C(=[O:5])C(C)C.[C:6](N)(=[O:13])[C:7]1[CH:12]=[CH:11][CH:10]=[CH:9][CH:8]=1.C(NC=C(C)C)(=O)C1C=CC=CC=1.[CH3:28][C@H:29]1[CH2:34][C@@H:33]([OH:35])[C@H:32]([CH:36]([CH3:38])[CH3:37])[CH2:31][CH2:30]1.N1C=CC=CC=1>C1COCC1>[C:6]([OH:13])(=[O:5])[C:7]1[CH:12]=[CH:11][CH:10]=[CH:9][CH:8]=1.[CH3:28][C@H:29]1[CH2:34][C@@H:33]([OH:35])[C@H:32]([CH:36]([CH3:38])[CH3:37])[CH2:31][CH2:30]10.10 mol of isobutyraldehyde and 0.20 mol of benzamide 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-benzoylamino-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), L-menthol (0.5 mmol), Co2 (CO)8 (0.05 mmol), pyridine (0.25 mmol), and 1-benzoylamino-2-methylpropene (0.5 mmol). The reactor is sealed, pressurized to 1500 psig with 15:1 CO:H2 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 valine derivatives, N-benzoyl-L-valine L-menthyl ester and N-benzoyl-D-valine L-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-valine, benzoic acid, and L-menthol, which is thereafter recycled to a repeat of the foregoing hydrocarboxylation reaction.
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