<unk>  is an annulated 2,5-diketopiperazine. It is also a 1,2,3,4-tetrahydro-β-carboline.<unk>  can be synthesized starting from (D)-tryptophan methyl ester and piperonal via a Pictet–Spengler reaction. This is followed by condensations with chloroacetyl chloride and methylamine to complete the diketopiperazine ring: 750px
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