacetylase inhibition. Preliminary testing indicates treatment of leukaemia cells with each of the analogues leads to significant inhibition of histone deacetylase and reduction in cell growth and proliferation.     

Shadowing of directional noise sources by finite noise barriers

The present study investigates the shadowing effect of barriers of infinite or finite length in the presence of directional noise sources. The diffraction model termed [Directive Line Source Model (DLSM) J. Acoust. Soc. Am. 107 (2000) 2973-2986] is employed. DLSM is appropriately modified and extended to include the effects of ground reflection, diffraction by the side edges of a finite length barrier, and diffraction by directional noise sources. Results obtained are shown to be in good agreement with available experimental data and known analytical solutions. An application of the enhanced DLSM is illustrated using helicopter type noise, which is highly directive. The noise source is modeled as a directional point source with far field directivity data and the enhanced DLSM is employed to compare the noise field with and without the barrier present for three different directivity patterns, various source locations and orientations, as well as, for various barrier lengths.     

Lateral flow dipstick test for genotyping of 15 beta-globin gene (HBB) mutations with naked-eye detection

For definitive diagnosis of thalassemia carriers and patients, as well as for prenatal diagnosis, genotype analysis is of fundamental importance. We report a dry-reagent, lateral flow dipstick test that enables visual genotyping (detection by naked eye) of 15 mutations common in Mediterranean populations in the beta-globin gene (HBB). The method comprises 3 simple steps: (i) PCR amplification of a single 1896 bp segment of the beta globin gene flanking all 15 mutations; (ii) a multiplex (10-plex and/or 30-plex) primer extension reaction of the unpurified amplification product using allele-specific primers. Biotin is incorporated in the extended product; (iii) a dry-reagent multi-allele (10-plex) dipstick assay for visual detection of the primer extension reaction products within minutes. The total time required for PCR, primer extension reaction and the dipstick assay is ∼2 h. The method was evaluated by genotyping 45 DNA samples of known genotypes and 54 blind samples. The results were fully concordant with reference methods. The method is simple, rapid, and cost-effective. Detection by the dipstick assay does not require specialized instrumentation or highly qualified personnel. The proposed method could be a particularly useful tool in laboratories with limited resources and a basis for point-of-care diagnostics especially in combination with PCR amplification from whole blood.     

Tricarbonyl (triquinacene)-molybdenum and-tungsten

Triquinacene reacts with hexacarbonylmolybdenum to give tricarbonyl(triquinacene)molybdenum, and with tris(acetonitrile)tricarbonyltungsten to give tricarbonyl(triquinacene)tungsten, whereas efforts to synthesize the corresponding chromium complex, tricarbonyl(triquinacene)chromium, were unsuccessful.The molybdenum complex was characterized by ¹H and ¹³C NMR spectroscopy, mass spectra, and a single crystal X-ray structure determination. The tungsten complex is thermally less stable and more susceptible to oxidation than its molybdenum analogue and was characterized by the mass spectrum and the ¹H NMR spectrum. The crystal structure of the tricarbonyl(triquinacene)molybdenum is compared to that for the free ligand. Besides the expected lengthening of the CC bonds, the complex shows a deepening of the triquinacene “basket”, presumably to give better overlap of the CC bonds with molybdenum orbitals.     

The alkaloids of Delphiniumbicolor nutt.

The structures of alkaloid-$\text{A}$ and -$\text{B}$ were established via X-ray crystallography of the former as its HI salt, and its chemical conversion to the latter.     

Crystal and moleclar structures of 5-allyl-25-methoxy-26,27,28-tribenzoylcalix[4]arene

The crystal and molecular structures of 5-allyl-25-methoxy-26,27,28-tribenzoylcalix[4]arene, an unsymmetrically substituted macrocycle, are reported. The space group is orthorhombic,P2₁2₁2₁, witha=13.4181(6),b=16.6652(10) andc=18.9936(14) Å andZ=4. Refinement by least-squares calculations converged with aR=0.060 for 4018 observed reflections. The molecule assumes a 1,3 alternate conformation with 2 benzoate rings and the disordered allyl side chain on one side and the third benzoate ring and the methoxy group on the opposite side of the mean plane of the methylene bridging groups. The four phenyl rings that comprise the macrocycle are approximately parallel in pairs; the members of a pair are 5.6 Å apart. The carbonyl oxygen atoms of the 3 benzoate groups are oriented away from the center of the cavity while the ester oxygen atoms and the methoxy oxygen atom are oriented toward the cavity center. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82033 (26 pages).