反应详情

温度

250 °C

0.10 mol of 2-(benzylthio)acetaldehyde and 0.20 mol of acetamide are heated together at 100° C. with stirring, and the product solid is heated in a sublimator at 250° C. and 1 mm Hg until formation of the enamide 1-acetamido-2-benzylthioethene is complete. A 70 mL stainless steel high pressure reactor fitted with a Pyrex glass liner and magnetic stir bar is charged with THF (5 mL), D-menthol (0.5 mmol), (PPh3)2PdCl2 (36 mg, 0.05 mmol), and 1-acetamido-2-benzylthioethene (0.5 mmol). The reactor is sealed, pressurized to 1000 psig with CO, and stirred for 24 hours at 100° C. The product mixture, isolated after removal of gas from the reactor vessel, contains a mixture of two diastereomeric cysteine derivatives, N-acetyl-L-benzylcysteine D-menthyl ester and N-acetyl-D-benzylcysteine D-menthyl ester. These diastereomers are separated by column chromatography on silica gel with benzene-ethyl acetate eluent and are separately hydrolyzed by heating to 100° C. in 1N HCl for 2 hours to give pure L- and D-cysteine, benzyl alcohol, acetic acid, and D-menthol, which is thereafter recycled to a repeat of the foregoing hydrocarboxylation reaction.

1. customA 70 mL stainless steel high pressure reactor fitted with a Pyrex glass liner and magnetic stir bar
2. customThe reactor is sealed
3. stirringstirred for 24 hours at 100° C
4. customThe product mixture, isolated
5. customafter removal of gas from the reactor vessel
6. additiona mixture of two diastereomeric cysteine
7. customThese diastereomers are separated by column chromatography on silica gel with benzene-ethyl acetate eluent
8. temperatureby heating to 100° C. in 1N HCl for 2 hours