(4S,6R)-4-(tert-Butyl-diphenyl-silanyloxymethyl)-4-methyl-2,2-dioxo-2λ6-[1,2,3]oxathiazinane-3,6-dicarboxylic acid 3-tert-butyl ester 6-ethyl ester

ethyl (2R)-4-(tert-butyldiphenylsilyloxymethyl)-2-hydroxy-4-pentenoate

Carbonic acid (2S,4S)-4-tert-butoxycarbonylamino-4-methyl-5-oxo-pyrrolidin-2-ylmethyl ester tert-butyl ester

(3S,5S)-3-tert-Butoxycarbonylamino-5-tert-butoxycarbonyloxymethyl-3-methyl-2-oxo-pyrrolidine-1-carboxylic acid tert-butyl ester

((3S,5S)-5-Hydroxymethyl-3-methyl-2-oxo-pyrrolidin-3-yl)-carbamic acid tert-butyl ester