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

1(R),5(S)-8-tert-butoxycarbonyl-3-(2,4-dimethoxybenzyl)-3,8-diaza-2-oxobicyclo[3.2.1]octane

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

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

6-allyl-2-benzyl-4-(2,4-dimethoxy-benzyl)-3-oxo-piperazine-1-carboxylic acid tert-butyl ester