Highly Selective Artificial Cholesteryl Crown Ether K+‐Channels

The bacterial KcsA channel conducts K⁺ cations at high rates while excluding Na⁺ cations. Herein, we report an artificial ion‐channel formed by H‐bonded stacks of crown‐ethers, where K⁺ cation conduction is highly preferred to Na⁺ cations. The macrocycles aligned along the central pore surround the K⁺ cations in a similar manner to the water around the hydrated cation, compensating for the energetic cost of their dehydration. In contrast, the Na⁺ cation does not fit the macrocyclic binding sites, so its dehydration is not completely compensated. The present highly K⁺‐selective macrocyclic channel may be regarded as a biomimetic of the KcsA channel.     

On the multiplicity of solutions in generation capacity investment models with incomplete markets: a risk-averse stochastic equilibrium approach

Investment in generation capacity has traditionally been evaluated by computing the present value of cashflows accruing from new equipment in a market with globally optimized capacity mix. The competition and risk that now prevail in the sector may require a more refined analysis. We consider a competitive market with agents investing in some mix of capacities: the risk exposure of a plant and the attitude towards risk of the owner depend on the plant and the portfolio of its capacities. They may also depend on hedging contracts acquired by the investor on the market if such contracts exist. We represent these effects through equilibrium models of generation capacity in incomplete markets. The models come in different versions depending on the portfolio of physical plants and hedging contracts. These modify the long-term risk of the plants, the attitude of the owners towards risk, and hence the incentive to invest. The models involve risk-averse producers and consumers, and their behavior is represented by convex risk measures. We use degree theory to prove existence and explore multiplicity of equilibrium solutions.     

One Pot Synthesis of Bisphosphonate Esters: A Way to Synthesize Tetraphosphonate Esters

Abstract

Several methods for the preparation of symmetrical bisphosphonates of general type (RO)₂P(O)(R′OH)P(O)(OR)₂, have been developed, and investigated for their pharmacological. Pharmacological screening of these bisphosphonates have shown that these compounds have potent cardiovascular activity and are. potentialy useful in the treatment of hypertension. In this work we described of new method “one pot” for the synthesis of hydroxy bis and tetra phosphonates (I, II, III and IV).     

Preparation of 1,3-Dithiol-2-ones from 1,2-Bis-triisopropylsilanylsulfanyl Alkenes Under Mild Acidic Conditions

1,2-Bis-triisopropylsilanylsulfanyl alkenes are readily converted to 1,3-dithiol-2-ones with phosgene under very mild acidic conditions at room temperature.     

Hydrophobic Effect Driven Esterification of Sucrose in Aqueous Medium 1

Sucrose is an attractive molecule for chemistry because it is pure, abundant, inexpensive, and produced from renewable sources. Amoung its derivatives, sucrose esters are valuable targets for the chemical valorization of sugar, either as polymerizable derivatives, surfactants, or non-caloric fat substitutes.² But although such potential commercially attractive sucrose derived molecules can be targeted, methods consistent with low-cost sucrouse diversification have still to be found. The issue of the solvent being critical, we have been interested in evaluating water as a possible solvent for some transformations of sucrose, and we report herein some preliminary results on the esterification of this sugar in basic aqueous medium.