JP2002060382A - Stereoisomer of monatin and use thereof, method for producing monatins and intermediate therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide monatin stereoisomers hopeful as sweeteners or ingredients thereof and having intense sweetness. SOLUTION: The stereoisomers (salts thereof) of a new substance monatin exhibit high sweetness and are hopeful as sweeteners or ingredients thereof therefore are usable as sweeteners, or the like. Thus, they afford foods/drinks, or the like, with sweetness. The above isomers include 13-epi-monatin, 11-epi- monatin and ent-monatin. Furthermore, the method for producing such monatins and a new intermediate for producing such monatins are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention includes novel stereoisomers of monatin (in the form of a salt and those in which the functional group is protected) which are excellent as sweeteners or active ingredients thereof. ), Their use, processes for the production of monatins and novel intermediates therefor. This isomer includes 13-epimonatin (13-epi-Monatin), 11-epimonatin (11-epi-Monatin), and entmonatin (ent-
Monatin).

[0002]

2. Description of the Related Art In recent years, with the sophistication of dietary habits, obesity due to excessive intake of sugar and various diseases associated therewith have become a problem, and the development of a low-calorie sweetener instead of sugar has been strongly desired. . In addition to the sweetness intensity, the sweetener required is required to have many characteristics and requirements such as low calorie, safety, stability to heat and acid, sweetness, and cost.

[0003] Various sweeteners are currently used or proposed. For example, it is presently used as a natural sweetener such as plant-derived thaumatin, glycyrrhizin, stevioside, etc. which are naturally present and can be collected in large quantities. In addition, sweeteners having high sweetness intensity and capable of being industrially produced in large quantities have been put to practical use.
For example, aspartame, which is widely used as such a sweetener, is excellent in safety and sweetness. Further, aspartame derivative research is also actively conducted. In addition to these, sweet substances having various properties as sweeteners have been proposed and studied for practical use.

Under such circumstances, practical use as a sweetener can be expected, and development of a sweet substance having a high degree of sweetness has been demanded.

[0005]

An object of the present invention is to provide a sweet substance which can be expected to be put to practical use as a sweetener and has a high degree of sweetness.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, succeeded in synthesizing monatin and three stereoisomers (optically active substances) of monatin other than monatin. It was also found that all of the stereoisomers other than monatin have excellent sweetness intensity, and that some of them are remarkably superior to monatin. Further, a sweetener or a food or drink can be provided by using the stereoisomer of monatin. Serine, particularly, an optically active form thereof (L-serine or D-serine) can be used as a starting material to produce the sweetener or food or drink. The present inventors have also found that an isomer and monatin can be synthesized, and have also found an important intermediate for the production thereof, and the present invention has been completed based on these various findings.

As described above, in the present invention, the synthesis of an optically active substance has been successfully achieved for the first time, and three kinds of optically active substances (stereoisomers) which do not exist in nature are synthesized for the first time as a pure product, and the synthetic intermediate γ -Lactone was found, and an indole site (indol-3-ylmethyl group) for this optically active substance (γ-lactone (29), (54) and the like described later) and the like.
Was found to proceed with high stereoselectivity. This stereoselective alkylation reaction can also be applied to various natural product syntheses.

That is, the present invention provides a novel compound, monatin (Mo
natin) stereoisomers, which include 13-epi-monatin (11-epi-Monatin) and 11-epimonatin (11-epi-monatin).
At least one of epi-Monatin and ent-Monatin is included.

The present invention includes the following contents.

It should be noted that monatin, 13-epi-monatin, 11-epimonatin (11-ep
i-Monatin) and entmonatin (ent-Monatin)
It is represented by the following structural formulas (1), (46), (43) and (44).

[0011]

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[0012]

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[0013]

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[0014]

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[1] A stereoisomer of the novel compound monatin. It may be in the form of a salt or in a form in which at least one of the functional groups is protected. The form of the salt contained in the novel chemical substance of the present invention is not limited. When used as food, naturally salts that can be used for food are used.

Examples of the salt form include salts with alkali metals such as sodium and potassium, salts with alkaline earth metals such as calcium and magnesium, ammonium salts with ammonia, salts with amino acids such as lysine and arginine;
Salts with inorganic acids such as hydrochloric acid and sulfuric acid, salts with organic acids such as citric acid and acetic acid, and saccharin, acesulfame, cyclamic acid, glycyrrhizic acid (g)
and a salt with another sweetening agent such as lycyrrhizic acid), which is also included in the stereoisomer of the present invention as described above.

As the protecting group, a protecting group used in peptide or nucleic acid synthesis can be employed.

Examples of the protecting group for the indolyl group include benzyloxycarbonyl group, t-butyloxycarbonyl group and formyl group, and examples of the protecting group for the amino group include benzyloxycarbonyl group, t-butyloxycarbonyl group and the like. Examples of a hydroxyl-protecting group such as 9-fluorenylmethyloxycarbonyl group and the like include a benzyl group,
As a protecting group for a carboxyl group such as a t-butyl group,
Examples thereof include a benzyl group and an alkyl group having 1 to 4 carbon atoms.

[2] 13-Epimonatin which is (2R, 4S) -form, 11-Epimonatin which is (2S, 4R) -form and (2R, 4R)-
The stereoisomer containing at least one of the following forms: enmonatin.

[3] The above stereoisomer, which is any of 13-epimonatin, 11-epimonatin and entmonatin.

[4] The above stereoisomer having a sweetness intensity at least 100 times that of sucrose.

[5] A sweetener containing at least one of the above novel stereoisomers.

It is known that it can be used for sweeteners and may contain carriers or extenders which will be developed for it in the future. In addition, it can of course contain additives that can be used as sweeteners. Sweetening agents are used for animals, such as mammals, especially humans.

[6] Sweetened foods and drinks containing at least one of the above-mentioned novel stereoisomers.

Particularly, it can be used as at least a part of a sweetener in foods and drinks for which sweetness is required in human foods and drinks. In addition, it is used for oral hygiene purposes such as toothpaste and medicine, or for products to be sweetened by oral use.

[7] The following general formula (3) characterized by reacting a γ-lactone represented by the following general formula (2) with an indole derivative represented by the following general formula (27 ′)
A method for producing an alkylated product represented by the formula:

[0027]

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[0028]

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[0029]

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In the above formulas (2), (27 ') and (3),
X represents a hydroxyl group or a halogen atom, and R ¹ , R ² and R ³ are different from each other and each represents a protecting group.

As the protecting group for the amino group, the indolyl group and the carboxyl group, the protecting groups used in peptide synthesis and the like can be employed. For example, an amino group includes a benzyloxycarbonyl group (Cbz), a t-butyloxycarbonyl group, a 9-fluorenylmethyloxycarbonyl group, and an indolyl group includes a benzyloxycarbonyl group (Cbz) and a t-butyloxycarbonyl group. And a carboxyl group such as a benzyl group and an alkyl group having 1 to 4 carbon atoms.

This method is applicable not only to the production of the above-mentioned novel stereoisomer of monatin, but also to the production of known monatin, and this production method is also included in the present invention.

