N-Boc 2-acyloxazolidines: Useful precursors to enantiopure 1,2-diols via highly diastereoselective nucleophilic additions

Article abstract of DOI:10.1016/0040-4020(95)00145-X

N-Boc 2-Acyloxazolidines were synthesized from norephedrine and phenylglycinol. This preparation involves: (i) a transformation or the above β-amino alcohols into N-Boc 2-ethoxycarbonyloxazolidines, (ii) the formation of the corresponding Weinreb amides and, (iii) a reaction between these amides and organometallic reagents. Such diastereomerically pure heterocycles react cleanly with various nucleophilic reagents (Grignard reagents, sodium borohydride and allylsilane) to afford the corresponding alcohols. Treatment of these hydroxyoxazolidines with trifluoro acetic acid, followed by hydrolysis and reduction of the intermediate α-hydroxy aldehydes afforded 1,2-diols. The overall transformation exhibited in most cases a complete diastereoselectivity which can be explained by a chelated model for the nucleophilic addition.