JPH0142937B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides formulas useful as sweeteners: intermediates for producing amides of L-aspartyl-D-amino acid dipeptides and physiologically suitable cation salts and acid addition salts thereof (wherein R ^a is CH ₂ OH or CH ₂ OCH ₃ ; R teeth

【formula】

【formula】

[Formula] (where R ³ and R ⁶ are methyl, R ⁴ and R ⁵ are hydrogen or methyl, X is S or SO ₂ , n and p are each zero or 1) or

[Formula]. The present invention is directed to the production of new, branched-chain L-aspartyl-D-serine, L-aspartyl-D-O-methylserine dipeptide amides that have strong sweetness and do not have undesirable taste at conventional usage amounts. supply intermediates for This intermediate is a D-amino acid amide of the formula: D-amino acid amide compound. (In the formula, R ^a is CH ₂ OH or CH ₂ OCH ₃ ; R is

【formula】

【formula】

[Formula] (where R ³ and R ⁶ are methyl, R ⁴ and R ⁵ are hydrogen or methyl, X is S or SO ₂ , n and p are each zero or 1) or

[Formula]. ) A good method for preparing compounds of formula () is as follows. In the formula, Q is one of the well-known amino protecting groups,
Advances in Urganic Chem by Boissonas.
3, 159-190 (1963), which can be selectively removed. Particularly good amino protecting groups are benzyloxycarbonyl, tert-butyroxycarbonyl. R ¹⁰ is alkyl having 1 to 4 carbon atoms or benzyl. The amino-protected D-amino acid or its carboxyl-activated derivative is reacted with an equivalent amount of RNH ₂ to yield the amino-protected D-amino acid amide (). Protecting group Q is removed by hydrogenolysis or hydrolysis as described above. The resulting free amino acid amide () is subjected to a condensation reaction with a diprotected L-aspartic acid derivative or its carboxyl activated derivative to produce a diprotected dipeptide amide of formula (). Sweeteners of formula () are obtained from this substance as described above. In a variation of this method, intermediates of formula () in which R carries a cyclic or acyclic sulfide residue (-S-) are oxidized to sulfoxides or sulfones before being converted to intermediates of formula (). The reaction is then carried out as described above to obtain a compound of formula () where R is sulfoxide or sulfone. A second method of making compounds of formula is
The D-amino acid amide of is reacted with L-aspartic acid N-thio-carboxylic anhydride as described above to directly prepare a compound of formula (). To carry out the process, intermediate () is reacted with an equivalent amount of L-aspartic acid N-thiocarboxylic anhydride in a suitable solvent at -25° to 10°C and mild alkaline PH to form a compound of formula (). get. The alkaline PH for this reaction is created with a strong base such as sodium hydroxide or potassium carbonate. Suitable solvents are those in which at least a portion of the reactants are dissolved under the reaction conditions used, which do not react appreciably with either reactant, and which allow the products formed in the reaction to be isolated relatively easily. good. Examples of solvents for this reaction include water, tetrahydrofuran, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, dimethyl sulfoxide, dimethylformamide, and mixtures thereof, but good ones include water and a mixture of water and tetrahydrofuran. be. The preferred pH range for this reaction is 8 to 10, with 8 being particularly preferred. A particularly good temperature is -10 to 0°C. Under the conditions described above, the reaction is usually complete in 1 to 2 hours. The product of formula () is then isolated by conventional methods, such as by bringing the reaction mixture to a pH of the isoelectric point of the product. Usually, when the pH is adjusted to 5.0 to 5.6, the product of formula () precipitates. The solvent is distilled off or filtered off and slurried with a solvent such as methanol, ethanol, ethyl ether, ethyl acetate, or mixtures thereof. The product of formula () is then isolated by filtration. If necessary, further purify by recrystallization or column chromatography. The sweetening power of compounds of formula is determined by comparison of sweetness with sucrose. Formula diluted to an appropriate concentration range ()
An aqueous solution of the compound is compared with a standard sucrose by a specialized taste judge. Comparisons are generally made with a 7-9% sucrose aqueous solution (ie, 7-9 g in 100 ml).
Higher concentrations of sucrose have a different mouth sensation that affects the results, and lower concentrations do not exhibit the conditions normally used. If a 0.014% solution of the compound of formula () is determined to have the same sweetness as a 7% sucrose solution, the sweetening power of this compound is 7/0.014 = 500 times that of sucrose. All sweetening power values given for compounds of formula were determined by this method. At the threshold concentration (the lowest concentration at which a sweet taste is first felt, typically 2-3% for sucrose), the potency of sweeteners such as the compounds of the present invention is generally twice that compared to the sweetness produced by 7-9% sucrose solutions. . Example 1 D-serine N-(dicyclopropylcarvinyl)
Amide 21 ml of 2N sodium hydroxide solution containing 4.41 g (0.042 mol) of D-serine was heated at 5 to 10°C.
After cooling and adjusting the pH to 10.0-11.5 with concentrated hydrochloric acid.
Add 6.9 ml (0.048 mol) of benzyl chloroformate in small portions over 1.5 hours. Meanwhile, keep the mixture in the above PH range by continuously adding 2N sodium hydroxide solution. The mixture was stirred at room temperature overnight, washed with ethyl ether, and the aqueous layer was removed.
