FR2929275A1 - PROCESS FOR THE CONTINUOUS SYNTHESIS OF AN N-ACYL COMPOUND INSTALLATION FOR IMPLEMENTING THE METHOD - Google Patents

Abstract

A process for synthesizing an N-acylated compound having a unit (M1): wherein n is 0, 1 or 2 and R1 is an aliphatic group, comprising: A reaction step of a compound having a unit (M2) wherein M represents an alkali metal atom, with an acid halide of formula (IV): wherein X represents a halogen atom, in aqueous solution and at pH greater than 7, to form an N-acyl compound comprising a unit (M3): A step B of hydrolysis at a pH below 7, of the N-acyl compound comprising at least one unit (M3) obtained in stage A, to form said N-acylated compound containing a unit ( M1); characterized in that step A is carried out by placing in contact continuously with time, a stream of said acid halide of formula (IV), a flow rate d2, said compound comprising a unit (M2) and an alkaline aqueous solution stream, while maintaining the molar ratio of acid halide of formula (I V) / N-acyl compound having a unit (M2) of less than 1. Installation for carrying out the method.

Description

Process for the continuous synthesis of an N-acyl compound installation for the implementation of the method

The invention relates to the acylation of amino acids and the use of the acylated products obtained to prepare cosmetic and pharmaceutical compositions. The acylation reaction of amine functions by an acid chloride has been known as the Schotten Baumann reaction for more than a century; it is widely used to prepare N-acyl derivatives of α-amino acids, N-acyl derivatives of partial or total hydrolysates of proteins. Such an implementation is for example disclosed in US Pat. No. 2,463,779 and in international applications published under the numbers WO 92/21318 and WO 94/26694. The conventional acylation process comprises a prior step of salifying the amino acid, followed by a step of acylating the amino acid salt with an acid chloride, and then hydrolyzing the N-acylated salt obtained. In such a process, however, the acylation reaction competes with the next side reaction, which generates the fatty acid homologous to the undesired acid chloride: R1-C (= O) -Cl + NaOH This latter secondary reaction is limited by dissolving the acid chloride or the mixture of acid chloride and amino acid in an organic solvent such as acetone, to prevent that the secondary reaction with soda, which is in the aqueous phase, develops. Acetone is however a potentially dangerous solvent, which makes the process difficult to implement. In addition, the process is carried out batchwise in batches of 700 kg of finished product, which involves the use of a reactor of approximately 0.5 m 3 and large amounts of solvent. Another solution, that described in US 2,463,779, consists of using an excess of acid chloride, from 1 to 1.5 moles of acid chloride per mole of amine function, to ensure the acylation of all the functions. amines taking into account the existence of the secondary reaction. This solution is unsatisfactory because it unnecessarily consumes acid chloride and produces the undesired fatty acid. Therefore, as part of their research to change the existing process, to a less hazardous process and implementing smaller equipment, while respecting the quality standards of the finished product in terms of the amount of Residual fatty acids, the inventors have developed the process that is the subject of the present patent application. According to a first aspect, the subject of the invention is a process for synthesizing an N-acyl compound comprising at least one divalent functional unit (M1) or a mixture of N-acyl compounds containing at least one functional unit. divalent (Ml):

Wherein n represents an integer of 0, 1 or 2, and R1 represents a linear or branched, saturated or unsaturated, aliphatic radical having 1 to 17 carbon atoms, comprising: Step A reacting a compound having at least one divalent functional unit (M2) or a mixture of compounds having at least one divalent functional unit (M2): ## STR2 ## wherein n is such that defined above in the divalent functional unit (M1), M represents an alkali metal atom, with an acid halide of formula (IV): R1 O (IV), wherein R1 is as previously defined in said divalent functional unit (Ml), X represents an atom of the halogen class, or with a mixture of acid halides of formulas (IV), in aqueous solution and at pH greater than 7, to form an N-acyl compound having at least minus one divalent functional unit (M3): ## STR5 ## wherein n, M and R1 are as defined above, or a mixture of N-acyl compounds having at least one divalent functional unit (M3); A step B of hydrolysis at a pH of less than 7, of the N-acyl compound comprising at least one divalent functional unit (M3) or of the mixture of N-acyl compounds containing at least one divalent functional unit (M3) obtained from step A, to form said N-acyl compound having at least one divalent functional unit (M1) or said mixture of N-acyl compounds having at least one divalent functional unit (M1); characterized in that step A is carried out by contacting, in a continuous manner over time, a flow of di flow, said acid halide of formula (IV), a flow rate of d2, said compound N-acyl compound comprising at least one divalent functional unit (M2) or a mixture of N-acyl compounds containing at least one divalent functional unit (M2) and a d3 flow rate of alkaline aqueous solution, while maintaining the molar ratio of halide of acid of formula (IV) / N-acyl compound having at least one divalent functional unit (M2) of less than 1. In the process as defined above, per atom of the class of halogens, is designated primarily for X in the formula (IV), a chlorine atom or a bromine atom.

