(1'R,5S)-1-(1'-phenylethyl)-5-methyldihydropyrimidin-2,4-dione

(S)-N-(2'-cyanopropyl)acetamide

(2S,3S)-2-amino-3-methylbutanedioic acid

(R)-3-(Boc-氨基)异丁酸

4-氨基-2-甲基-4-氧代-(2S)-丁酸