Acidify with 6N hydrochloric acid (PH2.5-3.0). Extraction with ethyl acetate, washing of the extract with brine and drying (MgSO ₄ ) gives 3.14 g of the product as a colorless solid, which is recrystallized from 20 ml of ethyl acetate to give a yield of 2.64 g. Rf0.43 [Thin layer chromatography (TLC), ethyl acetate/hexane/acetic acid, 9:9:2, (volume)] 2.4 g (0.01 mol) of N-C _b2 − obtained in step A
Slurry D-serine with 75 ml of chloroform and add 1.1 ml (0.01 mol) of N-methylmorpholine.
Add. The liquid becomes a clear solution and is cooled to -12°C. To this solution was added 0.96 ml (0.01 mol) of ethyl chloroformate, and the mixture was heated to -10°C for 5 minutes.
Stir for a minute. 5 ml of a chloroform solution of 1.11 g (0.01 mol) of dicyclopropylamine was added, and the mixture was further stirred at -15°C for 5 minutes. The reaction mixture was allowed to warm to room temperature and washed with 0.5N hydrochloric acid, 5% sodium bicarbonate, and water in this order, and the chloroform was distilled off under vacuum. The washed aqueous layers are combined and extracted with ethyl acetate. The residue obtained by distilling off the chloroform with an ethyl acetate extract was dissolved, and the ethyl acetate was dried (MgSO ₄ ) and then distilled off under vacuum to obtain a white solid, which was dried overnight in a vacuum oven to obtain the desired product. 3.2 g of product are obtained. Rf0.54 This material will be used as is in the next step. 3.2 g of N-C _b2 -amide obtained in step B (9.6
mmol) in 70 ml methanol, 1.0 mmol)
g of 5% P _d /C catalyst added to 60 psi (4.2 Kg/cm ² )
Hydrogenate for 30 minutes. The catalyst was removed by filtration and the liquid was distilled off under vacuum to give 1.93 g of product as a soapy solid. Reference example 1 3.4 g (9.5 mmol) betabenzyl N
-Benzyloxycarbonyl-L-aspartate; A mixture of 1.0 ml (9.5 mmol) N-methylmorpholine and 0.9 ml (9.5 mmol) ethyl chloroformate was stirred at -15 to -10°C for 5 minutes, and -15 D- obtained in Example 1 Step C at °C
Serine N-dicyclopropylcarbinylamide
A solution of 1.9 g (9.5 mmol) dissolved in 10 ml of chloroform is added. The reaction mixture was stirred at -10°C for 5 min, allowed to warm to room temperature, and then incubated for an additional 1 min.
Stir for an hour. The solvent of the reaction mixture was distilled off under vacuum, and the residue was dissolved in ethyl acetate (250ml) and diluted with 1N
Wash with hydrochloric acid, 5% sodium bicarbonate, and brine in this order, and dry with anhydrous magnesium sulfate. The solvent is removed under vacuum to obtain a gelatinous solid.
Dissolve this in 75 ml of hot ethyl acetate. Upon cooling, a crystalline solid is obtained, which is dried under vacuum at 40° C. to obtain the desired 2-protected dipeptide amide as a fine white solid in a yield of 2.75 g.
Rf0.30. B 2-protected dipeptide amide obtained in step A
2.75g and 200ml methanol and 1.0g 5% Pd/
C catalyst mixture at 60 psi (4.2 Kg/cm ² ) for 1 hour.
Hydrogenate with During this time, the product will precipitate.
The catalyst/product mixture is filtered and the mass is slurried with 100 ml of hot water and filtered again. The combined liquids were evaporated to dryness, water was added, kneaded, filtered and dried under vacuum to give 260 mg of product as a pure white fluffy solid. M.
P252−254℃, Rf0.58 (TLC.n-butanol/
Water/acetic acid 4:1:1, ninhydrin spray) The mass taken out during hydrogenation is 50ml of 0.1N.
Diatomaceous earth made into a slurry with hydrochloric acid (Supercell)
The liquid (PH1.6) was adjusted to pH5.9 with sodium hydroxide solution, the precipitated product was collected, and dried under vacuum.
Obtain mg of product. Overall yield 68%. Mass spectrum (m/e) 313 (M ⁺ ) Sweetness intensity: 700 times that of sucrose Example 2 D-serine N-(2,4-dimethyl-3-pentyl)amide The mixed anhydride is prepared as follows. After dissolving 1.0 g (4.3 mol) of N-benzyloxycarbonyl-D-serine in 50 ml of tetrahydrofuran and cooling to -10°C under nitrogen atmosphere.
Add 0.47 ml (4.3 mmol) N-methylmorpholine and 0.41 ml (4.3 mmol) ethyl chloroformate. The mixture is stirred for 30 minutes at -10°C. 2,4-dimethyl-3-aminopentane dissolved in a small amount of chloroform in a solution of mixed anhydrides.
Add 495 mg (4.3 mmol) and stir at -10°C for 15 minutes, then leave to warm to room temperature. 40 ml of ethyl acetate is added and the mixture is washed with 1N hydrochloric acid, sodium bicarbonate solution and brine, and the organic layer is dried over anhydrous magnesium sulfate. When the solvent was distilled off under vacuum, 1.27 g of a colorless solid was obtained, which was kneaded with ethyl ether, taken out and air-dried to obtain 1.0 g of a colorless product. Rf0.77 (TLC, ethyl acetate/hexane, 7:3, volume, vanillin spray) Dissolve 1.0 g of product from step A in 50 ml of methanol, add 0.5 g of 5% Pd/C catalyst, and heat to 50 psi.
