Palladium-catalyzed coupling of alkenyl iodides with ethynyl oxiranes: Synthesis of epoxy enediyne core intermediates related to neocarzinostatin chromophore

Coupling of functionalized cyclopentenyl iodides with ethynyl oxiranes has been achieved by using catalytic amount of Pd(CH₃CN)₂Cl₂ and CuI in the presence of i-Pr₂NEt in moderate to good yields.     

Polymerization of coordinated monomers. I. Stereoregulation in the free-radical polymerization of methyl methacrylate-zinc chloride or methyl methacrylate–stannic chloride complexes

Stereoregulation in free-radical polymerization was studied for the polymerization of the 2:1 or 1:1 complex of methyl methacrylate with ZnCl₂ or SnCl₄. The complexes were polymerized with the use of a free-radical initiator or γ-ray irradiation either in the liquid or solid state at various temperatures ranging from ?196 to 110°C, and the tacticities of the resulting polymers were determined by NMR spectroscopy. The polymers had different and characteristic values of tacticities depending upon the complex species, i.e., the kind of metal chloride and the stoichiometry. The tacticities were found to be independent of the polymerization temperature in both the liquid and solid states, in contrast with the fact that tacticities of the polymer from pure monomer changed markedly with the temperature. A temperature dependence appeared in the polymerization system, which contained more monomer than that corresponding to the 2:1 complex. The effect of the viscosity or the solid phase on the stereoregulation was examined in comparison with the polymerization of a mixture of methyl methacrylate and liquid paraffin. Two possible explanations regarding the stereoregulation mechanism are offered in relation to the structures of the complexes.     

Simple and rapid identification of phosphorylated peptides from bovine brain myelin basic protein by reversed-phase high-performance liquid chromatography

The phosphorylation sites of the myelin basic protein from bovine brain were determined after phosphorylation with a cyclic 3':5'-phosphate-dependent protein kinase from the same source. Three phosphorylated peptides were selectively and rapidly separated, before and after dephosphorylation, by reversed-phase high-performance liquid chromatography on a styrene 250 column under alkaline conditions. Partial sequencing of the peptides by automated Edman degradation revealed that the serine-115 residue located in the main encephalitogenic determinant of the protein was a phosphorylation site, in addition to the two phosphorylation sites established (threonine-34 and serine-55).     

Reaction of α,β-unsaturated carbodiimides with enamines leading to fused pyridine derivatives

The treatment of (5,5-dimethyl-3-oxo-1-cyclohexenyl)iminotriphenylphosphorane ( 2 ) with phenyl isocyanate ( 3a ) gave N-(5,5-dimethyl-3-oxo-1-cyclohexenyl)-N'-phenylcarbodiimide ( 4a ) in situ. The reaction of 4a with enamines proceeded smoothly to afford the pyridine ring formation with the elimination of amine. This means that 4a is regarded as a new class of 2-aza-1,3-butadiene. The scopes and limitation of this reaction are also discussed.     

Isotope effect of retention value between64Cu and66Cu in neutron-irradiated copper phthalocyanine

Copper phthalocyanine ( and forms) in neat solid or in dissolved state in conc. H₂SO₄ was neutron-irradiated, and retention values of⁶⁴Cu and⁶⁶Cu were estimated to study whether or not there is any isotope effect in retention between these two (n, )-produced radionuclides. The data show that there is an isotope effect expressed by the ratio of retention of⁶⁶Cu to that of⁶⁴Cu, ranged from 1.29±0.12 for form dissolved in conc. H₂SO₄ to 1.09±0.02 for form in neat solid irradiation. This result coincides with the tendency anticipated from the recoil energy spectra which were computed by a program using Monte-Carlo method.     