[8] The above production method, wherein the reaction is carried out in the presence of a base.

[9] The above production method wherein γ-lactone is a stereoisomer.

[10] The above-mentioned production method comprising a step of separating a stereoisomer of the alkylated product. As the separation method, various chromatographies, recrystallization methods, preferential crystallization methods, and the like can be used.

[11] The stereoisomer is (2S, 4S) -isomer, (2
The above-mentioned production method, which is any one of (R, 4S) -form, (2S, 4R) -form and (2R, 4R) -form.

[12] The above-mentioned production method, wherein saponification and reduction steps are further performed to produce monatin and at least one of its stereoisomers. At least one of the stereoisomers may be in the form of a salt, or at least one of the functional groups may be protected.

[13] The above production method, further comprising a step of separating one or two of monatin and a stereoisomer (including a salt form). As a separation method, various chromatographic fees, a preferential crystallization method, or the like can be used.

[14] The isomer is 13-epimonatin, 1
The above production method comprising 1-epimonatin and entmonatin.

[15] A method for producing monatins represented by the following general formula (3), which is characterized by subjecting an alkylated stereoisomer to a saponification and reduction step. Monatins include those in the form of a salt and those in which at least one of the functional groups is protected.

[0041]

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In the above formula, R ¹ , R ² and R ³ are different from each other and each represents a protecting group.

[16] The method according to the above item, wherein the monatin is at least one of monatin and its stereoisomer.

[17] The production method according to the preceding paragraph and the production method including a step of separating monatin or a stereoisomer of monatin.

[18] An alkylated product characterized by having the following general formula (4):

[0046]

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In the above formula, R ¹ , R ² and R ³ are different from each other and each represent a hydrogen atom or a protecting group.

As the protecting group for the amino group and the carboxyl group, protecting groups used in peptide synthesis and the like can be employed. For example, an amino group includes a benzyloxycarbonyl group (Cbz), a t-butyloxycarbonyl group, a 9-fluorenylmethyloxycarbonyl group and the like, and a carboxyl group includes a benzyl group and an alkyl group having 1 to 4 carbon atoms. , Each can be adopted.

[19] The above alkylated product containing at least one stereoisomer.

[20] R ¹ is a benzyl group or a group having 1 to 4 carbon atoms
R ² is a benzyloxycarbonyl group,
the above alkyl, wherein R ^{3 represents} any one of a benzyloxycarbonyl group, a t-butyloxycarbonyl group, and a formyl group, each of a t-butyloxycarbonyl group and a 9-fluorenylmethyloxycarbonyl group; Incarnation.

[21] A γ-lactone characterized by being represented by the following general formula (5).

[0052]

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In the above formula, R ¹ and R ² are different from each other and each represent a hydrogen atom or a protecting group.

As the protecting groups for the amino group and the carboxyl group, those protecting groups used in peptide synthesis and the like can be employed. For example, an amino group includes a benzyloxycarbonyl group (Cbz), a t-butyloxycarbonyl group, a 9-fluorenylmethyloxycarbonyl group and the like, and a carboxyl group includes a benzyl group and an alkyl group having 1 to 4 carbon atoms. , Each can be adopted.

[22] The above γ-lactone which is a stereoisomer.

[23] R ¹ is a metal atom, an alkyl group having 1 to 4 carbon atoms or a benzyl group, and R ² is a benzyloxycarbonyl group, a t-butyloxycarbonyl group or 9-fluorenylmethyloxy The above γ-lactone each representing any of carbonyl groups.

As the metal atom, an alkali metal such as sodium or potassium or an alkaline earth metal such as calcium can be selected.

Natural monatin (Monatin) is a kind of shrub native to South Africa, Schlerochiton ilicifolius
An amino acid derivative ((2S, 4S) -4-hydroxy-4- (ind) isolated and structurally determined from R. Vleggaar et al.
ol-3-ylmethyl) glutamic acid; see the above structural formula (1). ) Has been reported to have about 800 times the sweetness of sucrose (R. Vleggaar, LGJ Ackerman, and P.
S. Steyn, J. Chem. Soc. Perkin Trans. 1 , 3095 (199
See 2). ). Monatin is also a low molecular weight, multifunctional compound having a structure that is difficult to produce synthetically.

The synthesis of racemic Monatin was carried out in 1994 by CWH
olzapfel et al., but the synthesis and isolation of an optically active form has not been achieved yet (CW Holzapfel,
K. Bischofberger, and J. Olivier, Synthetic Commun
ications, 24 , 3197 (1994). ). Therefore, there is no report or suggestion on the taste or the like of the optically active substance of monatin other than natural monatin.

[0060]

Embodiments of the present invention will be described below.

From L-serine to 11-epimonatin (4
3) and a route for synthesizing enmonatin (44) and a route for synthesizing 13-epimonatin (46) and monatin (1) from D-serine. The present invention includes, but is not limited to, these.

Γ-lactone represented by the general formula (2) (4-hydroxy-2-amino-4-butanolide, which includes a racemic form and an optically active form. The carboxyl group and the amino group are protected.) With an indole derivative represented by the general formula (27 ′) (the indolyl group is protected with a benzyloxycarbonyl group (Cbz), a t-butyloxycarbonyl group, a formyl group, and the like). An alkylated compound represented by the general formula (3) can be produced. In the above formula (27 ′), X represents a hydroxyl group or a halogen atom such as a bromine atom.

By hydrolyzing and catalytically reducing the (2R, 4S) -isomer (55), 13-epimonatin (46) can be produced, and if hydrolysis is carried out under conditions accompanied by racemization at the 2-position. , Monatin (1) can also be produced. On the other hand, 11-epimonatin (43) can be produced by hydrolysis and catalytic reduction of the (2S, 4R) -isomer (41), and if hydrolysis is carried out under conditions accompanied by racemization at the 2-position, the enantiomer can be obtained. Monatin (44) can also be produced.

In order to separate the optically active substance from 13-epimonatin (46) and monatin (1) and the optically active substance from 11-epimonatin (43) and entmonatin (44), various types of chromatography and It can be carried out using a preferential crystallization method or the like.

(Synthesis of γ-lactone (29) or (54)) The synthesis of γ-lactone (29) can be carried out according to the following synthesis route for γ-lactone (29) (Formula 17).

[0066]

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The starting material L-serine (7) can be methyl-esterified in the presence of thionyl chloride to prepare methyl ester hydrochloride (35). The methyl ester hydrochloride (35) is treated with sodium hydrogen carbonate and benzyloxycarbonyl chloride (CbzCl) to prepare an amino-protected alcohol (36). Alcohol (36)
Can be converted to tosylate (37) using p-toluenesulfonyl chloride (TsCl). The tosylate (37) is treated with sodium iodide to prepare iodide (38). The iodide (38) was subjected to ultrasonic irradiation in the presence of a copper-zinc alloy to form a homo-reformatsky type reactant. Subsequently, by adding a palladium catalyst and benzyl chloroglyoxylate in this order, the desired α-keto ester (39) can be obtained. α-ketoester (3
The ketone moiety of 9) is reduced with sodium borohydride, and α
-Hydroxy ester (40) can be obtained. The ester (40) is heated under reflux in methylene chloride in the presence of tosylic acid to give the desired optically active γ-lactone (2
9) [(S) -form] can be synthesized.

