tert-butyl (5-((1S,2S)-1-hydroxy-2-methylbut-3-en-1-yl)-2,2-dimethyl-1,3-dioxan-5-yl)carbamate

tert-butyl (3R,4S)-2,4-dihydroxy-3,8,8-trimethyl-7,9-dioxa-1-azaspiro[4.5]decane-1-carboxylate

methyl (2S,3S,4R)-2-((S)-1-acetoxy-2-methylpropyl)-3-hydroxy-4-methyl-5-oxopyrrolidine-2-carboxylate

(2R,3S)-1-tert-butyl 2-methyl 2-((S)-1-acetoxy-2-methylpropyl)-3-hydroxy-5-oxopyrrolidine-1,2-dicarboxylate

1-(tert-butyl) 2-methyl (2S,3S,4R)-2-((S)-1-acetoxy-2-methylpropyl)-3-hydroxy-4-methyl-5-oxopyrrolidine-1,2-dicarboxylate