tert-butyl (1S,3R,5R)-3-(tert-butyl)-6-oxo-7,7-(ethylenedithio)-2-oxa-4-azabicyclo[3.2.0]heptane-4-carboxylate

(2R,4S)-methyl 2-tert-butyl-3-formyl-4-methyloxazolidine-4-carboxylate

(2R,5R)-2-(tert-butyl)-6-hydroxy-5-methoxycarbonyl-8-oxo-7-phenyl-3-oxa-1-azabicyclo[3.3.0]oct-6-ene

(2R,4S)-2-(tert-Butyl)-4-ethyl-2-formyloxazolidin-4-carbonsaeure-methylester

(2R,5R,7S)-2-tert-Butyl-7-hydroxy-5-methoxycarbonyl-7-methyl-6,8-dioxo-1-aza-3-oxabicyclo[3.3.0]octane