Protonation of the enolates lL1 and 2Li by using standard con-in THF yields (S)-1 with 68% ee (47%) and (S)-2 with 77% ditions yields enantioselectivities up to 54 and 50% ee, re-ee (39%) but only if ester 4 ist employed as chiral proton spectively, depending on the chiral proton sourcell]. These source (Figure 2).(iv) Chiral Lewis bases create (S)-2 with up values may change dramatically by the following variations to 30% ee on protonation with achiral ...