In the process as defined above, an aqueous alkaline solution is mainly an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide. The term alkali metal is used principally for M in the divalent functional units M2 and M3, sodium or potassium. In the process as defined above by an acid halide of formula (IV): ## STR1 ## denotes any liquid acid halide at atmospheric pressure at a temperature of less than or equal to 40 ° C. The term "linear or branched, saturated or unsaturated aliphatic radical containing 1 to 17 carbon atoms" denotes more particularly for R 1 in formula (IV) and for the divalent functional units M 1 and M 3, a linear or branched alkyl radical or a linear or branched alkenyl radical containing from 5 to 13 carbon atoms and even more particularly the radicals pentyl, hexyl, heptyl, octyl, nonyl, decenyl, decyl or undecyl. By N-acyl compound containing at least one divalent functional unit (M2), the following is used principally in the process as defined above: N-acyl partial hydrolysates of proteins of all origins which consist essentially of mixtures of oligopeptides having oligomerization degrees less than or equal to 10 and more particularly less than or equal to 5, neutralized with an alkaline solution such as an aqueous solution of sodium hydroxide or potassium hydroxide; N-acylated total hydrolysates of protein of all origins which consist essentially of mixtures of amino acids and oligopeptides having lower oligomerization degrees equal to 2 and more particularly less than or equal to 1.5 neutralized by a solution alkaline such as an aqueous solution of soda or potash; Alkaline salts, and more particularly the sodium salts or potassium salts of amino acids and mainly naturally occurring α-amino acids or their derivatives and more particularly the alkaline salts of glycine and alanine , serine, aspartic acid, glutamic acid, valine, threonine, arginine, lysine, proline, leucine, phenylalanine, isoleucine , histidine, tyrosine, tryptophan, asparagine, glutamine, cysteine, cystine, methionine, hydroxyproline, hydroxylysine, sarcosine ornithine, 2-amino isobutyric acid; or the alkaline salts of the 3-amino acids such as β-alanine or the alkaline salts of the γ-amino acids, such as γ-amino butyric acid, which are used for the partial hydrolysates or in the process as defined above, may be of animal origin, such as, for example, collagen, elastin, fish flesh protein, fish gelatin, keratin or casein, vegetable origin, such as proteins of cereals, flowers or fruits, such as, for example, proteins derived from soya beans, sunflower, oats, wheat, maize, barley, peanuts, sorghum, rice, buckwheat, rye, potato, carrot, tomato, lupine, faba bean, sweet almond, kiwi, mango, banana , coconut nut, palm kernel, orange, plum, white grape, pear or apple, it can also be protein obtained naked from chorella (unicellular algae), pink algae, yeast or silk. The obtaining of the hydrolysates is carried out, for example, by heating, at temperatures between 60 and 130 ° C., a protein placed in an acid or alkaline medium. This hydrolysis can also be carried out enzymatically with a protease, optionally coupled to an alkaline or acidic post-hydrolysis. The aminograms of some proteins of vegetable origin are recorded in the following table: Table A Origin of the protein (proportions in amino acids expressed in% by weight) Oat Soy Wheat Sunflower Glycine 6.9 4.2 3.2 6.2 Alanine 5.9 4.2 2.6 4.8 Serine 5.6 5.1 1.7 5.1 Aspartic acid 16.2 11.7 3.4 10.6 Glutamic acid 28.3 19.1 37.9 23.6 Valine 2.9 5.0 4.2 4.8 Threonine 3.1 3.9 2.7 4.4 Arginine 6.6 7.6 3.8 8.4 Lysine 3.6 6.2 1 , 9 3.2 Proline 4.7 5.4 11.7 3.0 Leucine 6.4 8.1 7.1 6.4 Phenylalanine 1.4 5.0 5.4 4.3 Isoleucine 2.2 4, 8 3.7 4.1 Histidine 1.7 2.6 2.4 2.0 Tyrosine 1.5 3.5 3.1 2.7 Methionine 1.2 1.2 1.6 1.8 Cysteine / Cystine 1 , 9 1.5 1.9 1.9 Tryptophan - 1.0 1.0 1.3 Table A (continued) Origin of the protein (proportions in amino acids expressed in% by weight) Lupine Potato Bean Corn Glycine 0, 9 4.8 4.0 2.4 Alanine 2.4 5.0 4.0 7.95 Serine 6.1 5.8 4.9 5.1 Aspartic acid 15.8 12.5 10.5 10.6 Glutamic acid 8.0 11.5 16.8 23.6 Val ine 7.9 7.1 4.5 4.8 Threonine 8.1 6.1 3.6 4.4 Arginine 16.1 5.0 9.21 8.4 Lysine 7.1 7.8 6.5 6 , 2 Proline - 5.1 4.4 3.0 Leucine 7.45 10.4 7.4 8.1 Phenylalanine 8.6 6.4 4.4 4.3 Isoleucine 8.7 6.1 3.9 4 , 1 Histidine - 2,2 2,6 2,0 Tyrosine - 5,7 3,6 2,7 Methionine 0.6 2,4 0,8 1,8 Cysteine / Cystine - 1,6 1,7 1,9 Tryptophan 1,2 1,4 1,2 1,3 Ornithine 0,4 - - - According to a particular aspect of the process as defined above, step A is carried out with a mixture of compounds of formulas (IV), wherein R1 represents alkyl radicals having from 7 to 11 carbon atoms. According to this particular aspect the mixture of compounds of formula (IV) is a mixture of acid chlorides prepared from a mixture of fatty acids derived from coconut oil. According to another particular aspect of the process as defined above, the progress of the chemical reaction of step A is monitored by controlling the pH of the reaction medium and adjusting it if necessary by adding an aqueous alkaline solution.

According to another particular aspect of the process as defined above, step A is carried out while maintaining the temperature below 35 ° C.

According to another particular aspect of the process as defined above, step A is carried out while maintaining the pH less than or equal to 9.5 and greater than or equal to 8.0. According to another particular aspect of the process as defined above, step A is carried out by maintaining the molar ratio of acid halide of formula (IV) / compound comprising a divalent functional unit (M2) of less than 1.00 and greater or equal to 0.75. In the process as defined above, step A of the process is preferably carried out with vigorous stirring so as to promote contact between the compound comprising a divalent functional unit (M2) and the acid halide of formula (IV) . According to another particular aspect of the process as defined above, step A is carried out while maintaining contact between the acid halide of formula (IV) and the compound comprising a divalent functional unit (M2) for a shorter duration or equal to 5 minutes. In the process as defined above, stage B of the process is preferably carried out with a strong acid with stirring so as to promote contact between the compound having a divalent functional unit (M3) and the acidic aqueous solution. The strong acid is more particularly chosen from hydrochloric acid, sulfuric acid or phosphoric acid. According to another particular aspect of the process as defined above, step B is carried out while maintaining the pH less than or equal to 2.

According to another particular aspect of the process as defined above, step B is followed by a step C of washing with water and filtering the precipitate dispersion obtained in step B. According to another particular aspect of method as defined above, step C is followed by a step D of drying the precipitate obtained in step C.

In a more particular aspect of the process as defined above, the precipitate obtained in step C is dried and atomized to obtain a powder. According to another particular aspect of the invention, the subject of the invention is a process as defined above, for the synthesis of an N-acylated α-amino acid of formula (I): ## STR1 ## I) wherein R 1 is as previously defined in said divalent functional unit (M 1), R 2 represents a hydrogen atom, or a radical selected from methyl, benzyl, isobutyl, 1-methyl propyl or isopropyl and R 3 represents a hydrogen atom or a methyl radical, comprising: A reaction step A of the alkali metal salt of the α-amino acid of formula (II): wherein R 2 and R 3 are such that defined in formula (I) above, and M represents an alkali metal atom, with an acid halide of formula (IV):

Wherein R1 represents a linear or branched, saturated or unsaturated aliphatic radical having from 1 to 17 carbon atoms and X represents a halogen atom, or with a mixture of acid halides of formulas (IV), in aqueous solution and at pH greater than 7, to form a compound of formula (III): wherein M, R1, R2 and R3 are as defined above, or a mixture of compounds of formula (III); A step B of hydrolysis with a pH below 7, of the compound of formula (III), or of the mixture of compounds of formula (III), obtained in step A, to form said of an α-amino acid N -acylated formula (I); characterized in that step A is carried out by contacting, in a continuous manner over time, a flow of flow di, of said acid halide of formula (IV), with a flow rate d2, of said acid a -amine of formula (II) and a d3 flow rate of alkaline aqueous solution, maintaining the molar ratio of acid halide of formula (IV) / α-amino acid of formula (II) less than 1. According to a particular aspect of the process as defined above, in the formula (IV), X represents a chlorine atom.

