Studies of the Factors Controlling Regioselective Nucleophilic Addition to Dienylium-Iron Complexes

Tricarbonyl(4-alkoxyl-1-alkylcyclohexadienylium)iron complexes (I) react with metal-cation enolate nucleophiles to give in most cases a mixture of products (II) and (III), resulting from attack at the C-1 and C-5 termini of the dienylium ring. Factors that control the regioselectivity of nucleophilic addition, including the steric and electronic effects of the 4-alkoxyl and 1-alkyl substituents, the degree of association between the enolate nucleophiles and their counterions, and the polarity of the solvents, were investigated.     

DNA cleavage reaction of antitumour antibiotic, kapurimycin A3, with deoxytetranucleotide d(CGCG)2

Kapurimycin A3 (kap A3, 1 ), an antitumour antibiotic, alkylates N7 of guanine₂ (G₂) and G₄ of d(C₁G₂C₃G₄)₂ to produce their covalent adducts 2 (64 %) and 3 (7.0 %), respectively. Heating at 90 °C for 5 min degraded both adducts to kap A3 - G adduct (5) with the concurrent release of their respective abasic-site containing oligomers 4 and 6.     

A rapid 1H NMR assay for enantiomeric excess of alpha-substituted aldehydes

In situ derivatization of a variety of alpha-substituted aldehydes via reaction with chiral amines allows convenient and efficient determination of enantiomeric excess. (1)H NMR analysis of the imine diastereomer ratio can be conducted immediately after the aldehyde and amine have been mixed. The results correlate well with ee values determined by more traditional (and slower) methods. This approach may be broadly applicable to alpha-substituted aldehydes. [reaction: see text]     

Carbene-catalyzed enantioselective annulation of dinucleophilic hydrazones and bromoenals for access to aryl-dihydropyridazinones and related drugs

4,5-Dihydropyridazinones bearing an aryl substituent at the C6-position are important motifs in drug molecules. Herein, we developed an efficient protocol to access aryl-dihydropyridazinone molecules via carbene-catalyzed asymmetric annulation between dinucleophilic arylidene hydrazones and bromoenals. Key steps in this reaction include polarity-inversion of aryl aldehyde-derived hydrazones followed by chemo-selective reaction with enal-derived α,β-unsaturated acyl azolium intermediates. The aryl-dihydropyridazinone products accessed by our protocol can be readily transformed into drugs and bioactive molecules.

Polarity inversion of arylidene hydrazones to react with bromoenals via carbene organic catalysis is disclosed. The reaction enantioselectively affords 6-aryl-4,5-dihydropyridazinones and related drugs with proven commercial applications.     

Generation of peptide radical dications via low-energy collision-induced dissociation of [Cu<Superscript>II</Superscript>(terpy)(M + H)]<Superscript>·3+</Superscript>

The first example of the formation of hydrogen-deficient radical cations of the type [M + H](.2+) is demonstrated to occur through a one-electron-transfer mechanism upon low-energy collision-induced dissociation (CID) of gas-phase triply charged [Cu(II)(terpy)(M + H)](.3+) complex ions (where M is an angiotensin III or enkephalin derivative; terpy = 2,2':6',2'-terpyridine). The collision-induced dissociation of doubly charged [M + H](.2+) radical cations generates similar product ions to those prepared through hot electron capture dissociation (HECD). Isomeric isoleucine and leucine residues were distinguished by observing the mass differences between [z(n) + H](.+) and w(n)(+) ions (having the same residue number, n) of the Xle residues. The product ion spectrum of [z(n) + H](.+) reveals that the w(n)(+) ions are formed possibly from consecutive fragmentations of [z(n) + H](.+) ions. Although only the first few [M + H](.2+) species have been observed using this approach, these hydrogen-deficient radical cations produce fragment ions that have more structure-informative patterns and are very different from those formed during the low-energy tandem mass spectrometry of protonated peptides.     

模板组装Fe纳米线阵列及其微结构

铝在硫酸溶液中经直流阳极氧化,得到多孔铝阳极氧化膜(AAO). 以AAO膜为模板,通过交流电沉积的方法,在AAO模板孔内成功组装了Fe纳米线.TEM分析表明,Fe纳米线的长度约为2.5 μm,其长度分布十分均匀；粗细均匀,直径约为25 nm. XRD实验分析证实,所制备的Fe纳米线为α-Fe.选区电子衍射（SAED）实验分析表明,α-Fe纳米线具有单晶结构.     

