Asymmetric Michael additions via 6- and 7-membered lactone SAMP-hydrazones: Diastereo- and enantioselective synthesis of substituted lactone esters

Lactone esters (S/R,S)-5a-f were synthesized in good overall yields (37-61% , two steps) and diastereo- and enantiomeric excesses (de = 88 - greater th an or equal to 96%, cc = 81 - greater than or equal to 96%) by 1,4-addition of metalated lactone-SAMP-hydrazones (S)-2 to enoate Michael accepters 3 a nd subsequent oxidative cleavage of the product hydrazones by ozonolysis. T he relative and absolute configuration was determined by X-ray structure an alysis of (R, S)-5c.