Synthesis of enantiomerically pure β-hydroxy-γ-sulfinylaldehyde dimethyl acetals

Lithium alkyl p -tolylsulfinyl anions generated from 2 or 3 react with methyl 3,3-dimethoxypropanoate ( 1 ) yielding the corresponding β-ketosulfoxides 4 and 5 respectively. The presence of two methoxy groups in the δ-position of these β-ketosulfoxides has little or no influence on the stereoselectivity of DIBAL and DIBAL/ZnX 2 reductions, allowing the synthesis of the title acetals in high diastereoisomeric excess.