(3.52Kg/cm ² ) until hydrogen absorption stops. Evaporation of the filtrate yields 700 mg of the desired product. Reference example 2 1.36 g (3.8 mmol) betabenzyl N-benzyloxycarbonyl-L-aspartate was dissolved in 10 ml tetrahydrofuran,
Cool to −10° C. and add 0.42 ml (3.8 mmol) of N-methylmorpholine. In this solution
Add 0.36 ml (3.8 mmol) of ethyl chloroformate dropwise and stir at -10°C for 5 minutes. Then 566 mg (2.8 mmol) of D-serine N-(2,
A solution of 4-dimethyl-3-pentyl)amide (obtained in Step B of Example 2) dissolved in several milliliters of tetrahydrofuran was added dropwise, and then
Continue stirring for 15 minutes. The reaction mixture is allowed to warm to room temperature and the solvent is distilled off under vacuum to obtain a solid residue. This was dissolved in ethyl acetate, washed with 1N hydrochloric acid, and the organic layer was washed with 5% sodium bicarbonate solution and brine, dried (MgSO ₄ ), and the solvent was distilled off, yielding 1.6 g of an amorphous solid product. and use it as is in the next process. B 1.5 g of a methanol solution of 2.7 g of protected dipeptide amide (preparation method shown in step A above)
of 5% P _d /C catalyst is added and the mixture is hydrogenated at 50 psi (3.52 Kg/cm ² ) until no hydrogen gas is absorbed. The catalyst is removed by filtration and the liquid is concentrated under vacuum to a small volume and left at room temperature. The precipitated product is collected by filtration and dried under vacuum to give 342 mg of colorless solid. Sweetness, 180 times more than sucrose Example 3 D-serine N-(2,2,4,4-tetramethylethane-3-yl)amide The method for producing t-Boc-amino acids is described by Moroder et al., Z.
According to the method of Physiol.Chem. 357 , 1651 (1976). 2.18g in 10ml each of dioxane and water
(10 mmol) of di-tert-butyl dicarbonate, 1.6 ml (11.5 mmol) of triethylamine and 1.05 g (10 mmol) of D-serine are added. The mixture is stirred at room temperature for 30 minutes and the dioxane is distilled off under vacuum. Cool the remaining aqueous solution with ice, add ethyl acetate, and add dilute acidic potassium sulfate solution while stirring the mixture to adjust the pH to 2-3. The aqueous layer was separated and extracted twice with ethyl acetate, and the ethyl acetate layers were combined, washed with water, dried (Na ₂ SO ₄ ), and the solvent was distilled off under vacuum to give 1.7
The product is obtained as a sticky paste with a yield of g. The mixed anhydride contains 2.85 g (14 mmol) of N-t
-Butoxycarbonyl-D-serine, obtained by dissolving 1.55 ml of N-methylmorpholine and 1.34 ml of ethyl chloroformate in 75 ml of methylene chloride at -12 to -10°C as described in Step B of Example 1. . 2.01 g (14 mmol) of 3-amino-2,2,4,4-tetramethylthiethane was added to the mixture and stirred for an additional 5 minutes at -12°C. The product is separated in the manner described in Example 1, Step B to obtain 4 g of sticky liquid residue. Dissolve this residue in 40ml of methylene chloride and make 12ml of
of trifluoroacetic acid (d=1.480) is added and the mixture is stirred at room temperature for 3 hours. 40% reaction mixture
The mixture is made alkaline with sodium hydroxide solution and the organic layer is separated, and the aqueous layer is made into a saturated solution with sodium chloride and then extracted with methylene chloride. The extracts are combined, dried (MgSO ₄ ), and concentrated to dryness under vacuum to yield 2.21 g of an amorphous off-white solid. Crystallization from ethyl ether/hexane gives 1.92 g of product as a finely divided white solid. Reference example 3 2.3 g (8.0 mmol) beta-t-butyl N-t-butoxycarbonyl-L-aspartate, 0.88 ml (8.0 mmol) N-methylmorpholine and 0.77 ml (8.0 mmol) ethyl chloroformate in 40 ml The mixture dissolved in methylene chloride is stirred at -12°C for 5 minutes.
1.85 g (8.0 mmol) of D-serine N-(2,
2,4,4-tetramethylethane-3-yl)
A solution of amide dissolved in 5 ml of the same solvent is added and stirred for an additional 10 minutes at -12 to -10°C. The mixture is allowed to warm to room temperature, is stirred for a further hour at this temperature and the solvent is distilled off. Dissolve the residue in ethyl acetate, dilute hydrochloric acid, sodium hydrogen carbonate solution,
After washing with brine and drying (MgSO ₄ ), ethyl acetate was distilled off to obtain 3.34 g of an amorphous solid. Crystallize from ethyl ether/hexane
Obtain 2.91 g of colorless solid product, Rf0.70
(Ethyl acetate/hexane, 7:3) B 2.4 g (4.78 mmol) of the product obtained in step A
Dissolve in 60 ml of chloroform, attach a gas inlet tube, and add anhydrous hydrogen chloride to the solution.
