Off-White Crystalline Solid
Intermediate for the synthesis of Tryptophan derivatives.
D-Tryptophan Methyl Ester Hydrochloride is an intermediate in the synthesis of Tryptophan derivatives.
The Pictet–Spengler reaction of D-Tryptophan methyl ester hydrochloride with piperonal in various solvents has been extensively studied, the solvent-dependence of stereoselectivities could be principally attributed to the solubility difference between cis and trans products 5-HCl in the used solvent, the best stereoselectivity (cis/trans = 99:1) was obtained using nitromethane or acetonitrile as the solvent. Cialis, 12a-epi-Cialis, deuterium-labeled, 3,3,12a-d3-Cialis, and 3,3,12a-d3-12a-epi-Cialis could be efficiently synthesized from D-Tryptophan methyl ester hydrochloride[1].
D-tryptophan and methyl sulfonate are reacted in a solvent at 25 to 100°C to generate D-tryptophan methyl ester sulfonate. Dissolve the obtained D-tryptophan methyl ester sulfonate in water and adjust the pH to alkaline with alkali to convert it into D-tryptophan methyl ester. After the reaction, extract with an organic solvent, add a desiccant for dehydration, and obtain an extract containing D-tryptophan methyl ester. Finally, dry hydrogen chloride gas is passed into the obtained extract containing D-tryptophan methyl ester for reaction to obtain D-tryptophan methyl ester hydrochloride.
[1] Xiao-Xin Shi. “Highly stereoselective Pictet–Spengler reaction of d-tryptophan methyl ester with piperonal: convenient syntheses of Cialis (Tadalafil), 12a-epi-Cialis, and their deuterated analogues.” Tetrahedron, asymmetry 19 4 (2008): Pages 435-442.
