di-tert-butyl (4-{(3R,4S,5S)-4-amino-3-[(tert-butoxycarbonyl)amino]-5-methylpiperidin-1-yl}pyridin-3-yl)imidodicarbonate

di-tert-butyl (4-{(3R,4S,5S)-3-[(tert-butoxycarbonyl)amino]-4-[(methoxycarbonyl)amino]-5-methylpiperidin-1-yl}pyridin-3-yl)imidodicarbonate

tert-butyl methyl [(3R,4S,5S)-1-(3-aminopyridin-4-yl)-5-methylpiperidine-3,4-diyl]biscarbamate

tert-butyl methyl [(3R,4S,5S)-1-(3-{[(3-{[(benzyloxy)carbonyl]amino}-7-bromoquinolin-2-yl)carbonyl]amino}pyridin-4-yl)-5-methylpiperidine-3,4-diyl]biscarbamate