FR2719592A1 - N-alkylated di:peptide sweetening agents - Google Patents

Abstract

Sweetening agents of formula (I) and their non toxic salts are new. R = (CH3)3-C-CH2-CH2- or (CH3)2-CH-CH2-CH2-; n = 1; X = COOCH3; Y = -CH2-S-C(CH3)3, -CH2-O-C(CH3)3, -CH2-O-CH2-C(CH3)3, -CH2-CH2-O-C(CH3)3, -CH2-CONH-C(CH3)3, or -CH2-NHCO-C(CH3)3.

Description

 The present invention relates to novel compounds useful as sweetening agents.

 These novel compounds are particularly useful for sweetening various products, especially beverages, foods, confectionery, pastries, chewing gum, hygiene products and toiletries, as well as cosmetic, pharmaceutical and veterinary products.

 It is known that a sweetening agent, to be used on an industrial scale, must have, on the one hand, an intense sweetening power to limit the use cott, and, on the other hand, a satisfactory stability, c that is to say compatible with the conditions of use.

 Among the currently marketed sweetening agents, a dipeptide derivative, N-L-aaspartyl-L-phenylalanine 1-methyl ester, known under the name of aspartame, is today the most used (US 3,492,131).

One of the strengths of this compound is its chemical constitution based on two natural amino acids, the acid
L-aspartic and L-phenylalanine. The sweetening power of this compound is less than 200 times that of sucrose on a weight basis.

 Despite its excellent organoleptic qualities, this compound has the main disadvantage of being an expensive product, because of its relatively low sweetening intensity, and of having a relatively low stability under certain conditions of use of the sweeteners, especially in a neutral medium. , which limits its fields of industrial applications.

 Consequently, it appeared necessary for the food industry to be able to have a new sweetening agent which would have a high sweetening activity, in order to reduce its cost price, and which would be at least as stable and even more stable than aspartame, especially in a neutral environment.

 Thus, many sweet dipeptide derivatives have since been synthesized (see for example J.M.

Janusz, in "Progress in Sweeteners", TH Grenby ed.,
Elsevier, London, 1989, pp. 1-46).

 But to date, apart from aspartame, none of these derivatives seemed to meet the main requirements that are asked of a sweetener, namely: excellent organoleptic qualities, sweetening intensity high enough to reduce the cost of use sufficient stability.

 Unexpectedly, it has been discovered, and this constitutes the basis of the present invention, that the sweetening power of some of these dipeptide derivatives can be greatly increased, up to about 25 times, by fixing on their alpha group. amino-free a suitably selected hydrocarbon radical, which achieves sweetening powers up to 20,000 (twenty thousand) times higher than that of sucrose, that is to say 100 (one hundred) times that of the aspartame.

dans laquelle
R est (CH3)3CCR2CH2 ou (CH3)2CHCH2CH2; n est égal a 1;
X est COOCH3;
Y est choisi dans le groupe comprenant les radicaux CH2SC(CH3)3, CH2OC(CH3)3, CH2OCH2C(CH3)3, CH2CH2OC(CH3)3, CH2CONSC(CH3)3 et CH2NHCOC(CH3)3; et les sels physiologiquement acceptables de ces composés.The present application therefore aims to cover the sweetening compounds of the formula

in which
R is (CH3) 3CCR2CH2 or (CH3) 2CHCH2CH2; n is 1;
X is COOCH3;
Y is selected from the group consisting of CH2SC (CH3) 3, CH2OC (CH3) 3, CH2OCH2C (CH3) 3, CH2CH2OC (CH3) 3, CH2CONSC (CH3) 3 and CH2NHCOC (CH3) 3; and the physiologically acceptable salts of these compounds.

dans laquelle les radicaux X et Y répondent aux définitions précédentes.In a preferred embodiment, R is the group (Ca3) 3CCH2CH2, and the compounds have the following general formula

wherein the radicals X and Y are as defined above.

A compound of a particularly preferred embodiment of the invention is N- [N- (3,3-dimethylbutyl) -L-aspartyl] - (S-tert-butyl) -L-cysteine 1-methyl ester of formula

Another compound of a particularly preferred embodiment of the invention is N- [N- (3,3-dimethylbutyl) -L-α-aspartyl] - (O-tert-butyl) -L-serine 1 methyl ester of formula

 It has been described (Z. Lebensm, Unters.-Forsch., 1975, 159, 337-343) that NLa-aspartyl- (S-tert-butyl) -t-cysteine 1-methyl ester has sweetening properties, with a sweetness equal to 900 times that of sucrose. The N-alkylation of this dipeptide derivative by the hydrocarbon group (CH3> 3CCH2CH2 selected in the context of the present invention has led to a new compound which has been unpredictably revealed to be approximately 22 times sweeter, its sweetening power being equal about 20,000 (twenty thousand) times that of sucrose.

