Search

The reaction of the arylphosphonic acid esters 4,4′-[( i-PrO)2P(O)]C6H4C6H4[P(O)(O i-Pr)2] ( L1), 1,3,5-[( i-PrO)2P(O)]3C6H3 ( L2), and 5- t-Bu-1,3-[( i-PrO)2P(O)]2C6H3 ( L3), respectively, with bismuth halides BiX3 (X=Cl, Br, I) gave seven novel bismuth coordination polymers that have been characterized by single-crystal X-ray diffraction analysis. The solid-state structures of [(BiCl3)( L1)] ( 1), [(BiBr3)( L1)]·0.25CH3CN ( 2·0.25CH3CN), [(BiI3)2( L1)]·0.25CH3CN ( 3·0.25CH3CN), [(BiCl3)( L2)] ( 4), [(BiCl3)2( L2)] ( 5), [(BiBr3)2 ( L2)]·CH3CN ( 6·CH3CN), and [(BiCl3)( L3)] ( 7) are presented. Thermal analysis of [(BiCl3)2( L2)] ( 5) is indicative of a conversion of the complexes into a bismuth phosphonate by complete i-PrX elimination, whereas for [(BiBr3)2( L2)] ( 6), elimination of i-PrBr and BiBr3 is assumed. Compounds 1- 3 form one-dimensional coordination polymers, whereas two-dimensional networks are observed for compounds 4- 7. [ABSTRACT FROM AUTHOR]

A novel synthetic route based on [4+2] cycloaddition for dibromobenzobarrelene derivatives starting from in situ generated 3,5-dibromo-1,2-didehydrobenzene and mesitylene, 1,2,4,5-tetramethylbenzene, 1,2,3,5-tetramethylbenzene, pentamethylbenzene, 1,3-dimethoxybenzene, and 2,4,6-trimethylbromobenzene, respectively, was developed. Thus, six novel dibromobenzobarrelenes with diverse substitution patterns at the barrelene framework including chiral derivatives are reported. The benzobarrelene 6,8-dibromo-1,3,10-trimethyl-1,4-dihydro-1,4-ethenonaphthalene ( 1a) was functionalized at the annulated benzene ring to give three novel carboxylic acids and two novel phosphonic acid esters. Selected benzobarrelene complexes with RhICl were tested for their catalytic activity in the 1,4-addition of phenylboronic acid towards cyclohex-2-enone. Turnover frequencies up to 3405 h-1 were observed, which are among the highest reported so far for Rh-diene complexes in this type of C-C coupling reaction. [ABSTRACT FROM AUTHOR]

In biology-oriented synthesis, the scaffolds of biologically relevant compound classes inspire the synthesis of focused compound collections enriched in bioactivity. This criterion is, in particular, met by the scaffolds of natural products selected in evolution. The synthesis of natural product-inspired compound collections calls for efficient reaction sequences that preferably combine multiple individual transformations in one operation. Here we report the development of a one-pot, twelve-step cascade reaction sequence that includes nine different reactions and two opposing kinds of organocatalysis. The cascade sequence proceeds within 10-30 min and transforms readily available substrates into complex indoloquinolizines that resemble the core tetracyclic scaffold of numerous polycyclic indole alkaloids. Biological investigation of a corresponding focused compound collection revealed modulators of centrosome integrity, termed centrocountins, which caused fragmented and supernumerary centrosomes, chromosome congression defects, multipolar mitotic spindles, acentrosomal spindle poles and multipolar cell division by targeting the centrosome-associated proteins nucleophosmin and Crm1. [ABSTRACT FROM AUTHOR]

N-Phenyl-C-chromonyl nitrones 1 and the allenoate zwitterion 2, generated by addition of phosphine to acetylenedicarboxylates, undergo a cascade reaction sequence involving an unprecedented [5+3] annulation followed by deoxygenative rearrangement leading to dihydropyridine-fused benzopyrones. Unusual electronic control by the N-substituents of 1 directs the annulation pathway, leading to two different ring-systems. [ABSTRACT FROM AUTHOR]

