DE1052991B - Process for the optical cleavage of DL-serine - Google Patents

Description

GERMAN

The invention relates to a method for the optical cleavage of DL-serine (formula I).

CH ₂ -OH CH ₂ -OH

CH-NH ₂ CH-NH-CO

CO ₂ H

CO ₂ H
II

NO ₉

NO,

Serine is an a-amino-ß-oxyacid that is in its levorotatory Form (L-Serine) plays a role in animal metabolism. It also takes it among his D- and L-forms take part in the structure of various polypeptides: The D-form occurs, for example, in certain polymyxins, the L-form in viomycin, hypertensin, azaserin and numerous polypeptides of the most varied Origin on.

Since the methods for the synthesis of the serine lead to the racemate, it is necessary to have a method for optical To have cleavage that can be carried out easily, without difficulty and quickly optically pure D- and L-serine which z. B. in the synthesis of the polypeptides that contain these amino acids, can be used.

It has already been suggested that L (+) - threol-p-nitrophenyl-2-aminopropanediol- (l, 3) to use for the optical cleavage of N-acyl-DL-tryptophans. Likewise, it has been suggested that the d (-) - and l (+) - threo-l-p-nitrophenyl-2-aminopropanediol- (l, 3) for the optical splitting of DL-proline and DL-oxyproline use, the reaction taking place in a solvent in which one of the two enantiomorphs add a little soluble salt with the cleavage reagent.

It has now been found that the DL-serine in the form of its N-3,5-dinitrobenzoyl derivative (II) can be used these reagents can also be cleaved.

According to the method of the invention, when an essentially hemimolecular amount of L (-f) -threo-lp-nitrophenyl-2-aminopropanediol- (1,3) was added to a solution of N-3,5-dinitrobenzoyl-DL ~ serine in an organic solvent such as a lower alcohol e.g. B. methanol, the preferred formation of the salt from N-3,5-dinitrobenzoyl-L-serine with L (+) - threo -1 - ρ - nitrophenyl -2 - aminopropanediol - (1,3). This slightly soluble salt precipitates in a crystalline state. The yield in the separation can be further improved by adding a variable amount of a water-immiscible solvent, such as ethyl acetate or ether, to the reaction mixture. Conversely, the N-3,5-dinitrobenzoyl-D-serine preferably and in the same way forms a sparingly soluble salt
of DL-serine

Applicant:
UCLAF, Paris

^ rtreter: Dr. F. Zumstein, patent attorney,
Munich 2, Bräuhausstr. 4th

Claimed priority:
France May 20, 1954

Dr. Gaston Amiard, Noisy-le-Sec, Seine,
Rene Heymes, Romainville, Seine,

and Dr. Leon Velluz, Paris (France),
have been named as inventors

with the d (-) - threo-l-p-nitrophenyl-2-aminopropane

In any case, the alkaline treatment of the crystalline precipitate and subsequent acidification result after almost quantitative recovery of the cleavage agent to the desired optically active form of the N-3,5-Dinitrobenzoylserine, the corresponding serine by acid hydrolysis without noticeable racemization supplies. From the mother liquors from which the salt crystallized, the corresponding can be made in the same way Separate enantiomorphs, which are generally contaminated with small amounts of racemate is. This enantiomorph can either be recrystallized from a suitable solvent or by precipitation with the corresponding d (-) - threo-lp-nitrophenyl-2-aminopropanediol- (l, 3) be cleaned or directly by a known method or by alkaline treatment of the corresponding free Serine according to Crawhall and Elliot (Biochem. J., 48 [1951], p. 237) and racemized to a new batch of to cleaving racemates are given. By alternating successive cleavages and racemizations it is possible to convert the entire originally present racemate into the desired emantiomorph.

D (-) - and L (-j -) - threo-l -p-nitrophenyl-2-aminopropanediol- (l, 3), which intermediate products of the synthesis of Chlorarnphenicols are, according to that of Velluz, Amiard and JoIy (BuI. Soc. Chim. [1953], P. 342). You own

809 770/469

the structure III. Their properties are as follows: mp 162 to 163 ° C; [α] _{D of} the D-base: -28 ± 2 ° (c = 2 ° / ₀ in 0.1 N hydrochloric acid); [α] _{D of} the L base: +28 ± 2 ° (c = 2 ⁰ J ₀ in 0.1 η hydrochloric acid).

NH,

O ₉ N- <f ^ -CH-CH-CH ₉ OH III

OH

The N-3,5-dinitrobenzoylation is carried out in a manner known per se. In making the Salts of d (-) - or L (+) - threo-l-p-nitrophenyl-2-aminopropanediols- (l, 3) can be the solvent that Solution and crystallization temperatures and the cooling time can be varied.