According to a particular aspect of the process as defined above, in the formula (IV) and for the divalent functional units M1 and M3, R1 represents a heptyl radical. According to another particular aspect of the invention, the subject of the invention is a process as defined above, for the synthesis of N-octanoyl glycine of formula (I '):

Wherein R1 represents the heptyl radical, R2 and R3 each represent a hydrogen atom, comprising: A sodium glycinate reaction step A of formula (II ') NH 2 (II ') corresponding to formula (II) in which M represents a sodium atom, with octanoyl chloride (IV'):

Wherein R 1 represents a heptyl radical and X represents a chlorine atom, in aqueous sodium hydroxide solution and at a pH of greater than 8 and less than or equal to 9.5, to form a compound of formula (III '): ## STR2 ## corresponding to formula (III) in which R 1 represents a heptyl radical, M represents a sodium atom, R 1 represents the heptyl radical and R2 and R3 each represent a hydrogen atom; A hydrolysis step B at a pH of less than 2, of the compound of formula (III ') obtained in step A, to form said N-octanoyl glycine of formula (I'); A step C of washing with water and filtering the aqueous dispersion of precipitate obtained in step B. A drying step D / atomization of the wet precipitate obtained in step C to obtain the N-octanoyl glycine under fine powder form; characterized in that step A is carried out by continuously contacting in time a flow rate di of said acid halide of formula (IV ') with a flow rate d2, said acid a -amine of formula (II ') and a flow rate d3 of aqueous sodium hydroxide solution 15 by maintaining the molar ratio of acid halide of formula (IV) / α-amino acid of formula (II') less than 1 and greater than or equal to 0.8. According to another particular aspect of the process as defined above, in the formula (IV) and for the divalent functional units M1 and M3, R1 represents a 9-decenyl radical. According to another particular aspect of the invention, the subject of the invention is a process as defined above, for the continuous preparation of an N-acylated amino acid, characterized in that the amino acid in aqueous solution at a flow rate of 2 the acid chloride at a flow rate d 1 and an aqueous solution of sodium hydroxide at a flow rate d 3 are introduced simultaneously in a molar ratio of acid chloride / amino acid greater than or equal to 0.8 and less than 1, in a reactor equipped with an agitator for obtaining a fine homogenization of said reaction medium and dimensioned so that the residence time of the reaction medium formed in the reactor is less than or equal to 5 minutes, said reaction medium being maintained at a temperature less than or equal to 35 ° C and the pH of said reaction medium being maintained at a value between 8.5 and 9.5; in that said reaction medium is allowed to transfer to a precipitation reactor equipped with a worm, in which it is treated with an aqueous solution of phosphoric acid introduced at a flow rate d4 able to maintain in said precipitation reactor a pH of less than or equal to 2 to form at the end of the course in said precipitation reactor, an aqueous dispersion of a precipitate of said amino acid which is then washed, filtered and the wet precipitate obtained is, if necessary, dried and then atomized. According to another aspect, the subject of the invention is an installation for carrying out the process as defined above comprising: a reactor (RE1) with a double jacket and provided with an agitator (AG1) and with a measuring device the internal temperature (TICRE1) allowing the control and the adjustment of the temperature within it by circulating in said envelope, a refrigerant fluid, said fluid being cooled by recirculation within a heat exchanger (El). Three containers ZB1, ZB2 and ZB3, from which three pumps (P1), (P2) and (P3) are respectively withdrawn continuously, the compound comprising at least one divalent functional unit (M2), the acid halide of formula (IV) and the aqueous alkaline solution. Three fluid circulation lines (1), (2) and (3), allowing the circulation of the reagents from said containers (ZB1), (ZB2) and (ZB3) and their introduction via 3 inputs located at its base in said reactor (rEL). A precipitation reactor (PR1) equipped with an endless screw (AG2), connected to an inlet located in the upper part of said reactor (RE1), by a fluid circulation line (4), and connected to a container ( ZB4), via a fluid circulation line (5), from which is drawn off by means of a pump (P4), the acidic aqueous solution intended for hydrolysis within said precipitation reactor (PR1) of the compound comprising at least one unit functional divalent (M3), said precipitation reactor (PR1) being wrapped in its first half said half upstream, by a double-envelope for the control and adjustment of the temperature therein by circulation in said envelope, a refrigerant, and in its second half, said half downstream, by a double jacket, for controlling and adjusting the temperature therein, by circulating in said casing, a heating fluid. A reservoir (R02) for collecting the precipitate dispersion flowing from said precipitation reactor (PR1), provided with a pH control device (PHR02), connected in its downstream part by fluid circulation lines (6). ), (7) and (8) to a filter bank (F1), (F2) and (F3) arranged in parallel, allowing through a pump (P5) and a connection to the water network, washing and filtering the precipitate dispersion from said reservoir (R02); said filters (F1), (F2), (F3) being connected downstream to a fluid circulation line (9) issuing from an overflow of said tank (R02). According to a last aspect of the invention, the subject of this invention is the use of N-acyl partial hydrolysates of proteins of all origins which consist essentially of mixtures of oligopeptides having oligomerization degrees of less than or equal to 10 and more particularly less than or equal to 5, neutralized with an alkaline base such as an aqueous solution of sodium hydroxide or potassium hydroxide; total N-acyl hydrolysates of proteins of all origins which consist essentially of mixtures of amino acids and oligopeptides having lower oligomerization degrees equal to 2 and more particularly less than or equal to 1.5 neutralized by an alkaline base such as an aqueous solution of sodium hydroxide or potassium hydroxide, N-acylated α-amino acids and more particularly N-acylated glycine, N-acylated alanine, N-acylated serine, N-acylated aspartic acid, N-acylated glutamic acid, N-acylated valine, N-acylated threonine, N-acylated arginine, N-acylated lysine, N-acylated proline, N-acylated leucine, N-acylated phenylalanine, N-acylated isoleucine, N-acylated histidine, N-acylated tyrosine, N-acylated tryptophan, N-acylated asparagine , N-acylated glutamine, N-acylated cysteine, N-acylated cystine, N-acylated methionine, N-acylated hydroxyproline, N-acylated N-acylated hydroxy-lysine, N-acylated α-amino acid derivatives and more particularly N-acylated sarcosine, obtained by the process as defined above, as active ingredients and / or as excipients in cosmetic topical compositions. Cosmetic topical compositions comprising the N-acylated hydrolysates of proteins of all origins and / or the total N-acylated hydrolysates of proteins obtained by the process as defined above are generally in the form of dilute or hydrous aqueous or hydro-alcoholic solutions. glycol, as single or multiple emulsions, such as water-in-oil (W / O), oil-in-water (O / W), water-in-oil (W / O / W) or oil-in-water emulsions oil (O / W / H), in which the oil is of vegetable or mineral or animal nature. They can also be dispersed or impregnated on textile or non-woven materials such as wipes, paper towels or clothing. In general, the N-acylated hydrolysates of proteins of all origins and / or the total N-acylated hydrolysates of proteins obtained by the process as defined above, are associated with many types of adjuvants or active principles used in the cosmetic formulations, whether of fatty substances, organic solvents, thickeners, gelling agents, softeners, antioxidants, opacifiers, stabilizers, foaming agents, emollients, perfumes, ionic or nonionic emulsifiers, fillers, sequestering agents, chelators, preservatives, essential oils, dyestuffs, pigments, hydrophilic or lipophilic active agents, humectants such as glycerin, preservatives, cosmetic active ingredients, mineral and / or organic sunscreens, mineral fillers such as iron oxides, titanium oxides and talc, synthetic fillers such as nylons and poly (methyl methacrylate) r ticles or not, silicone elastomers, sericites or plant extracts or lipid vesicles or any other ingredient usually used in cosmetics.

