An amino acid furanone ester latent aroma compound and its synthesis method and application

Abstract

Disclosed herein are amino acid furanone ester latent aroma compounds, their synthesis methods, and applications. The compound has the general chemical formula #imgabs0#. Its synthesis method uses a substituted amino acid and furanone as starting materials. In the presence of a condensing agent and a catalyst, the carboxyl group of the amino acid and the hydroxyl group of the furanone condense to produce the amino acid furanone ester latent aroma compound. The compound prepared by the present invention exhibits low volatility and releases furanone, a sweet, burnt aroma, upon pyrolysis. Adding it to cigarettes can significantly improve the draw quality.

Description

Technical Field

[0001] The invention belongs to the field of preparation of novel latent aroma fragrances, and particularly relates to an amino acid furanone ester latent aroma compound and a synthesis method and application thereof. Background Art

[0002] Burnt-sweet aroma compounds are a class of flavoring compounds that can reduce bitterness and sourness while enhancing sweetness and roasted aromas. In 1971, Elmenhorst first discovered maltol, a substance with a burnt-sweet aroma, from cigarette condensate (Acta Chemica Scandinavica, 1990, 44:916-926). Since then, tobacco companies in Japan, Sweden, and other countries have conducted in-depth research on the burnt-sweet aroma of cigarettes, discovering compounds with burnt-sweet aroma characteristics, including furans, furanones, cyclopentenones, and pyrones. The most important of these compounds are methylcyclopentenolone (cyclotene), furanone (furaneol), and maltol. These burnt-sweet aroma ingredients have been widely used in sweet flavors (for beverages, candies, chocolate, dairy products, etc.), savory flavors (for meat products, etc.), and tobacco flavors. These compounds exist in tobacco as latent aroma compounds in structures such as glycosides and esters.

[0003] Amino acids are an important class of nitrogen-containing compounds in tobacco. Their content affects tobacco quality and is also a key aroma precursor (Analytical Testing Technology and Instrumentation, 2019, 25:48-52). There are over 20 common amino acids in tobacco. During tobacco combustion, they react with reducing sugars to form various heterocyclic compounds, such as pyrans, pyrazines, pyrroles, and pyridines, which have aromas characteristic of cooking, roasting, and popcorn. Some amino acids, such as phenylalanine, can also decompose into aroma compounds such as benzyl alcohol and phenylethanol.

[0004] Latent aroma compounds are a class of compounds that have no inherent fragrance or a subtle aroma, but release their aroma components only after being decomposed or cracked by enzymes or heating (Recent Advances in Tobacco Science, 1981, 7, 107-153; Australian Journal of Chemistry, 1989, 42: 2071-2084). Under natural conditions, latent aroma compounds are characterized by low volatility and stable chemical properties. When added to cigarettes, they maintain an odorless, stable structure when the cigarette is not inhaled. When the cigarette is inhaled, they crack and release the desired aroma substances. The expected aroma release amount remains consistent throughout the cigarette inhalation process, thus achieving a stable aroma compensation effect. Therefore, the use of latent aroma compounds in cigarette flavoring and filling not only overcomes the shortcomings of conventional flavors and fragrances, but also ensures a certain degree of confidentiality in the flavor formula of cigarettes. This is something that traditional flavoring and filling technologies cannot achieve, meeting the needs of the development of low-tar cigarette products. Summary of the Invention

[0005] The purpose of the present invention is to provide an amino acid furanone ester latent aroma compound, which has weak volatility and releases furanone, a burnt-sweet aroma substance, after pyrolysis. When applied to cigarette products, it can give cigarettes a burnt-sweet aroma and improve the sensory quality of cigarettes.

[0006] Another object of the present invention is to provide a method for synthesizing amino acid furanone ester latent aroma compounds, wherein the method comprises condensing amino acids and furanone to synthesize novel amino acid furanone ester latent aroma compounds.

[0007] To achieve the purpose, the present invention adopts the following technical solutions:

[0008] The present invention provides an amino acid furanone ester latent aroma compound, the general structural formula of which is as follows:

[0009]

[0010] Wherein: R is hydrogen, methyl, isopropyl, sec-butyl, hydroxymethyl, 1-hydroxyethyl, mercaptomethyl, (methylthio)ethyl, carboxymethyl, carboxyethyl, carbamoylmethyl, carbamoylethyl, imidazolylmethyl, guanidinopropyl, benzyl or 4-hydroxybenzyl, (3-indolyl)methyl; R' is hydrogen, alkyl, aryl or alkoxycarbonyl.

