Para-Carboxy Modified Amphiphilic Calixarene, Self-Assembly and Interactions with Pharmaceutically-Relevant Molecules

The self-assembly properties of the amphiphilic 5,11,17,23-tetra-carboxy-25,26,27,28-tetradodecyloxycalix[4]arene have been investigated at the air–water interface as monomolecular Langmuir layers and in water. The interactions of this amphiphile with salicylic acid (SA), acetyl-salicylic acid (ASA) and acetaminophene (APAP) have been studied at the air–water interface by means of the Langmuir balance technique. It has been demonstrated that the calix-arene molecules, when self-assembled as Langmuir monolayers, have the ability to interact with all the tested compounds. While APAP causes a stabilization of the monolayer, ASA and SA cause a slight loss of stability and a drastic change of the compressibility of the monolayer. The study of the self-assembly properties of the title compound in water revealed that this amphiphile can be self-assembled as solid lipid nanoparticles (SLNs). The atomic force microscopy investigations of the colloidal suspension, spread on a solid surface and dried, revealed the coexistence of the SLNs with layered structures

Temperature Induced Fracturing of Rock Salt Mass

During the operation of gas storage caverns in rock salt mass the internal pressure changes during filling and withdrawal phases. Additionally temperature variations occur versus operation time. During withdrawal phases the temperature decreases which can lead to stress states in tensile regions at the cavern wall. Because the tensile strength of rock salt is relatively low compared to its compressive strength it is likely that tensile stresses lead to discrete fractures orthogonal to the direction of the tensile stresses. If fractures of this kind are created – whether vertical or horizontal – the gas will penetrate into the fracture at the relevant pressure and further extend the length of the fractures under certain circumstances. There are currently no theoretical approaches describing the manner in which the fractures might propagate into the not by temperature changes influenced rock salt mass during repeated cyclic pressure changes. This aspect is topic of prospective research. Salt caverns cannot be entered but only explored by sonar measurements, with which it is not possible to detect tensile fractures at the cavern wall. Within this paper examples from mining configurations will be shown where temperature changes lead to tensile fractures in the surrounding rock salt. These fractures have been well mapped while the temperature development is well documented. The paper deals with recalculations under consideration of different salt properties of the temperature distributions and the resulting stress state in the surrounding rock salt mass. The stress calculation results and the consequences for the dimensioning of natural gas caverns are going to be discussed and assessed

Asymmetric synthesis of beta-substituted Baylis-Hillman products via lithium amide conjugate addition

A three-step protocol for the asymmetric synthesis of a range of beta-substituted Baylis-Hillman products has been developed. This procedure involves the diastereoselective conjugate addition of lithium (R)-N-methyl-N-(alpha-methylbenzyl) amide to an alpha, beta-unsaturated ester to generate an N-protected beta-amino ester in high de. Subsequent asymmetric aldol reaction via deprotonation with LDA, transmetallation with B(OMe)(3) and addition of an aldehyde gives a range of syn-aldol products in moderate to high de. Purification of the syn-aldol products to homogeneity followed by tandem N-oxidation and Cope elimination gives the desired b-substituted Baylis-Hillman products in good yield and high de and ee. (C) 2007 Elsevier Ltd. All rights reserved.</p