In a 1-l. Erlenmeyer flask, 25 g. (0.13 mole) of tryptamine hydrochloride (Note 1) is dissolved in 400 ml. of water by stirring and warming on a steam bath to approximately 45°. After cooling to room temperature, a solution of 13.2 g. (0.143 mole) of glyoxylic acid monohydrate (Note 2) in 30 ml. of water is added followed by the slow addition (about 3 minutes) of a cooled solution of 7.05 g. (0.126 mole) of potassium hydroxide in 35 ml. of water (Note 3). Precipitation of tetrahydro-β-carboline-1-carboxylic acid takes place during the addition of the potassium hydroxide solution or soon thereafter. After stirring at ambient temperature for 1 hour, the solid is collected on a filter and washed thoroughly with 100 ml. of water. The damp filter cake is transferred to a 1-l. beaker and suspended in 240 ml. of water; 34 ml. of concentrated hydrochloric acid is slowly added (Note 4) with stirring. The mixture is boiled on a hot plate for 30 minutes before an additional 35 ml. of concentrated hydrochloric acid is added. Heating is continued for another 15 minutes, and the resulting solution is allowed to cool to room temperature. The precipitated hydrochloride salt is collected on a filter and washed with 30 ml. of water. The product is dissolved in 400 ml. of water by stirring and warming on a steam bath to approximately 55°, and the solution is adjusted to pH 12 with 20% aqueous potassium hydroxide (approximately 50 ml. is required). After cooling to room temperature, the product is collected by suction filtration, washed with 400 ml. of water, and dried in a vacuum desiccator over phosphorus pentoxide, yielding 17.0–17.6 g. (78–80%) of 1,2,3,4-tetrahydro-β-carboline, m.p. 204–205° (Note 5); ¹H NMR spectrum (dimethyl sulfoxide-d₆): δ 2.70 (t, 2H, CH₂CH₂N), 2.72 (s, 1H, NH), 3.00 (t, 2H, CH₂CH₂N), 3.85 (s, 2H, CCH₂N), 6.80–7.50 (m, 4H, C₆H₄), and 10.53 (s, 1H, NH).