On the other hand, instead of L-serine (7), D
-By repeating the same steps as above using serine (45), the desired optically active γ-lactone (5
4) [(R) -form] can be synthesized.

The racemic γ-lactone can be produced by repeating the same reaction using the racemic serine as a starting material. The optically active substance can be separated from the racemate by an optical resolution method, but a complicated resolution step is required. In order to separate each optically active substance, it is possible to separate it after converting it into an indole derivative in the next step, but it is not preferable because it becomes more complicated.

(Alkylation of γ-lactone enolate)
Regarding the alkylation of γ-lactone enolate, alkylation of γ-lactone enolate shown below is used.
Can be performed according to

[0071]

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The alkylating agent is represented by the general formula (2)
This may be reacted using an indole derivative represented by 7 ′).

In the above formula (27 '), X represents a hydroxyl group or a halogen atom such as a bromine atom.

As the alkylating agent, bromide (27) wherein X is a bromine atom is more preferred. Indolyl groups are protected. Examples of the protecting group include a protecting group usable as a protecting group for an indolyl group in nucleic acid and peptide synthesis, such as a benzyloxycarbonyl group, a t-butyloxycarbonyl group, and a formyl group.

For example, alkylation with an indole moiety (indol-3-ylmethyl group) is carried out using γ-lactone (29) synthesized as described above. When bromide (27) is used as an alkylating agent, triphenylphosphine is converted from indole derivative (14), which is an alcohol.
It can be prepared by reacting with carbon tetrabromide.

When the alkylation reaction is performed, it can be performed in the presence of a base. Examples of the base include lithium diisopropylamide (LDA), lithium hexamethyldisilazane (LiHMDS), and n-butyllithium (n-
BuLi) or the like can be used. After 2.1 equivalents of LDA was generated in the reaction vessel with respect to γ-lactone (29), the mixture was cooled to −78 ° C., and a solution of γ-lactone (29) in tetrahydrofuran (THF) was added dropwise. Decomposition of γ-lactone (29) is apt to occur.
Since the stability of the enolate of the dianion generated using a base is low, it is necessary to allow the reaction to proceed immediately after the generation of the dianion. Therefore, in order to be able to react immediately after the generation of the dianion, the bromide (2
If 7) and γ-lactone (29) are added, the reaction can be promoted. For example, 2.1 equivalents of LiHMDS
The alkylated compounds (41) and (42) can be obtained by dropping at −78 ° C. into a solution of HMPA-THF in the presence of 1.2 equivalents of bromide (27) and γ-lactone (29).

The three-dimensional structures of the alkylated products (41) and (42) were determined by the nuclear Overhauser effect method (NOE). The stereostructure of the precursor of monatin (1) is (42), but NOE was observed between the proton at the base of the nitrogen and the indolyl position in compound (42) which is a by-product. there were. That is, compound (41), which is the main product, is 11-epi-monatin.
The by-product (42) is monatin (1)
Is a precursor of

(Synthesis of 11-epimonatin and entmonatin) 11-epi-Monatin (43) and ent-
Based on the synthetic route (Formula 19) of Monatin (44),
Each of 11-epi-Monatin (4
3) and ent-Monatin (44) can be synthesized.

[0079]

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For example, the alkylated product (41) separated by column chromatography is saponified with 2.5 equivalents of a 1 M aqueous lithium hydroxide solution of lactone, treated with an ion exchange resin, and then hydrogenated with a palladium catalyst to obtain 11-epi-M.
Onatin (43) and ent-Monatin (44) can be obtained as a 5: 1 mixture. It is considered that ent-Monatin (44) was caused by partial isomerization of the asymmetry at the carbonyl α-position during saponification. Compounds (43) and (4
From the mixture of 4), each can be isolated by reverse-phase high performance liquid chromatography (HPLC) fractionation. The ¹ H-NMR spectrum of the obtained ent-Monatin (44) was in good agreement with that described in the literature. The specific rotation, [α] D ^24.0 46.7 (c = 1.00, H ₂ O) is also a literature value except for the sign, and [α] D ^20.0 -49.6 (c = 1.00, H _2).
Good agreement with O).

(Synthesis of 13-Epimonatin and Monatin) Synthesis route of Monatin (1) shown below
Based on 13-epimonatin (13-Monatin) (4
6) and monatin (1) can be respectively synthesized.

[0082]

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Starting from D-serine (45), an optically active γ-lactone (54) was produced in the same manner as in the route from which ent-Monatin (44) was obtained. 13-epi-Monatin (4
6) and Monatin (1) can be obtained. The total yield was 1.42% in 10 steps. The 1H-NMR spectrum of the obtained Monatin (1) was in good agreement with that described in the literature. In addition, specific rotation, [α] D ^24.9 −45.8 (c =
1.00, H ₂ O) are also literature values, [α] D ^20.0 −49.6 (c =
1.00, H ₂ O).

For the purpose of selectively synthesizing Monatin,
In order to preferentially obtain the compounds (1) and (44) by efficiently isomerizing the lactone α-position of the alkylated product, the isomerization conditions may be examined. It is possible to improve the target isomerization ratio by examining thermodynamic equilibrium conditions by reflux in the presence of DBU and kinetic protonation using LDA.

(Total Synthesis of Monatin and Its Stereoisomers) Next, the total synthesis route of Monatin and the other three stereoisomers (Chemical Formula 21) is summarized. Thereby, individual isomers can also be synthesized.

[0086]

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When the derivative of the present invention (including the compound of the present invention and a salt thereof) is used as a sweetening agent, it may be used in combination with another sweetening agent as long as there is no particular problem. Of course.

When the derivative of the present invention is used as a sweetener, a carrier and / or a bulking agent may be used, if necessary. For example, a carrier or a bulking agent for a sweetener conventionally known or used is used. Can be used.

The derivative of the present invention can be used as a sweetener or a sweetener component. However, products such as foods and drinks that require further sweetening, such as confectionery, chewing gum, hygiene products, cosmetics, pharmaceuticals and humans Can be used as a sweetener for various products such as animal products. Furthermore, the derivative of the present invention can be used in the form of a product imparted with sweetness containing the derivative of the present invention, or in a method of imparting sweetness to the product requiring the imparting of sweetness. Can be performed according to a conventional method or a known method commonly used as a method for using a sweetener.

[0090]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

The IR spectrum was measured by Jasco FT / IR-
Measured using 230. ¹ H-NMR spectrum, JNM-AL300 (300 MHz), JNM α-500 (500 MHz), Bruke
Use AC-300 (300MHz) manufactured by r Company and use CDC unless otherwise specified.
The residual CHCl ₃ in l ₃ was measured as an internal standard (7.26).

The optical rotation used was Jasco DIP-1000 manufactured by JASCO Corporation.

[0093] The thin layer chromatography (TLC) analysis was used Merck MERCK Kieselgel 60 F _{2 54.}

The silica gel used for column chromatography was MERCK Kiesel manufactured by Merck unless otherwise specified.
gel 60 Art.7734 was used.

