N-Acetyl-DL-methionine → L-Methionine

Participants

Reaction Steps

717 g (3.75 mol) N-Acetyl-D,L-Methionine and 140 g (3.50 mol) sodium hydroxide were dissolved in water and made up to 1.5 liters. The pH value was adjusted to 7 with 50% aqueous sodium hydroxide solution. After addition of 3.6 g acylase (activity 31.000 E/g), the mixture was stirred for 5 days at room temperature. The suspension was cooled to 5° C. and the precipitate filtered off, washed with 300 ml of ice water and dried. There was obtained 174 g (1.17 mol) L-methionine. The filtrate (1800 g) which contained, in addition to 21.8 wt % N-Acetyl-D(L)-Methionine, 2.8 wt % L-Methionine was warmed to 60° C. and treated with 6 g (0.60 mol) acetic anhydride. After 30 minutes no methionine was detectable in the solution. There was added 223 g (1.17 mol) N-Acetyl-D,L-Methionine and concentrated under vacuum to 1200 g. The solution was concentrated to 752 g in a Sambay-evaporator under 170° C. and 10 mbar. Into the still warm melt were added 15 g of acetic anhydride, heated for 10 minutes at 140° C., then this was dissolved in water and made up to 1.5 liters. The specific rotation of the solution was 0. The content of N-Acetyldipeptide amounted to 0.8% relative to N-Acetyl-methionine. After the pH value was adjusted to 7 with aqueous sodium hydroxide as described above, acylase splitting was again carried out. The yield was 166 g (1.11 mol) L-Methionine.

Provenance & Evidence