Precipitation of solid is observed after 5 minutes. The introduction of hydrogen chloride is continued for a further 10 minutes, after which the mixture is stirred for 1 hour at room temperature and then evaporated to dryness under vacuum. Dissolve the residue in water, wash with chloroform, adjust the pH to 5.6, wash again with chloroform, and remove the water from the aqueous layer under vacuum. Add ethanol to the residue and evaporate to dryness under vacuum. Dissolve the residue in 25 ml of hot water and leave to cool. The precipitated product was taken and dried under vacuum to obtain the product with a yield of 1.12g (60%).MP193-196℃Rf0.32 (n-butanol/
water/acetic acid, 4:1:1). Elemental analysis C ₁₄ H ₂₅ N ₃ O ₅ Calculated value as S, 48.39; H, 7.25; N, 12.09; S, 9.23 Actual value C, 46.77; H, 7.48; N, 11.91; S, 8.82 Sweetness intensity Sucrose Example 4 D-serine N-(2,2,4,4-tetramethyl-1,1-dioxothietan-3-yl)amide A 3-amino-2,2,4,4-tetramethylthiethane-1,1-dioxide 14.53 g (0.1 mol) of 3-amino-2,2,
4,4-tetramethylthietane and 64.17g (0.3
mol) of m-sodium periodate is dissolved in 500 ml of water and stirred overnight at room temperature. The reaction mixture is adjusted to pH 13 with a solution of sodium hydroxide to remove precipitated sodium iodate. liquid
Wash with 100 ml of ethyl ether and continuously extract the aqueous layer with methylene chloride for 18 hours. The extracts are dried (MgSO ₄ ) and the solvent is removed under vacuum.
When the solid residue is recrystallized from ethyl acetate, 8.5 g
yielding a product of MP104−106.5°C. Another 2.7 g of crystals are obtained from the mother liquor, MP 103-106°C. Overall yield 63%. B D-serine N-(2,2,4,4-tetramethyl-1,1-dioxothietan-3-yl)
Amide 1.33 g (6.5 mmol) of N-benzyloxycarbonyl-D- by the method of Example 1, Step B
serine, 0.715 ml N-methylmorpholine,
0.62 ml of ethyl chloroformate and 1.15 g (6.5
mmol) of 3-amino-2,2,4,4-tetramethylethane-1,1-dioxide
2.3g N-benzyloxycarbonyl-D-
Serine N-(2,2,4,4-tetramethyl-
1,1-dioxothietan-3-yl)amide is obtained as a sticky liquid, Rf 0.37 (ethyl acetate/hexane, 7:3). This liquid was dissolved in methanol and 5% Pd/c catalyst was added, Example 1,
Hydrogenate using the method of step C. After removing the catalyst by filtration, methanol was distilled off under vacuum and the residue was
Dissolve in 1N hydrochloric acid and extract with chloroform. The aqueous layer is saturated with sodium chloride, made alkaline with sodium hydroxide solution, and continuously extracted with chloroform overnight. When the solvent is distilled off, 1.54 g of the product is obtained as a sticky liquid, which solidifies on standing, Rf0.32 (n-butanol/water/acetic acid,
4:1:1). Reference example 4 The di-protected dipeptide amide of the above structure is prepared on a scale of 4.7 mmol using the method of Step A of Reference Example 1, i.e. 1.7 g of beta-benzyl N-benzyloxycarbonyl-L-aspartate;
0.51 ml of N-methylmorpholine, 0.45 ml of ethyl chloroformate and D-serine N-(2,2,4,
1.24 g of 4-tetramethyl-1,1-dioxo-thietan-3-yl)amide. 2.45 g of product are obtained as a colorless amorphous solid. 2g
This material is purified by chromatography using 60 g of silica gel. Elution with ethyl acetate yields 1.2 g of amorphous solid product,
Rf0.30 (ethyl acetate/hexane, 7:3). B A mixture of 1.2 g of the product purified in step A, 75 ml of methanol, and 0.6 g of 5% Pd/c was heated to 80 psi.
(5.6Kg/cm ² ). When hydrogen absorption has ceased, the catalyst is removed by filtration and the liquid is distilled off to obtain a colorless solid residue. This residue is dissolved in water, washed with chloroform, and the aqueous layer is evaporated to dryness under vacuum. Crystallization of the solid residue from ethanol yields 255 mg of the desired dipeptide amide as a finely powdered white solid, MP170−173, Rf0.20. 180 more than the mass removed during hydrogenation
Obtain mg of product. Sweetness intensity: 850 times that of sucrose Example 5 D-O-methylserine N-(dicyclopropylcarvinyl)amide 12.31 g (0.079 mol) of D-O-methylserine is dissolved in 40 ml of water containing 6.32 g (0.158 mol) of sodium hydroxide and cooled to 5-10°C. 11.74 ml (0.0806 mol) of benzyl chloroformate and 4M sodium hydroxide are simultaneously added to the solution to adjust the pH to 8-9. The reaction mixture is stirred until the pH remains at 8 without the addition of further base. After washing with methylene chloride, the aqueous layer is acidified with concentrated hydrochloric acid and extracted four times with methylene chloride. After drying (MgSO ₄ ), the solvent is distilled off under vacuum. When hexane is added to the sticky liquid residue and stirred, a precipitate will form, which will yield 18.6g.
(93%), [alpha] _D −
2.7゜(C=1, NaOH, Rf0.43. Add 1.68 ml of 3.80 g (0.015 mol) of N-benzyloxycarbonyl-D-O-methylserine to 75 ml of methylene chloride.
(0.015 mol) of N-methylmorpholine was added.
Cool to 15°C. Add 1.43 ml (0.015 mol) of ethyl chloroformate to this solution, stir at -20 to -15°C for 10 minutes, and then add 1.68 g (0.015 mol) of dicyclopropyl-carbinylamine. The mixture is allowed to warm to room temperature and stirred for a further 2 hours. The reaction solution was washed twice with 1N sodium hydroxide, twice with 1N hydrochloric acid, and dried over magnesium sulfate. When the solvent is distilled off under vacuum, 5.1 g (98%) of the target substance is obtained.
