benzyl 3-(1,3-dioxolan-2-ylmethyl)-4-oxopiperidine-1-carboxylate

benzyl 3-(1,3-dioxolan-2-ylmethyl)-4-ethoxycarbonylmethylenepiperidine-1-carboxylate

benzyl rel(3S,4R)-4-ethoxycarbonylmethyl-3-(2-hydroxyethyl)-piperidine-1-carboxylate

(3R,4S)-4-Ethoxycarbonylmethyl-3-(2-oxo-ethyl)-piperidine-1-carboxylic acid benzyl ester

benzyl rel(3S,4R)-3-(1,3-dioxolan-2-ylmethyl)-4-ethoxycarbonylmethylpiperidine-1-carboxylate