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A direct diastereoselective aldol reaction of cyclic or acyclic α‐azido ketones with α‐trifluoromethyl (CF3) pyruvate catalysed by DABCO is developed, which allowed the facile access of CF3‐containing multifunctional organoazides with vicinal tetrasubstituted carbons in good to high yields and diastereoselectivities. Moreover, phenylethynyl trifluoro‐ and difluoromethyl ketones are also viable substrates. Up to 50 % enantioselectivity could be obtained in the initial exploration of the catalytic asymmetric variant. [ABSTRACT FROM AUTHOR]

We report the first highly enantioselective construction of silicon‐stereocenters by asymmetric enamine catalysis. An unprecedented desymmetric intramolecular aldolization of prochiral siladials was thus developed for the facile access of multifunctional silicon‐stereogenic silacycles in high to excellent enantioselectivity. With an enal moiety, these adducts could be readily elaborated for the diverse synthesis of silicon‐stereogenic compounds, and for late‐stage modification. [ABSTRACT FROM AUTHOR]

Catalytic asymmetric isomerization of allylic or homoallylic alcohols into synthetically useful carbonyl compounds is a redox‐neutral and 100 % atom‐economic transformation, which is of great interest and has gained increasing attention from both academic and industry. This minireview summarizes the advances in catalytic enantioselective isomerization and it involved tandem reactions over the past five years, also discusses their advantages and limitations, and expounds the synthetic chances still open for further development. [ABSTRACT FROM AUTHOR]

Enantioenriched fluorinated α‐ and β‐amino acids are often encountered in numerous pharmaceuticals and bioactive molecules, and also of great importance as probes in PET and NMR for studying the behavior of enzymes and for incorporation into peptides and drug candidates. Among various synthetic strategies developed, catalytic enantioselective synthesis proves to be one of the most facile and powerful protocols to construct such privileged structures. The past decade has witnessed considerable progress in the catalytic enantioselective construction of chiral fluorinated α‐ and β‐amino acid derivatives with structural diversity. In this review, we summarize these impressive achievements according to the bond‐forming way of fluorinated α‐ or β‐amino acids, respectively, and underline the remaining challenges. This information would provide important guidance and some inspiration for the researchers engaged in organic fluorine and medicinal chemistry. [ABSTRACT FROM AUTHOR]

Azacycles such as indoles and tetrahydroquinolines are privileged structures in drug development. Reported here is an unprecedented regiodivergent intramolecular nucleophilic addition reaction of imines as a flexible approach to access N‐functionalized indoles and tetrahydroquinolines, by the control of reaction at the N‐terminus and C‐terminus, respectively. Using ketimines derived from 2‐(2‐nitroethyl)anilines with isatins or α‐ketoesters, the regioselective N‐attack reaction gives N‐functionalized indoles, while the catalytic enantioselective C‐attack reaction affords chiral tetrahydroquinolines featuring an α‐tetrasubstituted stereocenter. Mechanistic studies reveal that hydrogen‐bonding interactions may greatly facilitate such unusual N‐attack reactions of imines. The utility of this protocol is highlighted by the catalytic enantioselective formal synthesis of (−)‐psychotrimine, and the construction of various fused aza‐heterocycles. [ABSTRACT FROM AUTHOR]

Purpose To determine the temporal evolution of diffusion abnormalities of in vivo experimental spinal cord infarction. Materials and Methods Guided by a digital subtract angiography (DSA) monitor, an agent of 1:1 match of lipiodol and diatrizoate meglumine was injected into bilateral T9-11 intercostal arteries of six dogs to embolize the spinal branches of intercostal arteries and establish the canine spinal cord infarction models. The progression of experimental spinal cord infarction was followed by dynamic MRI, including diffusion-weighted imaging (DWI) on a 1.5 Tesla MR system from one hour to 168 hours postembolization. Apparent diffusion coefficient (ADC) values were calculated and analyzed. At the end of the MRI experiments, the spinal cords of the animals were fixed for histology. Results A total of six experimental models were successfully established. In all cases, DWI images showed slight hyperintensity within one hour postembolization, whereas only four cases presented slight hyperintensity on T2-weighted images. ADC values of spinal cord infarction lesions decreased rapidly at early stage (several hours to 24 hours) and then increased gradually. Conclusion The temporal evolution of diffusion abnormality of experimental spinal cord infarction may help us better understand various DWI signals in the process of spinal cord infarction. J. Magn. Reson. Imaging 2007;26:848-854. © 2007 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]