Rf0.59, silica gel TLC, 1:1 ethyl acetate/hexane, molybdenum phosphate spray. The structure of the product was confirmed by ¹ H-NMR spectrum. When 5.1 g of N-benzyloxycarbonyl-D-O-methylserine N-(dicyclopropylcarvinyl)amide obtained in Step B above was hydrogenated by the method of Step C of Example 1, 2.96 g (95%) of D Obtain -O-methylserine N-(dicyclopropyl-carbinyl)amide as a liquid substance, Rf0.39; [Alpha] _D -23.2° (C=0.7,
1NHCl). The structure was confirmed by ¹ H-NMR spectrum. Reference example 5 A C ₆ H ₅ CH ₂ OCOCH ₂ CH (NHCb ₂ ) CONHCH (CH ₂ OCH ₃ ) CONHCH (△) ₂ 4.97 g (13.9 mmol) of beta-benzyl N-benzyloxycarbonyl-L-aspartate and A mixture of 15.5 ml (13.9 mmol) of N-methylmorpholine and 1.33 ml (13.9 mmol) of ethyl chloroformate was added to Step B of Reference Example 1.
When reacted by the method described in , 7.43g (97
%) of the 2-protected dipeptide amide which is recrystallized twice from ethyl acetate to give 4.25 g of colorless product, Rf 0.45 (7:3 ethyl acetate/hexane). The structure was verified by ¹ H-NMR. B 4.25 g of the purified di-protected dipeptide amide obtained in Step A above is hydrogenated by the method described in Step B of Reference Example 1 to obtain 2.4 g (95%) of the desired dipeptide amide. MP215−217°C (decomposition); [Alpha] _D +37.6° (C=0.8,
1.2NHCl); Rf0.41. Sweetness intensity, 85 times that of sucrose Example 6 D-O-methylserine N-(2,2,4,4-
Tetramethylthietan-3-yl)amide In a solution of 2.89 g (18.6 mmol) of D-O-methylserine hydrochloride in 11 ml of water, 6.48
ml (46.5 mmol) triethylamine, 5.10
g (20.7 mmol) of 2-(t-butoxycarbonyloxyimino)-2-phenylacetonitrile ("Boc-ON") and 11 ml of tetrahydrofuran are added. The mixture was stirred overnight at room temperature;
Add 25 ml of water and wash with ethyl acetate. The aqueous layer is brought to pH 1.8 with 1N hydrochloric acid and extracted with ethyl acetate (3 x 75 ml), dried (MgSO ₄ ) and evaporated in vacuo to give 4.2 g of product as a sticky liquid. Rf0.65 (9:9:2 ethyl acetate/hexane/acetic acid, molybdenum phosphate spray) B N-t-Boc-D-O-methylserine N-
(2,2,4,4-tetramethylthiethane-3
-yl)amide 4.2 g (18.6 mmol) of Nt-Boc-D-
Add 2.08 ml of N-methylmorpholine to a solution of O-methylserine in 90 ml of methylene chloride, cool to -15°C, and add 1.78 ml of ethyl chloroformate. After stirring for 8 minutes at −20 to −15°C, 2.70 g (18.6 mmol) of 3-
A solution of amino-2,2,4,4-tetramethylthiethane in 10 ml of methylene chloride is added at the same temperature, and then allowed to warm to room temperature. After stirring for 2 hours, the reaction mixture was washed with dilute sodium hydroxide solution and dilute hydrochloric acid, dried over magnesium sulfate, and the solvent was distilled off under vacuum to give 6.04 g.
(94%) yield of colorless solid, Rf0.35 (3:
7 ethyl acetate/hexane, molybdenum phosphate spray). The structure was verified by ¹ H-NMR. C D-O-methylserine N-(2,2,4,4
-tetramythylthietan-3-yl)amide 6.04 g (17.4 mmol) of N-t-Boc-D
-O-methylserine N-(2,2,4,4-tetramethylthietan-3-yl)amide 13.4
6.7 in solution dissolved in ml methylene chloride
ml (87 mmol) of trifluoroacetic acid (sp.
gr.1.480) and stir at room temperature for 3 hours. Further, a solution of 1 ml dissolved in 2 ml of methylene chloride was added, and the mixture was stirred for 1 hour. reaction mixture 40
% (wt.) Make alkaline with sodium hydroxide solution, remove the organic layer, and extract the aqueous layer several times with fresh methylene chloride. The combined extracts were dried (MgSO ₄ ) and the solvent was distilled off under vacuum to obtain 4.29 g of crude liquid product. This was dissolved in 20 ml of 1N hydrochloric acid, washed with ethyl ether, and the aqueous layer was made alkaline with sodium hydroxide solution (40% by weight).
After saturation with sodium chloride, extract with methylene chloride. The extract was distilled off and 3.21g (75
%) of the target substance, Rf0.41; [Alpha] _D
−19.8° (C=0.8, 1NHCl). The structure of this product was confirmed by ¹ H-NMR spectrum. Reference example 6 3.76 g of the product obtained in Step C of Example 6 was dissolved in 50 ml on a scale of 13 mmol by the method of Step A of Reference Example 3.
