(2S,4R)-5-(benzyloxy)-2-((tert-butoxycarbonyl)amino)-4-methyl-5-oxopentanoic acid

1-benzyl 5-methyl (2S,4S)-4-((tert-butoxycarbonyl)amino)-2-methylpentanedioate

(2R,4S)-1-benzyl 5-methyl 4-((tert-butoxycarbonyl)amino)-2-methylpentanedioate

(2R,4S)-4-((tert-butoxycarbonyl)amino)-5-((tert-butyldiphenylsilyl)oxy)-2-methylpentanoic acid

(2R,4S)-benzyl 4-((tert-butoxycarbonyl)amino)-5-((tert-butyldiphenylsilyl)oxy)-2-methylpentanoate