Diastereoselective formation of highly functionalised a-substituted amino acid derivatives via aldol addition

Highly diastereoselective aldol additions of (2R,4S)-3-tert-butyl 4-methyl 2-tert-butyloxazolidine-3,4-dicarboxylate (1) are reported. The utility of the highly substituted oxazolidines of type 1 for diastereoselective a-addition of the fully protected amino acid L-serine with achiral and chiral carbonyl compounds is demonstrated and the relative and absolute configuration of the aldol products are discussed on the basis of NOESY data and solid state structures of selected examples. The aldol products represent highly useful intermediates in the syntheses of sphingosine-related metabolites. q 2004 Elsevier B.V. All rights reserved.