of methylene chloride as solvent yields 5.0 g (74%) of the desired diprotected dipeptide amide as a friable foam, Rf 0.40 (ethyl acetate/hexane, 1:1;
molybdenum phosphate spray). The structure of the product is
Confirmed by ¹ H-NMR spectrum. B 5.0g (9.7 mmol) of 2 obtained in step A above
Anhydrous hydrogen bromide gas is passed through the solution of the protected dipeptide amide and stirred for 1 hour at room temperature. The reaction mixture is evaporated to dryness under vacuum and the resulting yellow solid residue is dissolved in water. This solution was mixed with ethyl ether twice,
Wash once with methylene chloride, adjust the aqueous layer to pH 5.8 with sodium hydroxide solution, and evaporate to dryness under vacuum. The solid residue is dissolved in 10 ml of 95% ethanol and ethyl ether is added to precipitate the title compound in two groups at once. 1.66g, [Alpha] _D +13.4゜(C=0.9,
1.2NHCl), MP85-95℃; 1.20g, [Alpha] _D +13.9°, (C=0.8,
1.2NHCl). Each cluster contains a small amount of substance exhibiting an Rf value of 0.44 in addition to the target substance's Rf value of 0.51 in thin layer chromatography. Purification through C p-toluenesulfonate Combined precipitates from the above steps 1.39
g (3.85 mmol) and 0.66 g (3.83 mmol)
of p-toluenesulfonic acid to 10 ml of water. The dissolved solution is stirred at room temperature for 2 hours. When the resulting precipitate is removed and washed with a small amount of water, it becomes 0.94.
g of p-toluenesulfonate is obtained. Add this salt to 3 ml of liquid anion exchange resin (Amberlite LA-1), 6 ml of hexane,
Stir the mixture with 2 ml of water for 2 hours. The aqueous layer was separated, washed with hexane, and then evaporated to dryness under vacuum to obtain 0.72 g of a grayish white solid.
[Alpha] _D +22.43° (C = 0.8, 1.2NHCl);
Rf0.48. Sweetness intensity: 320 times more than sucrose. Because it has no scent and the sweetness hits quickly, it was able to judge sweet tastes with unusual accuracy. Registered trademark of Rohm and Haas Co. Example 7 D-O-methylserine N-(2,2,4,4-
Tetramethyl-1,1-dioxothiethane-3
-yl)amide 3.8 g (15 mmol) of N-benzyloxycarbonyl-D-O-methylserine was dissolved in 75 ml of methylene chloride, N-methylmorpholine (1.68 ml) was added, and after cooling to -15 °C.
Add 1.43 ml of ethyl chloroformate. After stirring the reaction solution at -15°C for 8 minutes, 2.18 g (15 mmol) of 3-amino-2,2,4,4-tetramethylthiethane was added, and the mixture was allowed to warm to room temperature. After further stirring for 2 hours, the reaction mixture was washed with dilute sodium hydroxide solution and dilute hydrochloric acid, dried (MgSO ₄ ), and the solvent was distilled off under vacuum to give 6.11
g of liquid product, Rf0.58 (ethyl acetate/
Hexane, 1:1; molybdenum phosphate spray). B Oxidation to 1,1-dioxide 6.11 g of the product obtained in step A above is dissolved in 75 ml of chloroform, and 7.12 g of m-chloroperbenzoic acid is added little by little under ice cooling. The reaction mixture was allowed to warm to room temperature and stirred for 3 hours. Add more chloroform (75 ml) to dilute the solution to 5%
(Weight/volume) Wash twice each with sodium carbonate solution, 0.5N sodium thiosulfate, and 1N hydrochloric acid. After drying the organic layer (MgSO ₄ ) and evaporating the solvent, 6.24 g of product was obtained as a sticky liquid, Rf 0.22 (ethyl acetate/hexane, 1:1,
(Molybdate Spray) This contains starting materials and traces of sulfoxide. ¹ H−
The NMR spectrum was consistent with the structure of the desired sulfone containing a small amount of chloroform. 6.11g N-benzyloxycarbonyl-D
-O-methylserine N-(2,2,4,4-tetramethyl-1,1-dioxothiethane-3-
yl)amide, 250 ml of methanol and 3.0 g of 5
% palladium-carbon catalyst mixture at 50psi
(3.52/cm ² ) for 2 hours. The catalyst is removed by filtration, the solvent is distilled off under vacuum, and the residue is dissolved in 1N hydrochloric acid. The acidic solution is washed three times with chloroform, then made alkaline with solid sodium hydroxide, saturated with sodium chloride and extracted three times with 50 ml of chloroform. The extracts are combined and dried (MgSO ₄ ) and the solvent is distilled off under vacuum to obtain 3.37 g (80%) of the alpha-amino amide product as a colorless liquid, Rf 0.29;
[Alpha] _D -15.7° (C=0.8, 1NHCl). The structure is
Confirmed by ¹ H-NMR spectrum. Reference example 7 Using 3.37 g (12 mmol) of the product obtained in Step C of Example 7 as a starting material, the desired di-protected dipeptide amide was obtained as a transparent glassy substance by the method of Step A of Reference Example 1. 6.73 g (91%) ),
Rf0.28 (ethyl acetate/hexane, 70:30). The ¹ H-NHR spectrum was in good agreement with this structure. B 6.73 g of beta-benzyl N-Cb ₂ -L-aspartyl-D-O-methylserine N-(2,
A mixture of 2,4,4-tetramethyl-1,1-dioxothiethan-3-yl)amide, 250 ml of methanol and 2.0 g of 5% Pd/C catalyst is hydrogenated as in Step C above. The residue left after evaporation of the solvent was stirred in ethyl ether overnight,
The solid product was taken and dried in a vacuum oven, yielding 3.3 g (77%) of the desired dipeptide amide.
