Sodium Hydroxide → L-Phenylalanine

Participants

Reaction Steps

The aqueous layer obtained was adjusted to pH 8 by adding 1 N aqueous sodium hydroxide. To this aqueous layer was added a solution of 1 g of the N-acetyl-DL-phenylalanine methyl ester obtained in step (iv) of Example 3 in 5 ml of 3-heptanone. The resultant two-layer-system mixture was shaken in the same manner as above at a temperature of 37° C. for 12 hours (repeated reaction run No. 1). When the reaction was completed, the pH of the aqueous layer was 5.50. Upon cooling the reaction mixture composed of the aqueous layer and 3-heptanone layer to room temperature, a supersaturation portion (0.11 g) of L-phenylalanine precipitated out on the aqueous layer side. Crystals of L-phenylalanine were separated by filtration. Then the filtrate was allowed to separate into the aqueous layer and 3-heptanone layer and the organic layer was removed. The aqueous layer was subjected to pH adjustment (pH 8) and reaction with N-acetyl-DL-phenylalanine methyl ester in 3-heptanone solution with shaking in the same manner as mentioned above and the resultant crystalline L-phenylalalnine precipitate (0.15 g) was collected by filtration (repeated run No. 2). By using the aminoacylase-containing aqueous layer of the filtrate in the above manner, the overall procedure comprising pH adjustment, reaction and L-phenylalanine separation was further repeated. The yields of L-phenylalanine in repeated runs No. 3, No. 4 and No. 5 were 0.16 g, 0.13 g and 0.12 g, respectively. The L-phenylalanine crystals obtained in the above repeated runs Nos. 1-5 (0.67 g in total) were combined and washed with methanol. The optical purity of the L-phenylalanine after washing (0.65 g) was found to be 98.9 percent.

Provenance & Evidence