Stereoselective synthesis of beta-substituted aspartic acids via tetrahydro-1,3-oxazin-6-ones

Oxazinones have been synthesised and used as chiral templates in the synthe sis of beta-substituted aspartic acids. Use of a Brebereck's reagant/Grigna rd/hydrogenation strategy gave cis-oxazinones with complete stereoselectivi ty, whereas an alkylation strategy, although trans-selective, gave mixtures of isomers. The oxazinones could be convened to beta-substituted aspartic acids and to regioselectively protected beta-substituted aspartic acids wit hout loss of stereochemistry at either centre. (C) 1999 Elsevier Science Lt d. All rights reserved.