Structural and conformational studies on citreoviridinol and isocitreoviridinol: syntheses of some 2,6-dioxabicyclo[3.2.1]octanes

Isocitreoviridinol has been newly isolated from the mycelium of $\text{Penicillium citreo-viride}$ B. (IFO 6050) together with citreoviridinol, and their stereostructures have also been elucidated by means of chemical method: the 2,6-dioxabicyclo[3.2.1]octanes have been made, one of which is regarded as a promising synthetic intermediate of citreoviridinol. In addition, isocitreoviridinol diacetate has been derived from citreoviridin in 3 steps.     

Rapid and highly sensitive method for determination of methamphetamine and amphetamine in urine by electron-capture gas chromatography

A rapid and sensitive method for determination of methamphetamine and amphetamine in urine was developed by using electron-capture gas chromatography. The extraction procedure, the experimental conditions for pentafluorobenzoyl derivative formation and the percentage recovery of the drugs from urine are described. The pentafluorobenzoyl derivative of methamphetamine showed a higher electron-capture sensitivity and was detected in at least 23-fold lower concentration than the heptafluorobutyryl derivative which is commonly used as a derivatizing agent for the amine. The detection limit of pentafluorobenzoyl derivatives of methamphetamine and amphetamine was ca. 10 pg. A concentration as low as 10 ng/ml of methamphetamine and amphetamine in urine was easily detected by this method.     

Preconcentration of copper,lead, cadmium and zinc ions from water with 2-mercaptobenzothiazole loaded on glass beads with the aid of collodion

2-Mercaptobenzothiazole (MBT) loaded on glass beads with the aid of collodion was prepared and used for selective preconcentration of μg l^?1 levels of copper(II) and lead from aqueous solutions. Copper and lead were quantitatively retained on the loaded beads from solutions of pH 5.0–6.0 and >5.0, respectively, while cadmium(II) and zinc(II) were retained at ? pH 6.0 and 7.0, respectively. The retention capacity of the loaded beads was ca. 108 μg Cu g^?1 (1.7 μmol g^?1) at pH 5.5 for beads of 0.3–0.4 mm diameter. The mole ratios of MBT to copper(II) and lead(II) were ca. 10 and 45, respectively, regardless of the amount of MBT loaded on the beads. Copper was completely retained on the column at a high flow rate (21.7 ml min^? cm^?2) and lead(II) at up to 12.7 ml min^? cm^?2. Cadmium(II) and zinc(II) were not retained quantitatively even at low flow rates (< 1.2 ml min^?1 cm^?2). Thus, selective preconcentration of copper and lead was achieved by passing the sample through the column at high flow rate at pH 6.5. The copper and lead retained on the column were complete eluted together with the collodion with 5 ml of MIBK by batch-mode elution, and determined directly by one-drop atomic absorption spectrometry. Copper(II) and lead(II) in several kinds of water were determined.     

Core-exciton induced resonant photoemission in the covalent semiconductor black phosphorus

Valence band photoemission spectra of black phosphorus have shown anomalous behavior at the excitation of 2p core-excitons. The intensity of the 2.7 ev peak shows a clear Fano type interference due to a direct recombination of core-excitons leaving one hole in valence bands. Besides, strong enhancement of the 10.8 eV peak is interpreted as due to a core-exciton induced resonance with two-hole final states. The role of core-excitons as intermediate states for photoemission processes is newly revealed in the experiments.     

The resolution of α-amino acid by chiral polymer-copper complex

The (N-benzyl-l-leucinato) copper(II) complex was shown pH titration to coordinate l-amino acids more strongly than d enantiomers. A chiral polymer complex, containing N-alkylated amino acid residue and copper(II) ion, was used partially to resolve some optically active amino acids. Unlike the (N-benzyl-l-amino acidate)-copper(II) complex, the polymer—copper(II) complex coordinates d-amino acids more strongly than l-enantiomers; the effect was explained by formation of (N,N-dialkylated-amino acidate) copper(II) complex in the polymer.     

A structure analysis of Ag-adsorbed Si(111) surface by LEED/CMTA

The Ag induced superstructures on the Si(111) surface have been studied by low energy electron diffraction constant momentum transfer averaging (LEED/CMTA) technique. The vertical displacements of the atoms are determined from the analysis of the specularly reflected (00) beam intensities. Unexpected behavior of the Ag atoms is clarified: For the √3 × √3-Ag surface it is verified that the Ag atoms are embedded in the first double layer of Si, leading to a considerable rearrangement of the substrate. In contrast, for the 3 × 1-Ag surface, the Ag atoms are riding on the Si surface and the reconstruction of the substrate is small.