Synthesis of Methyl α-D-Kijanoside

Abstract

In 1981, Mallams and coworkers reported¹ the discovery of - D-kijanose 1, a branched-chain nitro sugar, isolated from the antitumor antibiotic kijanimicin by acid hydrolysis. The structure of this unusual carbohydrate was established ^1,2 as 2,3,4,6-tetadeo xy-4 - (methoxy carbony1 amino 1-3-c-methyl - 3 -nitro - D-xylo-hexopyranose by spectroscopic and crystallographic analysis, and comparison with D-rubranitrose 2, a carbohydrate found in the antibiotic rubradirin .³Two other nitro sugars, L-evernitrose 3 and - L-decilonitrose 4⁵, have been discoveredas components of antibiotics.     

Platinum Carbonyl Clusters Chemistry: Four Decades of Challenging Nanoscience

The state of art of the chemical, spectroscopic and structural characterization of platinum carbonyl clusters is reviewed. We begin by enlightening the fundamental contribution given to this chemistry of two great scientists: Paolo Chini and Larry Dahl, two without equal maestros of science and life. We then focus the main body of this review on the challenge represented by studying molecular ions already belonging to the nano regime by size almost 50 years ago, and the challenges their chemistry continues to present also nowadays. In detail, the possible reasons which enable the [Pt_3n (CO)_6n ]^2? oligomers to grow up to n = 10, and why the oligomers with n > 5 may self-assemble in infinite molecular conductor wires are suggested. The interplay between the CO/Pt_surface ratios and electronic effects in driving the platinum cluster from pseudo one- to tri-dimensional globular structures, often representing chunks of the fcc metal lattice or interpenetrated pentagonal prisms and icosahedra, is examined by means of two significant examples. The nanocapacitor behavior of most high-nuclearity carbonyl clusters is briefly recalled and is confirmed by most recent results. The size-induced transition of their metal kernels from insulator to semiconductor and the expected consequences of their eventual transition to a metallic state are also discussed. Finally, we conclude by commenting the present lack of Pt cluster interstitially lodging a main group element and not yet quantitatively-assessed aggregation phenomena in solution, perhaps peculiar of ionic salts of carbonyl clusters, which could make undetectable the NMR signal of any spin-active nuclei beyond a cluster nuclearity of ca. 20–25.     

The role of ethanol in extremely diluted solutions

We carried out a systematic study on the role of ethanol as a cosolvent in the preparation of aqueous extremely diluted solutions (EDS). We have studied EDS prepared in water containing 1 % ethanol and measured their electrical conductivity and heat of mixing to determine how these solutions differ from those prepared in pure water. The results showed that, as occurs also for the EDS in water, these ethanolic solutions exhibit peculiar effects relating to container volume and storage time (ageing). Our data show a remarkable increase in the conductivity of the EDS in 1 % ethanol, as compared to EDS prepared in water solvent, especially after prolonged storage higher than about 250 days (ageing effect). In each case, the values of conductivity for the hydroalcoholic solvent were approximately four times those for water after an ageing period of 2,178 days. For the study of volume effect, we found that conductivity changes only slightly with decreasing volume. It’s important to underline that the studied volumes were in the 0.25/2.0 mL range. The calorimetric measurements reveal that the presence of ethanol affects heat of mixing with alkaline solutions differently compared to the conductivity. In fact, heat of mixing is not very sensitive to the presence of ethanol, but in contrast with conductivity it shows remarkable sensitivity to volume effects. Our working hypothesis to account for these peculiarities is the presence of water molecule aggregates.     

Lyapunov exponent for Lipschitz maps

Nonlinear Dynamics - It is well known that the Lyapunov exponent plays a fundamental role in dynamical systems. In this note, we propose a definition of Lyapunov exponent for Lipschitz maps, which...     

FT-IR analysis of single human normal and leukemic lymphocytes

The infrared spectra of single human normal and leukemic lymphocytes have been obtained by means of the microscope-FT-IR system. Substantial differences between the two kinds of cells have been observed at level of the O-P-O vibrations of the DNA and of the proteic components. This determination opens up the possibility in determining the early stages of leukemia, in following the course of patients under therapy, and in evaluation of the residual neoplastic disease.     

Quantum ratchets in dissipative chaotic systems

Using the method of quantum trajectories, we study a quantum chaotic dissipative ratchet appearing for particles in a pulsed asymmetric potential in the presence of a dissipative environment. The system is characterized by directed transport emerging from a quantum strange attractor. This model exhibits, in the limit of small effective Planck constant, a transition from quantum to classical behavior, in agreement with the correspondence principle. We also discuss parameter values suitable for the implementation of the quantum ratchet effect with cold atoms in optical lattices.     

Dissipative quantum chaos: transition from wave packet collapse to explosion

Using the quantum trajectories approach, we study the quantum dynamics of a dissipative chaotic system described by the Zaslavsky map. For strong dissipation the quantum wave function in the phase space collapses onto a compact packet which follows classical chaotic dynamics and whose area is proportional to the Planck constant. At weak dissipation the exponential instability of quantum dynamics on the Ehrenfest time scale dominates and leads to wave packet explosion. The transition from collapse to explosion takes place when the dissipation time scale exceeds the Ehrenfest time. For integrable nonlinear dynamics the explosion practically disappears leaving place to collapse.     

Recycling asymmetric hydrogenation catalysts by their immobilisation onto ion-exchange resins

New systems based on cationic chiral phosphine-rhodium complexes anchored to a commercial cation-exchange gel-type resin showed high efficiency and easy recycling in the asymmetric hydrogenation of prochiral olefins.