The ultrasonic generator was SU-9TH (450 W, 5
0/60 Hz).

The cation exchange resin was AG 50W-X8 manufactured by BioRad.
It was used.

Preparative high-performance liquid reverse phase silica gel column chromatography was performed using Inertsil ODS-3 (5 μm) manufactured by GL Sciences.
m, 10 × 250 mm).

Example 1 Methyl (R) -2- (benzyloxycarbonyl) amino-3-hydroxyp
Preparation of ropanoate (49) Methyl ester hydrochloride (48) (180.5 g, 1.16 mol) obtained from D-serine and tetrahydrofuran (TH
F; 1800 ml) was placed in a reaction vessel and cooled to 4 ° C. While stirring, 1 M NaHCO ₃ aq (2000 ml) was added dropwise over 20 minutes, and then Cbz
Cl (200 ml, 1.39 mol) was added dropwise over 45 minutes, and the mixture was stirred for 1 hour. The reaction solution was extracted with ethyl acetate (2000 ml) and 10% KHS
After adjusting the pH value to 2 to 3 with O ₄ , the mixture was washed successively with water and a saturated aqueous solution of sodium chloride. The obtained solution was dried over magnesium sulfate, filtered through celite, and concentrated under reduced pressure. The crude product was recrystallized from hexane and ethyl acetate to give alcohol (49).
(263.0 g, 1.11 mol) was obtained. 96% yield.

Melting point: 30 ° C.

(Rotation) [α] D ^25.5 -10.4 (c = 1.00, CHCl ₃ ).

(Infrared absorption spectrum) IR ν _max cm ^-1 (nujol): 3550 (m), 3305 (m), 2960 (s),
1945 (w), 1730 (s), 1710 (s), 1695 (s), 1560 (m), 1540
(m), 1455 (s), 1380 (s), 1350 (s), 1215 (s), 1065 (s),
975 (m), 755 (m), 730 (m), 695 (s).

(NMR spectrum) ¹ H NMR (300 MHz, CDCl ₃ ) δ ppm: 2.03 (1H, br), 3.79 (3H,
s), 3.97 (2H, d, J = 9.3), 4.36 (1H, m), 5.13 (2H, s), 5.68
(1H, d, J = 8.1), 7.32-7.36 (5H, m).

(Elemental analysis) C ₁₂ H ₁₅ NO ₅ (FW = 253.25) Calcd. N 5.53 C 56.91 H 5.97 Found N 5.10 C 56.96 H 5.97.

Example 2 Methyl (R) -2- (benzyloxycarbonyl) amino-3-p-toluenes
Preparation of ulfonyl oxypropanoate (50) Under an argon atmosphere, pyridine (500 ml) dried with potassium hydroxide was added to alcohol (49) (56.0 g, 220 mmol), and the mixture was cooled with ice. Under stirring, TsCl (48.3 g, 253 mmol) was added little by little,
The mixture was stirred in a cold room at 4 ° C. for 24 hours. The reaction solution was poured into 2 liters (1) of ice water and stirred for 10 minutes, and then the crude product was filtered and washed with distilled water. After air drying, recrystallization from ethanol gave tosylate (50) (79.3 g, 194 mmol). Yield 88
%.

Melting point: 119 ° C.

(Optical rotation) [α] D ^25.7 -26.2 (c = 1.00, CHCl ₃ ).

(Infrared absorption spectrum) IR ν _max cm ^-1 (nujol): 3275 (s), 2920 (s), 2855 (s),
1930 (w), 1755 (s), 1720 (s), 1695 (s), 1595 (m), 1550
(s), 1495 (m), 1460 (m), 1435 (m), 1380 (m), 1355 (m),
1335 (m), 1260 (m), 1240 (m), 1225 (m), 1190 (m), 1170
(m), 1070 (m), 1015 (m), 960 (m), 930 (m), 895 (m), 840
(m), 820 (m), 770 (m), 740 (m), 700 (m), 665 (m).

(NMR spectrum) ¹ H NMR (300 MHz, CDCl ₃ ) δ ppm: 2.38 (3H, s), 3.66 (3H,
s), 4.28 (1H, dd, J = 10.2, J = 6.9), 4.38 (1H, dd, J = 1
0.2, J = 6.9), 4.47 (1H, dt, J = 8.1, J = 3.3), 5.02 (2H,
d, J = 3.0), 5.52 (1H, br), 7.29-7.30 (7H, m), 7.70 (2
H, d, J = 8.1).

(Elemental analysis) C ₁₉ H ₂₁ NO ₇ S (FW = 407.44) Calcd. N 3.44 C 56.01 H 5.20 Found N 3.48 C 55.77 H 5.20.

Example 3 Methyl (S) -2- (benzyloxycarbonyl) amino-3-iodopropan
Production of oate (51) Tosylate in a brown eggplant flask for light shielding under an argon atmosphere
(50) (79.3 g, 194 mmol) and acetone (200 ml) dried over calcium chloride were added, and sodium iodide (43.6 g, 291 mmol) dissolved in dry acetone (200 ml) was added dropwise with stirring over 20 minutes. After stirring at room temperature for 24 hours, the mixture was filtered through celite, and then concentrated under reduced pressure. The residue was dissolved in chloroform (2000 ml) and washed sequentially with water, 1 M sodium thiosulfate, water, and a saturated aqueous sodium chloride solution. The obtained solution was dried over magnesium sulfate, filtered through celite, and concentrated under reduced pressure. The crude product was recrystallized from hexane and ethyl acetate to obtain iodide (51) (63.4 g, 175 mmol). 90% yield.

Melting point: 69 ° C.

(Rotation) [α] D ^26.2 -6.32 (c = 1.00, CHCl ₃ ).

(Infrared absorption spectrum) IR ν _max cm ^-1 (nujol): 3320 (m), 3300 (m), 3050 (s),
3035 (s), 2920 (m), 2850 (m), 1760 (s), 1685 (m), 1550
(s), 1540 (s), 1465 (m), 1455 (m), 1310 (m), 1275 (s),
1220 (m), 1145 (m), 1065 (m), 1040 (m), 1020 (m), 790
(m), 750 (m), 725 (m), 695 (m).

(NMR spectrum) ¹ H NMR (300 MHz, CDCl ₃ ) δ ppm: 3.50 (2H, d, J = 3.6),
3.71 (3H, s), 4.52 (1H, dt, J = 7.5), 5.04 (2H, s), 5.6
7 (1H, d, J = 7.5), 7.28 (5H, s).

(Elemental analysis) C ₁₂ H ₁₄ INO ₄ (FW = 363.15) Calcd. N 3.86 C 39.69 H 3.89 Found N 3.91 C 40.15 H 3.92.

