(2S,3R)-2-tert-butoxycarbonylamino-3,5-dihydroxy-3-methylpentanoic acid methyl ester

(3R)-5-tert-butoxycarbonylamino-3-hydroxy-3-methyl-2-oxopentanoic acid ethyl ester

(2S,3R)-3-hydroxy-3-methylpyrrolidine-1,2-dicarboxylic acid 1-tert-butyl ester 2-ethyl ester

(3R)-3-hydroxy-3-methyl-4,5-dihydro-3H-pyrrole-2-carboxylic acid ethyl ester

(2R,3R)-2-acetoxymethyl-1-(tert-butoxycarbonyl)-3-hydroxy-3-methylpyrrolidine