CN108752228B

CN108752228B - Preparation method and application of N-lauroyl-L-alanine

Info

Publication number: CN108752228B
Application number: CN201810562220.1A
Authority: CN
Inventors: 张健
Original assignee: Suzhou Oulite Biomedical Co ltd
Current assignee: Suzhou Oulite Biomedical Co ltd
Priority date: 2018-06-04
Filing date: 2018-06-04
Publication date: 2022-09-30
Anticipated expiration: 2038-06-04
Also published as: CN108752228A

Abstract

The invention discloses a preparation method of N-lauroyl-L-alanine, which comprises the steps of preparing L-alanine salt, preparing pasty N-lauroyl-L-alanine salt, obtaining a crude product of the N-lauroyl-L-alanine and the like. The invention also provides the application of the amino acid in the fields of daily chemicals, agriculture and medicine. The amino acid provided by the invention has good performance, and has obvious effects on bacteriostasis, pesticide removal and peculiar smell elimination.

Description

Preparation method and application of N-lauroyl-L-alanine

Technical Field

The invention belongs to the technical field of amino acid type surfactant preparation, and particularly relates to a preparation method and application of N-lauroyl-L-alanine.

Background

The surfactant is an essential component in many fields such as daily chemical industry, agriculture, pharmaceutical industry and the like. There are dozens of surfactants currently in use, but the surfactants mainly used are sodium dodecylbenzenesulfonate (SLS), sodium laureth sulfate (AES), and sodium laureth sulfate (K12). Since the three surfactants have been used for decades or even hundreds of years, their negative effects have gradually appeared during the use, and the effects on the safety and environment of human body are often reported.

Other surfactants such as alkyl glycoside of saccharide (APG), amino acid surfactants such as lauroyl-L-glutamic acid, lauroyl glycine, lauroyl sarcosine, etc. Although they belong to biological substance-based surfactants, which have high safety, good biodegradability and excellent skin feel, and are receiving more and more attention, these surfactants are rarely used alone as primary surfactants and often used in combination with other primary surfactants due to their poor detergency, and thus the negative problems of safety and biodegradability of daily use primary surfactants are not fundamentally solved.

Pure N-lauroyl-L-alanine is used as a surfactant, has good wettability, foamability, antibacterial property, corrosion resistance and antistatic property, is basically nontoxic and harmless, is mild to skin, has no influence on environment due to the degradation products of amino acid and fatty acid, and has the advantage of good compatibility with other surfactants.

However, the N-lauroyl-L-alanine prepared by the existing method such as Schotten-Banmann condensation reaction is used as a surfactant for testing, the decontamination capability of the N-lauroyl-L-alanine is not as high as the theoretical value, and the applicant finds that after a series of exploration tests, the main reason of low decontamination capability of the N-lauroyl-L-alanine is that the N-lauroyl-L-alanine prepared by the method contains high-content lauric acid, so that the product purity is low, the quality of the N-lauroyl-L-alanine is seriously influenced, impurities are removed, the product can be further purified by chromatography on the original production process, the operation is troublesome, the cost is high, and the industrial production is difficult to realize.

Based on the above, the preparation method and application of N-lauroyl-L-alanine are expected, the lauric acid content in the N-lauroyl-L-alanine prepared by the method cannot be detected by HPLC, the decontamination effect is good, and meanwhile, the method is simple in process, low in cost and easy to realize industrial production.

Disclosure of Invention

The invention aims to overcome the defects that N-lauroyl-L-alanine prepared by the prior art is low in purity, high in impurity content and seriously affects the product quality, and provides a preparation method and application of N-lauroyl-L-alanine.

The object of the present invention and the technical problem to be solved are achieved by the following technical means. The invention provides a preparation method of N-lauroyl-L-alanine, which comprises the following steps:

(1) dissolving L-alanine and metal inorganic base in a mixed solution of distilled water and an organic solvent, and uniformly stirring to obtain an L-alanine salt solution;

(2) sequentially adding lauroyl chloride and metal inorganic alkali into the obtained L-alanine salt solution at the temperature of 5-50 ℃ to ensure that the pH of a reaction system is 8-10, and then continuously stirring under a certain condition to obtain pasty N-lauroyl-L-alanine salt;

(3) acidifying the obtained pasty N-lauroyl-L-alanine salt to the pH value of 3-4, gradually precipitating a white solid, then placing the white solid in an ice bath for 1-3 hours, and filtering to obtain a crude product of N-lauroyl-L-alanine;

(4) adding a solvent, L-alanine and a catalyst into the obtained crude N-lauroyl-L-alanine, stirring under a certain condition, cooling, filtering, washing the obtained solid, and drying to obtain the N-lauroyl-L-alanine free of lauric acid.

The method described above, wherein the molar ratio of the L-alanine to the metal inorganic base in the step (1) is 1 (1-1.5).

The method described in the preceding, wherein the metal inorganic base in the step (1) is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate.

The method described in the preceding, wherein the organic solvent in the step (1) is one or more selected from acetone, methanol, ethanol, acetonitrile, and tetrahydrofuran.

The method comprises the step (1), wherein the volume ratio of the distilled water to the organic solvent in the step (1) is 1 (1-1.5).

The method described above, wherein the charging molar ratio of lauroyl chloride to L-alanine in the step (2) is (0.8-1): 1.

