Versatile enantiocontrolled synthesis of (+)-fostriecin

Fostriecin, a potent protein phosphatase inhibitor and antitumor agent, has been enantioselectively synthesized in naturally occurring form via a versatile route, which also allows one to secure all possible stereoisomeres of the C1-C13 fragment including the C11 stereocenter and the geometry of the delta 12-double bond.     

Phase boundary between uniaxial and planar ferromagnets in layered perovskite manganite La2−2xSr1+2xMn2O7 (0.313⩽x⩽0.350)

We have examined magnetizations as a function of temperature and magnetic field in layered perovskite manganites La_2−2xSr_1+2xMn₂O₇ single crystals (x=0.313, 0.315, 0.318, 0.320 and 0.350) in order to determine the phase boundary between two ferromagnets (one is an uniaxial ferromagnet whose easy axis is parallel to the c-axis and the other is a planar ferromagnet whose easy axis is within the ab-plane) and following results are obtained: (i) all the present manganites exhibit magnetic transitions from a ferromagnet to a paramagnet at 76, 107, 116, 120 and 125 K for x=0.313, 0.315, 0.318, 0.320 and 0.350, respectively; (ii) for x=0.318, 0.320 and 0.350, the magnetic structure is a planar ferromagnet below Curie temperature; (iii) for x=0.313 and 0.315, the magnetic structure changes from an uniaxial to a planar ferromagnet at 66 and 85 K, respectively. From the results described above we have constructed the magnetic phase diagram of layered perovskite manganite La_2−2xSr_1+2xMn₂O₇ (0.313?x?0.350).     

Dual Radon transforms on affine Grassmann manifolds

Fix , and let and denote the affine Grassmann manifolds of - and -planes in . We investigate the Radon transform associated with the inclusion incidence relation. For the generic case and n$">, we will show that the range of this transform is given by smooth functions on annihilated by a system of Pfaffian type differential operators. We also study aspects of the exceptional case .

     

Raman spectroscopic study on the structure of water in aqueous solution of zwitterionic surfactants

The structure and hydrogen bonding of water in aqueous solutions of various surfactants were analyzed using the contours of the O-H stretching in the polarized Raman spectra. From the relative intensity of the collective band (C value) corresponding to a long-range coupling of the O-H stretching in the aqueous surfactant solutions, the number of hydrogen bonds disrupted due to the presence of one surfactant molecule (N(corr) value) was evaluated. The N(corr) value for decylsulfobetaine was slightly negative, whereas those for ordinary ionic surfactants such as sodium dodecylsulfate and dodecyltrimethylammonium chloride were large positive values. Furthermore, the N(corr) for carboxybetaine surfactant was a small positive value. These results suggest that zwitterionic surfactants do not disturb the hydrogen-bonded network structure of water significantly, probably due to the counteraction of the electrostriction effect by the proximity between the anionic and cationic groups.     

Stereoselective synthesis of alkynyl C-2-deoxy-beta-d-ribofuranosides via intramolecular nicholas reaction: A versatile building block for nonnatural C-nucleosides

The reaction of 3,5-di-O-benzyl-2-deoxy-d-ribofuranose with various alkynyllithium reagents afforded diastereomeric mixtures of the corresponding ring-opened alkynyldiols. The resulting diastereomeric mixtures were successively treated with Co(2)(CO)(8), a catalytic amount of TfOH, Et(3)N, and iodine in one pot to give alkynyl C-3,5-di-O-benzyl-2-deoxy-beta-d-ribofuranosides with high beta-selectivities. The cobalt-mediated cyclization (intramolecular Nicholas reaction) is reversible; thus, thermodynamically more stable beta-anomers were obtained preferentially. The alkynyl C-deoxyribofuranosides were converted to a variety of C-deoxyribofuranoside derivatives.     

Two Beam Collection Mode Photon Scanning Tunneling Microscope

We studied the image deformation due to the surface inclination of objects in photon scanning tunneling microscopes (PSTM). A novel collection mode PSTM with two light sources is proposed to reduce the deformation and experimental results show that the PSTM system is effective.     

Foreword

The world of catalysis has grown and broadened greatly. The necessity of catalytic technology in solving the contemporary environmental and industrial problems is obvious. Catalysis will be even more important in the next century in relation to global preservation and the supply of energy and resources. What we now need are truly innovative and useful catalysts and what we lack is the methodology of how to make those catalysts. We may have to admit that, in spite of a large number of published papers, there are many mere trial-and-error type repetitions and very few new and significant findings or concepts. This is due to the very complex nature of catalysts, industrial catalysts in particular. It is not easy to find the right way to proceed. One positive step to assist in finding the right way may be to promote a close and quick exchange of information and new concepts worldwide. We now start a new journal from Japan affiliated with the Catalysis Society of Japan: Catalysis Surveys from Japan. The main aim of this new journal is to disseminate as early as possible the important findings or movements from Japan which possibly lead to new concepts for the design of useful catalysts. Rapid, invited, short reviews or accounts from academia and industry will constitute the major part of Catalysis Surveys from Japan. Surveys of recent progress and activities in catalytic science and technology and related areas in Japan will be covered regularly as well. The journal will be issued twice a year. We would appreciate it if colleagues around the world who read the articles in Catalysis Surveys from Japan would send us critical comments. If requested and deemed appropriate, the comments will be included in the journal. We will be very happy if this small, new journal stimulates global communication between scientists and engineers in the world of catalysis, and assists in the development of innovative useful catalysts.