DOUBLE CHIRAL INDUCTION IN UL-SELECTIVE MICHAEL ADDITIONS OF METAL ENOLATES OF N-BORNYLIDENEGLYCINATES TO (E)-4,5-DIOXY-2-PENTENOATES - EXCLUSIVE UL,LK-1,2-CHIRAL INDUCTION LEADING TO L,U-MICHAEL ADDUCTS

ul-Selective Michael additions of metal enolates of ethyl N-[(1R,4R)-b ornylidene]glycinate to optically pure (E)-4,5-dioxy-2-pentenoates, su ch as ethyl (E)-3-(2,2-dimethyl-1,3-dioxolan-4-yl)propenoate, ethyl (E )-3-(1,3-dioxolan-4-yl)propenoate, and ethyl (E)-4,5-diacetoxy-2-pente noate, proceed through ul,lk-1,2-induction to provide pure enantiomers of 4-substituted 2-oxopyrrolidine-5-carboxylates as single diastereom ers. Exclusive ul,lk-1,2-induction is achieved by use of the racemic e nolates. Origin of such high stereocontrol is discussed by Kozikowski' s antiperiplanar transition model.