Ethanol → (3R)-2-[(Methylthio)thiocarbonyl]-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid

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Reaction Steps

To a mixture of (3R)-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid (6.49 g), KOH (3.5 g) and 50% ethanol (110 ml) is added dropwise carbon disulfide (1.82 ml) under ice-cooling. The mixture is stirred at room temprature for one hour, and thereto is added dropwise methyl iodide (2.5 ml). The mixture is further stirred at room temperature for 4 hours. The reaction mixture is distilled to remove the solvent. The residue is dissolved in water. The solution is acidified with 10% HCl and extracted with ethyl acetate. The extract is washed with water, dried and distilled to remove the solvent. The residue is purified by silica gel column chromatography (solvent, chloroform:methanol:acetic acid=97:2:1), and the product is crystallized from aqueous ethanol to give the title compound (5.5 g, 60%), m.p. 103°-106° C. (decomp.).

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