obtained with a yield of Rf 0.23; MP 140-150°C (decomposition); [Alpha] _D +20.3° (C=1, 1.2NHCl). Sweetness intensity: 200 times that of sucrose Example 8 D-serine N-(dl-cis, trans-2,6
-dimethylcyclohexyl)amide A dl-cis-trans-2,6-dimethylcyclohexylamine 2.1 g of trans-2,6-dimethylcyclohexanone oxime are dissolved in 30 ml of dry ethanol and heated to reflux. Add 3.1 g of sodium metal little by little to this solution. When the addition is complete, reflux is continued for an additional 30 minutes, and then allowed to cool to room temperature. The reaction solution becomes a gel, so dissolve it in water, adjust the pH to 2.0 with hydrochloric acid, and wash with ethyl ether. The aqueous layer is made alkaline with sodium hydroxide and extracted with ether. The extract is dried (MgSO ₄ ) and then distilled off to obtain the desired amine as a colorless liquid. B D-serine N-(dl-cis, trans-2,
6-dimethylcyclohexyl)amide 1.47 g as described in steps B and C of Example 1
(6.15 mmol) of N- _Cb2 -D-serine, 775
mg (6.15 mmol) of dl-cis, trans-
2,6-dimethylcyclohexylamine is reacted with an equal amount of N-methylmorpholine and ethyl chloroformate, and the amino protecting group is removed by catalytic reduction to obtain 0.70 g of the desired D-serinamide as a white solid. Rf0.64 (ethyl acetate/hexane,
7:3). Reference example 8 A 2-protected dipeptide amide 600 mg (2.8 mmol) of D-serine-N-
Step A of Reference Example 1 using (dl-cis, trans-2,6-dimethylcyclohexyl)amide
Betabenzyl N-benzyloxycarbonyl-L-aspartyl-D- corresponding to the procedure
1.2 g of serine amide is obtained as a colorless solid. Recrystallization from isopropyl ether yields 1.0 g. Rf0.35 (ethyl acetate/hexane, 7:3). B The 2-protected dipeptide amide (1.0 g) obtained in Step A above was catalyzed by the method of Example 6 in the presence of 0.6 g of 5% palladium/carbon catalyst in methanol to give the title compound as an off-white color. Obtained in a yield of 435 mg as a crystalline solid. Sweet intensity: 200 times that of sucrose Example 9 D-O-methylserine N-(3,5-dimethyltetrahydrothiopyran-4-yl)amide Mixture of cis/trans and trans/trans isomers A 3,5-dimethyltetruhydrothiopyran-
4-one A mixture of 2 g of sodium acetate and 25 ml of ethanol is saturated with hydrogen sulfide gas. In this solution
Add 7.0 g (0.063 mole) diisopropenyl ketone. During this time, cool in an ice bath until the heat generated by the reaction disappears. The mixture was stirred at room temperature for 4 hours while passing hydrogen sulfide gas through it, and then left overnight. Ethanol and excess H ₂ S are distilled off under vacuum and the residue is dissolved in ether and washed successively with water, potassium carbonate solution, dilute hydrochloric acid and water. The ether extract is dried (Na ₂ SO ₄ ) and evaporated to give 6.8 g of oil.
This is distilled under vacuum through a 10 cm Vigreaux column to obtain 1.67 g of product, BP83-
86℃/9mm. This is used in the next step without further purification. B 4-oximino-3,5-dimethyltetrahydrothiopyran 1.67 g (0.011 mol) of the cyclic ketone obtained in Step A, 1.6 g (0.023 mol) of hydroxylamine hydrochloride and 1.9 g (0.023 mol) of sodium acetate in 30 ml A mixture of water and 10 ml of ethanol was heated under reflux for 3 hours, and after cooling, the precipitate was collected. When recrystallized from methanol-water 1:1
1.5 g of oxime is obtained as a white solid. M.
P.60−85℃. This is a mixture of isomers that is sufficiently pure to be used in the next step. C trans/trans and cis/trans-4-
Amino-3,5-dimethyltetrahydrothiopyran oxime obtained in step B 1.45 g (0.009 mol)
5 g of sodium is added little by little to a solution of 15 ml of ethanol, then 25 ml of ethanol is added, and the reaction mixture is heated under reflux for about 30 minutes.
The reaction mixture is diluted with water, extracted with ethyl ether and the extract is washed with water. The ether layer is then extracted with dilute hydrochloric acid and the aqueous layer is washed with fresh ether. The aqueous layer is made alkaline by adding sodium hydroxide solution and extracted again with ether. After drying the organic layer (MgSO ₄ ), the ether is distilled off to give 1.1 g of a colorless oil. Gas chromatography (program to raise temperature from 80 to 100℃ using OV-1 column)
The results showed that the product contained two main components in a 60/40 ratio. ^1H -NMR
(CDCl ₃ ) means that the product is 4-amino-3-
It was suggested to be a mixture of trans-5-trans-dimethyltetrahydrothiopyran and the corresponding 3-cis-5-trans-isomer. D N(3,5-dimethyltetrahydrothiopyran-4-yl)-t-butoxycarbonyl-D
-O-methylserinamide 1.96 g obtained in step A of Example 6 under anhydrous conditions
A mixture of Nt-Boc-D-O-methylserine (8.9 mmol), 1.98 g (19 mmol) triethylamine and 40 ml tetrahydrofuran is cooled to -10°C. To this was added dropwise 0.96 g (8.9 mmol) of ethyl chloroformate and the mixture was stirred at -10°C for 20 minutes. In this solution
1.1 g (7.5 mmol) of the mixture of isomers of 4-amino-3,5-dimethyltetrahydrothiopyran obtained in step C was added and the reaction mixture was heated to -10 °C.
