The synthesis of a series of enantiopure malonaldehyde monocycloacetals is described. Treatment of 8b with l-tryptophan methyl ester, 5-methoxytryptamine, and tryptamine, respectively, in the Pictet-Spengler condensation gave the corresponding enantiomerically pure key precursors 1-3 and 17-21 in only two steps. Using a chiral amino-diol successfully realized the kinetic resolution of racemic carbolines 23 and 24.
![N-[2-(2,2-dimethoxyethyl)-1,3-dioxan-5-yl]benzamide Structure](https://image.chemsrc.com/caspic/050/296766-47-7.png)