(1R,3S,4R,5R)-3-[(1RS)-1-benzyloxymethyl-1-trichloroacetylamino-2-propenyl]-4-methyl-7,7-dimethyl-2,6,8-trioxabicyclo[3.3.0]octane

(3R,4S)-1-tert-butoxycarbonyl-4-hydroxy-3,8,8-trimethyl-2-oxo-1-aza-7,9-dioxaspiro[4,5]decane

(S)-ethyl 2-isobutyryl-5-oxopyrrolidine-2-carboxylate

ethyl 2-((1S)-1-hydroxy-2-methylpropyl)-5-oxo-D-prolinate

ethyl (1S)-1-[(tert-butoxycarbonyl)amino]-2-isopropylcyclopent-2-ene-1-carboxylate