The method described above, wherein the stirring conditions in the step (2) are: the temperature is 5-50 ℃, and the time is 0.5-3.5 h.

In the method, the concentration of the inorganic alkali metal in the step (2) is 30-80%.

The method described in the preceding, wherein the metal inorganic base in the step (2) is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate.

The method described above, wherein the solvent in the step (4) is selected from acetone, methanol, ethanol, acetonitrile, tetrahydrofuran or a mixed solvent of the above solvents and water.

The method described in the preceding, wherein the catalyst in the step (4) is selected from one or more of sulfuric acid, p-toluenesulfonic acid and emulsifiers.

In the method, the molar ratio of the crude N-lauroyl-L-alanine, the solvent, the L-alanine and the catalyst in the step (4) is 1 (5-10): (0.2-0.5): 0.01-0.2.

In the method, the drying temperature in the step (4) is 40-70 ℃.

The method described above, wherein the stirring conditions in the step (4) are: the temperature is 25-100 ℃, the pressure is 5-50 kg, and the time is 1-3 h.

The object of the present invention and the technical problem to be solved are also achieved by the following technical means. The N-lauroyl-L-alanine obtained by the preparation method provided by the invention is used as a surfactant and is applied to the fields of daily chemicals, agriculture and medicine industry.

The object of the present invention and the technical problem to be solved are also achieved by the following technical means. The supramolecular amino acid provided by the invention is formed by the connection of the N-lauroyl-L-alanine monomers obtained by the preparation method through hydrogen bonds.

Compared with the prior art, the invention has the beneficial technical effects that:

1. the preparation method of the N-lauroyl-L-alanine has simple process steps, is prepared by condensing natural lauric acid and natural L-alanine, exists stably in a normal state, is non-toxic and harmless to a human body, can be quickly degraded into the lauric acid and the L-alanine after entering the human body and being natural, can recycle due to the degradation product being a natural product, has mild reaction conditions, and is suitable for industrial production.

2. The lauric acid content in the N-lauroyl-L-alanine prepared by the method can not be detected by HPLC (high performance liquid chromatography), is basically over 97 percent and basically does not contain lauric acid, i.e. the lauric acid content does not influence the structure and the performance of the N-lauroyl-L-alanine, and the influence of the lauric acid on the product quality is effectively avoided.

3. The N-lauroyl-L-alanine obtained by the method is a three-dimensional network structure, has strong oil stain and other organic matters, has the pH value of 6-7 in use, is more suitable for the pH requirement of a human body, more than 90 percent of the N-lauroyl-L-alanine exists in the form of sodium salt, the rest part exists in the form of acid, and coexists in a two-dimensional and three-dimensional mode, so that the N-lauroyl-L-alanine has strong washing capacity and has the properties of adsorbing bacteria, pesticides, odors and the like.

4. The N-lauroyl-L-alanine prepared by the method has stable structural performance and supermolecule property, and the molecules drive liquid components to be static in solution due to the existence of various gel factors such as hydrogen bonds, electrostatic force, hydrophobic force and pi-pi interaction to form amino acid with a three-dimensional network space structure, so that the N-lauroyl-L-alanine has the characteristics of physical degerming, odor removal, pesticide residue removal and the like: the antibacterial agent has good antibacterial rate, and the inhibition rate to escherichia coli, staphylococcus aureus and candida albicans can reach 100%; pesticide residues are effectively removed, the removal rate of the methamidophos can reach 64.63%, and the removal rate of the acephate can reach 74.66%; meanwhile, the deodorant has good peculiar smell removal performance.

5. The N-lauroyl-L-alanine prepared by the method of the invention exists in the form of countless columns, huge gaps exist among molecules, and organic matters such as medicine molecules, pesticide residues and tiny inorganic particles can be coated. In the application of the medicine field, the N-lauroyl-L-alanine can wrap medicine molecules, slowly release effective components of the medicine under the action of enzyme and play a role of a slow release agent; in the application of the pesticide field, the N-lauroyl-L-alanine can wrap the pesticide to prevent the pesticide from permeating into the plant; in the application of the cosmetic field, the physical properties of the oil can be changed after the N-lauroyl-L-alanine is combined with the natural oil, the oil is close to the oil secreted by a human body, and the experience feeling is good. N-lauroyl-L-alanine can encapsulate cosmetic active substance, so that the active substance is not easy to oxidize and deactivate, and the particles can be uniformly dispersed and suspended in cosmetic system.

Drawings

FIG. 1 is a chemical reaction formula for preparing N-lauroyl-L-alanine according to the synthesis method in example 3 of the present invention;

FIG. 2 is an infrared spectrum of N-lauroyl-L-alanine obtained by the synthesis method in example 3 according to the present invention;

FIG. 3a is a 1H-NMR spectrum of N-lauroyl-L-alanine obtained by the synthesis method in example 3 according to the present invention; wherein ppm is a unit of million molecules of chemical shift;

FIG. 3b is a 13C-NMR spectrum of N-lauroyl-L-alanine obtained by the synthesis method in example 3 according to the present invention;

FIG. 4 is a standard chromatogram of N-lauroyl-L-alanine;

FIG. 5 is a high performance liquid chromatogram of N-lauroyl-L-alanine obtained by the synthesis method in example 3 of the present invention measured under the same conditions as in FIG. 4;

