Highly Diastereoselective Nitrone Cycloaddition onto a Chiral Ketene Equivalent: Asymmetric Synthesis of Cispentacin
作者:Varinder K. Aggarwal、Stephen J. Roseblade、Juliet K. Barrell、Rikki Alexander
DOI:10.1021/ol025665f
日期:2002.4.1
[reaction: see text] A highly diastereoselective intramolecular nitrone cycloaddition onto a chiral ketene equivalent, obtained by Horner-Wadsworth-Emmons olefination of either enantiomer of bis-sulfinyl phosphonate6, is described. Cycloaddition gave 5,5-disubstituted isoxazolidine 10 in good yield as a single diastereomer. Catalytic hydrogenolysis of 10 furnished either enantiomer of optically pure
Stereoselective Epoxidation of bis-Sulfinyl Alkenes and Application to the Asymmetric Synthesis of α-Substituted Carboxylic Acids
作者:Varinder K. Aggarwal、Julia M. Worrall、Rikki Alexander
DOI:10.1080/10426509708545544
日期:1997.1.1
thioacetals 3 can be easily prepared in optically pure form and react diastereoselectively with metal peroxides. The resulting bis-sulfinyl oxiranes can be converted in a single step to α-substituted acids.
The use of enantiomerically pure ketene dithioacetal bis(sulfoxides) in highly diastereoselective intramolecular nitrone cycloadditions. Application in the total synthesis of the β-amino acid (–)-cispentacin and the first asymmetric synthesis of cis-(3R,4R)-4-amino-pyrrolidine-3-carboxylic acid
作者:Varinder K. Aggarwal、Stephen Roseblade、Rikki Alexander
DOI:10.1039/b212719a
日期:2003.2.11
corresponding 5,5-disubstituted isoxazolidine as a single diastereomer in good yield. This reaction has been used as the key step in an asymmetricsynthesis of the naturally occurring antibiotic, (-)-cispentacin. An asymmetricsynthesis of 4-amino-pyrrolidine-3-carboxylic acid has also been carried out using the intramolecular nitrone cycloaddition as the stereocontrolling step.