AMINO ACID PREPARATION METHOD COMPRISING A STEP OF HYDROFORMYLATION OF AN UNSATURATED FATTY NITRILE The work which led to this invention received financial support from the 5 European Union in the context of Framework Program 7 (FP712007-2013) under project No. 241718 EUROBIOREF. Field of the invention: The present invention relates to a novel process for synthesizing 10 o-aminoalkanoic acids which can be used in the polymer industry, in particular polyamides, said process comprising a step of hydroformylation of an unsaturated fatty nitrile. The term "unsaturated fatty nitrile" is intended to mean any compound of formula (I): RI-CH=CH-[(CH2),-CH=CH],-(CH2),CN in which R1 is H or an alkyl radical comprising 15 from 1 to 11 carbon atoms, comprising, where appropriate, a hydroxyl function, and q, m and r are integer indices such that q = 0 or 1, 0 5 m S 2 and 4 5 r 5 13, and mixtures thereof. At the current time, it is known how to produce these unsaturated fatty nitrile compounds from unsaturated fatty acid or ester compounds, or from saturated compounds comprising a hydroxyl function, which may be both of fossil origin and of 20 renewable origin. For the purposes of the invention, the term "to-aminoalkanoic acids", hereinafter "a-amino acids" or simply "amino acids", is in fact intended to mean any long-chain w-amino acid, i.e. in which the chain comprises at least 8 carbon atoms. Indeed, the polyamides targeted by the present invention are technical polyamides, i.e. 25 performance polyamides, high performance polyamides, or even very high performance polyamides, produced from monomers comprising at least 8 carbon atoms, preferably at least 10 carbon atoms, as opposed to the "commodity" polyamides, such as "nylon 6 , the marketed amounts (volumes) of which are much higher and the costs of which are much lower than those of the technical polyamides. 30 Prior art: The polyamide industry uses an entire range of monomers formed from diamines and diacids, from lactams, and especially from w-amino acids. The latter are defined by the length of the methylene chain (-CH,), separating two amide functions 35 -CO-NH-. These monomers are generally produced by chemical synthesis using as the starting materials C, to C, olefins, cycloalkanes or benzene, which are hydrocarbons derived from fossil sources. For example, C2 olefins are used to produce the C9 amino acid used in nonanoic acid; Cq olefins are used to produce hexamethylenediamine; laurolactam and caprolactam are produced from cycloalkanes; adipic acid, nylon 6 and 5 nylon 6,6 are produced from benzene. With regard to the preparation of polyamides from unsaturated nitrile ' compounds, patent US 7 026 473 describes the hydroxycarbonylation or the methoxycarbonylation of a pentenenitrile to give 5-cyanovaleric acid or ester (6 C atoms), in the presence of CO (carbon monoxide) and respectively of water or of 10 alcohol. Only the methoxycarbonylation with methanol is in fact exemplified. By means of reduction, the 5-cyanovaleric acid (ester) forms 6-aminocaproic acid (ester), which in turn gives E-caprolactam by cyclization (this is the monomer of nylon-6). The process described in said document has several drawbacks. The methoxycarbonylation step is slow and costly in terms of catalysts. The conversion is not full and requires lengthy 15 reaction times. Furthermore, many co-products are formed, in particular branched products, which must be separated from the linear product that it is desired to produce. Said document does not relate to a process comprising a hydroformylation step, nor to the production of amino acids having a carbon number at least equal to 8. The process described uses nitrile compounds with a short chain, 5 carbons, to produce 6-carbon 20 products with chemical properties very different than those sought by the present invention. Moreover, said document does not relate to the production of biobased amino acids. Patent document WO 97133854 describes a process for producing terminal aldehyde by hydroformylation of an alkene, such as hexene, butadiene, methyl 25 3-pentenoate or 3-pentenenitrile. Said document shows that it is much more difficult to obtain a linear aldehyde (low proportion of linears obtained) from a nitrile (3-pentenenitrile) than from an ester. Furthermore, in the case of hydroformylation, a high proportion (21%, 16.3%) of reduced product (valeronitrile), i.e. no longer containing aldehyde, is obtained from nitrile of the prior art because of the hydrogenation of the 30 double bond by the catalyst. In addition, the obtaining of linear products in the prior art occurs to the detriment of the conversion. Once again, said document does not relate to the production of amino acids having a carbon number at least equal to 8. The process described uses nitrile compoilnds with a short chain, 5 carbons, to produce 6- carbon products with chemical properties very different than those sought by the present invention. Moreover, said document does not relate to the production of biobased amino acids. Current developments with regard to the environment are resulting in the use of natural starting materials originating from a renewable source being favored in the 5 fields of energy and chemistry. Only a few monomers are produced at the current time from biobased starting materials, such as castor oil, which makes it possible to produce polyamide 11 sold under the tradename ~ i l s a ne~ru; cic oil which makes it possible to produce polyamide 13/13, or else lesquerolic oil which makes it possible to produce polyamide 13. 