Enantiomerically pure sulphinyl-4,5-dihydroisoxazoles. Part 1. Stereocontrolled synthesis of optically active β-ketols and γ-amino alcohols

exo-Metallation of racemic 3-methyl-4,5-dihydroisoxazoles and reaction of the products with (-)-(S)-menthyl toluene-p-sulphinate afforded diastereoisomeric 3-sulphinylmethyl derivatives which can be separated and individually converted either into the corresponding enantio- and diastereoisomericaliy pure 4,5-dihydroisoxazoles or β-ketols, depending on the desulphurization conditions; furthermore, stereoselective reduction of the former provides an entry to optically active γ-amino alcohols.