After stirring for 10 minutes, leave to warm to room temperature. The reaction mixture is diluted with water and extracted with ethyl acetate. The organic layer is washed with sodium hydrogen carbonate, dilute hydrochloric acid, water, and brine, dried (Na ₂ SO ₄ ), and the solvent is distilled off under reduced pressure to obtain the desired product. E N-(3,5-dimethyltetrahydrothiopyran-4-yl)-D-O-methylserinamide Dissolve the t-Boc-amide obtained in step D in a mixture of 15 ml of ethanol and 5 ml of concentrated hydrochloric acid, and add 10 ml of
Add water. The liquid is heated under reflux for 30 minutes, and after cooling, ethanol is removed by distillation under vacuum. After washing the aqueous residue with ethyl acetate, it is made alkaline with sodium hydroxide solution and extracted with ether, and the extract is dried (Na ₂ SO ₄ ). The desired aminoamide is obtained by distilling off the solvent. Reference Example 9 A Condensation of D-O-methylserinamide and L-aspartic acid N-thiocarboxyanhydride 1.25 g (5.1 mmol) of D-O-methylserinamide obtained in Step E of Example 9 was added to 5 ml of tetrahydrofuran. Dissolve and add 5 ml of water. Cool the clear solution with ice, 0.89 g (5.1 mmol)
of L-aspartic acid N-thiocarboxylic anhydride in one portion. If this solution requires
Add 0.5M sodium hydroxide and bring the mixture to pH9.
Keep it. After stirring for 30 minutes, the reaction mixture is washed with ethyl ether and ethyl acetate, and the washings are discarded. The aqueous layer was made acidic to PH5.6 with dilute hydrochloric acid,
Evaporate to dryness under reduced pressure. Hot methanol (100 ml) was added to the residue, filtered, and methanol was distilled off. Hot methanol was added to the residue again and filtered.
After decolorizing the liquid with activated carbon, it is passed through diatomaceous earth, and the liquid is distilled off to obtain a crude product. The crude product was dissolved in hot water (11 ml), filtered and concentrated to 5 ml under a stream of nitrogen, and upon cooling with ice a precipitate formed, which was collected and dried. In the procedure of Step D of Example 9 above, t-Boc
-T-Boc- instead of -D-O-methylserine
N-t-Boc-D (or
DL) - When amino acids are reacted by the method of Example 9 Steps D and E and Reference Example 9 Step A, the structural formula ()
Each corresponding compound is obtained. However, R is 3,
5-dimethyltetrahydrothiopyran-4-yl and R ^a is CH ₂ OH or CH ₂ OCH ₃ . Example 10 D-serine N-(2,2,4,4-tetramethyltetrahydrothiophen-3-yl)amide: To a solution of 2.26 g (11 mmol) N-t-butoxycarbonyl-D-serine in 75 ml tetrahydrofuran is added 1.47 ml (10 mmol) triethylamine and the mixture is cooled to -10°C. At this temperature, add 0.96 ml (10 mmol) of ethyl chloroformate and continue stirring for 15 minutes. 1.6 g (10 mmol) after cooling to −20 °C
dl-3-amino-2,2,4,4-tetramethyltetrahydrothiophene is added and the mixture is allowed to warm to room temperature. Ethyl acetate is added and the mixture is washed twice with 50 ml of 5% (by weight) citric acid solution, sodium bicarbonate solution (50 ml, once) and saturated saline (50 ml, once). The organic layer was dried (Na ₂ SO ₄ ) and evaporated to dryness under pressure.
-(2,2,4,4-tetramethyltetrahydrothiophen-3-yl)-t-butoxycarbonyl-D-serinamide is obtained. This product is used in the next step without purification. 5 ml of methanol and 30 ml of 1M hydrochloric acid were added to 3 g of the product obtained in step A, and the mixture was placed on a steam bath.
Heat for 30 minutes. Methanol is distilled off and the residue is extracted with ether. The ether is discarded, the aqueous layer is adjusted to pH 11.0 with sodium hydroxide solution, and extracted with ethyl acetate. When the extract was dried (Na ₂ SO ₄ ) and evaporated to dryness, D-serine N-
(2,2,4,4-tetramethyltetrahydrothiophen-3-yl)amide is obtained. Reference example 10 A Condensation to dipeptide amide D-serinamide obtained in Example 10 step B 1.03
g (4.25 mmol) in 10 ml of water, cooled with ice, and adjusted to pH 9.2 with 0.5N sodium hydroxide solution. To this is added 0.8 g (4.25 mmol) of L-aspartic acid N-thiocarboxyalhydride in small portions while stirring, while maintaining the pH of the mixture at 9 with sodium hydroxide solution (0.5 N). Once the addition is complete, heat the mixture to 0°C.
Stir for 45 minutes, adjust the pH to 5.2 with hydrochloric acid, and evaporate to dryness under vacuum. The residue is made into a slurry with methanol, precipitated solids are removed by filtration, and the liquid methanol is distilled off under reduced pressure. The crude product thus obtained is purified by column chromatography on silica gel.

Claims (1)

[Claims] 1 Formula: D-amino acid amide compound. (In the formula, R ^a is CH ₂ OH or CH ₂ OCH ₃ ; R is [Formula] [Formula] [Formula] (where R ³ and R ⁶ are methyl, R ⁴ and R ⁵ are hydrogen or methyl, and X is S or SO ₂ , n and p are each zero or 1) or [Formula]) 2 R is dicyclopropylcarbinyl, 2,2,
The compound of claim 1 which is 4,4-tetramethylthietan-3-yl or 2,2,4,4-tetramethyl-1,1-dioxo-thietan-3-yl. 3. The compound of claim 2, wherein R ^a is CH ₂ OH.