Staudinger Ligation of α-Azido Acids Retains Stereochemistry
摘要:
The Staudinger ligation of peptides with a C-terminal phosphinothioester and N-terminal azide is an emerging method in protein chemistry. Here, the first Staudinger ligations of nonglycyl azides are reported and shown to proceed both in nearly quantitative yield and with no detectable effect on the stereochemistry at the a-carbon of the azide. These results demonstrate further the potential of the Staudinger ligation as a general method for the total synthesis of proteins from peptide fragments.
An Expedient Reduction of<i>sec</i>-Phosphine Oxides to<i>sec</i>-Phosphine-boranesby BH<sub>3</sub>˙SMe<sub>2</sub>
作者:K. Michał Pietrusiewicz、Marek Stankevič
DOI:10.1055/s-2003-39304
日期:——
Secondary phosphine oxides can be expeditiously converted into secondary phosphine-boranes by treatment with an excess of BH3ËSMe2 at room temperature. Selectivity of the conversion towards the formation of secondary phosphine-boranes is greatly improved by the addition of a small amount of water to the reaction mixture.
7a-f can be diastereoselectively alkylated, using O-protected amino-alcohols as chiral inducers, to furnish alpha-substituted beta-amidophosphine boranes 8a-f and 9-12 with up to 72% diastereoisomeric excess. Selective deprotection afforded optically pure carboxylic derivative 13 which is a key intermediate for the synthesis of various potential chiral ligands for asymmetriccatalysis.
Development of pinene-derived N,P ligands and their utility in catalytic asymmetric hydrogenation
作者:J. Johan Verendel、Pher G. Andersson
DOI:10.1039/b713257n
日期:——
New diastereomeric N,P-ligands, derived from the natural product (+)-α-pinene, have been synthesized and evaluated in iridium-catalyzed asymmetrichydrogenation. The ligands are tetrahydroquinoline derivatives synthesized directly from commercially available α-pinene utilizing resolution or recrystallization to separate diastereomers. In reduction of a range of different trisubstituted alkenes the
Regio- and Stereoselective Hydrophosphination Reactions of Alkynes with Phosphine−Boranes: Access to Stereodefined Vinylphosphine Derivatives
作者:David Mimeau、Annie-Claude Gaumont
DOI:10.1021/jo030096q
日期:2003.9.1
Vinylphosphine-borane complexes are easily synthesized by regio- and stereoselective hydrophosphination of terminal alkynes with use of secondary phosphine-boranes as hydrophosphinating agent. The regioselectivity of the reaction is efficiently controlled by the choice of the activation process: thermal or metal catalyst activation. The vinylphosphine derivatives are purified by chromatography on silica
complexes are easily synthesized by palladium-catalyzed C−P cross-coupling of vinyltriflates with secondary phosphine−boranes. This method allows the synthesis of phosphine derivatives not always easily accessible by other approaches. The vinylphosphine derivatives are purified by chromatography on silica gel. The versatility of the method is proved by using various triflates and diaryl-, dialkyl- and al