JPS59225152A - Preparation of alpha-l-aspartyl-l-phenylalanine-methyl ester of its hydrochloride - Google Patents

Abstract

PURPOSE:To obtain the titled compound useful as a peptide sweetener inexpensively and easily in high yield, by subjecting alpha-L-aspartyl-L-phenylalanine-beta- methyl ester to intramolecular ester exchange under specific conditions. CONSTITUTION:alpha-L-Aspartyl-L-phenylalanine-beta-methyl ester is dissolved in a mixed solvent comprising 0-20vol% methanol, 8-55vol% conc. hydrochloric acid, and the rest of water to give 0.01-0.3mol/dl solution, which is kept at 0- 60 deg.C, so that intramolecular ester exchange is carried out. Prepared alpha-L-aspartyl- L-phenylalanine methyl ester is precipitated as a hydrochloride, isolated, neutralized with an alkali in case of necessity, so that alpha-L-aspartyl-L-phenylalaninemethyl ester and its hydrochloride is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing L-aspartyl-L-phenylalanine methyl ester (α-APM) or its hydrochloride.

It is known that there are many methods for producing α-APM.

Looking at those methods, most of the methods are
-e The amino group of lagic acid (L-Asp) is protected by some method, such as a carbobenzoxy group, formyl group, or hydrogen 9ine, and then converted to anhydride to form L-Asp.
The aspartyl-enylalanine methyl ester skeleton is synthesized by condensation with 7-enylalanine methyl ester (PM), and the target α-APM is obtained by deprotection.

However, by this method, kakiri β-L-7 spartel-L-phenylalanine methyl ester (β-AP
Since the synthesis of α-APM from L-Asp or L-phenylalanine (L-phe) cannot be avoided, there is a limit to the synthetic yield of α-APM from L-Asp or L-phenylalanine (L-phe). Furthermore, this requires an operation to separate only α-APM from the α,β-APM mixture.

On the other hand, a method of condensing L-Asp's NTA (N-thiocarboxylic acid anhydride) and PM has been announced as a method to chemically synthesize only α-APM (
Japanese Patent Publication No. 56-73054. ) There are difficulties in implementing it on an industrial scale, such as the produced APM having an odor. or,
N-Carbobenzoxy-L-Asp (7) NCA (N-carboxylic acid anhydride) of β-benzyl ester is condensed with PM and then disengaged by catalytic reduction to form α-APM.
A method (Japanese Unexamined Patent Publication No. 48-96557) has been published, but this method is also difficult to implement industrially due to cost and other reasons. In addition to this, there are several known methods for producing α-APM that do not produce β-APM as a by-product; In terms of raw materials, etc., it is considered that the implementation part 1 is ~.

The present inventor separately condensed NCA of β-methyl ester of L-Asp with L-pHe to obtain α-L-aspartyl-L-phenylalanine-β-methyl ester (
Methyl ester of β-carboxyl group of aspartic acid residue of α-L-aspartyl-phenylalanine) f: Invented a method for producing it and applied for a patent. This dipeptide is naturally derived from its synthetic route, L-Asp.
and L-phe.

The present inventors have invented the method of the present invention for easily synthesizing α-APM in good yield using, for example, the dipeptide synthesized by the above method.

The present inventor previously developed α-APM i methanol (MeO
H) ~ When dissolved in a mixed solvent of hydrochloric acid, α-APM hydrochloride was precipitated, and at the same time, it was found that a small amount of α-L-asno-4rutile-L-phenylalanine-β-methyl ester was formed as a by-product in the solution. . This was presumed to be due to the transesterification of α-APM in the mixed solvent to produce the β-methyl ester. Incidentally, these compounds are considered to be in an equilibrium relationship.

Based on these findings, the present inventor further researched and found that α-L-Q aspartyl-monophenylalanine-β-methyl ester was dissolved in a specific proportion of MeOH ~ concentrated hydrochloric acid ~ concentrated hydrochloric acid solution water mixed solvent eOH ~ 20%.

Concentrated hydrochloric acid (concHct) was added to a mixed solvent containing 8 to 55% and the remainder was water (volume - %) at a concentration of 0.01 mol/a to 0.3 mol/de. If dissolved and kept at 0-60℃, intramolecular transesterification will occur,
α-APM is generated, which is subsequently precipitated as α-APM hydrochloride, which shifts the equilibrium and ultimately results in a high yield (approx.
5%), the raw material α-L-asi9rutile-L-phenylalanine-β-methyl ester was converted to α-APM hydrochloride, and the present invention was completed. A method for synthesizing α-APM using such an intramolecular transesterification reaction has not been developed so far.

In the method of the present invention, hydrochloric acid of a certain degree is used as a solvent, to which MeOH may be further added.

Its composition is hydrochloric acid V),! If expressed in terms of concentration, as mentioned above, MeoHO ~ 20%, concHct
The composition is 8 to 55%, with the remainder being water (all percentages by volume). If the hydrochloric acid resistance is too high, peptide bonds are likely to be cleaved, and if it is too low, it will not crystallize in the form of α-APM hydrochloride. MeO
When H0%, that is, no MeOH is added, ester hydrolysis progresses, and when too much MeOH is used, diesterification progresses.