[0011] The typical structural formulas 1-3 of the amino acid furanone ester latent aroma compounds of the present invention are as follows:

[0012]

[0013] The synthesis method of the amino acid furanone ester latent aroma compound is as follows: using substituted amino acids and furanone as starting materials, under the action of a condensing agent and a catalyst, the carboxyl group of the amino acid and the hydroxyl group of the furanone condense to produce the amino acid furanone ester latent aroma compound. The structural formula of the substituted amino acid is The structural formula of the furanone is The specific steps include:

[0014] Step 1, dissolving the substituted amino acid and furanone in an organic solvent, adding a condensing agent and a catalyst, reacting at 25-100° C. for 1-24 hours, and monitoring the conversion of the reaction raw materials by thin layer chromatography;

[0015] Step 2: After the reaction is completed, filter with suction, rinse the filter layer with an organic solvent, evaporate the filtrate to dryness using a rotary evaporator, and then separate and purify by column chromatography to obtain the target product.

[0016] Furthermore, in step 1, for every 5 to 7 mmol of the substituted amino acid reacting with 5 mmol of furanone, 5 to 10 mmol of a condensing agent, 0.05 to 0.5 mmol of a catalyst and 25 to 50 mL of an organic solvent are used.

[0017] Furthermore, in step 1, the condensing agent is at least one of dicyclohexylcarbodiimide, diisopropylcarbodiimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, more preferably dicyclohexylcarbodiimide.

[0018] Furthermore, in step 1, the catalyst is at least one of 4-dimethylaminopyridine and 4-pyrrolidinylpyridine, more preferably 4-dimethylaminopyridine.

[0019] Furthermore, in step 1, the organic solvent is at least one of ethyl acetate, acetonitrile, dichloromethane, 1,2-dichloroethane, chlorobenzene, tetrahydrofuran, 2-methyltetrahydrofuran, diethyl ether and methyl tert-butyl ether, more preferably dichloromethane.

[0020] Furthermore, in step 2, the column chromatography separation refers to column chromatography under air pressure, the silica gel is 200-300 mesh, and the eluent is a mixture of petroleum ether and ethyl acetate in a volume ratio of 100-1:1 or a mixture of dichloromethane and methanol in a volume ratio of 100-10:1.

[0021] For example, when dichloromethane is used as the organic solvent, and dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP) are used as the condensation agent and catalyst, the reaction formula is as follows:

[0022]

[0023] When used, the amino acid furanone ester latent aroma compound of the present invention can be dissolved in alcohol or an alcohol-water mixed solvent and then evenly sprayed onto tobacco or papermaking sheets. The added amount of the latent aroma compound accounts for 0.0001%-0.1% of the weight of the tobacco or papermaking sheets, and more preferably 0.001%.

[0024] The beneficial effects of the present invention are embodied in:

[0025] 1. The present invention is the first to design and synthesize amino acid furanone ester latent aroma compounds. By organically combining amino acids with furanone, the stability of the furanone flavor is greatly improved. During combustion and pyrolysis, furanone can be released as a sweet and burnt aroma substance. Adding it to cigarettes can give cigarettes a sweet and burnt aroma and improve the sensory quality of cigarettes.

[0026] 2. The synthesis method of the present invention has simple process operation, little environmental pollution, low production cost, and is convenient for industrial production. It is a production process with great industrial application prospects.

[0027] 3. Compared with furanones, amino acid furanoesters have significantly improved thermal stability. Specifically, the thermal decomposition temperature of Boc-L-phenylalanine furanoester increased from 127°C to 158°C, and the maximum weight loss temperature increased from 187°C to 247°C; the thermal decomposition temperature of Boc-L-proline furanoester increased from 127°C to 174°C, and the maximum weight loss temperature increased from 187°C to 235°C; and the thermal decomposition temperature of N-Boc-N'-Boc-L-tryptophan furanoester increased from 127°C to 139°C, and the maximum weight loss temperature increased from 187°C to 217°C. This indicates that amino acid furanoesters have a more stable structure and are less susceptible to oxidation and deterioration. During combustion and pyrolysis, they release the sweet and caramelized aroma substance methylcyclopentenolone, significantly improving the sensory quality of cigarettes. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Boc-L-phenylalanine furanone ester 1 H NMR spectrum.

