Efficient synthesis of an imidazole-substituted delta-amino acid by the integration of chiral technologies

Two methods to produce (2S)-5-amino-2-(1-n-propyl-1H-imidazol-4-ylmethyl)-pentanoic acid were investigated. Diastereoisomeric salt resolution, using the quinidine salt, gave the desired intermediate in 98% ee and 33% yield. Asymmetric hydrogenation of various substrates gave high conversions, with up to 83% ee. Integration of these two approaches via asymmetric hydrogenation of a quinidine salt substrate followed by crystallization provided the desired intermediate in 94% ee and 76% yield.     

The reduction of oxygen in molten lithium carbonate

Oxygen reduction on immersed gold electrodes has been studied in Li₂CO₃ melt under steady-state conditions and by the potential-sweep method. Reaction order measurements have established that the species being reduced is not molecular oxygen, but the peroxide ion. The latter is in chemical equilibrium with molecular oxygen and oxide ions. The rate-determining step is the primary charge transfer

where (O^?) is a transient species. The exchange current densities and activation energies have been determined. Under conditions where O₂^2? diffusion is not limiting (e.g. meniscus electrodes) the rate of neutralization of oxide by CO₂ at the electrode surface is probably rate-determining.     

Reduction of oxygen in lithium-potassium carbonate melt

The oxygen reduction reaction on smooth gold electrodes on Li/K (53: 47 at.%) carbonate melt has been examined in the temperature range 700–800°C. As in previous work on the Na/K melt [2], two chemically produced species (O₂^2? O₂^?) are reduced in parallel steps. The waves for the reduction of these species are close together in this melt, as distinct from those in the Na/K eutectic [2]. Exchange currents are somewhat higher than in the Na/K melt. Again, neutralization of the O^2? ion by CO₂ in rather slow, and may be rate-determining in porous electrodes.     

SICs and Algebraic Number Theory

We give an overview of some remarkable connections between symmetric informationally complete measurements (SIC-POVMs, or SICs) and algebraic number theory, in particular, a connection with Hilbert’s 12th problem. The paper is meant to be intelligible to a physicist who has no prior knowledge of either Galois theory or algebraic number theory.     

Properties of QBist State Spaces

Every quantum state can be represented as a probability distribution over the outcomes of an informationally complete measurement. But not all probability distributions correspond to quantum states. Quantum state space may thus be thought of as a restricted subset of all potentially available probabilities. A recent publication (Fuchs and Schack, , 2009) advocates such a representation using symmetric informationally complete (SIC) measurements. Building upon this work we study how this subset—quantum-state space—might be characterized. Our leading characteristic is that the inner products of the probabilities are bounded, a simple condition with nontrivial consequences. To get quantum-state space something more detailed about the extreme points is needed. No definitive characterization is reached, but we see several new interesting features over those in Fuchs and Schack (, 2009), and all in conformity with quantum theory.