Uronic acids are carbohydrates carrying a terminal carboxylic acid and have a unique reactivity in stereoselective glycosylation reactions. Herein, the competing intramolecular stabilization of... Show moreUronic acids are carbohydrates carrying a terminal carboxylic acid and have a unique reactivity in stereoselective glycosylation reactions. Herein, the competing intramolecular stabilization of uronic acid cations by the C-5 carboxylic acid or the C-4 acetyl group was studied with infrared ion spectroscopy (IRIS). IRIS reveals that a mixture of bridged ions is formed, in which the mixture is driven towards the C-1,C-5 dioxolanium ion when the C-5,C-2-relationship is cis, and towards the formation of the C-1,C-4 dioxepanium ion when this relation is trans. Isomer-population analysis and interconversion barrier computations show that the two bridged structures are not in dynamic equilibrium and that their ratio parallels the density functional theory computed stability of the structures. These studies reveal how the intrinsic interplay of the different functional groups influences the formation of the different regioisomeric products. Show less
Uronic acids are carbohydrates carrying a terminal carboxylic acid and have a unique reactivity in stereoselective glycosylation reactions. Herein, the competing intramolecular stabilization of... Show moreUronic acids are carbohydrates carrying a terminal carboxylic acid and have a unique reactivity in stereoselective glycosylation reactions. Herein, the competing intramolecular stabilization of uronic acid cations by the C-5 carboxylic acid or the C-4 acetyl group was studied with infrared ion spectroscopy (IRIS). IRIS reveals that a mixture of bridged ions is formed, in which the mixture is driven towards the C-1,C-5 dioxolanium ion when the C-5,C-2-relationship is cis, and towards the formation of the C-1,C-4 dioxepanium ion when this relation is trans. Isomer-population analysis and interconversion barrier computations show that the two bridged structures are not in dynamic equilibrium and that their ratio parallels the density functional theory computed stability of the structures. These studies reveal how the intrinsic interplay of the different functional groups influences the formation of the different regioisomeric products. Show less
Sasiadek, M.; Kocer, N.; Szikora, I.; Vilela, P.; Muto, M.; Jansen, O.; ... ; Ricci, P. 2020
This document sets out standards for training in Interventional Neuroradiology (INR) in Europe. These standards have been developed by a working group of the European Society of Neuroradiology ... Show moreThis document sets out standards for training in Interventional Neuroradiology (INR) in Europe. These standards have been developed by a working group of the European Society of Neuroradiology (ESNR) and the European Society of Minimally Invasive Neurological Therapy (ESMINT) on the initiative and under the umbrella of the Division of Neuroradiology/Section of Radiology of the European Union of Medical Specialists (UEMS). Show less
A new technique for the imaging of flow territories of individual extra- and intracranial arteries is presented. The method is based on balanced pseudocontinuous arterial spin labeling but employs... Show moreA new technique for the imaging of flow territories of individual extra- and intracranial arteries is presented. The method is based on balanced pseudocontinuous arterial spin labeling but employs additional time-varying gradients in between the radiofrequency pulses of the long labeling train. The direction of the additional gradient vector is perpendicular to the selected artery and its azimuthal angle is switched after every radiofrequency pulse. The phases of the radiofrequency pulses are adopted to cancel out the phase accrual of the spins at the center of the target vessel due to the extra applied gradients. This results in efficient inversion at the targeted position, whereas elsewhere time-varying phase changes will result in marginal inversion efficiency. By changing the moment of the added gradients, the size of the labeling focus can be adjusted. Influence of the temporal order of the additional gradients on the labeling efficiency and on the selectivity was investigated by simulations and experimental measurements. In a volunteer study, the acquisition of high signal-to-noise ratio flow territory images of small branches of the anterior cerebral artery distal to the circle of Willis was demonstrated. This shows the method's flexibility for dealing with complicated arterial geometries and its ability to super-selectively label small intracranial arteries. Magn Reson Med 64:777-786, 2010. (C) 2010 Wiley-Liss, Inc. Show less