[0029] Figure 2 Boc-L-phenylalanine furanone ester 13 C NMR spectrum.

[0030] Figure 3 Boc-L-proline furanone ester 1 H NMR spectrum.

[0031] Figure 4 Boc-L-proline furanone ester 13 C NMR spectrum.

[0032] Figure 5N-Boc-N'-Boc-L-tryptophan furanone ester 1 H NMR spectrum.

[0033] Figure 6 N-Boc-N'-Boc-L-tryptophan furanone ester 13 C NMR spectrum.

[0034] Figure 7 TG-DTG graphs of furanone, Boc-L-phenylalanine furanone ester, Boc-L-proline furanone ester and N-Boc-N'-Boc-L-tryptophan furanone ester, where (a) is the TG curve and (b) is the DTG curve.

[0035] Figure 8 This is the GC spectrum of the thermal decomposition products of Boc-L-phenylalanine furanone ester at 300°C.

[0036] Figure 9 This is the GC spectrum of the thermal decomposition products of Boc-L-proline furanone ester at 300°C.

[0037] Figure 10 This is the GC spectrum of the thermal decomposition products of N-Boc-N'-Boc-L-tryptophan furanone ester at 300°C. DETAILED DESCRIPTION

[0038] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the following detailed description of the specific embodiments of the present invention is given in conjunction with the accompanying drawings and examples. The following is merely an example and illustration of the concept of the present invention. Those skilled in the art may make various modifications, supplements, or replace the specific embodiments described in the description with similar methods. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they shall fall within the scope of protection of the present invention.

[0039] Example 1: Preparation of Boc-L-phenylalanine furanone ester

[0040]

[0041] To a round-bottom flask, Boc-L-phenylalanine (1.2915 g, 6 mmol, 1.2 equiv), furanone (0.5607 g, 5 mmol, 1 equiv), and dichloromethane (25 mL) were added sequentially. Dicyclohexylcarbodiimide (1.2380 g, 6 mmol, 1.2 equiv) and 4-dimethylaminopyridine (0.0244 g, 0.2 mmol, 0.04 equiv) were then added. The mixture was allowed to react at room temperature for 3 h. After completion of the reaction, the mixture was filtered, and the filter cake was rinsed with dichloromethane. The solvent was removed from the filtrate using a rotary evaporator, and the product was isolated by column chromatography (PE:EA = 10:1). The yield was 1.5569 g, with a yield of 83%. 1 H NMR(600MHz,Chloroform-d)δ7.29(dt,J=30.7,7.5Hz,5H),4.99–4.95(m,1H),4.72(q,J=7.2Hz,1H,4.58(q, J=7.5Hz,1H),3.21(ddd,J=49.5,14.1,6.3Hz,2H),2.12(d,J=8.2Hz,2H),1.50(d,J=7.2Hz,3H),1.40(s,9H); 13 C NMR(151MHz,Chloroform-d)δ195.89(195.86),181.24(181.20),169.84(169.78),155.73,136.04(135.97),130.09 ,130.04,129.27,127.78,82.11(82.09),80.81,54.90(54.79),38.44(38.40),28.81,16.89(16.86),14.62(14.61). HRMS(ESI)m / z[M+H] + Calcdfor C 20 H 26 NO6:376.1755; Found:376.1756.

