Method for producing enantiomeric form of 2,3-diaminopropionic acid derivatives

A compound of formula II:

• where:
• R1 and R2 are the same or different and are each independently:
• —(C6-C14)-aryl where aryl is unsubstituted or mono-, di- or trisubstituted independently by R11, where R11 is:
• F, Cl, I or Br,
• —(C1-C4)-alkyl,
• —CN,
• —CF3,
• —OR5 in which R5 is a hydrogen atom or —(C1-C4)-alkyl,
• —N(R5)—R6 in which R5 and R6 are each independently a hydrogen atom or —(C1-C4)-alkyl;
• —C(O)—R5 in which R5 is a hydrogen atom or —(C1-C4)-alkyl;
• or
• —S(O)x—R5 in which x is the integer zero, 1 or 2, and R5 is a hydrogen atom or —(C1-C4)-alkyl;
• or
• a 4- to 15-membered Het ring where the Het ring is unsubstituted or mono-, di- or trisubstituted independently by —(C1-C5)-alkyl, —(C1-C5)-alkoxy, halogen, nitro, amino, trifluoro-methyl, hydroxyl, hydroxy-(C1-C4)-alkyl, methylenedioxy, ethylenedioxy, formyl, acetyl, cyano, hydroxycarbonyl, amino-carbonyl or —(C1-C4)-alkoxycarbonyl;
• R3 is:
• —(C6-C14)-aryl in which aryl is unsubstituted or mono-, di- or trisubstituted independently by —NO2, —O—(C1-C4)-alkyl, F, Cl or bromine;
• —O—C(CH3)3;
• or —O—CH(R7)-aryl in which aryl is unsubstituted or mono-, di- or trisubstituted independently by —NO2, —O—CH3, F, Cl or bromine, in which R7 is a hydrogen atom or —(C1-C4)-alkyl;
• R4 is:
• a hydrogen atom;
• —(C1-C4)-alkyl;
• or
• —CH(R8)-aryl in which R8 is a hydrogen atom or —(C1-C4)-alkyl.