Oxalyl chloride → (+/-)-4-[[2-[(Acetylthio)methyl]-1 oxo-3-phenylpropyl]amino]butanoic acid, methyl ester

Beteiligte Stoffe

Reaktionsschritte

Oxalyl chloride (0.37 ml., 4.2 mmole) is added, under nitrogen, to a solution of (±)-2-[(acetylthio)methyl]-3-phenylpropanoic acid (0.95 g., 4.0 mmole) in ethyl ether (8 ml.). This mixture is cautiously treated with a catalytic amont of dimethylformamide (3 drops), and then stirred for one hour at room temperature. After concentrating in vacuo, the residue is treated with tetrahydrofuran (10 ml.) and again concentrated to remove excess oxalyl chloride. The resulting residue is treated with methylene chloride (5 ml.), and the soluble portion is transferred to a dropping funnel. This soluton is added, dropwise over 10 minutes, to a cold (-5°), stirred solution of 4-aminobutanoic acid, methyl ester, hydrochloride (0.68 g., 4.4 mmole) and diisopropylethylamine (1.6 ml., 9.0 mmole) in methylene chloride (10 ml.) under nitrogen. After stirring for 3 hours in the cold, the yellow solution is concentrated in vacuo. The residue is treated with ethyl acetate (60 ml.), filtered to remove diisopropylethylamine hydrochloride, and washed sequentially with 10% potassium bisulfate, water, 50% saturated sodium bicarbonate, and 50% brine (30 ml. each). The organic layer is dried (Na2SO4) and concentrated to a light brown solid (1.34 g.). This solid is adsorbed onto a small amount of silica gel (230- 400 mesh), dried, and applied to column of 80 g. of the same silica. Elution with 5:2 hexane/acetone yields 1.09 g. of (±)-4-[[2-[(acetylthio)methyl-1-oxo-3-phenylpropyl]amino]butanoic acid, methyl ester as a white solid; m.p. 81°-82°.

Herkunft & Nachweise