Aldol condensation reactions of (dienone) tricarbonyliron complexes .4. Enantioselective total synthesis of 3-deoxypentoses from (-)-myrtenal.

The trimethylsilyl enol ether of the tricarbonyliron complex (-)-1 deriving from (R)-(-)-myrtenal undergoes highly stereoselective cross aldol reactions with TiCl4-coordinated beta-alkoxyaldehydes. With BF3,Et2O as Lewis acid the reaction is only poorly stereoselective, allowing the synthesis of pairs of easily separable diastereomeric optically active ketols. These features are useful to have access to chiral polyols, as illustrated hereby the synthesis of the protected deoxypentoses (+)-10 and (-)-11. (C) 1997 Elsevier Science Ltd.