10 Typically, the process for producing 11-aminoundecanoic acid comprises the following steps: 1) alcoholysis (methanolysis) of castor oil to give methyl ricinoleate (MR), 2) cracking (pyrolysis) of the MR, 3) distillation so as to recover methyl undecylenate, 15 4) hydrolysis of the methyl undecylenate to give undecylenic acid, 5) hydrobromination so as to obtain I I-bromoundecanoic acid, 6) ammonolysis with an ammoniacal aqueous solution so as to give ll-aminoundecanoic acid. The polycondensation of the 11-aminoundecanoic acid, by hydrolytic polymerization in 20 the presence of phosphoric acid as catalyst, subsequently makes it possible to obtain polyamide 11. The process for synthesizing 11-aminoundecanoic acid, carried out industrially for several decades, is satisfactory by and large. However, it has a certain number of drawbacks. The first drawback is that the implementation thereof is in practice subject 25 to access to a single specific starting material, castor oil. Furthermore, the castor bean contains a toxin: ricin, which is extremely toxic. The second drawback is linked to certain reagents used, ammonia and bromine in particular, which require expensive storage and use precautions, and need investment in specific units for separating and recycling the ammonium bromide formed. The third drawback is linked to the co- 30 products obtained via the process: glycerol but also numerous by-products that need to be exploited separately, such as heptanaldehyde, esterol: mixture of uncracked fatty acid esters. Document US 6 307 108 (see in particular column 9, lines 25-58) describes the production of methyl 12-aminododecanoate from methyl undecylenate (MU), derived 35 from castor oil. The process comprises a step of hydroformylation of the MU so as to form the C12 aldehyde ester, and then a step of reductive amination so as to produce the C,Z amino ester. In order to be able to produce the corresponding amino acid, this process makes it necessary to carry out an additional step of hydrolysis of the amino ester under conditions which have the drawback of leading to its direct 5 polycondensation to "polyamide", the chain growth of which is limited by the presence of the ester groups. The objective of the present invention is therefore to find a novel process for direct synthesis of w-amino acids, involving other starting materials and reagents, which avoids the formation of by-products, which minimizes the number of steps, and 10 which does not have the abovementioned drawbacks. The objective of the present invention is also to find a novel process for synthesizing the whole range of long-chain w-amino acids, which is simple to implement, and which as much as possible uses renewable starting materials, which are preferably widely accessible. 15 The expression "renewable starting materials which are widely accessible" is intended to mean those which are readily available, for example derived from plants which are already grown andlor easy to grow, in an amount compatible with industrial production, and inexpensive. In this "bio" approach, the applicant 'has already described several processes 20 for synthesizing o-amino acids from unsaturated fatty nitriles of renewable origin. Patent documents W0 20101055273, FRI 1.55174, FRI 1.56526 and FRI 1.57542 describe, in particular, the steps for synthesis of an 01-amino acid from an unsaturated fatty nitrile by oxidative cleavage or by cross metathesis with an acrylate resulting in a nitrile acid, and then the hydrogenation thereof to give an amino acid. These processes 25 comprise a metathesis using catalysts and starting co-materials which are relatively expensive, such as acrylonitrile or methyl acrylate. In particular, the ruthenium ligands used to catalyze the metathesis are very specific and constitute most of the costs of the catalyst. Furthermore, on all the carbons of the amino acid formed by means of these processes, at least 2 carbons are not biobased if the methyl acrylate or the acrylonitrile 30 are not themselves biobased, improvement thereof still being sought, the objektive being to produce amino acids which aim to be 100% renewable. Moreover, in document WO 20101055273 in particular, the process comprises