As examples of oils that can be combined with N-acylated hydrolysates of proteins of all origins and / or total N-acylated hydrolysates of proteins obtained by the method which is the subject of the invention, mention may be made of mineral oils such as paraffin oil, vaseline oil, isoparaffins or mineral white oils; oils of animal origin, such as squalane or squalane; vegetable oils, such as sweet almond oil, coconut oil, castor oil, jojoba oil, olive oil, rapeseed oil, olive oil peanut, sunflower oil, wheat germ oil, corn germ oil, soybean oil, cottonseed oil, alfalfa oil, poppy oil, pumpkin oil, evening primrose oil, millet oil, barley oil, rye oil, safflower oil, bancoulier oil, passionflower oil, hazelnut oil, palm oil, shea butter, apricot kernel oil, calophyllum oil, sysymbrium oil, avocado oil, calendula oil; ethoxylated vegetable oils; synthetic oils such as fatty acid esters such as butyl myristate, propyl myristate, cetyl myristate, isopropyl palmitate, butyl stearate, hexadecyl stearate, isopropyl stearate, octyl stearate, isocetyl stearate, dodecyl oleate, hexyl laurate, propylene glycol dicaprylate, esters derived from lanolic acid, such as isopropyl lanolate, isocetyl lanolate , monoglycerides, diglycerides and triglycerides of fatty acids such as glycerol triheptanoate, alkylbenzoates, polyalphaolefins, polyolefins such as polyisobutene, synthetic isoalkanes such as isohexadecane, isododecane, perfluorinated oils and silicone oils. Among these, mention may be made more particularly of dimethylpolysiloxanes, methylphenylpolysiloxanes, amine-modified silicones, silicones modified with fatty acids, silicones modified with alcohols, silicones modified with alcohols and fatty acids, and silicones. modified with polyether groups, modified epoxy silicones, silicones modified with fluorinated groups, cyclic silicones and silicones modified with alkyl groups. As another fat that can be associated with N-acylated hydrolysates of proteins of all origins and / or total N-acylated hydrolysates of proteins obtained by the method of the invention, mention may be made of fatty alcohols or acids fat. Among the thickening and / or emulsifying polymers which can be associated with the N-acylated hydrolysates of proteins of all origins and / or the total N-acylated hydrolysates of proteins obtained by the process which is the subject of the invention, there is for example , homopolymers or copolymers of acrylic acid or derivatives of acrylic acid, homopolymers or copolymers of methacrylic acid or derivatives of methacrylic acid, homopolymers or copolymers of acrylamide, homopolymers or copolymers acrylamide derivatives, homopolymers or copolymers of acrylamidomethyl propanesulfonic acid, vinyl monomers, trimethylaminoethylacrylate chloride, hydrocolloids of vegetable or biosynthetic origin, for example xanthan gum, karaya gum, carrageenates alginates; silicates; cellulose and its derivatives; starch and its hydrophilic derivatives; polyurethanes. Among the polyelectrolyte type polymers that can be used in the production of a gelled aqueous phase suitable for use in the preparation of W / O, O / W, W / O / W or O / W emulsions. or an aqueous gel containing the guar protein extracts, their derivatives or their hydrolysates which are the subject of the present invention, there are, for example, the copolymers of acrylic acid and methylmethyl [(1-oxo-2) acid; propenyl) amino] propane sulfonic acid (AMPS), copolymers of acrylamide and methyl ([(1-oxo-2-propenyl) amino] propanesulfonic acid, copolymers of methylmethyl [(1-oxo-2-propenyl) ) amino] propane sulphonic acid and (2-hydroxyethyl acrylate), homopolymer of methyl ([(1-oxo-2-propenyl) amino] propane sulphonic acid, homopolymer of acrylic acid, copolymers of acryloyl ethyl trimethyl ammonium chloride and acrylamide, copolymers of AMPS and vinylpyrrolidone, copolymers of acrylic acid and alkyl acrylates whose carbon chain comprises between ten and thirty carbon atoms, copolymers of AMPS and alkyl acrylates whose carbon chain comprises between ten and thirty atoms of carbon. Such polymers are marketed under the names SIMULGELTM EG, SEPIGELTM 305, SIMULGELTM NS, SIMULGELTM 800, SIMULGELTM A, SIMULGELTM EPG, SIMULGELTM INS, SIMULGELTM FL, SEPIGELTM 501, SEPIGELTM 502, SEPIPLUSTM 250, SEPIPLUSTM 265, SEPIPLUSTM 400, SEPINOVTM EMT. 10, CARBOPOLTM ULTREZTM 10, ACULYNTM, PEMULENTM TRI, PEMULENTM TR2, LUVIGELTM EM, SALCARETM SC91, SALCARETM SC92, SALCARETM SC95, SALCARETM SC96, FLOCARETM ET100, FLOCARETM ET58, HISPAGELTM, NOVEMERTM EC1, ARISTOFLEXTM AVC, ARISTOFLEXTM HBM, RAPITHIXTM A60, RAPITHIXTM A100, COSMEDIA SP and STABILEZETM 06. Among the waxes that can be used in cosmetic topical compositions comprising the N-acylated hydrolysates of proteins of all origins and / or the total N-acylated hydrolysates of proteins obtained by the process which is the subject of the invention, for example, beeswax; carnauba wax; candelilla wax; ouricoury wax; wax of Japan; wax of cork fiber or sugar cane; paraffin waxes; lignite waxes; microcrystalline waxes; lanolin wax; ozokerite; polyethylene wax; hydrogenated oils; silicone waxes; vegetable waxes; fatty alcohols and solid fatty acids at room temperature; glycerides solid at room temperature. Among the emulsifiers that may be used in cosmetic topical compositions comprising the N-acylated hydrolysates of proteins of all origins and / or the total N-acylated hydrolysates of proteins obtained by the method which is the subject of the invention, mention may be made of: optionally alkoxylated alkylpolyglycosides, and especially ethoxylated methylpolyglucoside esters such as PEG 120 methyl glucose trioleate and PEG 120 methyl glucose dioleate respectively marketed under the names GLUCAMATETM LT and GLUMATETM DOE120 respectively. alkoxylated fatty esters such as PEG 150 pentaerythrityl tetrastearate marketed under the name CROTHIX ™ DS53, PEG 55 propylene glycol oleate sold under the name ANTIL ™ 141; fatty chain polyalkylene glycol carbamates such as PPG 14 laureth isophoryl dicarbamate marketed under the name ELFACOSTM T211, PPG 14 palmeth 60 hexyl dicarbamate sold under the name ELFACOSTM GT2125; fatty acids, ethoxylated fatty acids, fatty acid and sorbitol esters, fatty acid esters of mannitol, ethoxylated fatty acid esters, polysorbates, polyglycerol esters, ethoxylated fatty alcohols sucrose esters, alkylpolyglycosides, sulphated and phosphated fatty alcohols or mixtures of alkylpolyglycosides and fatty alcohols described in French patent applications 2,668,080, 2,734,496, 2,756,195, 2,762,317, 2 784,680, 2,784,904, 2,791,565, 2,790,977, 2,807,435, 2,804,432, 2,830,774, 2,830,445, combinations of emulsifying surfactants selected from alkylpolyglycosides, alkylpolyglycoside and alcohol associations. polyglycerol or polyglycol esters or polyols such as polyhydroxystearates of polyglycol or polyglycerol used in French patent applications 2,852,257, 2,858,554, 2820316 and 2852258. As examples of active ingredient that the we can associate with hyd N-acylated rolysates of proteins of all origins and / or total N-acylated hydrolysates of proteins obtained by the process which is the subject of the invention, mention may be made of compounds having a lightening or depigmenting action, such as, for example, arbutin, kojic acid, hydroquinone, ellagic acid, vitamin C, magnesium ascorbyl phosphate, polyphenol extracts, grape extracts, pine extracts, wine extracts, olive extracts, extracts of marc, apple juice extracts, amino acids, peptides, total protein hydrolyzates, partial protein hydrolysates, polyols (eg, glycerin or butylene glycol), urea, acid pyrrolidonecarboxylic acid or derivatives thereof, glycyrrhetinic acid, alpha-bisabolol, sugars or derivatives of sugars, polysaccharides or derivatives thereof, hydroxy acids for example lactic acid, vitamins, vitamin derivatives such as retinol, vitamin E and its derivatives, minerals, enzymes, co-enzymes, such as, Coenzyme Q10, hormones or "hormone like", eg PHYTO-AGETM, eg soy extracts , RaffermineTM, wheat extracts, for example TensineTM or GliadineTM, plant extracts, such as tannin-rich extracts, isoflavone-rich extracts or terpenes-rich extracts, freshwater algae extracts or marine extracts, essential waxes, bacterial extracts, minerals, lipids in general, lipids such as ceramides or phospholipids, active agents having a slimming action such as caffeine or its derivatives, the active agents having an antimicrobial activity or a purifying action with regard to oily skin, the active ingredients having an energizing or stimulating property such as SEPITONICTM M3 or PhysiogenylTM, panthenol and its derivatives such as SEPICAPTM MP, anti-aging active ingredients such as SEPIVINOLTM, SEPIVITALTM, moisturizing active ingredients such as AQUAXYLTM EXTRAMELTM C, MANOLIVATM, "anti-photo aging" active ingredients, active agents with tensor action or immediate smoothing on the skin, for example SESAFLASHTM, the active agents protecting the integrity of the dermal-epidermal junction, such as PHYTO-AGETM, the active agents increasing the synthesis of extracellular matrix components such as SEPITONICTM M3, AQUAXYLTM, the active ingredients. a slimming, firming or draining activity such as, for example, caffeine, theophylline, cyclic Adenosyl Mono Phosphate (cAMP), ADIPOLESSTM, green tea, sage, ginko biloba, ivy, horse chestnut, bamboo, ruscus, small holly, centella asiatica, heather, ulmaine, fucus, rosemary, willow, parsnip extracts, potentilla extracts, active ingredients that create a feeling of warmth on the skin as the activ cutaneous microcirculation agents (example of nicotinates) or products creating a feeling of freshness on the skin (example of menthol and derivatives) active agents having an action on stem cells, active agents having an action on the epidermis , the dermis, the hypodermis and the cutaneous appendages (hair, nails, sebaceous glands, pores ...), the active agents having an action with respect to the cutaneous flora. As sunscreen which can be combined with N-acylated hydrolysates of proteins of all origins and / or total N-acylated hydrolysates of proteins obtained by the method of the invention, all those appearing in the cosmetic directive can be mentioned. 76/768 / EEC as amended Annex VII. The following examples illustrate the invention without limiting it.

