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1,3-Dipolar Cycloadditions of N-Benzyl-2,3-O-isopropylidene-D-glyceraldehyde Nitrone to Methoxyallene – Control of Site- and Diastereoselectivity of Isoxazolidine Formation by Lewis Acids

✍ Scribed by Branislav Dugovič; Lubor Fišera; Hans-Ulrich Reißig

Publisher
John Wiley and Sons
Year
2008
Tongue
English
Weight
189 KB
Volume
2008
Category
Article
ISSN
1434-193X

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✦ Synopsis

Abstract

The siteselectivity of cycloadditions of the D‐glyceraldehyde‐derived nitrone 1 and methoxyallene (2) is strongly influenced by Lewis acids. The uncatalyzed reaction results in the formation of isomeric isoxazolidines 3a–3d and 4a–4c, whereas in the presence of different Lewis acids exclusive formation of 4‐methylene‐substituted isoxazolidines 4a–4d is observed. Furthermore, the diastereofacial selectivity of the methoxyallene addition to nitrone 1 can be controlled, thus giving rise to both diastereomeric isoxazolidines 3,4′‐anti‐4 or 3,4′‐syn‐4, just by employing different Lewis acids. The redox ring‐opening of isoxazolidines 4 using Murahashi's protocol yields α‐methylene‐β‐amino acid esters 5a,b and 7a,b.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

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