Inexpensive, multigram-scale preparation of an enantiopure cyclic nitrone via resolution at the hydroxylamine stage
摘要:
The reduction of the chiral, racemic nitrone MiPNO provides a secondary hydroxylamine. Its O-acylation with O,O'-dibenzoyl-L-tartaric acid anhydride gives two diastereomers, that can be easily separated by selective dissolution in orthogonal solvents. The recovery of the enantiopure nitrone is then carried out in a single step. The process allows the straightforward isolation of (R) and (S)-MiPNO in 57% and 38% yield, respectively, from rac-MiPNO. (C) 2011 Elsevier Ltd. All rights reserved.
The resolution of chiral nitrones via derivatization of hydroxylamines was applied to MiPNO, a new, stable, easily prepared chiral cyclic nitrone. The application of MiPNO in totally regio- and diastereo-selective 1,3-dipolar cycloaddition reactions provides an expeditious enantioselective access to unusual γ-hydroxy α-amino acids.
Totally diastereoselective addition of aryl Grignard reagents to the nitrone-based chiral glycine equivalent MiPNO
作者:Maryse Thiverny、Daniel Farran、Christian Philouze、Véronique Blandin、Pierre Y. Chavant
DOI:10.1016/j.tetasy.2011.07.022
日期:2011.6
The reaction of the chiral nitrone MiPNO (2-isopropyl-2,3-dimethyl-1-oxy-2,3-dihydro-imidazol-4-one) with Grignard reagents is totally diastereoselective. Using simple and functionalized arylmagnesium reagents, enantiopure hydroxylamines were obtained in fair to good yields, which in turn could be easily transformed into new chiral ketonitrones. The preparation of enantiopure L-phenylglycine derivatives is also described. (C) 2011 Elsevier Ltd. All rights reserved.