1,721,126 research outputs found
Selective catalytic hydrogenation of g-amino a,b-unsaturated esters in the presence of hydrogenable protecting groups
No full textiodolactonization of 3-amino 4-pentenoic acid: a stereoselective synthesis of syn-g-hydroxy b-amino acids
Full text linkThe reaction of (S)-3-N-Cbz-4-pentenoic acid with iodine in acetonitrile in the presence of AgOTf gave the corresponding cis-iodo-lactone in excellent yield and in a highly diastereo-selective manner. The substitutions of the iodine by different Grignard reagents in the presence of CuI and the subsequent conversions into the functionalized syn-g-hydroxy-b-amino acids have been investigated. By the above reaction sequence,
(3S,4S)-3-amino-4-hydroxy-5-cyclohexyl pentanoic acid was synthesized with high enantioselectivity
Etude échographique et traitement chirurgical de l’insuffisance de la veine saphène antérieure de cuisse.
No full textStudy and prototyping of a permanent magnetic suspension for the alignment by gravity of the elevation angle for the next generation lunar reflector experiment
No full textThe research is focused on the design of a magnetic suspension employable to achieve Earth-pointing for a space reflector or other devices integrated on a lunar lander or rover deck just utilizing the local gravity. The classical solution is based on heavy and expensive actuators, still representing critical subsystems as their failure might often lead to severe or catastrophic effects on the mission. This proposal is based on a magnetic suspension realized with two small magnetic bearings. They can be contained in a cylinder smaller than 15 mm diameter and 20 mm height and capable of supporting 20 N. After designing, a prototype has been built employing commercially available neodymium permanent magnets. Preliminary results of carrying capacity have been correlated in good agreement both with analytical calculation and finite elements analysis. The study has showed that the goal of 20 N can be attainable. The structure stiffness and carrying load for the accurate alignment of each stator/rotor pack is crucial for the performance of the suspension. The next step is the design and build-up of an upgraded model to be qualified for the mission dynamic loads
Synthesis of both enantiomers of 4-vinyl oxazolidin-2-one from a single precursor: D-isoascorbic acid
Full text linkA convenient synthesis of (S)- and (R)-4-vinyl oxazolidin-2-one
from the same inexpensive starting material, D-isoascorbic acid, is described. The two compounds were obtained in 44% and 38% yield, respectively, by operationally simple steps. This approach is a suitable alternative to the literature methods and enhances the synthetic utility of these intermediates
Aromatic Prenyltransferases from Plant Cell Cultures: Specificity and Biotransformation Studies
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