FIG. 6 is a high performance liquid chromatogram of lauric acid measured under the same conditions as in FIG. 4;

FIG. 7 is a high performance liquid chromatogram of L-alanine measured under the same conditions as in FIG. 4;

FIG. 8 is a high performance liquid chromatogram of N-lauroyl-L-alanyl-L-alanine obtained by column preparative isolation measured under the same conditions as in FIG. 4;

FIG. 9 is a diagram showing the structure formation of supramolecular amino acids from N-lauroyl-L-alanine monomers obtained by the synthesis method in example 3 according to the present invention;

FIG. 10a is a 300-fold electron micrograph of N-lauroyl-L-alanine obtained according to the synthesis method in example 3 of the present invention;

FIG. 10b is a 1000-fold electron micrograph of N-lauroyl-L-alanine obtained according to the synthesis method in example 3 of the present invention;

FIG. 10c is a 2000-fold electron micrograph of N-lauroyl-L-alanine obtained according to the synthesis method in example 3 of the present invention;

FIG. 11a is a 500-fold electron micrograph of commercially available N-lauroyl-L-alanine (containing 2 to 5% of lauric acid);

FIG. 11b is a 1000-fold electron micrograph of commercially available N-lauroyl-L-alanine (containing 2 to 5% of lauric acid);

FIG. 11c is a 2000-fold electron micrograph of commercially available N-lauroyl-L-alanine (containing 2-5% lauric acid);

FIG. 12 is a diagram showing the formation process of N-lauroyl-L-alanine further forming supramolecular amino acid sodium salt according to the synthesis method in example 3 of the present invention.

FIG. 3b shows the following translation of Chinese and English: ppm is the unit of million molecules chemical shift

Archivedirectory:/export/home/vnmrl/vnmrsys/data

Filing a catalogue: output/home/warian nuclear magnetic system/data

Sampledirectory:

Sample catalog:

File：CARBON

file: carbon spectrum

PulseSequence:s2pul

Pulse sequence: s2pul

Solvent:DMSO

Solvent: dimethyl sulfoxide

Ambienttemperature

At room temperature

INOVA-400“suda400”

Brand name: suda 400 "

Relax.Delay3.000sec

Delay 3 seconds

Pulse45.0degress

Pulse 45 degree

Acq.time 0.799sec

Acquisition time 0.799 seconds

Width22111.7Hz

Width 22111.7 Hz

2328repetitions

2328 repeats

OBSERVEC13,100.5762127MHz

Observe C13, 100.5762127 MHz

DECOUPLEH1,399.9864541MHz

Attenuated split H1,399.9864541 MHz

Power33dB

Power 33 db

ContinouslyonWALTZ-16modulated

Continuously regulating in WALTZ-16

DATAPROCESSINGLinebroadening 1.0Hz

Data progression spectral line broadening 1.0 Hz

FTsize65536Totaltime 10hr,34min,35sec

FT model 65536 Total time 10 hours 34 minutes 35 seconds

FIG. 4 is a drawing illustrating: min means "min" and mAu means "milliabsorbance units".

FIG. 5 illustrates in the drawings: min means "min" and mAu means "milliabsorbance units".

Area percent report

SortedBy:Signal

The sorting mode is as follows: signal

Multiplier:1.0000

Multiplier: 1.0000

Dilution:1.0000

Diluting: 1.0000

UseMultiplier&DilutionFactorwithISTDs

Using multipliers and dilution factors

Signal 1:DAD1B,Sig＝210.4,Ref＝360.4

Signal 1: DAD1B, sig 210.4, ref 360.4

Peak: peak(s)

RetTime: retention time

Type: model number

Width: width of

Area: area of

Height

Area%: percentage of area

FIGS. 6-8 illustrate the drawings: min means "minutes" and mAu means "milliabsorbance units".

Detailed Description

The present invention is further illustrated by the following figures and examples, which are to be understood as merely illustrative and not restrictive. Furthermore, it should be understood that various changes and modifications of the present invention may be made by those skilled in the art after reading the teachings herein, and such equivalents may fall within the scope of the invention as defined in the appended claims.

It will be understood by those skilled in the art that the term "lauric acid-free N-lauroyl-L-alanine" as used herein is not absolutely free of lauric acid, but means that no lauric acid is detected, i.e. the content of lauric acid does not affect the properties and structure of N-lauroyl-L-alanine, for example, by high performance liquid chromatography (equipped with a UV detector; column: ODS-2HYPERSILC18250 x 4.6mm5 μm; mobile phase vacuum filtration degasser and 0.45 μm organic filter).

(1) dissolving L-alanine and metal inorganic alkali in a mixed solution of distilled water and an organic solvent, and uniformly stirring to obtain an L-alanine salt solution;

(4) adding a solvent, L-alanine and a catalyst into the obtained crude N-lauroyl-L-alanine, stirring under a certain condition, cooling, filtering, washing the obtained solid, and drying to obtain the N-lauroyl-L-alanine free of lauric acid. Embodiments of the method are further described below in conjunction with the following embodiments.

EXAMPLE 1 Synthesis of N-lauroyl-L-alanine

Example 1

In a 1L three-necked flask, 89g (1mol) of L-alanine and 40g (1mol) of sodium hydroxide were dissolved in a mixed solution of 150mL of distilled water and 150mL of acetone at room temperature and stirred to obtain a solution of L-alanine sodium.