 It has also been described in French patent FR 2 055 896 that NLa-aspartyl- (O-tert-butyl) -L-serine 1-methyl ester has sweetening properties with a sweetening power equal to 155 times that of sucrose. The N-alkylation of this dipeptide derivative with the hydrocarbon group (CH3) 3CCH2CH2 selected within the scope of the invention has led to a new compound which has unexpectedly been found to be approximately 25 times sweeter, its sweetening power being about 4,000 times that of sucrose.

 It has furthermore been observed that the stability of the characteristic compounds of the invention is higher than that of aspartame under the usual conditions of use for food preparations. This is an advantage all the more important as one of the limits to the use of aspartame in certain food preparations comes from its very low stability in environments close to neutrality, that is to say for pH 7, pH neighbors that are frequently encountered in products such as dairy products, weavings or other preparations that require high temperature cooking, chewing gums, toothpastes.

 An accelerated aging study by prolonged heating at 70 ° C. of an aqueous solution at pH 7 of a characteristic compound of the invention, namely N [N- (3,3-dimethylbutyl) -L-aspartyl] - ( S-tert-butyl) -L-cysteine 1-methyl ester, showed that this compound has a half-life of about 4 hours, while the half-life of aspartame under the same conditions is only 10 minutes, which corresponds, for the compound according to the invention, to a stability 24 times higher than that of aspartame.

 Comparable results were obtained for the other characteristic compounds of the invention.

 It has also been demonstrated that the stability of the compounds of the invention is at least equal to, or even improved, in an acid medium at a pH in the region of 3, which corresponds to that of carbonated beverages which constitute one of the major applications of sweeteners.

 Thus, an accelerated aging study, by prolonged heating to 70 OC of an aqueous solution at pH 3 of the abovementioned compound of the invention, has shown that this compound has a half-life of approximately 30 hours, whereas the half The life of aspartame under the same conditions is 24 hours, which corresponds, for the compound according to the invention, to a stability 1.25 times higher than that of aspartame.

 Comparable results were obtained for the other characteristic compounds of the invention.

 Because of their high sweetness, another advantage of the compounds of the invention, compared to aspartame, is to allow, in their application to food products, the use of very small amounts of active agent. For example, 550 mg of aspartame per 5.5 mg of N- (N- (3,3-dimethylbutyl) -La-aspartyl) can be replaced in one liter of soft drink. -L- (S-tert-butyl) -L-cysteine 1-methyl ester described in the present invention, and thereby reducing, up to 100 (one hundred) times, the amounts of sweetening agent that can be consumed, while maintaining identical organoleptic qualities.

 The present invention thus makes it possible to provide novel dipeptide derivatives which have excellent organoleptic qualities associated with a very high sweetening power, up to 20,000 (twenty thousand) times the sweetening power of sucrose on a weight basis, and a stability at less similar or greater compared to aspartame, which has the effect of broadening the possibilities of using sweeteners derived from dipeptides in food preparations.

 The compounds of the invention may also be salified with physiologically acceptable inorganic or organic acids or bases, which has the effect of increasing their solubility. Advantageously, these compounds are salified in the form of hydrochloride or of sodium, potassium, ammonium, calcium or magnesium salts.

 The present application is intended to cover the compounds of the invention as sweetening agents, the sweetening compositions incorporating as sweetening agent at least one compound defined as above, and the use of the compounds of the invention to sweeten the various products recalled in the introduction.

 The sweetening agents of the present invention may be added to any edible product in which it is desired to provide a sweet taste, provided they are added in sufficient proportions to achieve the desired sweetness level. The optimum use of the sweetening agent will depend on various factors such as, for example, the sweetening power of the sweetening agent, the conditions of storage and use of the products, the particular constituents of the products and the level of sweetness. desired sweetness. Any qualified person can easily determine the optimum proportion of sweetening agent that must be used to obtain an edible product by conducting routine sensory analyzes. The sweetening agents of the present invention will generally be added to the edible products in amounts ranging from 0.5 mg to 50 mg of sweetening agent per kilogram or per liter of edible product depending on the sweetness of the compound. The concentrated products will obviously contain higher amounts of sweetening agent, and will then be diluted according to the final use intention.

 The sweetening agents of the present invention can be added in pure form to the products to be sweetened, but, because of their high sweetening power, they are generally mixed with a carrier ("carrier") or a bulking agent ("bulking agent"). ") appropriate.

 Advantageously, the appropriate carriers or fillers are chosen from the group consisting of polydextrose, starch, maltodextrins, cellulose, methylcellulose, carboxymethylcellulose and other cellulose derivatives, sodium alginate, pectins, gums, lactose, maltose, glucose, leucine, glycerol, mannitol, sorbitol, sodium bicarbonate, phosphoric acid, citric acid, tartaric acid, fumaric acid, benzoic acid, sorbic acid, propionic acid, and their sodium salts , potassium and calcium, and their equivalents.

