Search results for "stereochemistry"
showing 10 items of 4831 documents
ChemInform Abstract: Transformation of Artemisin Into Artapshin and 8α-Hydroxy-11β,13-Dihydrobalchanin.
1987
Abstract Partial syntheses of the sesquiterpene lactones artapshin ( 1 ) and 8α-hydroxy-11β, 13-dihydrobalchanin ( 2 ) from artemisin ( 3 ) are described.
An efficient entry to optically active anti- and syn-beta-amino-alpha-trifluoromethyl alcohols.
2008
The reaction of chiral 5,6-dihydro-2H-1,4-oxazin-2-ones with TMSCF3 in the presence of a suitable activator leads to trifluoromethyl lactols, which can be selectively reduced to anti-beta-amino-alpha-trifluoromethyl alcohols. The corresponding syn diastereoisomers are obtained when the starting imines are reduced and the nitrogen atom is conveniently protected. In addition, a novel rearrangement of the CF3 group in the lactol intermediates has been observed. This represents a formal CF3 addition to the imine function in the starting substrates.
ChemInform Abstract: Catalytic Enantioselective Conjugate Alkynylation of α,β-Unsaturated 1,1,1-Trifluoromethyl Ketones with Terminal Alkynes.
2016
Financial support (Grant CTQ2013-47494-P) from the Ministerio de Economia y Competitividad (MINECO-Gobierno de Espana). A.S.M. thanks the MINECO for a predoctoral grant (FPI program). Access to NMR and MS facilities from the Servei Central de Suport a la Investigacio Experimental (SCSIE)-UV is also acknowledged.
ChemInform Abstract: Catalytic Asymmetric Conjugate Addition of Terminal Alkynes to β-Trifluoromethyl α,β-Enones.
2014
The first enantioselective conjugate alkynylation of β-trifluoromethyl α,β-enones (II) using terminal alkynes (I) and a taniaphos-Cu(I) complex as catalyst is described.
Innentitelbild: Synthesis and Application of β-Substituted Pauson-Khand Adducts: Trifluoromethyl as a Removable Steering Group (Angew. Chem. 20/2013)
2013
Inside Cover: Synthesis and Application of β-Substituted Pauson-Khand Adducts: Trifluoromethyl as a Removable Steering Group (Angew. Chem. Int. Ed. 2…
2013
Silicon-guided rearrangement of 10-methyl-4,5-epoxydecalins. Methyl versus methylene migration
2003
The Lewis acid-promoted rearrangement of two 10-methyl-4,5-epoxydecalins bearing a trimethylsilyl (TMS) group on C-1 or C-9 has been studied. Migration of the C-9 methylene group to C-5 is the major reaction pathway when the TMS and the oxirane groups are on the same ring while methyl migration results exclusively when they are on different rings.
Application of Molecular Topology to the Prediction of the Reaction Yield and Anticancer Activity of Imidazole and Guanidine Derivatives
2013
In this study molecular topology based QSAR has been applied to predict the reaction yield and anticancer activity of 18 imidazole and guanidine derivatives. Four properties were evaluated, namely reaction yield, anti prostatic-cancer activity, anti breast-cancer activity and anti lung-cancer activity. The four models have been validated by both internal and cross validation, and also by randomness tests. The results obtained are in full agreement with the experimental results and confirm the precision, accuracy and robustness of the method followed. After carrying out a virtual screening upon such models, new imidazole and guanidine derivatives with potential anticancer activity are propos…
Absolute Configuration Determination of 2,3-Dihydro-1H,5H-pyrazolo[1,2-a]pyrazoles Using Chiroptical Methods at Different Wavelengths
2016
A correlation between the absolute configuration and chiroptical properties of nonracemic 1,6,7-trisubstituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazoles was studied. A series of 16 novel representatives were prepared by Cu-catalyzed [3 + 2] cycloadditions of racemic (Z)-2-benzylidene-5-oxopyrazolidin-2-ium-1-ides to tert-butyl (S)-(3-oxopent-4-yn-2-yl)carbamate, and their structures were determined by NMR, VCD, ECD, and X-ray diffraction. A clear correlation between the sign of specific rotation and configuration at position C(1) allows for easy determination of the absolute configuration of 1,6,7-trisubstituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazoles by ECD and NMR. While VCD, requirin…