Enantioselective Synthesis of α-Alkyl,α-Vinyl Amino Acids via [2,3]-Sigmatropic Rearrangement of Selenimides
作者:Alan Armstrong、Daniel P. G. Emmerson
DOI:10.1021/ol1030926
日期:2011.3.4
Chiral α-alkyl,α-vinyl amino acids (quaternary vinyl glycine derivatives) are prepared with high levels of enantiomeric purity by [2,3]-sigmatropicrearrangement of allylic selenimides. The required trisubstituted allylic selenides are prepared by an organocatalytic α-selenenylation of aldehydes followed by Horner−Wadsworth−Emmons (HWE) olefination. Both (E)-and (Z)-geometrical isomers are available
Use of Standard Addition to Quantify In Situ FTIR Reaction Data
作者:George Hutchinson、Calum D. M. Welsh、Jordi Burés
DOI:10.1021/acs.joc.0c02684
日期:2021.1.15
FTIR spectroscopy is a common in situ reaction monitoring technique used in modern academic and industrial environments. The FTIR signals collected during the course of a reaction are proportional to the concentration of the reaction components but not intrinsically quantitative. To make FTIR data quantitative, precalibration or offline analyses of reaction samples are required, which diminishes the
Rationalization of an Unusual Solvent-Induced Inversion of Enantiomeric Excess in Organocatalytic Selenylation of Aldehydes
作者:Jordi Burés、Paul Dingwall、Alan Armstrong、Donna G. Blackmond
DOI:10.1002/anie.201404327
日期:2014.8.11
An unusual solvent‐induced inversion of the sense of enantioselectivity observed in the α‐selenylation of aldehydes catalyzed by a diphenylprolinol silyl ether catalyst is correlated to the presence of intermediates formed subsequent to the highly selective CSe bond‐forming step in the catalytic cycle. This work provides support for a mechanistic concept for enamine catalysis and includes a general
[2,3]-Sigmatropic Rearrangement of Allylic Selenimides: Strategy for the Synthesis of Peptides, Peptidomimetics, and <i>N</i>-Aryl Vinyl Glycines
作者:Alan Armstrong、Daniel P. G. Emmerson、Harry J. Milner、Robert J. Sheppard
DOI:10.1021/jo500341e
日期:2014.5.2
The scope of the NCS-mediated amination/[2,3]-sigmatropicrearrangement of enantioenriched allylic selenides has been expanded to provide access to three new product classes. The use of N-protected amino acid amides provides a novel strategy for accessing peptide chains containing unnatural vinyl glycine amino acid residues. Also reported is the use of amino acid esters, allowing the diastereoselective