Asymmetric and ‘anti’-Selective Aldolisations of Acetates and Propionates. Preliminary Communication

Starting from acetates 1 and propionates 6 , TiCl₄-mediated addition of their silyketene acetals 2 and 7 to aldehydes gave aldols 4 and 9 , respectively, with high π-face and ‘anti’ differentiation (Schemes, and Tables 1 and 2). Alternation of the (E/Z)-enolate geometry led to reversed α- and β-inductions ( 7 → 9b , 8 → 10b ). Non-destructive removal of the auxiliary yielded enantiomerically pure β -hydroxycarboxylic acids 13 .