The Use of Chiral Auxiliaries Prepared from (-)-β-Pinene in Stereoselective Reduction of β-Ketobutyrates

Abstract

Chiral auxiliaries previously prepared from (-)-β---pinene (3), alcohols 5a-e and 6, were transformed into β---ketobutyrates 7a-e and 8 respectively. These compounds were stereoselectively reduced by NaBH₄ in the presence of additives (MnCl₂ or CaCl₂), leading to the corresponding β-hydroxy butyrates 10a-e and 11 in good chemical yield and poor to moderate stereoselectivities (de 0%-60%). The configuration at the newly generated stereogenic center in 10a was determined to be S through its transformation into S-(+)-butanediol.