EXAMPLE 1 Preparation of N-octanoyl glycine (compound 1) An aqueous sodium hydroxide solution (30% by weight, 1.33 density) at a flow rate of 88.1 g / min is introduced simultaneously with stirring. octanoyl (0.95 density) at a rate of 72 g per minute, and a sodium glycine solution (1.105 density) comprising: 2220 g water, 412.5 g glycine (5.5 moles), 337.5 g sodium chloride and 431.5 g of 30% aqueous sodium hydroxide solution (3.24 moles), at a flow rate of 280.4 g / min, in a jacketed reactor of 0.5 liter cooled internal volume of to maintain a reaction temperature between 25 ° C and 30 ° C. The acylation reaction is controlled by controlling the pH of the medium so that it remains less than or equal to 9 and greater than or equal to 8 by adjusting the flow rate in sodium hydroxide solution if necessary. When the volume occupied by the reaction mixture reaches the useful volume of the reactor, it begins to flow into a precipitation reactor equipped with a worm, two double envelopes, the first on the introduction side to cool the precipitation to a minimum. temperature between 25 ° C and 30 ° C and the second exit side, to heat the precipitate and thus promote its flow, and wherein is simultaneously introduced an aqueous solution of phosphoric acid (20% by weight, density 1.11) at flow rate of 559.4 g / min. The neutralization of N-octanoyl glycine is controlled by controlling the pH of the medium in the precipitation reactor, so that it remains less than or equal to 2 and greater than or equal to 1, if necessary adjusting the flow rate in phosphoric acid solution. There is thus obtained 6460 g / hour of aqueous suspension of N-octanoyl glycine. The precipitate suspension obtained is discharged into a constant-level tank equipped with a pH meter, and is then washed and filtered continuously by means of CRICKETTM type 200D or equivalent filters, arranged in parallel so as to provide the continuity of filtration. About 828 g / hour of wet N-octanoyl glycine are thus obtained which are dried and, if desired, atomized, to produce about 165 g / hour of dry N-octanoyl glycine in the form of powder or agglomerates. The analysis of a final product sample by gas chromatography confirms the presence of free octanoic acid at a concentration of less than 1% by weight.

The test set out above demonstrates the advantages of implementing the continuous acylation process according to the invention over the batch process of the state of the art: use of organic solvent such as acetone, to prevent the secondary reaction: Acid Chloride + sodium hydroxide ---> Acid + Sodium Chloride by means of a permanent control of the pH and temperature conditions of the reactor and the reactor. precipitation, to control the contact time between the reagents; - The use of a reactor up to 104 times smaller (0.5 liter instead of 5 m3), to produce the same amount of N-acylated amino acid. Such advantages as well as the technical solution for achieving them have never been described or suggested in the state of the art at the filing date of the present patent application.

Example 2: Preparation of N-undecylenoyl phenylalanine (Compound 2) Operating in a similar manner to the method of Example 1, but using the sodium salt of phenylalanine, in place of sodium glycinate, and the chloride of N-undecylenoic acid in place of octanoyl chloride; N-undecylenoyl phenylalanine Examples of cosmetic formulations The following examples illustrate cosmetic formulations using compounds 1 and 2, obtained by the process that is the subject of the present invention. A MONTANOVTM 68: 5.00% Sweet almond oil: 5.00% DL alpha-tocopherol: 0.05% B Water: QSP 100% Glycerin: 5.00% Compound 1: 1.00% Sodium hydroxide: 0.50% C SEPIGEL ™ 305: 0.30% Example 3: Preservative free emulsion Formula 30 D Perfume: 0.30% Procedure Melt A at 70 ° C and heat B at 75 ° C. Emulsify B in A at 70 ° C then add C. At 35 ° C add the constituents of phase D. Adjust pH.

