(S)-4-Ethoxycarbonylmethyl-3-hydroxymethyl-5-oxo-piperazine-1-carboxylic acid tert-butyl ester

(S)-3-Hydroxymethyl-5-oxo-piperazine-1-carboxylic acid tert-butyl ester

((2S,3R,4S,5R)-2-Benzyloxycarbonylamino-3,4,5,6-tetrahydroxy-hexylamino)-acetic acid methyl ester

[((2S,3R,4S,5R)-2-Benzyloxycarbonylamino-3,4,5,6-tetrahydroxy-hexyl)-tert-butoxycarbonyl-amino]-acetic acid methyl ester

(S)-3-(tert-Butyl-dimethyl-silanyloxymethyl)-5-oxo-piperazine-1-carboxylic acid tert-butyl ester

(S)-3-(tert-Butyl-dimethyl-silanyloxymethyl)-4-ethoxycarbonylmethyl-5-oxo-piperazine-1-carboxylic acid tert-butyl ester

methyl [(2S)-2-(benzyloxycarbonylamino)-3-hydroxypropyl(tert-butoxycarbonyl)amino]acetate