tert-butyl (5S)-5-(tert-butyldiphenylsilyloxy)-3,4-dehydro-piperidine-2-one-1-carboxylate

(4R,5S)-tert-butyl 5-((tert-butyldiphenylsilyl)oxy)-4-methyl-2-oxopiperidine-1-carboxylate

tert-butyl (3S,4R)-3-(tert-butyldiphenylsilyloxy)-4-methyl-piperidine-1-carboxylate