(S)-4-{4-[(2,4-Diamino-pteridin-6-ylmethyl)-methyl-amino]-benzoylamino}-4-isopropylcarbamoyl-butyric acid

(S)-4-{4-[(2,4-Diamino-pteridin-6-ylmethyl)-methyl-amino]-benzoylamino}-4-isopropylcarbamoyl-butyric acid tert-butyl ester

(S)-4-Benzyloxycarbonylamino-4-isopropylcarbamoyl-butyric acid tert-butyl ester

(S)-4-Isopropylcarbamoyl-4-(4-methylamino-benzoylamino)-butyric acid tert-butyl ester

p-[N-methyl-N-(trifluoroacetyl)amino]benzoyl chloride

(S)-4-Isopropylcarbamoyl-4-{4-[methyl-(2,2,2-trifluoro-acetyl)-amino]-benzoylamino}-butyric acid tert-butyl ester