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Paper | Regular issue | Vol 65, No. 3, 2005, pp.591-605
Published online, 1st February, 2005
DOI: 10.3987/COM-04-10297
Nitrone 1,3-Dipolar Cycloadditions to Enol Ethers Catalyzed by Lewis Acids. An Access to β-Amino Acids

Branislav Dugovic, Tomás Wiesenganger, Lubor Fisera,* Christian Hametner, and Nada Prónayová

*Department of Organic Chemistry, Slovak University of Technology, Bratislava 812 37, Slovakia

Abstract

The stereoselectivity of nitrone cycloaddition with enol ethers (2 and 4) depends upon the nature of the Lewis acid. The 1,3-dipolar cycloaddition of nitrones (1, 6 and 8) with enol ether (2) under the catalysis of AlMe3 and Et2AlCl proceeded diastereoselectively; whereas nitrone substitution with TBDPS reverses the diastereoselectivity of the cycloaddition. The oxidative ring-opening of isoxazolidines (3 and 9) with the treatment of benzyl bromide results new β-amino acid esters (11, 13 and 15).