218.7g (1mol) of lauroyl chloride was slowly dropped into an L-alanine salt solution at 25 ℃, a 50% sodium hydroxide solution was further dropped so that the pH of the reaction system became 9, and after the dropping, stirring was continued at 25 ℃ for 2 hours to obtain a paste of N-lauroyl-L-alanine salt.

Adding hydrochloric acid into the pasty N-lauroyl-L-alanine salt, acidifying until the pH value is 3-4, gradually precipitating a white solid, then placing for 2 hours in an ice bath, and filtering to obtain a crude product of the N-lauroyl-L-alanine.

Adding a mixed solvent of water and acetone, L-alanine and p-toluenesulfonic acid into the crude N-lauroyl-L-alanine, wherein the crude N-lauroyl-L-alanine, the mixed solvent of water and acetone, L-alanine and p-toluenesulfonic acid are added according to the molar ratio of 1:7.5:0.35:0.1, stirring for 2 hours at the temperature of 60 ℃ and under the pressure of 27kg to completely consume a small amount of lauric acid, cooling and filtering, washing the obtained solid twice with pure water, and finally drying at the temperature of 60 ℃ to obtain the N-lauroyl-L-alanine without lauric acid.

The obtained N-lauroyl-L-alanine has the mass of 250.5g, the yield of 92.3 percent, the purity of over 97 percent and the melting point of 86-88 ℃.

Example 2

In a 1L three-necked flask, 89g (1mol) of L-alanine and 56g (1mol) of potassium hydroxide were dissolved in a mixed solution of 150mL of distilled water and 150mL of acetone and stirred at room temperature to obtain a L-alanine sodium solution.

218.7g (1mol) of lauroyl chloride was slowly added dropwise to the L-alanine salt solution at 25 ℃, a 50% sodium hydroxide solution was further added dropwise so that the pH of the reaction system became 9, and after completion of the addition, stirring was continued at 25 ℃ for 2 hours to obtain a paste of N-lauroyl-L-alanine salt.

Adding a mixed solvent of water and acetone, L-alanine and p-toluenesulfonic acid into the crude N-lauroyl-L-alanine, wherein the crude N-lauroyl-L-alanine, the mixed solvent of water and acetone, the L-alanine and the p-toluenesulfonic acid are added according to the molar ratio of 1:10:0.3:0.2, stirring for 2 hours at the temperature of 25 ℃ and the pressure of 63kg to completely consume a small amount of lauric acid, cooling and filtering, washing the obtained solid twice with pure water, and finally drying at 60 ℃ to obtain the N-lauroyl-L-alanine free of lauric acid.

The obtained N-lauroyl-L-alanine has the mass of 243.7g, the yield of 89.8 percent, the purity of over 97 percent and the melting point of 86-88 ℃.

Example 3

In a 1000L reaction kettle, 89kg (1Kmol) of L-alanine and 40kg (1Kmol) of sodium hydroxide are dissolved in a mixed solution of 150L of distilled water and 150L of acetone at normal temperature and are uniformly stirred to obtain an L-alanine sodium solution.

Under the condition of 25 ℃, 175kg (0.8Kmol) of lauroyl chloride is slowly dripped into an L-alanine salt solution, then a 50% sodium hydroxide solution is dripped to ensure that the pH of a reaction system is 9, and after the dripping is finished, the stirring is continued for 2 hours at 25 ℃ to obtain pasty N-lauroyl-L-alanine salt.

Adding a mixed solvent of water and acetone, L-alanine and p-toluenesulfonic acid into the crude N-lauroyl-L-alanine, wherein the crude N-lauroyl-L-alanine, the mixed solvent of water and acetone, the L-alanine and the p-toluenesulfonic acid are added according to the molar ratio of 1:5:0.5:0.2, stirring for 2 hours at the temperature of 100 ℃ and the pressure of 50kg to completely consume a small amount of lauric acid, cooling and filtering, washing the obtained solid twice with pure water, and finally drying at the temperature of 60 ℃ to obtain the N-lauroyl-L-alanine free of lauric acid.

The obtained N-lauroyl-L-alanine has the mass of 217.2kg, the yield of 98.5 percent, the purity of over 97 percent and the melting point of 86-88 ℃.

Example 4

In a 1L three-necked flask, 89g (1mol) of L-alanine and 106g (1mol) of sodium carbonate were dissolved in a mixed solution of 150mL of distilled water and 150mL of acetone and stirred at room temperature to obtain a L-alanine sodium solution.

218.7g (1mol) of lauroyl chloride was slowly dropped into an L-alanine salt solution at 50 ℃, a 30% sodium hydroxide solution was further dropped so that the pH of the reaction system became 8, and after the dropping, stirring was continued at 25 ℃ for 3.5 hours to obtain a paste of N-lauroyl-L-alanine salt.

Adding hydrochloric acid into the pasty N-lauroyl-L-alanine salt, acidifying until the pH value is 3-4, gradually precipitating a white solid, then placing for 3 hours in an ice bath, and filtering to obtain a crude product of the N-lauroyl-L-alanine.