Example 4 Methyl (R) -2- (benzyloxycarbonyl) amino-4-oxo-4-benz
Production of yloxycarbonylbutanoate (52) Iodide (51) (1.5 g, 4.13 mmol), copper-zinc alloy (450 mg,
6.86 mgatom) and dried overnight with a high-pressure vacuum pump.
l, 0.9 ml of distilled N, N-dimethylacetamide (DMA) was added, and the mixture was irradiated with ultrasonic waves at 18 ° C. for 20 minutes. After confirming the formation of the alanine derivative produced by protonating the homo Reformatsky reactant by thin layer chromatography (TLC), it was set in one of the three-necked eggplant flasks that had been charged beforehand. Triphenylphosphine palladium dichloride (150 mg, 0.21 mmol) was added from a powder dropping funnel, and the mixture was stirred with an ultrasonic device for 5 minutes. Thereafter, benzyl chloroglyoxylate (1.5 ml, 15.4 mmol) was added, and the mixture was stirred at 25 ° C. for 1 hour with an ultrasonic device. The copper-zinc alloy was removed by filtration through celite, and the residue was extracted into 300 ml of ethyl acetate, and washed sequentially with 1N hydrochloric acid, a saturated aqueous solution of sodium bicarbonate, water and a saturated aqueous solution of sodium chloride. The obtained solution was dried over magnesium sulfate, filtered through celite, and concentrated under reduced pressure. The obtained extract was purified by silica gel column chromatography (silica gel 300 g, hexane: ethyl acetate = 5: 1) to obtain α-ketoester (52) (868 mg, 2.23 mmol) as colorless crystals. Yield 54%.

Melting point: 71 ° C.

(Rotation) [α] D is being measured.

(Infrared absorption spectrum) IR ν _max cm ^-1 (nujol): 3320 (s), 2920 (s), 2855 (s),
1740 (s), 1730 (s), 1705 (s), 1545 (s), 1455 (m), 1385
(m), 1370 (m), 1315 (m), 1300 (m), 1275 (s), 1265 (s),
1240 (s), 1165 (w), 1080 (s), 1055 (s), 1005 (m), 910
(m), 750 (m), 700 (m).

(NMR spectrum) ¹ H NMR (300 MHz, CDCl ₃ ) δ ppm: 3.46 (2H, dd, J = 8.2, J
= 4.2), 3.70 (3H, s), 4.70 (1H, dt, J = 7.5, J = 4.2), 5.
01 (2H, s), 5.26 (2H, s), 5.63 (1H, d, J = 7.5), 7.27-7.
39 (10H, m).

Example 5 Methyl (R) -2-[(benzyloxycarbonyl) amino] -4-hydoroxy
Production of -4-benzyloxycarbonylbutanoate (53) α-ketoester (52) (4.95 g, 12.7 mmol) under a stream of argon
Was dissolved in THF (240 ml) and H ₂ O (80 ml), and sodium borohydride (180 mg, 4.8 mmol) was added at −10 ° C. while stirring. After stirring for 30 minutes, a saturated aqueous sodium chloride solution (100 ml) was added.
After warming to room temperature, the mixture was extracted with 500 ml of ethyl acetate and washed with a saturated aqueous sodium chloride solution. The obtained solution was dried over magnesium sulfate, filtered through celite, and concentrated under reduced pressure. The obtained extract was purified by silica gel column chromatography (silica gel 50 g, hexane: ethyl acetate = 5: 1) to give α-hydroxyester (53) (4.49 g, 11.5 mmol).
Was obtained as a brown oil. 90% yield.

(Infrared absorption spectrum) IR ν _max cm ^-1 (film): 3410 (m), 3070 (w), 2960 (w), 18
00 (m), 1750 (s), 1730 (s), 1710 (s), 1520 (s), 1455
(s), 1440 (m), 1330 (m), 1270 (s), 1215 (s), 1180 (s),
1100 (w), 1060 (s), 1030 (m), 910 (s), 800 (w), 735 (s),
700 (s), 650 (w).

(NMR spectrum) ¹ H NMR (300 MHz, CDCl ₃ ) δ ppm: 2.02-2.22 (3 / 2H, m),
2.46 (1 / 2H, dt, J = 4.6, J = 1.8), 3.68 (3 / 2H, s), 3.70
(3 / 2H, s), 4.27 (1 / 2H, dd, J = 8.2, J = 4.1), 4.34 (1/2
H, dd, J = 8.2, J = 4.1), 4.59 (1H ,, br), 5.01 (2H, s),
5.12 (2H, s), 5.79 (1 / 2H, d, J = 8.1), 5.84 (1 / 2H, d, J
= 8.1), 7.31 (10H, s).

Example 6 (R) -4-Benzyloxycarbonyl-2- (benzyloxycarbonyl) amino
Production of -4-butanolide (54) α-hydroxyester (53) (4.49 g, 1
1.5 mmol) was dissolved in dichloromethane (300 ml), p-toluenesulfonic acid (TsOH) (328 mg, 1.7 mmol) was added, and the mixture was stirred at 40 ° C. in a water bath and refluxed for 5 hours. The reaction solution was cooled to room temperature, and washed sequentially with a saturated aqueous solution of sodium bicarbonate, water and a saturated aqueous solution of sodium chloride. The obtained solution was dried over magnesium sulfate, filtered through celite, and concentrated under reduced pressure. The obtained crude crystals were recrystallized from hexane and ethyl acetate to give γ-
Lactone (54) (3.0 g, 8.05 mmol) was obtained. Yield 69%.

Melting point: 99 ° C.

(Infrared absorption spectrum) IR ν _max cm ^-1 (nujol): 3310 (m), 2920 (s), 2850 (s),
1795 (s), 1745 (s), 1690 (s), 1540 (s), 1455 (s), 1380
(m), 1360 (m), 1315 (m), 1280 (m), 1220 (s), 1185 (s),
1155 (s), 1080 (m), 1040 (m), 990 (m), 975 (m), 915 (m),
850 (w), 755 (m), 740 (m), 700 (s).

(NMR spectrum) ¹ H NMR (300 MHz, CDCl ₃ ) δ ppm: 2.17 (1 / 3H, dt, J = 12.
8, J = 10.2), 2.55 (2 / 3H, dt, J = 11.6, J = 10.5), 2.78 (2 /
3H, dd, J = 11.6, J = 9.3), 3.02 (1 / 3H, dt, J = 12.8, J =
9.7), 4.44 (2 / 3H, dt, J = 10.5, J = 5.8), 4.53 (1 / 3H, d
t, J = 9.7, J = 7.2), 4.87 (1 / 3H, dd, J = 10.3, J = 7.2), 4.
94 (2 / 3H, d, J = 9.3), 5.01 (2H, s), 5.21 (2H, s), 5.34
(1H, br), 7.32-7.35 (10H, m).

(Elemental analysis) C ₂₀ H ₁₉ NO ₆ (FW = 369.37) Calcd. N 3.79 C 65.03 H 5.18 Found N 3.68 C 64.53 H 5.18

Example 7 (S) -4-Benzyloxycarbonyl-2- (benzyloxycarbonyl) amino
Preparation of -4-butanolide (29) α-Hydroxy ester (40) was prepared according to Examples 1 to 5 using L-serine as a starting material.

Based on Example 6, the desired γ-lactone (29) (3.0 g, 8.05 mmol) was similarly obtained. Yield 69
%.

Melting point: 99 ° C.

(Infrared absorption spectrum) γ-lactone (5
Same as 4).

