[C:1]([N:4]1[CH2:9][C:8](=[O:10])[NH:7][C:6](=[CH:11][C:12]2[CH:17]=[CH:16][CH:15]=[CH:14][CH:13]=2)[C:5]1=[O:18])(=[O:3])[CH3:2].CI.[C:21]([O-])([O-])=O.[Na+].[Na+]>CN(C=O)C>[C:1]([N:4]1[CH2:9][C:8](=[O:10])[N:7]([CH3:21])[C:6](=[CH:11][C:12]2[CH:17]=[CH:16][CH:15]=[CH:14][CH:13]=2)[C:5]1=[O:18])(=[O:3])[CH3:2]1-Acetyl-3-benzylidene-2,5-piperazinedione (compound 18 prepared in Reference Example 2) was N-methylated by treatment with methyl iodide (2.0 equivalents) in the presence of Na2CO3 (1.0 equivalents) in DMF at room temperature for 24 hours. The solvent was removed and the residue purified by flash chromatography. The product 1-acetyl-3-benzylidene-4-methyl-2,5-piperazinedione, obtained in 45% yield, was treated with 4-methoxybenzaldehyde (1.0-1.1 equivalents) in the presence of Cs2CO3 in DMF at 80° C. for 206 hours to give compound 121, which is (3Z,6Z)-6-benzylidene-3-(4-methoxybenzylidene)-1-methyl-2,5-piperazinedione, in 35% yield.
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