Adding methanol solution, L-alanine and sulfuric acid into the crude N-lauroyl-L-alanine, wherein the crude N-lauroyl-L-alanine, the methanol solution, the L-alanine and the sulfuric acid are added according to the amount of 1:5:0.2:0.01, stirring for 1h at the temperature of 25 ℃ and the pressure of 5kg to completely consume a small amount of lauric acid, cooling and filtering, washing the obtained solid twice with pure water, and finally drying at 70 ℃ to obtain the N-lauroyl-L-alanine free of lauric acid.

The obtained N-lauroyl-L-alanine has the mass of 244.7g, the yield of 90.2 percent, the purity of more than 97 percent and the melting point of 86-88 ℃.

Example 5

218.7g (1mol) of lauroyl chloride was slowly dropped into an L-alanine salt solution at 5 ℃, an 80% sodium hydroxide solution was further dropped so that the pH of the reaction system became 10, and after the dropping, stirring was continued at 50 ℃ for 0.5h to obtain a paste of N-lauroyl-L-alanine salt.

Adding hydrochloric acid into the pasty N-lauroyl-L-alanine salt, acidifying until the pH value is 3-4, gradually precipitating a white solid, then placing for 1h in an ice bath, and filtering to obtain a crude product of the N-lauroyl-L-alanine.

Adding methanol solution, L-alanine and p-toluenesulfonic acid into the crude N-lauroyl-L-alanine, wherein the crude N-lauroyl-L-alanine, the methanol solution, the L-alanine and the p-toluenesulfonic acid are added according to the amount of 1:5:0.2:0.01, stirring for 3 hours at the temperature of 100 ℃ and under the pressure of 50kg to completely consume a small amount of lauric acid, cooling and filtering, washing the obtained solid twice with pure water, and finally drying at 40 ℃ to obtain the N-lauroyl-L-alanine free of lauric acid.

The obtained N-lauroyl-L-alanine has the mass of 235.4g, the yield of 86.7 percent, the purity of more than 97 percent and the melting point of 86-88 ℃.

Example 6

In a 1000L reaction kettle, 89kg (1Kmol) of L-alanine and 40kg (1Kmol) of sodium hydroxide are dissolved in a mixed solution of 150L of distilled water and 150L of acetone at normal temperature and are uniformly stirred to obtain an L-sodium alanine solution.

Adding a tetrahydrofuran solution, L-alanine and p-toluenesulfonic acid into the crude N-lauroyl-L-alanine, wherein the crude N-lauroyl-L-alanine, the tetrahydrofuran solution, the L-alanine and the p-toluenesulfonic acid are added according to the amount of 1:7.5:0.5:0.2, stirring for 2 hours at 63 ℃ and under the pressure of 22.5kg to completely consume a small amount of lauric acid, cooling and filtering, washing the obtained solid twice with pure water, and finally drying at 60 ℃ to obtain the N-lauroyl-L-alanine free of lauric acid.

The obtained N-lauroyl-L-alanine has the mass of 218.2kg, the yield of 99.0 percent, the purity of over 97 percent and the melting point of 86-88 ℃.

Example 2 structural characterization of N-lauroyl-L-alanine

1. Infrared spectroscopy (GBT6040-2002)

The instrument comprises the following steps: fourier transform infrared spectrometer (FTS-1000)

Spectral conditions: fully mixing N-lauroyl-L-alanine and potassium bromide (spectral purity, CP, purchased from national chemical reagent group) at a ratio of 1:100, grinding, and tabletting; the wave number scanning range is 4000cm ^-1 —400cm ^-1 Resolution of 4cm ^-1 (ii) a The number of scans was 16.

FIG. 2 is an infrared spectrum of N-lauroyl-L-alanine synthesized according to the method in example 3 of the present invention. As shown in FIG. 2, the infrared spectrum data of N-lauroyl-L-alanine synthesized according to the method in example 3 is:

IRVmax(KBr)：3322cm-1(N-H)；2955cm-1,2871cm-1,1377cm-1(CH3)；2919cm-1,2850cm-1,1469cm-1,720cm-1(＝CH2)；1646cm-1(C＝O)；1541cm-1(C-N,N-H)；1271cm-1,2120cm-1(COOH)；1707cm-1(C＝O)；1414cm-1(-OH)；1241cm-1(C-O)。

2. NMR analysis (JY/T007-1996)

The obtained N-lauroyl-L-alanine was subjected to NMR analysis using a UNITY-400NMR spectrometer. FIG. 3a is a 1H-NMR spectrum of N-lauroyl-L-alanine obtained by the synthesis method in example 3 according to the present invention; FIG. 3b is a diagram of the synthesis of N-lauroyl-L-alanine according to the present invention in example 3 ¹³ C-NMR spectrum. The data obtained according to NMR are as follows:

¹ HNMR(DMSO):δ7.95(d,1H)；4.15(m,1H)；2.08(t,2H)；1.48(m,2H)；1.2(m,19H)；0.86(t,3H)；

¹³ C NMR(CDCl3):δ174.63；171.77；47.74；35.11；31.33；29.08；29.06；29.01；28.87；28.76；28.67；25.24；22.13；18.03；13.92。

3. HPLC analysis (GBT 16631-

High performance liquid chromatography uses an ultraviolet detector to identify and determine N-lauroyl-L-alanine. The sample N-lauroyl-L-alanine was compared with its standard for retention time to identify the substance and quantified by area normalization. Except as otherwise specified, the reagents were chromatographically pure, and the water was ultrapure water.

