Proline-catalyzed asymmetric aldol reactions between ketones and alpha-unsubstituted aldehydes

[GRAPHICS] With this communication we extend the methodology of proline-catalyzed dire ct asymmetric aldol reactions to include a unsubstituted aldehydes as accep ters. This important aldehyde class gives the corresponding aldols in 22-77 % yield and up to 95% ee when the reactions are performed in pure acetone o r in ketone/chloroform mixtures. On the basis of these results we have deve loped a concise new synthesis of (S)-ipsenol.