The preparation of optically active boronic ester substituted Δ2-isoxazolines

In this paper we report our recent results in the area of nitrile oxide cycloaddition to optically active vinylboronic esters to afford optically active boronic ester substituted Delta(2)-isoxazolines. In these studies, a number of optically active diols were investigated and TADDOLs have been found to afford the best diastereoselectivity. The mixture of diastereomers obtained in these reactions can be readily purified by formation of the diethanolamine-boron complexes and recrystallized to afford the pure enantiomers. (C) 1999 Elsevier Science S.A. All rights reserved.