Methanol → L-Valine

Participants

Reaction Conditions

Reaction Steps

0.10 mol of isobutyraldehyde and 0.20 mol of L-menthoxyacetamide 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-(L-menthoxyacetylamino)-2-methylpropene 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), methanol (0.5 mmol), Co2 (CO)8 (0.05 mmol), pyridine (0.25 mmol), and 1-(L-menthoxyacetylamino)-2-methylpropene (0.5 mmol.) The reactor is sealed, pressurized to 1000 psig with CO, and the reaction mixture is stirred for 24 hours at 100° C. The product mixture, isolated after removal of gas from the reactor vessel, contains a mixture of N-(L-menthoxyacetyl)-D-valine methyl ester and N-(L-menthoxyacetyl)-L-valine methyl ester. Separation of these products is effected by silica gel chromatography with ether-toluene eluent, and the diastereomers are treated separately with 2N HCl solution at 100° C. for 3 hours to give pure L-valine and D-valine.

Provenance & Evidence