Popis: |
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 diastereoselectively obtained. Syn,syn isomers of oxazolines 3 were selectively achieved by an aldol-like reaction in protic conditions between α-metallated ethyl isocyanoacetate 1 and α-acyl alaninates 2. Derivatives 4 with a syn,anti-configuration were obtained under epimerization reaction conditions, whereas derivatives 5–7 with a syn,syn-configuration were selectively obtained under kinetic reaction conditions. |