The crystal structure of the title compound shows the [K(18-crown-6)]+ cation and [{2,6-(Me2NCH2)2C6H3}SnF4]- anion, which are held together through two potassium-fluorine and one potassium-tin electrostatic interaction. The tin atom is hexacoordinated by one carbon and four fluorine atoms, and an intramolecular N→Sn interaction. It has a distorted octahedral configuration. Electrostatic interactions between two fluorine atoms and hydrogen atoms from two different cation-anion pairs generate a double-chain polymeric supramolecular structure, containing both isomers. [ABSTRACT FROM AUTHOR]

In Biology Oriented Synthesis the scaffolds of biologically relevant compound classes inspire the synthesis of focused compound collections enriched in bioactivity. This criterion is met by the structurally complex scaffolds of natural products (NPs) selected in evolution. The synthesis of NP-inspired compound collections approaching the complexity of NPs calls for the development of efficient synthetic methods. We have developed a one pot 4-7 step synthesis of mono-, bi-, and tricyclic oxepanes that resemble the core scaffolds of numerous NPs with diverse bioactivities. This sequence entails a ring-closing ene-yne metathesis reaction as key step and makes productive use of polymer-immobilized scavenger reagents. Biological profiling of a corresponding focused compound collection in a reporter gene assay monitoring for Wntsignaling modulation revealed active Wntepanes. This unique class of small-molecule activators of the Wnt pathway modulates the van-Gogh-like receptor proteins (Vangl), which were previously identified in noncanonical Wnt signaling, and acts in synergy with the canonical activator, protein (Wnt-3a). [ABSTRACT FROM AUTHOR]

In biology-oriented synthesis the underlying scaffold classes of natural products selected in evolution are used to define biologically relevant starting points in chemical structure space for the synthesis of compound collections with focused structural diversity. Here we describe a highly enantioselective synthesis of natural-product-inspired 3,3′-pyrrolidinyl spirooxindoles—which contain an all-carbon quaternary centre and three tertiary stereocentres. This synthesis takes place by means of an asymmetric Lewis acid-catalysed 1,3-dipolar cycloaddition of an azomethine ylide to a substituted 3-methylene-2-oxindole using 1–3 mol% of a chiral catalyst formed from a N,P-ferrocenyl ligand and CuPF6(CH3CN)4. Cellular evaluation has identified a molecule that arrests mitosis, induces multiple microtubule organizing centres and multipolar spindles, causes chromosome congression defects during mitosis and inhibits tubulin regrowth in cells. Our findings support the concept that compound collections based on natural-product-inspired scaffolds constructed with complex stereochemistry will be a rich source of compounds with diverse bioactivity. [ABSTRACT FROM AUTHOR]

The synthesis of the cyclic tin-modified silanes 1-6 are described by the reaction of t Bu 2 SnCl 2 with different dichloromono- and -disilanes in the presence of magnesium. Reacting dimethyldichlorosilane with diphenyldichlorosilane and magnesium yielded the 1,1-dimethylhexaphenylcyclotetrasilane 8 in reasonably good yields. [ABSTRACT FROM AUTHOR]

This paper reports a case of acute severe thrombocytopenia (platelet count: 1 × 10[sup 9]/liter) occurring within minutes of an initial abciximab bolus during coronary angioplasty and stenting in a patient with unstable angina. After six days with platelets again in the normal range the patient developed stent thrombosis. The stent was reopened and the glycoprotein receptor inhibitor tirofiban (Aggrastat) was administered without any adverse effects on platelet count. Antibodies against heparin-platelet factor 4 complexes could be excluded. Allo- and autoantibodies (IgG, IgA, IgM) directed against platelets with and without binding of abciximab could not be detected by indirect and direct platelet fluorescence antiglobulintest. A possible activation or lysis of the platelets by abciximab could also be excluded by an in vitro bleeding test investigating the effect of abciximab on heparin and citrate blood of the patient and two healthy donors. The mechanisms of abciximab-induced thrombocytopenia in this case remain unclear. The possible mechanisms are discussed. [ABSTRACT FROM AUTHOR]

We developed an enantioselectively catalyzed tandem synthesis of structurally and stereochemically complex molecules that forms four carbon-carbon bonds and sets eight stereocenters with high regio-, diastereo- and enantioselectivity. It can be programmed to yield different stereoisomers by varying only the order of combination of a common set of reagents and catalysts. We report what is to our knowledge the first synthesis of both enantiomers of a chiral compound using the same chiral catalyst. [ABSTRACT FROM AUTHOR]