SU368241A1 - METHOD OF OBTAINING N - ACETHYL-D-LYSIN - Google Patents

Description

one

This invention relates to a process for the selective acetylation of lysine. No. -Acyl lysine derivatives are used as a feed additive, additive to bread or other food products.

Chemical methods are known for the acetylation of lysine to α-acetyllysin using the lysine copper complex as a starting compound in order to protect the c-amino group, and acetic anhydride or p-nitrophenylacetate as acetylating agents. Methods of acylation in the absence of copper complexes using esters or the action of acetic anhydride on lysine carbamate are also described, both reactions being carried out in the presence of caustic alkali. It was also established that co-acetylation of free a, y-diamino acids is possible with the help of certain M, N-diacetylamines.

A method is proposed for the preparation of N-α-acetyl-DL-lysine by selectively treating a lysine base in an aqueous medium with acetic anhydride in an amount of 1.2 mol per 1 mol of lysine at ordinary temperature in the absence of protective reagents or other auxiliary additives. The yield of the target product 55-56% (on the original lysine). In this case, 25-35% of the initial lysine recovered as base is returned, which can be reused for acetylation. The output of N- -acetyl lysine, taking into account unreacted lysine, is 73-86% of theory. The advantages of the proposed method

compared with the known ones, there is a simplification of the acetylation process, as well as the use of a minimum set of cheap reagents. Achieved with the outputs of the target product, taking into account the returned lysine comparable to the outputs by known methods.

Example 1. To a solution of 7.3 g (0.05 mol) of the base of the jDL-lysica in 75 ml of water for 30 minutes and with continuous displacement, 6.1 g (0.06 mol) of acetic acid are added dropwise

anhydride, after which the reaction solution is diluted with water to 200 ml, mixed with 200 cm of Dowex 50WX 1 or KU-2 ion exchange resin and left for 4 hours. The resin is then filtered and washed with water.

(4X100 ml). The filtrate, along with the washings, is evaporated to dryness on a rotary evaporator in a vacuum created by a water-jet pump, giving 1.1 g (9%) of chromatographically pure N-diacetyl-lysine (the thick syrup gradually crystallizes) in the residue, Rf 0.76, mp. . 136-138 ° C (from ethyl acetate); by lit. According to t. pl. 140-141 ° C.

The resin after separation of the diacetyl lysine is filtered off and washed with water.

(4X100 ml). The combined filtrate and washings were evaporated in vacuo to dryness, and the resulting α-acetyl-OH-lysine was further dried in a vacuum desiccator. The product is chromatographically pure, Rj 0.21, so pl. 215-220 ° C (from water syirt); Ri is no different from the known N-acetyllysia. Yield 5.2 g (55.3%).

Found,%: C 50.98, 50.81; H 8.44, 8.49; N 14.85, 14.78.

CsHieNaOs.

Calculated,%: C 51.04; H 8.56; N 14.88.

After the separation of N-α-acetyl lysine, the resin is treated for 2 hours with 250 ml of co-centrated aqueous ammonia and the filtered ammonia solution is evaporated in vacuo to obtain (after additional drying) 1.8 g (25% of the initial) of the chromatographically pure DL-lysine base, Ri 0 , 08. The yield of N-acetyl lysine, taking into account the returned lysine, is 73%.

Example 2. A solution of 9.1 g (0.05 mol of monohydrochloride) L-lysine in 75 ml of water is neutralized with 8.4 g (0.05 mol of sodium bicarbonate and then acetylated in Example 1 using 6.1 g (0.06 g mole of acetic anhydride. The reaction products are also isolated in Example 1. The yield of N-acetyl lysine is 5.2 g (55.3%); the product contains traces of lysine. This returns 2.6 g (35.6%) of lysine. apacetyl lysine 1.1 g (9.4%), and α-acetyl lysine (including the returned lysine) 86%.

Example 3. 7.3 g (0.05 jol) of base 1) -lysine, returned from acetylation experiments, is reacted with acetic anhydride under the conditions of Example 1.

The output of N-acetyl lysine 5.3 g (56.47); The product contains traces of lysine. The output of N-diacetyllysine 1.0 g (8.6%). Returns 1.8 g (24.6%) lysine. Output No.-acetyllysia (including return lysine) 74.7%.

Example 4. 14.6 g (0.1 mol) of 1-lysine base in 150 ml of water are acetylated in Example 1 using 12.2 g (0.12 mol of acetic anhydride. The reaction products are also isolated in Example 1. The yield is chromatographic pure L-diacetyl-1-lysine 2.4 g (10%). Its hydrolysis with 15% hydrochloric acid (boiling for 8 hours leads to the formation of L-lysine dihydrochloride. Yield 70-71%, (a) o + 45.6 ° (c 2.5 n. HC1) in terms of base, literary data: (a) + 25.8 ° (c 5 n HC1). The yield of chromatographically pure n-acetyl lysine 9.0 g (47.8%); this substance does not possess optical rotation. Returns 5.1 (34.8%) of chromatographically pure 1-lysine.

Output No. -acetyl lysine (including returned lysine) 73.5%.

Subject of the Invention A method for producing N -detyl-D / - lysine by selective acetylation of a lysine base, characterized in that, in order to simplify the process, acetic anhydride in an amount of 1.2 mol per 1 mol of lysine is used as the acetylating agent and aquatic environment.