(S)-2-(4-Methylamino-benzoylamino)-5-oxo-5-piperidin-1-yl-pentanoic acid tert-butyl ester

(S)-2-(4-Methylamino-benzoylamino)-5-morpholin-4-yl-5-oxo-pentanoic acid tert-butyl ester

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

(S)-4-tert-Butylcarbamoyl-4-{4-[(2,4-diamino-pteridin-6-ylmethyl)-methyl-amino]-benzoylamino}-butyric acid

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