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Preparation of N ‐Glycosylhydroxylamines and Their Oxidation to Nitrones for the Enantioselective Synthesis of Isoxazolidines

2003; Wiley; Volume: 2003; Issue: 21 Linguagem: Inglês

10.1002/ejoc.200300353

1434-193X

Stefano Cicchi, Marco Marradi, Massimo Corsi, Cristina Faggi, Andrea Goti,

Fluorine in Organic Chemistry

Abstract N ‐benzyl‐ and N ‐methyl‐ N ‐glycosylhydroxylamines 3a − i were conveniently obtained by reaction of sugars with N ‐substituted hydroxylamines according to a novel procedure. Subsequent oxidation occurred at the alkyl group, selectively affording the corresponding C ‐phenyl‐ and C ‐unsubstituted N ‐glycosylnitrones. C ‐phenyl‐ N ‐glycosylnitrones 10 and 13 underwent highly stereoselective 1,3‐dipolar cycloaddition with dimethyl maleate, with the sugar moiety acting as a chiral auxiliary. Final removal of the glycosyl moiety afforded enantiopure enantiomeric isoxazolidines 17 and ent ‐17 which are oxa‐analogues of proline diester derivatives. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)