(NMR spectrum) Same as for γ-lactone (54).

(Elemental analysis) Same as for γ-lactone (54).

Example 8 Preparation of 1-Benzyloxycarbonyl-indole-3-carbaldehyde (13)
Concrete argon atmosphere indole-3-carbaldehyde (7.26
g, 50 mmol) in dichloromethane (300 ml), and sodium hydroxide powder (5.0 g, 125 mmol) and benzyltrimethylammonium chloride (BTMAC) (92.85 mg,
0.5 mmol) was added. After stirring, benzyloxycarbonyl chloride (CbzCl) (17.8 g, 125 mmol) was added dropwise over 15 minutes, followed by stirring at 4 ° C. in a low-temperature room for 5 hours. The reaction solution was washed sequentially with 1N hydrochloric acid (125 ml), a saturated aqueous solution of sodium bicarbonate, water and a saturated aqueous solution of sodium chloride. The obtained solution was dried over magnesium sulfate, filtered through celite, and concentrated under reduced pressure. The resulting crude crystals were recrystallized from hexane and ethyl acetate,
Aldehyde (13) (13.3 g, 48 mmol) was obtained. 95% yield.

Melting point: 71 ° C.

(Infrared absorption spectrum) IR ν _max cm ^-1 (nujol): 2920 (s), 2855 (s), 1760 (s),
1675 (s), 1550 (m), 1455 (s), 1440 (m), 1390 (m), 1380
(m), 1345 (s), 1335 (m), 1260 (s), 1230 (s), 1165 (m),
1130 (m), 1095 (m), 1040 (m), 1015 (m), 970 (w), 835
(m), 780 (m), 760 (s), 730 (m), 690 (m).

(NMR spectrum) ¹ H NMR (300 MHz, CDCl ₃ ) δ ppm: 5.49 (2H, s), 7.37-7.4
8 (7H, m), 8.17 (1H, d, J = 7.2), 8.24 (1H, s), 8.27 (1H,
d, J = 9.0), 10.1 (1H, s).

[0139] (elemental _{analysis) C 17 H 13 NO 3 (} FW = 363.15) Calcd. N 5.02 C 73.11 H 4.69 Found N 5.06 C 72.71 H 4.71.

Example 9 Preparation of 1-Benzyloxycarbonyl-3-hydroxymethylindole (14)
In a 500 ml eggplant flask under an argon atmosphere, ethanol (30 m
l), sodium borohydride (378 mg, 10 mmol)
After cooling to 78 ° C, the aldehyde (13) (8.38 g, 30 mmo
A solution of l) in THF (180 ml) was added dropwise over 30 minutes with stirring. 4 ℃
Then, the mixture was stirred for 8 hours. The reaction solution was poured into a saturated aqueous sodium chloride solution, extracted with ethyl acetate (500 ml), and washed with a saturated aqueous sodium chloride solution. The obtained solution was dried over magnesium sulfate, filtered through celite, and concentrated under reduced pressure. The resulting crude crystals were recrystallized from hexane and ethyl acetate to obtain alcohol (14) (7.26 g, 26 mmol). Yield 86
%.

Melting point: 86 ° C.

(Infrared absorption spectrum) IR ν _max cm ^-1 (nujol): 3295 (m), 3160 (m), 2960 (s),
2920 (s), 2855 (s), 1745 (s), 1610 (w), 1600 (w), 1500
(w), 1455 (s), 1400 (s), 1380 (m), 1350 (s), 1300 (w),
1255 (s), 1225 (s), 1125 (w), 1090 (s), 1040 (m), 1020
(m), 1000 (s), 980 (m), 940 (s), 900 (s), 810 (w), 765
(s), 750 (s), 700 (s), 650 (w), 620 (m). ¹ H NMR (300 MHz, CDCl ₃ ) δppm: 4.18 (2H, s), 5.24 (2H,
s), 7.19-7.50 (7H, m), 7.60-7.64 (2H, m), 8.16 (1H,
d, J = 7.5).

(Elemental analysis) C ₁₇ H ₁₅ NO ₃ (FW = 281.31) Calcd. N 4.98 C 72.58 H 5.37 Found N 4.98 C 72.16 H 5.39.

Example 10 Production of 1-Benzyloxycarbonyl-3-bromomethylindole (27) Under argon atmosphere, alcohol (14) (7.26 g, 26 mmol) and carbon tetrabromide (10.7 g, 32 mmol) were added to dichloromethane (100 ml). After dissolving and cooling to -20 ° C, triphenylphosphine (1
0.2 g, 39 mmol) and stirred for 5 minutes. The reaction solution was concentrated under reduced pressure, and crystals formed by adding 100 ml of diethyl ether were filtered. This operation was repeated until no crystals were generated, and then concentrated under reduced pressure. The resulting crude crystals were recrystallized without heating with hexane and ethyl acetate, and bromide (27) (5.95 g, 17 mmol)
I got Yield 69%.

Melting point: 118 ° C. (dec).

(Infrared absorption spectrum) IR ν _max cm ^-1 (nujol): 2920 (s), 2855 (s), 1720 (s),
1570 (w), 1455 (s), 1400 (s), 1370 (m), 1350 (m), 1310
(m), 1260 (s), 1240 (m), 1205 (m), 1090 (m), 915 (m), 7
60 (m), 750 (s), 700 (m).

(NMR spectrum) ¹ H NMR (300 MHz, CDCl ₃ ) δ ppm: 4.64 (2H, s), 5.43 (2H,
s), 7.29-7.48 (7H, m), 7.48-7.70 (2H, m), 8.24 (1H,
d, J = 7.2).

(Elemental analysis) C ₁₇ H ₁₄ BrNO ₂ (FW = 344.20) Calcd. N 4.07 C 59.32 H 4.10 Found N 4.14 C 59.14 H 4.13.

Example 11 (2R, 4S) -4-Benzyloxycarbonyl-2- (benzyloxycarbonyl)
amino-4- (1-benzyloxycarbonyl) -3-indolyl-4-butanoli
Preparation of de (55) and (2R, 4R) -body (56) γ-lactone (54) (406 m
g, 1.1 mmol), bromide (27) (454 mg, 1.3 mmol), distilled THF (5
0 ml) and hexamethylphosphoramide (HMPA) (2 ml), and cooled to -78 ° C. 1M LiHMD also cooled to -78 ° C
A solution obtained by diluting S (n-hexane solution, 2.3 ml, 2.3 mmol) with distilled THF (5 ml) was dropped at once with a cannula under stirring. Five
After stirring for minutes, a saturated aqueous sodium chloride solution (50 ml) was added, and the temperature was raised to room temperature. The reaction solution was extracted with 300 ml of ethyl acetate and washed with a saturated aqueous solution of sodium chloride. The obtained solution was dried over magnesium sulfate, filtered through celite, and concentrated under reduced pressure. The obtained extract is subjected to silica gel column chromatography (silica gel 200 g, benzene: ethyl acetate = 2
0: 1), and the alkylated product (55) (282 mg, 2.23 mmol)
Was obtained as a viscous oil. Yield 42%.

