(S)-2-[N2-[(tert-butyloxy)carbonyl]amino]-N-methoxy-N-methyl-4-penteneamide

tert-butyl (S)-1-formylbut-3-enylcarbamate

(S)-5-allyl-4-tert-butoxycarbonyl-1-(2,4-dimethoxybenzyl)-2-piperazinone

(S)-4-tert-butoxycarbonyl-1-(2,4-dimethoxybenzyl)-5-(2-oxoethyl)-2-piperazinone

(1S)-tert-butyl-1-{[(2,4-dimethoxybenzyl)amino]methyl}but-3-enylcarbamate