Diastereoselective synthesis of syn,syn- and syn,anti-2,4-diamino-3-hydroxyglutaric acid derivatives from ethyl alpha-acyl alaninates

Syn,syn- and syn,anti-isomers of the four possible diastereomers of O,N,N'- protected 2,4-diamino-3-hydroxyglutaric acid derivatives 3-7 were diastereo selectively obtained. Syn,syn isomers of oxazolines 3 were selectively achi eved by an aldol-like reaction in protic conditions between a-metallated et hyl isocyanoacetate 1 and alpha-acyl alaninates 2. Derivatives 4 with a syn ,anti-configuration were obtained under epimerization reaction conditions, whereas derivatives 5-7 with syn,syn-configuration were selectively obtaine d under kinetic reaction conditions. (C) 1999 Elsevier Science Ltd. All rig hts reserved.