(Infrared absorption spectrum) IR ν _max cm ^-1 (film): 3370 (m), 3070 (m), 3035 (m), 296
0 (m), 1800 (s), 1740 (s), 1730 (s), 1715 (s), 1610 (m),
1590 (m), 1520 (s), 1505 (s), 1455 (s), 1400 (s), 1360
(s), 1330 (s), 1310 (m), 1250 (s), 1220 (s), 1170 (s),
1080 (s), 1060 (m), 1030 (m), 1000 (m), 975 (m), 910
(m), 820 (m), 750 (s), 700 (s), 665 (s).

(NMR spectrum) ¹ H NMR (500 MHz, CDCl ₃ ) δ ppm: 2.31 (1 H, t, J = 12.5),
3.00 (1H, dd, J = 12.5, J = 9.0), 3.30 (1H, d, J = 15.5),
3.50 (1H, d, J = 15.5), 4.57 (1H, dd, J = 18.0, J = 9.0),
5.08 (2H, s), 5.11 (2H, s), 5.39 (2H, s), 5.42 (1H,
s), 7.15-7.57 (19H, m), 8.19 (1H, br).

Example 12 (2R, 4S) -4-Hydoroxy-4- (indol-3-ylmethyl) glutamic ac
id (13-epi-Monatin) (46) and (2S, 4S) -4-Hydoroxy-4-
Production of (indol-3-ylmethyl) glutamic acid (Monatin) (1) Alkylated product (55) (50 mg, 0.08 mol) under argon stream in THF
(1 ml) and H ₂ O (1 ml), and a 1M aqueous lithium hydroxide solution (206 ul, 0.2 mmol) was added thereto while stirring. After stirring for 1 hour at room temperature,
The aqueous reaction solution was washed with dichloromethane. The aqueous layer was passed through a cation exchange resin (10 ml) and an 80% aqueous methanol solution (100 m
After washing in l), the mixture was concentrated under reduced pressure to obtain a dicarboxylic acid. This dicarboxylic acid was used in the next reaction immediately without isolation and purification because of its light sensitivity.

Methanol (5 ml) and 10% palladium-carbon catalyst (200 mg) were added to the dicarboxylic acid, and after hydrogen displacement, 30 minutes at room temperature.
Minutes. The reaction solution was filtered through celite, and the filtrate was adsorbed on a cation exchange resin (10 ml).
Then, the mixture was concentrated under reduced pressure. Crystal mixture 21.0 mg (0.064 mmol)
I got 80% yield. After treatment with 1% TFA solution, reverse phase HPLC (10-
20% acetonitrile aqueous solution, 0.05% TFA buffer), 13-epi-Monatin (46) and TFA salt of Monatin (1) are passed through a column of cation exchange resin, eluted with aqueous ammonia, and ammonium salt And purified.

13-epi-Monatin (46) ammonium salt: (optical rotation) [α] D ^26.0 26.1 (c = 1.00, H ₂ O).

(Infrared absorption spectrum) IR ν _max cm ^-1 (KBr): 3400 (m), 3160-3120 (m), 1625 (s),
1460 (m), 1440 (m), 1400 (s), 1340 (m), 1230 (w), 1130
(w), 1100 (w), 1010 (w), 830 (w), 745 (m).

(NMR spectrum) See FIG. ¹ H NMR (500 MHz, D ₂ O) δppm: 2.19 (1H, dd, J = 15.0, J =
10.0), 2.42 (1H, dd, J = 15.0, J = 3.0), 3.18 (2H, d, J =
3.5), 3.94 (1H, dd, J = 10.0, J = 3.0), 7.09 (1H, t, J = 7.
0), 7.17 (1H, t, J = 7.0), 7.19 (1H, s), 7.43 (1H, d, J
= 8.0), 7.68 (1H, d, J = 8.0) (The peak of 1,4-Dioxane is 3.
It was measured as 70 ppm. ).

[0157] Monatin (1) ammonium salt: (optical ^{rotation) [α] D 24.9 -45.8 (} c = 1.00, H 2 O).

(Infrared absorption spectrum) IR ν _max cm ^-1 (KBr): 3410 (m), 3160-3130 (m), 1650 (m),
1645 (m), 1635 (s), 1620 (s), 1400 (s), 1320 (m), 1100
(w), 1010 (w), 910 (w).

(NMR spectrum) See FIG. _{^{1 H NMR (500MHz, D 2}} O) δppm: 2.01 (1H, dd, J = 15.5, J =
12.0), 2.62 (1H, dd, J = 15.5, J = 1.8), 3.05 (1H, d, J =
14.5), 3.24 (1H, d, J = 14.5), 3.57 (1H, dd, J = 12.0, J
= 1.8), 7.11 (1H, dd, J = 7.5, J = 7.5), 7.17 (1H, dd, J =
7.5, J = 7.5), 7.18 (1H, s), 7.43 (1H, d, J = 8.0), 7.67
(1H, d, J = 8.0) (The peak of 1,4-Dioxane was measured as 3.70 ppm.)

The isolated literature (J. Chem. Soc. Perkin Tr, supra)
ans. 1 , 3095 (1992). ): Monatin (1) sodium sal
t (optical rotation) [α] D ^20.0 −49.6 (c = 1.00, H ₂ O).

(NMR spectrum) ¹ H NMR (500 MHz, D ₂ O) δ ppm: 2.01 (1 H, dd, J = 15.3, J =
11.7), 2.65 (1H, dd, J = 15.3, J = 1.7), 3.05 (1H, d, J =
14.3), 3.24 (1H, d, J = 14.3), 3.62 (1H, dd, J = 12.0, J
= 1.8), 7.11 (1H, dd, J = 8.0, J = 8.0), 7.17 (1H, dd, J =
8.0, J = 8.0), 7.19 (1H, s), 7.44 (1H, d, J = 8.1), 7.69
(1H, d, J = 7.9) (The peak of 1,4-Dioxane was measured as 3.70 ppm.)

(High-resolution mass spectrometry) (exact mass) Calcd. For C ₁₄ H ₁₆ N ₂ O ₅ (+ H) 293.1135 Found 293.1164

Example 13 (2S, 4R) -4-Benzyloxycarbonyl-2- (benzyloxycarbonyl)
amino-4- (1-benzyloxycarbonyl) -3-indolyl-4-butanoli
Preparation of de (41) and (2S, 4S) -Form (42) Alkylated products (41) and (42) were prepared in the same manner as in Example 11 using γ-lactone (29).

Example 14 (2S, 4R) -4-Hydoroxy-4- (indol-3-ylmethyl) glutamic ac
id (11-epi-Monatin) (43) and (2R, 4R) -4-Hydoroxy-4-
(indol-3-ylmethyl) glutamic acid (ent-Monatin) (44)
According to Example 12 of Production of similarly separated alkyl embodying (41) of was prepared stereoisomers similarly monatin perform saponification and reduction reactions.

11-epi-Monatin (43) ammonium salt: (optical rotation) [α] D ^25.6 -25.7 (c = 1.00, H ₂ O).