20mmol of buffer salt solution (pH 3.0): weighing potassium dihydrogen phosphate (KH) ₂ PO ₄ )1.36g, accurate to 0.001g, adding water to dissolve in a 100mL beaker, transferring to a 500mL volumetric flask, adding water to a constant volume to reach a scale, obtaining 20mmol of potassium dihydrogen phosphate solution, and adjusting the pH value to 3.0 by using phosphoric acid to obtain a buffer salt solution.

The instrument comprises the following steps: high performance liquid chromatograph: is provided with an ultraviolet detector; a chromatographic column: ODS-2HYPERSILC18250 × 4.6mm5 μm; a mobile phase vacuum filtration degasser and a 0.45 mu m organic filter membrane.

And (3) determination:

(1) preparation of Standard sample solution

Accurately weighing a standard sample of 30 mgN-lauroyl-L-alanine, dissolving a proper amount of mobile phase, metering the volume to a 10mL volumetric flask, and shaking up. Filtering with 0.45 μm organic filter membrane to obtain filtrate.

(2) Preparation of test solution

Accurately weighing a sample to be detected of 150 mgN-lauroyl-L-alanine, dissolving a proper amount of mobile phase, metering the volume to a 50mL volumetric flask, and shaking up. Filtering with 0.45 μm organic filter membrane, and collecting filtrate.

(3) Chromatographic conditions

Mobile phase: methanol: 20mmol of a buffered salt solution (ph3.0) 70:30 (v/v); the flow rate is 1.0 mL/min; column temperature: 30 ℃; detection wavelength: 210 nm; sample introduction amount: 20 μ L

(4) Sample measurement

Adjusting instrument parameters according to chromatographic conditions, respectively injecting 20 mu L of standard solution and sample solution into a chromatographic column after the baseline of the instrument is stable, and recording chromatograms of the standard solution and the sample solution of the N-lauroyl-L-alanine. And (3) determining the chromatographic peak of the N-lauroyl-L-alanine in the sample according to the retention time of the standard solution, and determining the percentage content of the test substance by adopting an area normalization method according to the peak area of the sample.

FIG. 4 is a standard chromatogram of N-lauroyl-L-alanine; FIG. 5 is a high performance liquid chromatogram of N-lauroyl-L-alanine obtained by the synthesis method in example 3 according to the present invention measured under the same conditions as in FIG. 4; FIG. 6 is a high performance liquid chromatogram of lauric acid measured under the same conditions as in FIG. 4; FIG. 7 is a high performance liquid chromatogram of L-alanine measured under the same conditions as in FIG. 4; FIG. 8 is a high performance liquid chromatogram of N-lauroyl-L-alanyl-L-alanine obtained by column preparative isolation measured under the same conditions as in FIG. 4. As can be seen from FIGS. 4-8, the impurities of the N-lauroyl-L-alanine prepared by the synthesis method do not contain lauric acid, the purity can reach more than 97%, the impurities are mainly N-lauroyl-L-alanyl-L-alanine, and the N-lauroyl-L-alanine is further dehydrated and condensed with L-alanine in the reaction process.

4. Optical rotation analysis

The (specific) optical rotation of N-lauroyl-L-alanine was determined according to a polarimeter:

to-16.7 ° (C ═ 2, CH) ₃ OH)

5. Description of structural features

FIG. 9 is a structural diagram of N-lauroyl-L-alanine monomer forming supramolecular amino acids obtained by the synthesis method in example 3 of the present invention. According to the infrared, NMR and HPLC analysis and optical rotation measurement, the N-lauroyl-L-alanine produced by the process does not contain impurity lauric acid, the N-lauroyl-L-alanine synthesized in the process can form two groups of hydrogen bonds, the N-lauroyl-L-alanyl-L-alanine can form three groups of hydrogen bonds, the carboxyl groups of two N-lauroyl-L-alanines are connected through the hydrogen bonds, and the two ends of each N-lauroyl-L-alanine are respectively provided with an alkane structure with eleven carbon chains, according to the principle of oil-oil intermiscibility, the oleophilic end is matched with the oleophilic end in a chain mode and connected end to form a circular ring, the circular ring and the circular ring are intermiscible with oil through hydrogen bonds and are infinitely superposed to form a columnar molecular cluster, and the columnar molecular cluster is infinitely superposed to form a special spatial structure called supermolecule amino acid.

FIGS. 10a, 10b and 10c show electron micrographs of 300 times, 1000 times and 2000 times, respectively, of N-lauroyl-L-alanine obtained according to the synthesis method in example 3 of the present invention. As shown in fig. 10a, 10b and 10c, the microstructure of N-lauroyl-L-alanine of the present invention is twined and constitutes "supramolecular amino acid". FIGS. 9, 10a, 10b and 10c better demonstrate the formation principle and structure of N-lauroyl-L-alanine monomer to supramolecular amino acids.

After the formation of supramolecular amino acids, the supramolecular amino acids further react with sodium hydroxide to generate the sodium salt structure of supramolecular amino acids as shown in figure 12. According to the figure 12, the sodium salt structure is hydrophilic and lipophilic, and the molecules are connected through hydrogen bonds to obtain a special two-dimensional net-shaped regular arrangement structure, has strong capacity of combining with oil stains, and can be used as a main surfactant.