Example 4: Lotion for acne-prone skin Formula A MONTANOXTM 20 DF: 05.00% Fragrance: 00.20% B Water: Qsp 100% Sodium hydroxide: 0.50% Compound 1: 0.100% Procedure Solubilize the fragrance in MONTANOXTM 20. Solubilize compound 1 in the water / NaOH mixture. Mix A and B.

EXAMPLE 5 Shampoo for the dandruff and squamous states Formula A Water: 20.00% Compound 1: 2.00% Soda lye at 32% by weight: 1.12% B PEG 120 methyl glucose dioleate: 3.00% Sodium lauryl ether sulfate at 28% by weight 33.00% AMONYLTM 675 SB: 4.70% PROTEOLTM OAT: 5.00% Perfume: 0.20% Water qs 100% Lactic acid: qs pH = 5.5 Sodium chloride: qs 3000 cps 30 Procedure Heat the water, add the sodium hydroxide and the compound 1; Melt the nonionic wax in this mixture and cool with stirring before incorporating the surfactants and other ingredients. The viscosity is regulated by addition of sodium chloride.

Example 6: Cleansing gel for sensitive skin faces without preservatives Formula A Compound 1 1.00% Sodium hydroxide at 48% by mass 0.35% Water: 20.00% B SIMULSOLTM 220TM: 3.00% Water: 10.00 % CAPIGELTM 98: 5.00% Water: 10.00% C ORONALTM LCG: 20.00% D Perfume: 0.10% Glycerin: 5.00% Water: QSP 100% Sodium hydroxide: qs pH = 9.0 Lactic acid : qs pH = 5.5 Color: Qs Procedure Solubilize compound 1 in hot water at 90 ° C in the presence of sodium hydroxide. Add SIMULSOLTM 220TM and shake, add ORONALTM LCG and pre-dispersed perfume in glycerine (D) and then make QS in water. Dilute CAPIGELTM 98 cold in water and add and mix. Adjust the pH if necessary (around 9) then re-acidify (about 0.8% lactic acid) to the desired pH. A MONTANOVTM 202: 3.00% Squalane: 5.00% SEPICALMTM VG: 3.00% B Water: QSP 100% Compound 1: 0.50% Sodium Hydroxide 32% by weight: 0.10% C Macadamia Oil Ternifolia and kiwi sprout oil: 3.00% Cyclomethicone: 3.00% D SEPIGELTM 305: 2.00% Example 7: Anti-aging comfort cream for sensitive skin 25 Formula 30 21 E SEPICIDETM HB: 0.20% Tocopherol: 0.10% Fragrance: 0.10% Sodium hydroxide: qs pH Procedure Heat the aqueous phase to 80 ° C. Add the sodium hydroxide, the compound 1 and the fatty phase previously heated to 80 ° C. Emulsify a few minutes then add the silicone oil and vegetable oil. At about 70 ° C, introduce SEPIGELTM 305. Cool and add SEPICIDETM HB, perfume and tocopherol to 30 ° C. If necessary readjust the final pH.

EXAMPLE 8 Very Gentle Foaming Gel Without Preservative Formula A Compound 1: 2.00% Sodium Hydroxide 24% by mass: 1.48% Water: 20.00% B CAPIGELTM 98: 3.00% Water: 10.00% C ORONALTM LCG: 14.00% PROTEOLTM OAT: 4.00% ORAMIDETM DL200AF: 3.00% Fragrance / Fragrance: 0.10% Glycerin: 5.00% Water: QSP. 100% Sodium hydroxide: qs pH = 9.5 Lactic acid: qs pH = 5.3 Procedure Solubilize compound 1 in hot water at 90 ° C in the presence of sodium hydroxide. Add in this solution (A) the ingredients listed in C and add the pre-diluted CAPIGELTM 98 (B). Add water and adjust the pH first by alkalinizing and then re-acidifying a pH of about 5.3.

Example 9: High tolerance skincare cream for sensitive skin Formula A MONTANOV ™ 202: 5.00% Vegetal squalane: 5.00% Coco-caprylate / caprate: 10.00% B Sodium and magnesium silicate: 1.00% Gum xanthane: 0.30% C Water: QSP 100% Compound 1: 1.00% Sodium hydroxide: qs pH = 5 D Fragrance: 0.10% SEPICIDETM HB: 0.20% Procedure Melt the fatty substances of the phase At 80-85 ° C. Heat phase C to 80-85 ° C. Disperse the powders (B: sodium and magnesium silicate, and xanthan gum) in the fatty phase and emulsify C in A at 80-85 ° C.

Example 10: Foaming gel without preservative Formula A AMONYLTM 675 SB: 16.00% ORAMIX ™ NS 10: 09.00% PEG-120 methylglucose dioleate: 04.00% Fragrance: 00.50% B Hot water (80-90 ° C. ): 20.00% Compound 1: 02.00% Propylene glycol: 05.00% Sodium hydroxide at 32% by mass: 01.00% C Water: QSP 100% Sodium hydroxide at 32% by mass: QS PH = 5 Procedure Mix the constituents of A in order. Mix the constituents of B in order. Add B to A then C. Readjust the final pH if necessary.

Example 11 Purifying Gel for Pimples and Blackheads Formula A SEPIGEL ™ 305: Tri-Heptanoine: 4.00% 4.00% 23 B Compound 1: Propylene Glycol: Procedure Hot solubilize compound 1 in propylene glycol. After cooling, gradually add phase B to phase A with continuous stirring. 4.00% QSP 100% Example 12: Emulsion-Lightening care for mature skin MONTANOVTM 202: 2.00% MONTANOVTM 68: 2.00% Caprylic capric triglycerides 10.00% Squalane 10.00% Water QSP 100% Compound 2 1 , 00% SEPIGELTM 305 0.70% Magnesium ascorbyl phosphate 2.00% SEPICIDETM HB 0.30% SEPICIDETM CI 0.20% Perfume 0.50% Example 13: Emulsion - Lightening Firming Treatment MONTANOVTM 202: Sodium Hydroxide 24% Mass: Ethyl hexyl methoxycinnamate: LANOLTM 1688: Benzophenone-3: Water: Compound 2: SIMULGELTM NS: SEPILIFTTM DPHP: Dimethicone: Cyclomethicone: Arbutin: SEPICIDETM HB: 3.00% 0.06% 6.00 % 8.00% 4.00% QSP 100% 2.00% 0.50% 0.50% 2.00% 2.00% 0.30% 0.30% SEPICIDETM CI: Fragrance: Example 14: Gel- alpha-hydroxy acid lightening cream Hydroxyethylcellulose: Ethyl hexanoate: 60% by weight sodium lactate: Water: Compound 2: SEPIGEL ™ 305: SEPICIDETM HB: SEPICIDETM CI: Fragrance: Example 15: Emulsion - Lightening care MONTANOV TM L: Cetyl alcohol: Isodecyl neopentanoate: cetearyl octanoate: Glycerine: Water: Compound 2: SIMULGELTM EG: Kojic acid: SEPICIDETM HB: SEPICIDETM CI: Fragrance Example 16: Lightening lotion ORAMIXTM CG110: KATHONTM CG: Water: 0, 20% 0.10% 0.80% 5.00% 14.00% QSP 100% 3.00% 4.20% 2.00% 3.00% 0.10% 1.00% 2.00% 12 , 00% 10.00% 3.00% QSP 100% 1.00% 2.00% 1.00% 0.30% 0.20% 0.10% 5.00% 0.08% QSP 100% Compound 2: 1.00% Perfume: 0.10% This lotion can be sold in bottles or impregnated on wipes. Example 17: Pressed powder A Compound 2: 2.00% MICROPEARL TM M310: 5.00% Mica: 50.00% Talc: 32.50% Iron oxide yellow: 0.50% B SEPICALMTM VG: 5.00% C Dimethicone: 5.00% Procedure Weigh all the powders (phase A) and dry grind them in a knife mill.

