1-O-benzyl 2-O-methyl (2S)-5-oxopiperidine-1,2-dicarboxylate

(2S)-methyl 2-(((benzyloxy)carbonyl)amino)-6-chloro-5-hydroxyhexanoate

(2S)-methyl 2-(((benzyloxy)carbonyl)amino)-5-((tert-butyldimethylsilyl)oxy)-6-chlorohexanoate

(2S)-1-benzyl 2-methyl 5-((trimethylsilyl)oxy)piperidine-1,2-dicarboxylate

(2S)-1-benzyl 2-methyl 5-((tert-butyldimethylsilyl)oxy)piperidine-1,2-dicarboxylate