Trifluoroacetic acid → HCID 59125435, compound

Participants

Reaction Steps

An aqueous solution of (S)-(−)-tryptophan hydrochloride (1.45 g, 5.7 mmol) was made alkaline with a saturated sodium bicarbonate solution and extracted with ethyl acetate. The extract was washed once with aqueous sodium chloride solution, dried (sodium sulfate), filtered, and concentrated in vacuo. The free base-was dissolved in chloroform (50 mL) and treated with 3-methylbenzo[b]thiophene-2-carbaldehyde (1.0 g, 5.7 mmol) and trifluoroacetic acid (21.2 mmol, 1.32 g). The resulting mixture then was heated to reflux for 3 hours. The solution was cooled to room temperature, washed once with saturated sodium bicarbonate solution, dried (sodium sulfate), filtered, and concentrated in vacuo to provide a mixture of two diastereomers. The isomers were separated by chromatography (silica gel, 30% ethyl acetate:hexanes) to give 700 mg (38%) of (1R,3S)-1-(3-methylbenzo[b]thiophen-2-yl)-2,3,4,9-tetrahydro-1H-β-carboline-3-carboxylic acid methyl ester (Intermediate 5) and 400 mg (19%) of (1S;3S)-1-(3-methylbenzo[b]thiophen-2-yl)-2,3,4,9-tetra-hydro-1H-β-carboline-3-carboxylic acid methyl ester (Intermediate 6).

Provenance & Evidence