Enantioselective Synthesis of α,β-Disubstituted-β-amino Acids
摘要:
Highly diastereoselective and enantioselective addition of N-benzylhydroxylamine to imides 17 and 20-30 produces alpha,beta-trans-disubstituted N-benzylisoxazolidinones 19 and 31-41. These reactions proceed in 60-96% ee with 93-99% de's using 5 mol % of Mg(NTf2)2 and ligand 18. The product isoxazolidinones can be hydrogenolyzed directly to provide alpha,beta-disubstituted-beta-amino acids.
Enantioselective Cycloadditions with α,β-Disubstituted Acrylimides
作者:Mukund P. Sibi、Zhihua Ma、Kennosuke Itoh、Prabagaran Narayanasamy、Craig P. Jasperse
DOI:10.1021/ol050599d
日期:2005.6.9
The use of N-H imide templates provides a solution to the problem of rotamer control in Lewis acid catalyzed reactions of α,β-disubstituted acryloyl imides. Reactions proceed through the s-cis rotamer and with improved reactivity because A(1,3) strain is avoided. Enantioselective nitrone, nitrile oxide, and Diels-Alder cycloadditions demonstrate the principle.
Enantioselective Radical Addition/Trapping Reactions with α,β-Disubstituted Unsaturated Imides. Synthesis of <i>a</i><i>nti</i>-Propionate Aldols
作者:Mukund P. Sibi、Goran Petrovic、Jake Zimmerman
DOI:10.1021/ja043371e
日期:2005.3.1
This manuscript describes a highly diastereo- and enantioselective intermolecular radical addition/hydrogen atom transfer to alpha,beta-disubstituted enoates. Additionally, we show that anti-propionate aldol-like products can be easily prepared from alpha-methyl-beta-acyloxyenoates in good yields and high diastereo- and enantioselectivities.