(Infrared absorption spectrum) IR ν _max cm ^-1 (KBr): 3400 (m), 3160-3120 (m), 1625 (s),
1460 (m), 1440 (m), 1400 (s), 1340 (m), 1230 (w), 1130
(w), 1100 (w), 1010 (w), 830 (w), 745 (m).

(NMR spectrum) See FIG. ¹ H NMR (500 MHz, D ₂ O) δppm: 2.19 (1H, dd, J = 15.0, J =
10.0), 2.42 (1H, dd, J = 15.0, J = 3.0), 3.18 (2H, d, J =
3.5), 3.94 (1H, dd, J = 10.0, J = 3.0), 7.09 (1H, t, J = 7.
0), 7.17 (1H, t, J = 7.0), 7.19 (1H, s), 7.43 (1H, d, J
= 8.0), 7.68 (1H, d, J = 8.0) (peak of 1,4-Dioxane at 3.70)
Measured as ppm. ).

Ent-Monatin (44) ammonium salt: (rotation) [α] D ^24.0 46.7 (c = 1.00, H ₂ O).

(Infrared absorption spectrum) IR ν _max cm ^-1 (KBr): 3410 (m), 3160-3130 (m), 1650 (m),
1645 (m), 1635 (s), 1620 (s), 1400 (s), 1320 (m), 1100
(w), 1010 (w), 910 (w).

(NMR spectrum) See FIG. _{^{1 H NMR (500MHz, D 2}} O) δppm: 2.01 (1H, dd, J = 15.5, J =
12.0), 2.62 (1H, dd, J = 15.5, J = 1.8), 3.05 (1H, d, J =
14.5), 3.24 (1H, d, J = 14.5), 3.57 (1H, dd, J = 12.0, J
= 1.8), 7.11 (1H, t, J = 7.5), 7.17 (1H, t, J = 7.5), 7.1
8 (1H, s), 7.43 (1H, d, J = 8.0), 7.67 (1H, d, J = 8.0)
(The peak of 1,4-Dioxane was measured as 3.70 ppm.)

(Example 15) Production of monatin and a free form of a stereoisomer of monatin The monatin obtained in Examples 12 and 14 and the ammonium salt of the stereoisomer of monatin were added with an acid such as hydrochloric acid to give a medium. And purified by ion exchange chromatography and gel filtration chromatography.

(Example 16) Measurement of sweetness intensity A taste test was conducted on the synthesized monatin and three stereoisomers. 0.3% (w / v) aqueous solution of sucrose was used as the sweetness threshold (detection limit concentration), and 0.3% (w / v) aqueous solution was prepared for each isomer. , 1000 times, 1500 times, 2000 times. This was subjected to a sensory evaluation by 10 panelists. As a result, all of the monatin isomers exhibited a sweetness 1000 times or more that of sucrose.

[0173]

The stereoisomer of monatin, a novel substance of the present invention, exhibits high sweetness intensity and exhibits excellent taste as a sweetener. It is possible to provide a food or drink having a sweet taste.
Therefore, the present invention can provide a novel compound having excellent properties as a sweetener or a component thereof. Further, the present invention also provides an excellent method for producing monatins (monatin or its stereoisomer) and novel intermediates important for that purpose. Body and monatin can be easily manufactured.

[Brief description of the drawings]

FIG. 1 illustrates the ¹ H-NMR spectrum of monatin (1).

FIG. 2 is a diagram showing a ¹ H-NMR spectrum of entmonatin (44).

FIG. 3 shows a ¹ H-NMR spectrum of 11-epimonatin (43).

FIG. 4 is a diagram showing a ¹ H-NMR spectrum of 13-epimonatin (46).

Claims (23)

[Claims] 1. A stereoisomer of the novel compound monatin. It may be in the form of a salt thereof or in a form in which at least one of the functional groups is protected. 2. The stereoisomer according to claim 1, which contains at least one of 13-epimonatin, 11-epimonatin and entmonatin. 3. The stereoisomer according to claim 1, which is any of 13-epimonatin, 11-epimonatin and entmonatin. 4. The stereoisomer according to claim 1, which has a sweetness intensity at least 100 times that of sucrose. 5. A sweetener comprising the stereoisomer according to claim 1. It may contain carriers or bulking agents for sweetening agents. 6. A product such as a food or drink having a sweet taste, characterized by containing the stereoisomer according to claim 1. 7. An alkylation represented by the following general formula (3), characterized by reacting a γ-lactone represented by the following general formula (2) with an indole derivative represented by the following general formula (27 ′): How to make the body. Embedded image Embedded image Embedded image In the above formulas (2), (27 ′) and (3), X represents a hydroxyl group or a halogen atom, and R ¹ , R ² and R ³ are different from each other and each represents a protecting group. 8. The method according to claim 7, wherein the reaction is carried out in the presence of a base. 9. The γ-lactone is a stereoisomer.
The described method. 10. The method according to claim 7, further comprising the step of separating stereoisomers of the alkylated product. (11) The stereoisomer is (2S, 4S) -form, (2R, 4
The method according to claim 10, which is any one of (S) -form, (2S, 4R) -form and (2R, 4R) -form. 12. The method according to claim 7, further comprising subjecting at least one of monatin and its stereoisomer to a saponification and reduction step. At least one of the stereoisomers may be in the form of a salt, or at least one of the functional groups may be protected. 13. The method according to claim 12, further comprising the step of separating one or two of monatin and its stereoisomer. Monatin and its stereoisomers include those in the form of salts. 14. The method of claim 12, wherein said isomers include 13-epimonatin, 11-epimonatin and entmonatin. 15. A method for producing monatins, which comprises subjecting an alkylated stereoisomer represented by the following general formula (3) to a saponification and reduction step. Monatins include those in the form of a salt and those in which at least one of the functional groups is protected. Embedded image In the above formula, R ¹ , R ² and R ³ are different from each other and each represents a protecting group. 16. The method according to claim 15, wherein the monatin is at least one of monatin and its stereoisomer. 17. The method of claim 15, comprising the step of separating monatin or a stereoisomer of monatin. 18. An alkylated product represented by the following general formula (4). Embedded image In the above formula, R ¹ , R ² and R ³ are different from each other and each represent a hydrogen atom or a protecting group. 19. The alkylated product according to claim 18, comprising at least one stereoisomer. 20. R ¹ is a benzyl group or an alkyl group having 1 to 4 carbon atoms, R ² is a benzyloxycarbonyl group, t-
One of-butyloxycarbonyl and 9-fluorenylmethyloxycarbonyl group, R ³ is benzyloxycarbonyl group, t-one of-butyloxycarbonyl group and a formyl group, according to claim 18, wherein it Re respectively represent Alkylated form of 21. A γ-lactone represented by the following general formula (5). Embedded image In the above formula, R ¹ and R ² are different from each other,
Each represents a hydrogen atom or a protecting group. 22. The γ-claim according to claim 21, which is a stereoisomer.
Lactone. 23. R ¹ is a metal atom, an alkyl group having 1 to 4 carbon atoms and a benzyl group, and R ² is a benzyloxycarbonyl group, a t-butyloxycarbonyl group and a 9-
The γ-lactone according to claim 21, which represents any one of a fluorenylmethyloxycarbonyl group.