(2S)-2-acetamidobutanedioic acid

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: The condensation of Z-Pro-Ala with Ala-NH-Et by the procedure in Example 7 yields Z-Pro-Ala-Ala-NH-Et; m.p. 219°-220° C. from 2-propanol--AcOEt); (α)D20 =-36.2°; c=0.2 (dimethylformamide). This intermediate is successively converted, as described in Example 2, into (1) BOC-Asp(Obzl)-Pro-Ala-Ala-NH-Et, m.p. 133°-136° C. (AcOEt--petroleum ether), (α)D20 =-61.1°, c=0.2 (MeOH); (2) Asp(OBzl)-Pro-Ala-Ala-NH-Et.HCl, m.p. 189°-193° C. (MeOH--Et2O), and (3) Ac-Asp(OBzl(-Pro-Ala-Ala-NH-Et, m.p. 191°-193° C. (AcOEt--petroleum ether), (α)D20 =-68.5°, c=0.2 (MeOH). Hydrogenolysis of the latter product by the procedure in Example 1 yields the title compound, Nα -Acetylaspartyl-prolyl-alanyl-alanine ethylamide; m.p. 153°-155° C. (melting begins at 143° C.). (α)D20 =-36.2°

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: The condensation of Z-Pro-Ala with Ala-NH-Et by the procedure in Example 7 yields Z-Pro-Ala-Ala-NH-Et; m.p. 219°-220° C. from 2-propanol--AcOEt); (α)D20 =-36.2°; c=0.2 (dimethylformamide). This intermediate is successively converted, as described in Example 2, into (1) BOC-Asp(Obzl)-Pro-Ala-Ala-NH-Et, m.p. 133°-136° C. (AcOEt--petroleum ether), (α)D20 =-61.1°, c=0.2 (MeOH); (2) Asp(OBzl)-Pro-Ala-Ala-NH-Et.HCl, m.p. 189°-193° C. (MeOH--Et2O), and (3) Ac-Asp(OBzl(-Pro-Ala-Ala-NH-Et, m.p. 191°-193° C. (AcOEt--petroleum ether), (α)D20 =-68.5°, c=0.2 (MeOH). Hydrogenolysis of the latter product by the procedure in Example 1 yields the title compound, Nα -Acetylaspartyl-prolyl-alanyl-alanine ethylamide; m.p. 153°-155° C. (melting begins at 143° C.). (α)D20 =-36.2°

Conditions: temp:80.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A stirred suspension of N-Acetyl-L-aspartic acid (35.0 g, 199.9 mmol) in acetic anhydride (100 mL, 1.06 mol) was heated to 80° C. for ˜1 h until all the solid material had dissolved. The heating bath was removed, and the reaction mixture was stirred 4 h at ambient temperature. The product was collected by filtration and washed with tert-butyl methyl ether to afford N-acetyl-L-aspartic anhydride (27.8 g, 88%) as white crystals, [α]D−49.0° (c=2.5, Ac2O). had dissolved The heating bath was removed The product was collected by filtration washed with tert-butyl methyl ether

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: The condensation of Z-Pro-Ala with Ala-NH-Et by the procedure in Example 7 yields Z-Pro-Ala-Ala-NH-Et; m.p. 219°-220° C. from 2-propanol--AcOEt); (α)D20 =-36.2°; c=0.2 (dimethylformamide). This intermediate is successively converted, as described in Example 2, into (1) BOC-Asp(Obzl)-Pro-Ala-Ala-NH-Et, m.p. 133°-136° C. (AcOEt--petroleum ether), (α)D20 =-61.1°, c=0.2 (MeOH); (2) Asp(OBzl)-Pro-Ala-Ala-NH-Et.HCl, m.p. 189°-193° C. (MeOH--Et2O), and (3) Ac-Asp(OBzl(-Pro-Ala-Ala-NH-Et, m.p. 191°-193° C. (AcOEt--petroleum ether), (α)D20 =-68.5°, c=0.2 (MeOH). Hydrogenolysis of the latter product by the procedure in Example 1 yields the title compound, Nα -Acetylaspartyl-prolyl-alanyl-alanine ethylamide; m.p. 153°-155° C. (melting begins at 143° C.). (α)D20 =-36.2°