Add phase B and reproduce the same grinding time as for phase A. Add phase C and repeat the same milling operation as for phase B. The powder thus prepared is then pressed into cups by means of a KENWALL manual compactor with a pressure of 120 bar. Example 18: Clear Dyed Fluid 20 A Compound 2: 2.00% B MICROPEARL ™ M310: 3.00% Water: QSP 100% Carbomer: 0.25% Xanthan Gum: 0.20% 25 C Isononyl Isononoate: 5, 00% D SEPICIDETM HB: 0.30% SEPICIDETM CI: 0.20% Perfume: 0.30% DL a-Tocopherol: 0.05% 30 E Tromethamine: QS pH = 7.2 Procedure Solubilize Compound 2 in ethanol with stirring and then add MICROPEARLTM M310. Disperse carbomer and xanthan gum in water and add C in this phase B, stirring. Add phase D and adjust the final pH if necessary. The definitions of the commercial products used in the examples are the following: MONTANOV ™ 68 is an emulsifying agent based on cetearyl alcohol and cetearyl glucoside marketed by the company SEPPIC SEPIGEL 305 ™ is a thickening and stabilizing agent (INCI name: Polyacrylamide, C13- Isoparaffin, Laureth-7) marketed by the company SEPPIC MONTANOXTM 20 DF is a solubilizing agent based on Polysorbate 20 marketed by the company SEPPIC AMONYLTM 675 SB is a foaming agent based on cocamidopropyl hydroxysultaine marketed by the company SEPPIC PROTEOLTM OAT is a foaming agent based on amino acid lauroate of the oat protein marketed by the company SEPPIC SIMULSOL ™ 220TM is a foaming agent based on PEG-200 glyceryl stearate marketed by the company SEPPIC CAPIGELTM 98 is a thickening and stabilizing agent based on copolymers Acrylates marketed by the company SEPP IC 20 ORONALTM LCG is a foaming and detoxifying agent based on cocoeth sulfate in sodium form and PEG 40 glyceryl cocoate marketed by the company SEPPIC MONTANOVTM 202 is an emulsifier based on arachidyl alcohol, behenyl alcohol and arachidyl glucoside marketed by the company SEPPIC SEPICALMTM VG: (INCI name: sodium palmitoyl proline and Nymphea alba 25 flower extract) marketed by SEPPIC SEPICIDETM HB: a mixture of phenoxyethanol, methylparaben, ethylparaben, propylparaben and butylparaben, ( preservative) marketed by the company SEPPIC ORAMIDETM DL200AF is a foaming agent based on cocamide DEA marketed by the company SEPPIC ORAMIXTM NS 10 is a foaming agent based on Decyl glucoside marketed by the company SEPPIC SEPICIDETM CI is a preservative-based agent Imidazoline urea, marketed by the company SEPPIC LANOLTM 1688 is Ethylhe cetaryl xanoate marketed by the company SEPPIC SIMULGELTM NS is a self-invertible inverse latex of copolymers such as those described in the international publication WO 99/36445 (INCI name: hydroxyethylacrylate / Sodium acryloyldimethyl taurate copolymer and squalane and Polysorbate 60) marketed by the SEPPIC SEPILIFTTM DPHP company is Dipalmitoyl hydroxyproline, marketed by the company SEPPIC MONTANOVTM L is a C14-C22 alcohol-based emulsifier and C12-C20 alkyl polyglucoside such as those described in the European patent application EP 0 SIMULGEL ™ EG is a self-invertible inverse latex of copolymers such as those described in the international publication WO 99/36445 (INCI name: Sodium acrylate / sodium acryloyldimethyl taurate copolymer and Isohexadecane and Polysorbate 80) sold by the company SEPPIC ORAMIX TM CG110. a foaming agent based on octyl glucoside and decyl glucoside as marketed by the company SEPPIC KATHONTM CG is the methyl isothiazolinone / methyl chloroisothiazolinone marketed by the company ROHM & HAAS MICROPEARLTM M310 is an oil dispersing powder based on polymethyl methacrylate, having adsorbent and mattifying properties, marketed by the company SEPPIC.20

Claims (14)