[0042] Example 2: Preparation of Boc-L-proline furanone ester

[0043]

[0044] To a round-bottom flask, Boc-L-proline (2.1525 g, 10 mmol, 1.25 equiv) and furanone (1.025 g, 8 mmol, 1 equiv) were added sequentially, followed by dichloromethane (25 mL). Dicyclohexylcarbodiimide (2.0633 g, 10 mmol, 1.25 equiv) and 4-dimethylaminopyridine (0.04 g, 0.32 mmol, 0.04 equiv) were then added. The mixture was allowed to react at room temperature for 3 h. After completion of the reaction, the mixture was filtered, the filter cake rinsed with dichloromethane, and the filtrate collected. The solvent was removed from the filtrate using a rotary evaporator, and the product was separated by column chromatography (PE / EA = 6:1). 1.5087 g of the compound was obtained, with a yield of 58%. 1 HNMR(600MHz,Chloroform-d)δ4.54–4.46(m,1H),4.40(dt,J=8.6,4.4Hz,1H),3.58–3.31(m,2H),2.36–2.1 8(m,1H),2.16–2.10(m,3H),2.06–1.91(m,1H),1.92–1.81(m,2H),1.45–1.40(m,3H),1.40(d,J=2.2Hz,9H); 13 CNMR(150MHz,Chloroform-d)δ198.82,178.30(175.82),155.87(154.04),134.09,81.11(80.51),80. 33, 58.93, 46.87 (46.32), 30.78 (29.01), 28.36 (28.22), 24.26 (23.63), 20.74 (20.16), 16.43 (13.63). HRMS(ESI)m / z[M+H] + Calcd for C 16 H 24 NO6:326.1598; Found:326.1598.

[0045] Example 3: Preparation of N-Boc-N'-Boc-L-tryptophan furanone ester

[0046]

[0047] To a round-bottom flask, N-Boc-N'-Boc-L-tryptophan (4.0446 g, 10 mmol, 1.25 equiv) and furanone (1.0250 g, 8 mmol, 1 equiv) were added sequentially, followed by dichloromethane (25 mL). Dicyclohexylcarbodiimide (2.0633 g, 10 mmol, 1.25 equiv) and 4-dimethylaminopyridine (0.04 g, 0.32 mmol, 0.04 equiv) were then added. The reaction was allowed to react at room temperature for 8 h. After completion of the reaction, the mixture was filtered, the filter cake rinsed with dichloromethane, and the filtrate collected. The solvent was removed from the filtrate using a rotary evaporator, and the product was separated by column chromatography (PE:EA = 25:1). 1.4810 g of the compound was obtained, with a yield of 36%. 1 H NMR (600MHz, Chloroform-d) δ8.13(s,1H),7.59(dd,J=29.5,12.3Hz,2H),7.31(t,J=7.8Hz,1H),7.24(t,J=7.5Hz,1H),5.12(d,J=7.9Hz,1H),4.80(t,J=6. 2Hz,1H),4.58(dt,J=14.6,7.2Hz,1H),3.40(d,J=13.0Hz,1H),3.26(dd,J=14 .7,6.2Hz,1H),2.08(s,3H),1.66(s,9H),1.50(d,J=2.4Hz,3H),1.41(s,9H); 13 C NMR(150MHz,Chloroform-d)δ176.41,156.00,150.25,135.96,131.17,125.04,124.76,123.15,119.55,119.33, 115.76,84.28,81.99,80.79,61.09,54.07(55.18),32.46(30.25),28.74(28.85),28.31(28.08),21.59(14.72). HRMS(ESI)m / z[M+H] + Calcd for C 27 H 35 N2O8:515.2388; Found:515.2390.

[0048] Example 4: Thermal Stability Comparison

[0049] Depend on Figure 7It can be seen that furanone began to decompose at 127°C, with significant weight loss occurring in the temperature range of 127-395°C, with the maximum weight loss rate reaching 187°C, and the total weight loss rate reaching 99.5%. Boc-L-phenylalanine furanone ester began to decompose at 158°C, with significant weight loss occurring in the temperature range of 148-433°C, with the maximum weight loss rate reaching 247°C, and the total weight loss rate reaching 92.7%. Boc-L-proline furanone ester began to decompose at 174°C, with significant weight loss occurring in the temperature range of 174-428°C, with the maximum weight loss rate reaching 235°C, and the total weight loss rate reaching 98.3%. N-Boc-N'-Boc-L-tryptophan furanone ester began to decompose at 139°C, with significant weight loss occurring in the temperature range of 139-431°C, with the maximum weight loss rate reaching 217°C, and the total weight loss rate reaching 95.6%. From the data, it can be seen that compared with furanone, the thermal decomposition temperatures of Boc-L-phenylalanine furanone ester, Boc-L-proline furanone ester and N-Boc-N'-Boc-L-tryptophan furanone ester increased from 127°C to 158°C, 174°C and 139°C respectively, the thermal stability was improved, and the maximum thermal weight loss temperature increased from 187°C to 247°C, 235°C and 217°C respectively.

