Asymmetric Synthesis Of Beta-Amino-Gamma-Substituted-Gamma-Butyrolactones: Double Diastereoselective Conjugate Addition Of Homochiral Lithium Amides To Homochiral Alpha,Beta-Unsaturated Esters

chiral alpha,beta-unsaturated esters containing a single gamma-stereogenic centre show modest levels of substrate control upon conjugate addition of lithium dibenzylamide. Double diastereoselective conjugate additions of homochiral lithium N-benzyl-N-(alpha-methylbenzyl) amide to the homochiral alpha,beta-unsaturated esters display "matching" and mismatching" effects. In each case however these additions proceed under the dominant stereocontrol of the lithium amide to give the corresponding beta-amino esters in high de. A remarkable reversal in stereoselectivity is noted by changing the ester functionality to an oxazolidinone. Subsequent O-deprotection and cyclisation of the resultant beta-amino adducts gives access to the corresponding beta-amino-gamma-substituted-gamma-butyrolactones in good yield and high de.