Novel syntheses of murrayaquinone A and furostifoline through 4-oxygenated carbazoles by allene-mediated electrocyclic reactions starting from 2-chloroindole-3-carbaldehyde.

The formal total synthesis of murrayaquinone A (1) and the total synthesis of furostifoline (5) were completed by the construction of 4-oxygenated 3-methylcarbazoles 7 based on a new type of electrocyclic reaction through 2-alkenyl-3-allenylindole intermediates 8 derived from the 2-alkenyl-3-propargylindoles 9, starting from 2-chloroindole-3-carbaldehyde (11). The N,O-bisbenzyloxymethyl group of 16c and 22 underwent a Birch reduction followed by treatment with Triton B to produce the known 4-hydroxy-3-methylcarbazole (7a) and 4-hydroxy-3-methylfuro[3,2-a]carbazole (7b) as precursors of murrayaquinone A (1) and furostifoline (5), respectively. The trifluoromethanesulfonyloxy-3-methylfuro[3,2-alcarbazole (24), prepared from 7b, was subjected to reductive cleavage to provide furostifoline (5).     

Conformational analysis of nucleic acid molecules with flexible furanose rings in dihedral angle space

The computational algorithm that works in the coordinate space of dihedral angles (i.e., bond lengths and bond angles are kept fixed and only rotatable dihedral angles are treated as independent variables) is extended to deal with the pseudorotational m otion of furanose rings by introducing a variable of pseudorotation. Then, this algorithm is applied to a distance geometry calculation that generates three-dimensional (3D) structures that are consistent with given constraints of interatomic distances. This method efficiently generates 3D structures of an RNA hairpin loop which satisfy a set of experimental NMR data. © 1996 by John Wiley & Sons, Inc.     

Negative energy correction for nuclear polarization in muonic atoms

Negative energy corrections to the conventional calculations of nuclear polarization effects in muonic atoms are calculated. It is shown that the corrections are negligible as far as the NP effects due to low lying nuclear states and states in the giant resonance regions are concerned. However, the formula used for the muonic NP calculations breaks down if nuclear excitations with larger energies than the muonic mass are considered. This means that the method cannot be used for calculations of NP effects in electronic atoms. This revised version was published online in August 2006 with corrections to the Cover Date.     

Neutral radical detection in silane glow-discharge plasma using coherent anti-stokes raman spectroscopy

RF glow discharges of silane have been investigated using CARS technique, and a weak signal assigned to the ν₁ Q-band of SiH₂ has been observed at around 2030 cm^?1 for the first time. The number density of SiH₂ in the plasma has been estimated and is discussed in relation to the magnitude of SiH₄ dissociation rate independently determined also by CARS.     

Aromatic ring favorable and efficient H-D exchange reaction catalyzed by Pt/C

An effective and applicable Pt/C-catalyzed deuteration method of aromatic rings using D₂O as a deuterium source under hydrogen atmosphere was developed. Five percent Pt/C would lead to quite effective H-D exchange results on the aromatic ring systems. The reaction is general for a variety of aromatic compounds including biologically active compounds.     

High-resolution experimental techniques for cryomechanics—A study of mechanical behavior of materials at 4.2K

High-resolution measurement techniques to quantify minuscule energies (∼0.1 mJ) and microscopic displacements (∼0.01 μm) in a cryomechanics experiment are described. With cryomechanics we study mechanical behavior of materials at 4.2 K. In addition to energy and displacement measurements, we measure acoustic emission and temperature. Preliminary results of tensile and friction tests are presented to demonstrate the key features of our experimental techniques.