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.