It is known that racemic mixtures of optically active acids can be separated by separating the racemate converted into a suitable derivative and this is then converted into the enantiomers by means of an optically active base separates (see G. W. Wheland, Advanced Organic Chemistry, 2nd edition [1951], p. 235, line 4 ff ^. "" '^ &

But it was quite surprising and in "" no * way to foresee that the N-3,5-dinitro / Benzoyl derivative of serine which is used for the optical cleavage of the salt from this serine derivative with threo-1-p-nitrophenyl-2-aminopropanediol- (l , 3) would have necessary solubility properties. Experiments carried out namely have shown that other acyl derivatives of serine, such as. B. Acetylserine, Formylserine, Benzoylserine, p-Nitrobenzoylserine, in no way suitable for the optical splitting of dl-serine. The N-3,5-Dinitrobenzoylserine is the only derivative that can be used for the optical cleavage of serine by the method according to the invention suitable.

It should also be pointed out that a single process for the optical splitting of serine has so far become known from 1906 (cf. E. Fischer and Jacobs, Reports of the German Chemical Society, Vol. 39 [1906], p. 2942). This known method consists in preparing the p-nitrobenzoyl derivative of racemic serine and separating the optically active forms using quinine and brucine. This process is complicated and two cleavage agents must be used, taking into account that brucine is extremely dangerous to handle because of its great toxicity. It was therefore of great interest to find a new cleavage process for the serine. With the method according to the invention, a simple cleavage process has now been found in which a commercially available and non-toxic cleavage reagent is used. Apart from this, very much better yields can be obtained with the process according to the invention than with the process known from the literature. By E. Fischer (supra) for a total yield of 58 ° / ₀ for the D-serine and of 47.5 ° / ₀ is obtained for the L-serine in the cleavage. In contrast, according to the process according to the invention, a yield of 75% is obtained in the cleavage to L-serine and a yield of 81% in the case of the cleavage to D-serine.

example 1

a) Manufacture of the

N-3,5-dinitrobenzoyl-DL-serine

6.3 g of DL-serine are dissolved in 60 ecm of n-sodium hydroxide solution, cooled and 6.9 g of 3,5-dinitrobenzoyl chloride are added. 10 g of 3,5-dinitrobenzoyl chloride are then added, the medium being made alkaline by adding n-sodium hydroxide solution (75 ecm). 15 ecm of hydrochloric acid are added, the mixture is cooled, filtered off with suction, washed with ether to remove the dinitrobenzoic acid and dried. 16.7 g (93%) of NS.S-dinitrobenzoyl-dl-serine are obtained in this way. The monohydrate melts at 100 to 101 ⁰ C (block).

b) Preparation of the salt from N-3,5-dinitrobenzoyl-L-serine and L (+) - threo-l-p-nitrophenyl-2-aminopropan

First method: dissolve at 6O ⁰ C 10g N-3,5-dinitrobenzoyl-dl-serine in 30 cc of methanol and gives 4.2 g of L (+) threo-1 -p-nitrophenyl-2-aminopropandiol- (1 , 3) too. By cooling to +10 ° C, 6.8 g (80%) of the optically pure salt of N-3,5-dinitrobenzoyl-L-serine and L (+) - threo-lp-nitrophenyl-2-aminopropanediol- ( l, 3) from F. 160 to 161 ° C; [a] _D : + 33 + 1 ° (c = 1% in water).

Second method: 10 g of N-3,5-dinitrobenzoyl-dl-serine are dissolved at 60.degree in 5 ecm of methanol and gives 4.2 g of L (+) - threo -1 - ρ - nitrophenyl - 2 - aminopropanediol- (1,3) to. Then 55 ecm of ethyl acetate is added to the reaction mixture. One cools down and sucks the formed Salt, which is washed and dried. 8.2 g (96.5%) of the optically pure salt are obtained in this way N-3,5-dinitrobenzoyl-L-serine and L (+) - threo-l-p-nitrophenyl-2-aminopropanediol- (l , 3).

c) Preparation of N-3,5-dinitrobenzoyl-L-serine

8.2 g of the above salt are dissolved in 16.5 ecm n sodium hydroxide solution. The L (+) - threo-lp-nitrophenyl-2-aminopropanediol- (l, 3) which crystallizes out is filtered off with suction and washed. 3.1 g (74%) of the cleavage reagent are recovered in this way. After acidifying the filtrate with 1.7 ecm of concentrated hydrochloric acid, the N-3,5-dinitrobenzoyl-L-serine crystallizes out. The product is filtered off with suction, washed and dried, giving 4.5 g (90% based on the N-3,5-dinitrobenzoyl-DL-serine used) of crystallized product. Monohydrate: m.p. 110 to 12 ° C; [et] 2 ": +23.5 + 1 ° (c = 1% in 50% ethanol).
40

d) Production of the L-serine

A solution of 4.3 g of N-3,5-dinitrobenzoyl-L-serine in 60 ecm of 5N hydrochloric acid is heated under reflux for 1 hour.

