Asymmetric Michael Additions via SAMP‐/RAMP‐Hydrazones Enantioselective Synthesis of β‐Substituted Δ‐Oxopentanoates and δ‐Lactones1)

Asymmetric Michael addition of metalated acetaldehyde SAMP‐ or RAMP‐hydrazone (S)‐ or (R)‐2 to α,β‐unsaturated esters 3 and subsequent oxidative cleavage by ozonolysis yields the β‐substituted δ‐oxopentanoates (R)‐ or (S)‐5 with high enantiomeric excesses (ee = 90 to ≧ 96%). Racemization‐free reduction and cyclization affords the corresponding optically active δ‐lactones (R)‐ or (S)‐7.