[0050] Example 5: Pyrolysis products of target products

[0051] Accurately weigh 2 mg of Boc-L-phenylalanine furanone ester, place it in a pyrolysis instrument, and rapidly heat it to 300°C at a heating rate of 20°C / ms under a helium atmosphere. The pyrolysis products are analyzed; the samples are replaced with Boc-L-proline furanone ester and N-Boc-N'-Boc-L-tryptophan furanone ester, and the above operation is repeated. The total ion current of the pyrolysis products of the three amino acid furanone ester compounds is shown in Figure 2. Figure 8 、 Figure 9 、 Figure 10 ,The analysis results show that the three compounds can effectively release furanone (marked by the arrow in the figure) at 300°C, ,with a burnt sweet aroma.

[0052] Example 5: Evaluation of the flavoring of the target product in tobacco

[0053] The three amino acid furanone ester latent aroma compounds described above were dissolved in 95% ethanol to prepare a 0.1% solution. 1.0g of this solution was evenly sprayed onto 100g of blank cut tobacco. After 2 hours of equilibration, the resulting cigarettes were rolled into sample cigarettes. The sample cigarettes were equilibrated in a constant temperature and humidity chamber at 22°C ± 1°C and 60% ± 2% for 48 hours. They were then smoked against unflavored samples placed under the same conditions. The sensory evaluation results are shown in the following table:

[0054]

[0055] The above are merely exemplary embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An amino acid furanone ester latent aroma compound, characterized in that: Its structural formula is shown in Formula 1, Formula 2 or Formula 3: ； ； 。 2. A method for synthesizing the amino acid furanone ester latent aroma compound according to claim 1, characterized in that: Using substituted amino acids and furanone as starting materials, under the action of a condensing agent and a catalyst, the carboxyl group of the amino acid and the hydroxyl group of the furanone are condensed to generate amino acid furanone ester latent aroma compounds; the substituted amino acid is Boc-L-phenylalanine, Boc-L-proline or N-Boc-N'-Boc-L-tryptophan; the structural formula of the furanone is: 。 3. The synthesis method according to claim 2, characterized in that The method comprises the following steps: mixing a substituted amino acid, furanone, a condensing agent, a catalyst and an organic solvent, reacting at 25-100° C. for 1-24 hours, and obtaining a target product by column chromatography separation and purification after the reaction.

4. The synthesis method according to claim 2 or 3, characterized in that: For every 5-7 mmol of substituted amino acid reacted with 5 mmol of furanone, 5-10 mmol of condensing agent, 0.05-0.5 mmol of catalyst and 25-50 mL of organic solvent are used.

5. The synthesis method according to claim 2 or 3, characterized in that: The condensing agent is at least one of dicyclohexylcarbodiimide, diisopropylcarbodiimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide.

6. The synthesis method according to claim 2 or 3, characterized in that: The catalyst is at least one of 4-dimethylaminopyridine and 4-pyrrolidinopyridine.

7. The synthesis method according to claim 3, wherein: The organic solvent is at least one of ethyl acetate, acetonitrile, dichloromethane, 1,2-dichloroethane, chlorobenzene, tetrahydrofuran, 2-methyltetrahydrofuran, diethyl ether and methyl tert-butyl ether.

8. The synthesis method according to claim 3, wherein: The column chromatography separation refers to column chromatography under air pressure, the silica gel is 200-300 mesh, and the eluent is a mixture of petroleum ether and ethyl acetate in a volume ratio of 100-1:1 or a mixture of dichloromethane and methanol in a volume ratio of 100-10:

1.

9. Use of the amino acid furanone ester latent aroma compound according to claim 1 in cigarettes.

10. The use according to claim 9, characterized in that: The amino acid furanone ester latent aroma compound is dissolved in alcohol or an alcohol-water mixed solvent and then evenly sprayed onto tobacco or papermaking sheets. The added amount of the latent aroma compound accounts for 0.0001%-0.1% of the weight of the tobacco or papermaking sheets.

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