 The sweetening agents according to the invention may, in an edible product, be used alone, as a sole sweetening agent, or in combination with other sweetening agents such as sucrose, corn syrup, fructose, derivatives or the like. sugar dipeptide (aspartame, alitame), neohesperidin dihydrochalcone, hydrogenated isomaltulose, stevioside, L sugars, glycyrrhizin, xylitol, sorbitol, mannitol, acesulfame, saccharin and its sodium salts, potassium, ammonium and calcium, cyclamic acid and its sodium, potassium and calcium salts, sucralose, monellin, thaumatin, and the like.

 The compounds of the present invention can be prepared by various methods already described in the literature. One of the preferred methods is a reductive N-alkylation of the dipeptide derivative selected with the selected group R aldehyde precursor; this reaction taking place in the presence of a reducing agent such as sodium cyanoborohydride or hydrogen in the presence of a catalyst (see for example Ohfune et al., Chem Letters, 1984, pp. 441-444 or the review Rylander NP, "Catalytic Hydrogenation in Organic Syntheses," Academic Press, San Diego, 1993, pp. 165-174).

 The preparation of N- [N- (3,3-dimethylbutyl) -L-α-aspartyl] - (S-tert-butyl) -L-cysteine 1-methyl ester was, for example, carried out by reductive N-alkylation of the dipeptide derivative NLa-aspartyl- (S-tert-butyl) -L-cysteine 1-methyl ester with 3,3-dimethylbutyraldehyde of formula (CH3) 3CCH2CHO in the presence of sodium cyanoborohydride as reducing agent.

 Similarly, the preparation of N- [N- (3,3-dimethylbutyl) -L-aspartyl] - (O-tert-butyl) -L-serine methyl ester was carried out by reductive N-alkylation of the dipeptide derivative NLa. Aspartyl- (O-tert-butyl) -L-serine 1-methyl ester with 3,3-dimethylbutyraldehyde in the presence of hydrogen as a reducing agent and 5% platinum on activated carbon as catalyst.

 The preparation of the starting dipeptide derivatives was carried out according to the usual techniques of peptide synthesis and which have been described in particular in the aforementioned documents: Z. Lebensm.

Unters.-Forsch., 1975, 159, 337-343 and French patent FR 2,105,896.

 The purification of the compounds of the invention, in their acid or salified form, is carried out according to standard techniques such as recrystallization or chromatography. Their structure and purity were controlled by conventional techniques (thin layer chromatography, high performance liquid chromatography, infrared spectrometry, nuclear magnetic resonance, elemental analysis).

 The manner in which the invention can be realized and the advantages thereof will become more apparent from the following exemplary embodiments.

 In these examples, the sweetening power of the compounds described was evaluated by a group of eight experienced persons. For this, the compounds, in aqueous solution at varying concentrations, are compared, in terms of taste, with a 2%, 5% or 10% sucrose control solution. The sweetening power of the compound, tested with respect to sucrose, then corresponds to the weight ratio that exists between the compound and the sucrose at equal sweetening intensity, that is to say when the sweet flavors of the solution of the test compound and of the reference solution. of sucrose are considered by a majority of people to have the same sweetening intensity.

EXAMPLE 1
Preparation of N- (N- (3,3-dimethylbutyl) -L- (x-aspartyl) - (S-tert-butyl) -L-cysteine 1-methyl ester

<tb> formula
<tb><SEP> CH3
<tb><SEP> CO <SEP> - <SEP> NH <SEP>><SEP> C <SEP> r <SEP> H
<tb><SEP> CH3 <SEP> e <SEP> e
<tb><SEP> CH3 <SEP> C-CH-CH <SEP> -NH <SEP>><SEP> C <SEP><SEP> H <SEP> C
<tb><SEP> 2 <SEP> 2 <SEP> e <SEP> I
<tb><SEP> CH3 <SEP> CH2 <SEP> S
<tb><SEP> COOH <SEP> CH3-C-CH3
<tb><SEP> CH3
<Tb>
0.16 g (2 mmol) of 3,3-dimethylbutyraldehyde of commercial origin are added to a mixture, in 10 cm3 of methanol, of 0.5 g (1.63 mmol) of NLa-aspartyl (S-tert-). butyl) -L-cysteine 1-methyl ester and 0.073 g (1.16 mmol) of sodium cyanoborohydride. The solution is stirred for 24 hours at room temperature and is then concentrated to dryness under vacuum. The residue is then taken up in an aqueous solution of 1N hydrogen chloride until the pH is close to neutral.