α-L-aspartyl-L for mixed solvent with the above composition
The amount of -7enylalanine-β-methyl ester used is:
It is 0.01 to 0.3 mol/dl. If the amount is too small, the resulting α-APM hydrochloride will not crystallize; if the amount is too large, it will not dissolve in the mixed solvent having the above composition.

The intramolecular transesterification reaction is carried out at 0 to 60°C.

Within this range, the temperature may be constant or may be changed over time. When the temperature is too low, the transesterification rate is slow. Furthermore, when the temperature is too high, peptide bonds are likely to be cleaved.

Under such conditions, the transesterification reaction is almost completed in 2 to 14 days.

Since α-APM is crystallized in the form of hydrochloride in the transesterification reaction solution, this is separated by an appropriate method and, if necessary, neutralized to form free α-APM.

After separating α-APM hydrochloride by filtration or the like, the mother liquor is prepared using MeOH, hydrochloric acid, and water as appropriate to adjust the solvent composition to the above ratio again. By further adding -β-methyl ester, the used raw material β-methyl ester can be quantitatively converted into α-APM hydrochloride without waste.

Incidentally, α-APM hydrochloride can be converted to α-APM by an appropriate method such as neutralization with a suitable alkali, etc., depending on the necessity, and this f: Of course, it can be obtained as a crystal. be.

As described above, according to the present invention, α-AP can be chemically and inexpensively produced for the first time.
It became possible to synthesize only M.

Example I MeOH 1.0 ml, cone HCL 3.4
ml! and water 5.1 rnA and from this 7 tnl! f and shi, (χ-L-aspartyl-L-
Phenylalanine-β-methyl ester 4.2& was dissolved and kept at 25C. α-APM hydrochloride began to precipitate over time, and after 8' days, 2.93.9 p of α-APM hydrochloride (yield: about 62%) was obtained.

The same experiment was repeated and 14 days later, 3.8 g (yield 81
%) of α-APM hydrochloride.

Example 2 MeOH 1,37, conc HCL 3.4 m and water 5.1 m/! 6.4 K/! from a mixed solution of f and shi,
4.2 g of α-L-aspartyl-L-phenylalanine-β-methyl ester was dissolved and kept at 25°C. As in Example 1, α-APM salt M began to precipitate, and after 8 days, α-APM hydrochloride 3.3% (yield 70%) was obtained.

The same experiment was repeated, and after 11 days, α-APM hydrochloride 4.1F (yield: 87%) was obtained.

Example 3 1.2 m of conc HCL was added to the mother liquor obtained in Example 2.
1 was processed, 4.2 g of α-L-7 spartyl-L-phenylalanine-β-methyl ester was dissolved, and the mixture was kept at 30°C.

After 8 days, 4.61 APM hydrochloride was obtained. Yield: 97.

Example 4 MeQH1,2rn/3, cone HCL 3.
7m7 from a mixed solvent of Qml and 5.8rnl of water!
Then, 4.2 g of α-L-aspartyl to L-7 enylalanine-β-methyl ester was dissolved, and the mixture was initially heated to 40°C for 1 hour.
It was kept at 25°C for 5 days.

3.4g of α-APM was precipitated. Yield 72%.

Example 5 Water7. OrrLi, cone HCL 3. OmA
7 ml from the mixed solvent.

Toshi α-L-7 Subarthyl-7 Enylalanine-β
-Methyl ester 4.2y was bath dissolved and kept at 25°C for 8 days. The precipitated APM soil salt S: was 1.28 g, yield 27%.

Procedural amendment filed May 11, 1980 Kazuo Wakasugi, Commissioner of the Japan Patent Office Patent Application No. 98716 of 1987 2, Name of the invention Process for producing alpha-1-asvaldi-mono-phenylalanine methyl ester or its hydrochloride 3, Amendment Relationship with the case of the person who created the patent application Address of the patent applicant: 5-8-5 Kyobashi-chome, Chuo-ku, Tokyo Number of inventions increased by the amendment None 7 Contents of the amendment (1) Page 3 of the specification, 9 lines from the bottom The word ``experimental'' is corrected to ``laboratory-like.''

(2) Akira MJJnJ No. 4g4, rlvl in the second row from the bottom
a 0f-1~20%'' to rMeOl-10~20%''
I am corrected.

(3) Add the following example on page 9, line 10 and below of the specification.

[Example 6] 4 g of α-△PMjil was dissolved in 100 ml of water, and N
a. While cooling with a saturated aqueous solution of Coa,
) Neutralized to l-14,8. this stuff over

Claims (1)

[Claims] α-L-7 spartyl-L-7 enylalanine-β-methyl ester from methanol 0 to 20%. A mixed solvent containing 8 to 55% concentrated hydrochloric acid and the remainder ν being water (both by volume) was added at a concentration of 0.01 mol/dZ or 0.
3 moles/d7! α-L
α-L-aspartyl-L-7-enylalanine, which is characterized by precipitating 7-svarthyl-17-enylalanine methyl ester as a hydrochloride, isolating this, and, if necessary, neutralizing it with an alkali to convert it into a free ester. Method for producing methymethysteryl hydrochloride.