摘要:
A new chiral cyclic alpha,beta-didehydroalanine derivative, (6S)-6-isopropyl-3-methylene-5-phenyl-3,6,dihydro-2H-1,4-oxazin-2-one, has been prepared by in situ aminomethylation-elimination of a chiral glycine-derived precursor. This oxazin-2-one acts as a reactive dienophile ire highly diastereoselective Diels-Alder reactions with cyclopenta- and cyclohexadiene. The major cycloadducts have been isolated and hydrolyzed to afford enantiomerically pure (-)-endo-2-aminobicyclo[2.2.1]heptane-2- and exo-2-aminobicyclo[2.2.2]octane-2-carboxylic acids. (C) 1999 Elsevier Science Ltd. All rights reserved.