In addition, the present application also performed electron microscope scanning measurement on commercially available N-lauroyl-L-alanine (available from Changshapu biosciences, Inc.), wherein the N-lauroyl-L-alanine was measured to contain 2-5% of lauric acid, and the scanning results are shown in FIGS. 11a, 11b, and 11 c. FIGS. 11a, 11b, and 11c show the 500-, 1000-, and 2000-fold electron micrographs of commercially available N-lauroyl-L-alanine containing 2 to 5% lauric acid, respectively, and as shown in FIGS. 11a, 11b, and 11c, the electron micrographs of commercially available N-lauroyl-L-alanine show a random arrangement, and are different from the corresponding 500-, 1000-, and 2000-fold electron micrographs of N-lauroyl-L-alanine obtained by the process of the present invention, and the hemp rope shape in the electron micrographs of N-lauroyl-L-alanine of the present invention does not appear. It is presumed that this is caused by the fact that commercially available N-lauroyl-L-alanine contains lauric acid, and the presence of lauric acid disrupts the infinite bond formation of hydrogen bonds between N-lauroyl-L-alanine, thereby changing the structure and properties of N-lauroyl-L-alanine.

The process effectively solves the problems that the residual lauric acid impurity destroys the structure of the N-lauroyl-L-alanine and further influences the performance of destroying the N-lauroyl-L-alanine, so that the N-lauroyl-L-alanine is easy to form hydrogen bonds and is infinitely connected, and has special performance. The impurity N-lauroyl-L-alanyl-L-alanine generated by the process can also form hydrogen bonds like N-lauroyl-L-alanine, so that the structural stability is enhanced, and the performance of the N-lauroyl-L-alanine is not influenced.

In further experiments, the present inventors have conducted structural studies using N-decanoyl-L-alanine under the same conditions, and have not found the three-dimensional network structure, and have assumed that the carbon chain length of N-decanoyl-L-alanine is short, and the lipophilic ends of two molecules cannot form a ring, and similarly, it has been assumed that the carbon chain length of the lipophilic group is 12 to 18, and fatty acyl-L-alanine formed with L-alanine is compatible with oil through intermolecular hydrogen bonds under the condition of removing fatty acids, and the spatial structure can be formed. Once the structure is formed stably, experiments prove that the stability and performance application of the existing structure can not be damaged by adding less than 10% of fatty acid in a small amount.

EXAMPLE 3 use of N-lauroyl-L-alanine

EXAMPLE 1 evaluation of the inhibitory Effect of N-lauroyl-L-alanine on bacteria

10g of N-lauroyl-L-alanine synthesized according to the method of example 3 was added to water, and then a 10% aqueous solution of sodium hydroxide was added to neutralize the mixture to a pH of 6 to 7, thereby preparing 100mL of an aqueous solution. Diluting 5mL of stock solution to 100mL, respectively soaking the stock solution in a fruit tray which is inoculated with common bacteria such as staphylococcus aureus, escherichia coli, pseudomonas aeruginosa, candida albicans and the like in advance, acting for a certain time, washing the fruit tray once with clear water, and then determining the bacterial residue on the fruit tray. The detection results are shown in table 1:

table 1: analysis of bacteriostatic action of N-lauroyl-L-alanine

From the data, the N-lauroyl-L-alanine solution synthesized by the method has obvious inhibition effect on escherichia coli, staphylococcus aureus and candida albicans, after the stock solution, namely the N-lauroyl-L-alanine solution acts on the escherichia coli for 2min, the inhibition rate can reach 96.3 percent, and after 5min, the inhibition rate can reach 100 percent; the stock solution can reach the inhibition rate of 100 percent after being acted on staphylococcus aureus for 2 min; the 5min inhibition rate of the compound on Candida albicans can also reach 100 percent.

According to the common knowledge in the field, the size of the bacteria is usually 0.5-5 μm, and the gaps between the column groups of the supermolecular structure formed by the lauric acid-free N-lauroyl-L-alanine used in the invention are also micron-sized, so that the bacteria can be wrapped and removed, and the method can be called as the method capable of generating nano-scale foam micropores.

EXAMPLE 2 evaluation of the Effect of N-lauroyl-L-alanine on removal of agricultural chemical

Taking 100g of green leaf vegetables (big green vegetables) which are sprayed with pesticide methamidophos and acephate in advance, directly soaking one part of the green leaf vegetables (big green vegetables) in 1L of clear water, and then taking out the green leaf vegetables to detect pesticide residues on the leaves of the green leaf vegetables, wherein the parts are called before cleaning. The other portion was washed, referred to as after-washing, with a solution prepared from N-lauroyl-L-alanine synthesized according to the method of example 3. The operation is described as follows:

10g of N-lauroyl-L-alanine synthesized according to the method of example 3 was added to water, and then a 10% aqueous solution of sodium hydroxide was added to neutralize the mixture to a pH of 6 to 7, thereby preparing 100mL of an aqueous solution. Diluting 5mL of stock solution to 500mL, cutting another green leaf vegetable (Daqingcai) which is sprayed with pesticide methamidophos and acephate in advance to 100g, soaking in the solution for 2 minutes, taking out, washing with 500mL of clear water, and taking out to detect pesticide residue on vegetable leaves. Table 2 shows the comparison of pesticide data residues before and after washing:

table 2: analysis of pesticide-removing effect of N-lauroyl-L-alanine

Serial number	Inspection item	Mg/kg before washing	Mg/kg after cleaning	Removal rate%
					1	Methamidophos	16.06	5.68	64.63
2	Acephate	38.48	9.75	74.66

According to the data, the N-lauroyl-L-alanine solution used as the surface active substance has obvious removal effect on methamidophos and acephate, and after the action for 2min, the removal rate of the methamidophos can reach 64.63%; the removal rate of the acephate can reach 74.66%, and the effect is obvious.