After filtering, it is evaporated to dryness in vacuo and the L-serine hydrochloride obtained is recrystallized from acetone. The product is taken up in 1 ecm of water, 1.4 ecm of aniline and then 10 ecm of absolute alcohol are added. After cooling, 1.3 g (90%) of crystallized, optically pure L-serine with a melting point of 228 ° C .; [a] _D : + 15 ± 1 ° (c = 4% in n-hydrochloric acid).

e) Separation of the D-serine

The ethyl acetate-methanol solution is extracted, from which the salt of N-3,5-dinitrobenzoyl-L-serine is extracted the l (+) - threo-l-p -nitrophenyl-2-aminopropanediol- (l, 3) (Example 1, b) second method) crystallized with 10 ecm 0.5 N hydrochloric acid and then with 5 ecm water. The aqueous solutions are combined and then with Made n-caustic soda alkaline. In this way 0.4 g (10%) of the cleavage reagent is recovered. The organic Phase is then concentrated and petroleum ether is added. 4.85 g (97%, based on the amount used) are obtained in this way N-3,5 - Dinitrobenzoyl-DL - serine) N - 3,5 - Dinitrobenzoyl L-serine, which can be easily purified by recrystallization. The crude product melts at 109 to 111 ° C; [α]!?: -22 ± 1 ° (c = 1% in 50% ethanol). The corresponding D-serine is hydrolyzed by hydrochloric acid obtained as described in Example 1, d) for the L-serine.

Example 2

Preparation of N-3,5-Dinitrobenzoyl-D-serine
by means of d (-) - threo-lp-nitrophenyl-

2-aminopropanediol- (l, 3)

The N-3,5-dinitrobenzoyl-DL-serine prepared according to Example 1, a) is treated with d (-) - threo-lp-nitrophenyl-2-aminopropanediol- (l, 3) analogously to that in Example 1, b) described mode of operation. The salt of N-3,5-dinitrobenzoyl-D-serine and d (-) - threo-lp-nitrophenyl-2-aminopropanediol- (1,3) with a melting point of 160 ° to 161 ° C. is thus obtained; [α]!?: -33 ± 1 ° (c = 1% in water). As in the procedure given in Example 1, c), it leads to the optically pure N-3,5-dinitrobenzoyl-D-serine. Monohydrate: m.p. 110 to 112 °; [a] _D - -23.5 ± 1 ° (c = 1% in 50 ° / ₀ sodium ethanol); then analogous to example 1, d) one arrives at D-serine, [a] i>: -15 ± 1 ° (c = 4 ° / ₀ in n-hydrochloric acid).

Claims (5)

Claims: 20 1. A method for the optical cleavage of dl-serine, characterized in that one DL-serine in itself converted into N-3,5-dinitrobenzoyl-DL-serine in a known manner, this with an essentially foreign molecular weight Amount of L (+) - threo-l-p-nitrophenyl- Reacts 2-aminopropanediol- (l, 3) in a solvent, separates the resulting salt, from it through alkaline treatment and subsequent acidification releases N-3,5-dinitrobenzoyl-D- or -L-serine and the latter converted into D- or L-serine by acid hydrolysis. 2. The method according to claim 1, characterized in that the solvent used is a low molecular weight alcohol such as methanol. 3. The method according to claim 1 and 2, characterized in that the yield in the separation the sparingly soluble salt by adding a variable amount of a water-immiscible one Solvent, e.g. B. ethyl acetate or ether, improved to the reaction mixture. 4. The method according to claim 3, characterized in that the solvent used is 9 parts of ethyl acetate methanol used per part. 5. Modification of the method according to claim 1, characterized in that one takes place in an analogous manner D (-) -threo-1-p-nitrophenyl-2-aminopropanediol- (1,3) with N-3,5-dinitrobenzoyl-DL-serine. Considered publications:
GW Wheland, Advanced Organic Chemistry, 2nd Edition (1951), p. 235. © 809 770/469 3.59