Chemical behaviour of7Be recoils formed through12C/γ, nα/7Be reaction in several phthalocyanine complexes

The chemical effect of⁷Be recoils formed through a¹²C/, n/⁷Be process from ligand carbon atoms was investigated in a several phthalocyanines. It was found that⁷Be-phthalocyanine was synthesized by⁷Be recoil. Net radiochemical yields of⁷Be-phthalocyanine were estimated to be 10–20% for copper and zinc phthalocyanines, while for metal-free phthalocyanines, yields above 90% were obtained.     

Discovery of a novel serine protease inhibitor utilizing a structure-based and experimental selection of fragments technique

We report a set of strategies to develop novel ligands (Structure Based and Experimental Selection of Fragments: SbE-SF). First, a docking simulation utilizing DOCK3.5 is performed in order to screen the fragment database, which was generated with the in-house program FRAGMENT++ specifically for docking simulation purposes. Although the affinity of these small molecules (fragments) is expected to be low, the affinity of fragments selected by computation is assayed by experiment to determine which ones can be potent inhibitors. After determining such key fragments, additional fragments are attached to the key ones in order to increase the binding affinity,taking into account the binding modes predicted by computation. This method has been applied to a thrombin inhibitor study, resulting in the discovery of a novel inhibitor exhibiting pIC₅₀ = 7.9.     

Selective monofluorination of diols using DFMBA

Selective monofluorination of 1,2- and 1,3-diols was achieved by reaction with DFMBA. The method is applicable for the synthesis of optically-active fluorohydrin derivatives.     

First systematic band-filling control in organic conductors

The systematic study of band-filling control for four kinds of organic conductors with various kinds of ground states has succeeded. (1) By partial substitution of (GaCl(4))(-) by (MCl(4))(2-) [M = Co, Zn] in the anion blocking layer of lambda-ET(2)(GaCl(4))(-) [ET = bis(ethylenedithio)tetrathiafulvalene], single crystals of lambda-ET(2)(GaCl(4))(-)(1-x)(MCl(4))(2-)(x) [x = 0.0, 0.05, 0.06] have been obtained. The resistivity at room temperature decreases from 3 Omega cm (x = 0.0) to 0.1 Omega cm (x = 0.06) by doping to the antiferromagnet with an effective half-filled band (x = 0.0). (2) Another 2:1 (donor/anion) salt, delta'-ET(2)(GaCl(4))(-), which is a spin gap material, has been doped as delta'-ET(2)(GaCl(4))(-)(1-x)(MCl(4))(2-)(x) [x = 0.05, 0.14]. The resistivity is lowered from 10 Omega cm (x = 0.0) to 0.3 Omega cm (x = 0.14). For both 2:1 salts, the semiconducting behaviors have transferred to relatively conductive semiconducting ones by doping. (3) As for alpha-type 3:1 salts, the parent material is in a charge-ordering state such as alpha-(ET(+)ET(+)ET(0))(CoCl(4))(2-)(TCE), where the charge-ordered donors are dispersed in the two-dimensional conducting layer. Although the calculation of alpha-ET(3)(CoCl(4))(2-)(TCE) shows a band-insulating nature, and the crystal structure analysis indicates that this material is in a charge-ordering state, the metallic behavior down to 165 K has been observed. With doping of (GaCl(4))(-) to the alpha-system, isostructural alpha-ET(3)(CoCl(4))(2-)(1-x)(GaCl(4))(-)(x)(TCE) [x = 0.54, 0.57, 0.62] have been afforded, where the pattern of the horizontal stripe-type charge ordering changes with an increase of x. (4) By doping (GaCl(4))(-) to the 3:2 gapless band insulator which is isostructural to beta'-ET(3)(MCl(4))(2)(2-) [M = Zn, Mn], the obtained beta'-ET(3)(CoCl(4))(2-)(2-x)(GaCl(4))(-)(x) [x = 0.66, 0.88] shows metallic behavior down to 100 and 140 K, respectively. They are the first metallic states in organic conductors by band-filling control of the gapless band insulator. These systematic studies of band-filling control suggest that the doping to the gapless band insulator with a pseudo-1/2-filled band is most effective.