EXAMPLE 3 evaluation of Effect of N-lauroyl-L-alanine on Elimination of off-flavors

10g of N-lauroyl-L-alanine synthesized by the method of example 3 was added to water, and the mixture was neutralized with 10% aqueous sodium hydroxide solution until the pH was 6 to 7 to prepare 100mL of an aqueous solution. Taking 5mL of stock solution, diluting to 100mL, soaking cotton cloth with peculiar smell (smell, engine oil smell, stink smell and the like) in the solution for 2 minutes, taking out, washing with water, airing, and finding out that the peculiar smell on the cotton cloth completely disappears according to an experimental result, so that the N-lauroyl-L-alanine synthesized by the method has a good peculiar smell elimination effect.

Based on the above, the preparation method of the N-lauroyl-L-alanine has the advantages of simple process steps and mild reaction conditions, and is suitable for industrial production. The N-lauroyl-L-alanine prepared by the method has high purity which is basically more than 97 percent, and the lauric acid content is trace, so that HPLC (high performance liquid chromatography) can not detect the lauric acid, and the influence of the lauric acid on the product quality is effectively avoided. The obtained N-lauroyl-L-alanine has stable structural performance; the antibacterial agent has good antibacterial rate, and the inhibition rate to escherichia coli, staphylococcus aureus and candida albicans can reach 100%; pesticide residues are effectively removed, the removal rate of the methamidophos can reach 64.63%, and the removal rate of the acephate can reach 74.66%; meanwhile, the deodorant has good peculiar smell removal performance and can be well applied to the fields of daily chemicals, agriculture and medicine industry.

Furthermore, those skilled in the art will appreciate that while some embodiments described herein include some features included in other embodiments, rather than other features, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the following claims, any of the claimed embodiments may be used in any combination.

Claims

A method for the preparation of N-lauroyl-L-alanine, comprising the steps of:

(1) dissolving L-alanine and metal inorganic base in a mixed solution of distilled water and an organic solvent, and uniformly stirring to obtain an L-alanine salt solution;

(2) sequentially adding lauroyl chloride and metal inorganic alkali into the obtained L-alanine salt solution at the temperature of 5-50 ℃ to enable the pH of a reaction system to be 8-10, and then continuously stirring under a certain condition to obtain pasty N-lauroyl-L-alanine salt;

(3) acidifying the obtained pasty N-lauroyl-L-alanine salt to the pH value of 3-4, gradually precipitating a white solid, then placing the white solid in an ice bath for 1-3 hours, and filtering to obtain a crude product of N-lauroyl-L-alanine;

(4) adding a solvent, L-alanine and a catalyst into the obtained crude N-lauroyl-L-alanine, stirring under a certain condition, cooling, filtering, washing the obtained solid, and drying to obtain N-lauroyl-L-alanine containing N-lauroyl-L-alanyl-L-alanine without lauric acid;

wherein the stirring condition in the step (4) is 5 kg-50 kg of pressure, the temperature is 25-100 ℃, and the time is 1-3 h;

the catalyst in the step (4) is selected from sulfuric acid or p-toluenesulfonic acid.
2. The method according to claim 1, wherein the molar ratio of the L-alanine to the inorganic base metal in the step (1) is 1 (1-1.5).
3. The process of claim 1, wherein the metal inorganic base in step (1) is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate.
4. The method according to claim 1, wherein the organic solvent in step (1) is selected from one or more of acetone, methanol, ethanol, acetonitrile, tetrahydrofuran.
5. The method according to claim 1, wherein the volume ratio of the distilled water to the organic solvent in the step (1) is 1 (1-1.5).
6. The method according to claim 1, wherein the charging molar ratio of the lauroyl chloride to the L-alanine in the step (2) is (0.8-1): 1.
7. The method of claim 1, wherein the agitation conditions in step (2) are: the temperature is 5-50 ℃, and the time is 0.5-3.5 h.
8. The method according to claim 1, wherein the concentration of the metallic inorganic base in the step (2) is 30 to 80%.
9. The process of claim 1, wherein the metal inorganic base in step (2) is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate.
10. The method according to claim 1, wherein the solvent in step (4) is selected from acetone, methanol, ethanol, acetonitrile, tetrahydrofuran or a mixed solvent of the above solvents and water.
11. The method according to claim 1, wherein the molar ratio of the crude N-lauroyl-L-alanine, the solvent, the L-alanine and the catalyst in the step (4) is 1 (5-10): (0.2-0.5): 0.01-0.2.
12. The method according to claim 1, wherein the drying temperature in the step (4) is 40-70 ℃.
13. Supramolecular amino acid formed by hydrogen bonding between N-lauroyl-L-alanine monomers free from lauric acid and containing N-lauroyl-L-alanyl-L-alanine, obtained by the process according to any one of claims 1 to 12.