benzyl (3R,5S)-3-[(tert-butoxycarbonyl)amino]-5-methyl-4-oxopiperidine-1-carboxylate

benzyl (3R,4R,5S)-3-[(tert-butoxycarbonyl)amino]-4-hydroxy-4,5-dimethylpiperidine-1-carboxylate

tert-butyl [(3R,5S)-4-hydroxy-4,5-dimethylpiperidin-3-yl]carbamate

tert-butyl [(3R,5S)-4-hydroxy-4,5-dimethyl-1-(3-nitro-1-oxido-6,7-dihydro-5H-cyclopenta[b]pyridin-4-yl)piperidin-3-yl]carbamate