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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.

Original publication

DOI

10.1039/b712937h

Type

Journal

Org Biomol Chem

Publication Date

21/12/2007

Volume

5

Pages

3922 - 3931

Keywords

4-Butyrolactone, Amides, Amino Acids, Cyclic, Crystallography, X-Ray, Cyclization, Esters, Lithium Compounds, Models, Chemical, Molecular Structure, Stereoisomerism