(S)-2-[3-(2-Nitro-phenyl)-2-oxo-propionylamino]-propionic acid benzyl ester

(3Z)-1-acetyl-3-{[2-(1,1-dimethylprop-2-enyl)-1-methoxymethyl-1H-indol-3-yl]methylene}-6-methyl-2,5-piperazinedione

(-)-6S-(Z)-1-acetyl-4-(4-methoxybenzyl)-3-(2,4,5-trimethoxy-3-methylbenzylidene)-6-methylpiperazine-2,5-dione

(6S)-3-[(E)-isobutylidene]-6-methyl-2,5-piperazinedione

(S)-3-[(Z)-isobutylidene]-6-methyl-2,5-piperazinedione