Effect of brain lesions on [3H]ohmefentanyl binding site densities in the rat striatum and substantia nigra.

We have recently demonstrated that [3H]ohmefentanyl, a non-peptidergic opioid ligand which was suggested to cross the blood brain barrier in contrast to other peptidergic opioid ligands, bound not only to mu opioid receptor sites but also to sigma sites. In order to examine whether [3H]ohmefentanyl can be used as a marker for mu sites, we investigated the effects of brain lesions on [3H]ohmefentanyl binding site densities, as compared with [3H][D-Ala2, MePhe4, Gly-ol5]enkephalin ([3H]DAGO), a selective mu ligand. These binding site densities were measured by quantitative autoradiography in the rat striatum and substantia nigra, two brain structures known to contain a high density of mu receptors, following lesions of the nigro-striatal dopaminergic pathway and striatal intrinsic neurons. Following unilateral nigral lesion with 6-hydroxydopamine, [3H]ohmefentanyl binding site densities were decreased in the patches (-35%) and matrix (-20%) of the ipsilateral striatum and in the lesioned substantia nigra pars compacta (-49%). Unilateral striatal lesion with quinolinic acid induced 72%, 61% and 50% decreases in [3H]ohmefentanyl binding in the patches and matrix of the lesioned striatum and in the ipsilateral substantia nigra pars reticulata, respectively. Similar results were obtained in the binding of [3H]DAGO. Indeed, a significant linear correlation was observed between [3H]ohmefentanyl and [3H]DAGO binding site densities. Therefore, mu opioid receptors may be mainly located on intrinsic neurons in the striatum, dopaminergic cell bodies in the substantia nigra pars compacta and nerve terminals of striatal efferents in the substantia nigra pars reticulata.(ABSTRACT TRUNCATED AT 250 WORDS)     

Substituent control of hydrogen bonding in palladium(II)-pyrazole complexes

Inter- and intramolecular hydrogen bonding of an N-H group in pyrazole complexes was studied using ligands with two different groups at pyrazole C-3 and C-5. At C-5, groups such as methyl, i-propyl, phenyl, or tert-butyl were present. At C-3, side chains L-CH(2)- and L-CH(2)CH(2)- (L = thioether or phosphine) ensured formation of chelates to a cis-dichloropalladium(II) fragment through side-chain atom L and the pyrazole nitrogen closest to the side chain. The significance of the ligands is that by placing a ligating side chain on a ring carbon (C-3), rather than on a ring nitrogen, the ring nitrogen not bound to the metal and its attached proton are available for hydrogen bonding. As desired, seven chelate complexes examined by X-ray diffraction all showed intramolecular hydrogen bonding between the pyrazole N-H and a chloride ligand in the cis position. In addition, however, intermolecular hydrogen bonding could be controlled by the substituent at C-5: complexes with either a methyl at C-5 or no substituent there showed significant intermolecular hydrogen bonding interactions, which were completely avoided by placing a tert-butyl group at C-5. The acidity of two complexes in acetonitrile solutions was estimated to be closer to that of pyridinium ion than those of imidazolium or triethylammonium ions.     

重氮树脂-聚(4-羧酸苯基)乙炔自组装膜与光电转换

近年来 ,自组装及其形成的多层复合膜已经在导电、生物传感器及非线性光学等领域得到深入研究 ,特别是以聚阴离子与聚阳离子相互作用的静电自组装研究更为深入 .这一技术制备方法简单 ,无需特别的设备 ,对膜层厚度能随意调控 ,并以水作为介质 ,对环境无害 [1～ 3] .共轭高分子 (如聚苯胺、聚吡咯及聚苯亚乙烯等 )通过自组装形成共轭高分子膜 ,对制备具有导电、光电和传输等功能的薄膜半导体器件具有重要意义 .聚乙炔类是最早被发现且理论与应用研究最多的一类共轭高分子材料[4 ,5] .本文以聚 ( 4 -羧酸苯基 )乙炔 ( PCPA)为聚阴离子 ,以重…