REVENDICATIONS1. A method of synthesizing an N-acylated compound having at least one divalent functional unit (M1) or a mixture of N-acyl compounds having at least one divalent functional unit (M1): OO (M1), wherein n represents an integer of 0, 1 or 2, and R1 represents a linear or branched, saturated or unsaturated aliphatic radical having from 1 to 17 carbon atoms, comprising: A reaction step of a compound comprising at least one divalent functional unit (M2) or a mixture of compounds having at least one divalent functional unit (M2): ## STR1 ## wherein n is as defined above in the divalent functional unit (M 1), M represents an alkali metal atom, with an acid halide of formula (IV): R 1 O (IV), wherein R 1 is as previously defined in said divalent functional unit (M 1), X represents a halogen atom, or with a mixture of acid halides of formulas (IV), in aqueous solution and at pH greater than 7, to form an N-acyl compound having at least one divalent functional unit (M3): ## STR2 ## wherein n, M and R 1 are such as defined above, or a mixture of N-acyl compounds having at least one divalent functional unit (M3), A step B of hydrolysis with a pH of less than 7, of the N-acyl compound having at least one divalent functional unit ( M3) or a mixture of N-acyl compounds having at least one divalent functional unit (M3), obtained in step A, to form said N-acyl compound comprising at least one divalent functional unit (M1) or said mixture of compounds N-acyls having at least one divalent functional unit (M1); characterized in that step A is carried out by contacting, in a continuous manner over time, a flow of di flow, said acid halide of formula (IV), a flow rate of d2, said compound N-acyl compound comprising at least one divalent functional unit (M2) or a mixture of N-acyl compounds containing at least one divalent functional unit (M2) and a d3 flow rate of alkaline aqueous solution, while maintaining the molar ratio of halide acid of formula (IV) / N-acyl compound having at least one divalent functional unit (M2) of less than 1. 2. A process as defined in claim 1, wherein the course of the chemical reaction of step A is monitored by controlling the pH of the reaction medium and adjusting it if necessary by adding an aqueous alkaline solution. 3. Method as defined in one of claims 1 to 2, wherein step A is performed while maintaining the temperature below 35 ° C. 25 4. A method as defined in one of claims 1 to 3, wherein step A is performed while maintaining the pH less than or equal to 9.5 and greater than or equal to 8.0. 5. A process as defined in one of claims 1 to 4, wherein step A is carried out by maintaining the molar ratio acid halide of formula (IV) / compound comprising a divalent functional unit (M2), less than 1.00 and greater than or equal to 0.75. 29 n CH2 0M R1 6. Process as defined in one of claims 1 to 5, wherein step B is carried out while maintaining the pH less than or equal to 2. 7. A method as defined in one of claims 1 to 6, wherein step B is followed by a step C of washing with water and filtration of the precipitate dispersion obtained in step B. 8. The process as defined in claim 7, wherein step C is followed by step D of drying the precipitate obtained in step C. 9. A method as defined in one of claims 7 or 8, wherein the precipitate obtained in step C is dried and atomized to obtain a powder. 15 10. Process as defined in one of claims 1 to 9, for the synthesis of an N-acylated α-amino acid of formula (I): wherein R1 is as defined previously in said divalent functional unit (M1), R2 represents a hydrogen atom, or a radical chosen from methyl, benzyl, isobutyl, 1-methylpropyl or isopropyl radicals, and R3 represents a hydrogen atom or a methyl radical; , comprising: A reaction step A of the alkali metal salt of the α-amino acid of formula (II): wherein R2 and R3 are as defined in formula (I) preceding, and M represents an alkali metal atom, with an acid halide of formula (IV): R 1 O (IV) in which R 1 represents a linear or branched, saturated or unsaturated aliphatic radical containing from 1 to 17 atoms of carbon and X represents a halogen atom, or with a mixture of acid halides of formulas (IV), in solution and at a pH greater than 7, to form a compound of formula (III): wherein M, R 1, R 2 and R 3 are as defined above, or a mixture of compounds of formula (III): III); A step B of hydrolysis at pH below 7, of the compound of formula (III), or of the mixture of compounds of formula (III), obtained in step A, to form that of an α-amino acid N -acylated of formula (I) or a mixture of N-acylated α-amino acids of formula (I); characterized in that step A is carried out by continuously contacting in time a flow rate di of said acid halide of formula (IV) with a flow rate d2 of said acid a -amine of formula (II) and a flow rate d3 of aqueous sodium hydroxide solution by maintaining the molar ratio of acid halide of formula (IV) / α-amino acid of formula (II) less than 1. 11. Process as defined in claim 10, for the synthesis of N-octanoyl glycine of formula (I '): ## STR2 ## corresponding to formula (I) in which R 1 represents the heptyl radical, R2 and R3 each represent a hydrogen atom, comprising: A sodium glycinate reaction step A of formula (II '): ## STR2 ## corresponding to formula (II) in which M represents an atom of sodium, with octanoyl chloride (IV '): H3C Cl O (IV') corresponding to formula (IV) in which R1 represents a heptyl radical and X represents a chlorine atom, in aqueous sodium hydroxide solution and pH greater than 8 and less than or equal to 9.5, to form a compound of formula (III '): ## STR2 ## corresponding to formula (III) in which R 1 represents a heptyl radical M represents a sodium atom, R1 represents the heptyl radical and R2 and R3 each represent a hydrogen atom; A hydrolysis step B at a pH of less than 2, of the compound of formula (III ') obtained in step A, to form said N-octanoyl glycine of formula (I'); A step C of washing with water and filtering the aqueous dispersion of precipitate obtained in step B. A drying step D and atomization of the wet precipitate obtained in step C to obtain the N-octanoyl glycine under fine powder form, characterized in that step A is carried out by contacting, in a continuous manner over time, a flow rate di of said acid halide of formula (IV ') with a flow of flow d2, said α-amino acid of formula (II ') and a flow rate d3 of aqueous sodium hydroxide solution while maintaining the molar ratio of acid halide of formula (IV') / α-amino acid of formula (II) ') less than 1 and greater than or equal to 0.8. 12. Process as defined in one of Claims 1 to 11, for the continuous preparation of an N-acylated amino acid, characterized in that the amino acid in aqueous solution at a flow rate d 2, the acid chloride to a flow rate di and an aqueous solution of sodium hydroxide at a flow rate d3 are introduced simultaneously in a molar ratio of acid chloride / amino acid greater than or equal to 0.8 and less than 1, in a reactor equipped with a stirrer allowing to obtain a fine homogenization of said reaction medium and dimensioned so that the residence time of the reaction medium formed in the reactor is less than or equal to 5 minutes, said reaction medium being maintained at a temperature of less than or equal to 35 ° C and the pH of said reaction medium being maintained at a value between 8.5 and 9.5; in that said reaction medium is allowed to transfer to a precipitation reactor equipped with a worm, in which it is treated with an aqueous solution of phosphoric acid introduced at a flow rate d4 able to maintain in said precipitation reactor a pH less than or equal to 2 to form in the end of the course in said precipitation reactor, an aqueous dispersion of a precipitate of said amino acid which is then washed and filtered, and the wet precipitate obtained is, if necessary, dried and then atomized. 13. Installation for carrying out the process as defined in one of claims 1 to 12: A jacketed reactor (RE1) equipped with an agitator (AG1) and an indoor temperature measuring device ( TICRE1) allowing control and adjustment of the temperature within it by circulating in said envelope, a refrigerant fluid, said fluid being cooled by recirculation within a heat exchanger (El); Three containers ZB1, ZB2 and ZB3, from which three pumps (P1), (P2) and (P3) are respectively withdrawn continuously, the compound comprising at least one divalent functional unit (M2), the acid halide of formula (IV) and the aqueous alkaline solution; three fluid circulation lines (1), (2) and (3), allowing the circulation of reagents from said containers (ZB1), (ZB2) and (ZB3) and their introduction via 3 inputs located at its base in said reactor (RE1); A precipitation reactor (PR1) equipped with an endless screw (AG2), connected to an inlet located in the upper part of said reactor (RE1), by a fluid circulation line (4), and connected to a container ( ZB4), via a fluid circulation line (5), from which is drawn off by means of a pump (P4), the acidic aqueous solution intended for hydrolysis within said precipitation reactor (PR1) of the compound comprising at least one unit functional divalent (M3), said precipitation reactor (PR1) being wrapped in its first half said half upstream, by a double-envelope for the control and adjustment of the temperature therein by circulation in said envelope, a refrigerant fluid, and in its second half, said half downstream, by a double jacket, for controlling and adjusting the temperature within it, by circulating in said casing, a heating fluid; A reservoir (R02) for collecting the precipitate dispersion flowing from said precipitation reactor (PR1), provided with a pH control device (PHR02), connected in its downstream part by fluid circulation lines (6). ), (7) and (8) to a filter bank (Fl), (F2) AND (F3) arranged in parallel, allowing through a pump (P5) and a connection to the water network, washing and filtering the precipitate dispersion from said reservoir (R02); said filters (F1), (F2), (F3) being connected downstream to a fluid circulation line (9) issuing from an overflow of said tank (R02). 14. Use of partial N-acyl hydrolysates of proteins; N-acylated total hydrolysates of proteins, N-acylated α-amino acids or N-acylated sarcosine, obtained by the process as defined in one of claims 1 to 12, as active ingredients and / or as excipients in cosmetic topical compositions.