4-O-tert-butyl 1-O-methyl (2S)-2-aminobutanedioate

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

Procedure: m-(p-Cyanobenzamido)benzoic acid is activated in the same manner as described under a) and coupled with the p-toluenesulphonate of H-Asp(OtBu)OMe in DMF at room temperature. There is isolated 3-(t-butoxycarbonyl)-N-[m-(p-cyanobenzamido)benzoyl]-L-alanine methyl ester in the form of colourless crystals. Yield: 65%, m.p. 83°-84° C. (hexane).

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

Procedure: Analogously to Example 1 B)a), by coupling Z-Gly-OH and H-Asp(OtBu)-OMe there is obtained Z-Gly-Asp(OtBu)-OMe, m.p. 92°-95° C.(hexane), yield: 89% of theory.