After several hours, a white precipitate appears which is filtered off and dried. 0.27 g of N- (N- (3,3-dimethylbutyl) -L-α-aspartyl- (S-tert-butyl) -L-cysteine 1-methyl ester in the form of an amorphous white solid was thus obtained. (42% yield, 99 C melting point)
The sweetening potency of this compound is approximately 20,000 (twenty thousand) times that of sucrose on a weight basis compared to 2%, 5% and 10% sucrose solutions.

EXAMPLE 2
Preparation of N- [N- (3,3-dimethylbutyl) -L-ar-aspartyl) - (O-tert-butyl) -L-serine 1-methyl ester of formula

 In a reactor equipped with agitation to ensure a very good transfer of hydrogen gas into the liquid phase, is introduced with stirring and in the junk: 12 cm3 of a 0.1 aqueous acetic acid solution M, 200 mg platinum 5% activated carbon (Aldrich product 33,015-9), 0.51 g 3,3 dimethylbutyraldehyde, 6 cm3 methanol and 1 g NL- &alpha; -aspartyl- (O-tert) -butyl) -L-serine 1-methyl ester.

After purging the reactor with a stream of nitrogen, the mixture is subjected to hydrogenation at the relative pressure of 1 bar (0.1 MPa) and at room temperature.

After 2 hours of hydrogenation, the reaction is stopped by purging the reactor with a stream of nitrogen and separating the catalyst by filtration on a fine filter (0.5 Am). If necessary, the filtrate is adjusted to pH 5 by adding a few drops of a 1N sodium hydroxide solution. The methanol is then removed by evaporation under vacuum, the temperature being maintained below 40 ° C. After extraction with ethyl acetate (3 × 20 cm 3), drying over anhydrous sodium sulphate and concentration by evaporation in vacuo, 0.76 g of N- (N- (3,3-dimethylbutyl) -La are obtained. Aspartyl] - (O-tert-butyl) -L-serine 1-methyl ester as a viscous solid without definite melting point (yield 59%).

 The sweetening power of this compound is approximately 4,000 times that of sucrose on a weight basis compared to a 2% sucrose solution.

 The stability of the compounds of the invention with respect to aspartame was measured by assaying, by high performance liquid chromatography (HPLC), the amount of product remaining after accelerated aging by heating at 70 ° C. of their solutions, to the concentration of 1 g / L, in neutral medium (phosphate buffer pH 7) or in acid medium (phosphate buffer pH 3). The stability of the compound thus tested is evaluated by its half-life (time corresponding to 50% degradation).

 In the appended FIG. 1, is given a comparative diagram of the stability curve at pH 7 of aspartame (curve a) and of two characteristic compounds of the invention, namely N- [N- (3,3- dimethylbutyl) -La-aspartyl] - (S-tert-butyl) -L-cysteine 1-methyl ester (curve b) and N- [N- (3,3-dimethylbutyl) -L-aspartyl] - (O- tert-butyl) -L-serine methyl ester (curve c). The half-life of the two compounds of the invention is respectively about 4 hours and 6 hours, while the half-life of aspartame under the same conditions is only 10 minutes, which corresponds to a stability 24 and 36 times higher than that of aspartame.

 In the appended FIG. 2, is given a comparative diagram of the stability curve at pH 3 of aspartame (curve a) and of two characteristic compounds of the invention namely N- [N- (3,3-dimethylbutyl) ) -La-aspartyl] - (S-tert-butyl) -L-cysteine 1-methyl ester (curve b) and N- [N- (3,3-dimethylbutyl) -L-aspartyl] - (O-tert) -butyl) -L-serine 1-methyl ester (curve c). The half-life of the two compounds of the invention is respectively about 30 hours and 36 hours, while the half-life of aspartame under the same conditions is only 24 hours, which corresponds to a stability respectively 1.25 and 1.5 times higher than that of aspartame.

Claims (5)

EEVF: NDICATTONS 1. Sweetening compounds of the general formula

 in which R is (CH3) 3CCH2CH2 or (CH3) 2CHCH2CH2; n is 1; X is COOCH3; Y is chosen from the group of radicals CH2SC (CH3) 3, CH2OC (CH3) 3, CH2OCH2C (CH3) 3, CH2CH2OC (CH3) 3, CH2CONHC (CH3) 3 and CH2NHCOC (CH3) 3; and the physiologically acceptable salts of these compounds. Sweetening compounds according to claim 1, characterized in that they correspond to the following general formula

 wherein the radicals X and Y are as defined in claim 1. 3. A sweetening compound according to claim 1, characterized in that it is N- [N- (3,3-dimethylbutyl) -L-aspartyl] - (S-tert-butyl) -L-cysteine 1-methyl ester of formula

 4. A sweetening compound according to claim 1, characterized in that it is N- [N- (3,3-dimethylbutyl) -L-aspartyl] - (O-tert-butyl) -L-serine-methyl ester of formula

 5. sweetening composition characterized in that it comprises as a sweetening agent at least one compound according to claim 1, in combination with a food grade carrier.