a controlled ozonolysis, which amounts to removing a carbon from the carbon chain, whereas, on the contrary, in the case of the synthesis of specialty polyamides, the aim is to increase 35 the length of the carbon chain of the monomers produced. Furthermore, the metathesis process in the abovementioned documents results not in an amino acid, but in an amino ester when the starting materials are, for example, a fatty ester and acrylonitrile, or alternatively a fatty nitrile and methyl acrylate. In order to produce a conventional polyamide, the amino ester must be reconverted beforehand into an amino acid, which 5 requires an additional very complex step to hydrolyze an ester function under hot conditions, without initiating the polymerization of the amino ester. The objective of the present invention is therefore also to find a novel process using catalysts, in particular ligands, and co-materials which are simpler and less expensive, and make it possible to increase the content of material of renewable origin lo of the amino acids. The applicant has now found a novel synthesis process involving a step of hydroformylation of an unsaturated fatty nitrile, with hydrogen (Hz) and carbon monoxide (CO), and not comprising the abovementioned drawbacks. 15 Detailed description of the invention: In the present description, it is specified that, when reference is made to ranges, expressions of the type "ranging from ... to" or "containing/comprising from ... to" include the limits of the range. Conversely, expressions of the type "between ... and ..." exclude the limits of the range. 20 Unless otherwise mentioned, the percentages expressed are molar percentages. Unless otherwise mentioned, the parameters to which reference is made are measured at atmospheric pressure. A subject of the present invention is therefore a process for synthesizing an o-amino 25 acid compound of formula HOOC-R'-CH2NH2, where R' is an alkyl radical comprising from 6 to 15 carbon atoms or an alkylene radical comprising from 6 to 15 carbon atoms and from 0 to 2 unsaturations, comprising: 1) a step of hydroformylation of an unsaturated fatty nitrile chosen from the compounds 30 of formula: R1-(3H=CH-[(CH2)q-CH=CH],-(CHz)&N where Rt is H (a hydrogen) or an alkyl radical comprising from 1 to 11 carbon atoms comprising, where appropriate, a hydroxyl function, it being possible for the C=C double bond(s) to be in the cis or trans conformation, q, m and r are integer indices suchthatq=Oor1,Ormr2and4~rr13, 35 and mixtures'thereof, by reacting said nitrile with carbon monoxide and dihydrogen so as to obtain at least one fatty nitrile aldehyde of formula: HOC-R-CN, 2) a step of oxidation in the presence of dioxygen (molecular oxygen), during which the 5 nitrile aldehyde obtained in step 1 is converted into fatty nitrile acid of formula: HOOC-R-CN, 3) a reduction step during which the nitrile acid obtained in step 2 is converted into an w-amino acid of formula: HOOC-R'-CHZNH~. lo The novel process of the invention, in which a step of hydroformylation of an unsaturated fatty nitrile, followed by a step of oxidation of the resulting aldehyde to give an acid, and then by a step of reduction of the nitrile function to give an amine function, is carried out, results in the direct synthesis of amino acids. Advantageously, the process according to the invention also comprises a step of I5 catalytic cross metathesis with an alkene chosen from ethylene, propylene, but-I-ene and but-2-ene, preferably ethylene, propylene and but-I-ene, preferably ethylene or but-I-ene, carried out on the fatty nitrile before step 1) so as to produce an omegaunsaturated fatty nitrile corresponding to the formula: R,-CH=CH-(CH2),CN, where R2 is H or an alkyl radical comprising from 1 to 3 carbon 20 atoms, preferably corresponding to the formula CH2=CH-(CH2),-CN, i.e. preferably when R2 is H. When R2 is an alkyl radical, during the hydroformylation, the double bond can be brought back to the terminal position, before the addition of the CO, and can therefore result in a linear amino acid, which explains why the various abovementioned alkenes 25 can be used in the process of the invention. This step of catalytic cross metathesis with an alkene is conventionally carried out under the same conditions as those described, for example, in patent application WO 20101055273 on page 9, lines 12 to 18. The starting unsaturated fatty nitrile used in the process according to the invention is generally obtained from unsaturated (or hydroxylated) fatty acid or ester compounds by 30 nitrilation (ammoniation) of at least one acid or ester function of these compounds which can be derived from starting materials of fossil origin or of renewable origin. The unsaturated fatty acid or ester compounds can be obtained, for example, according to the process described by patent document US 4 510 331. The latter describes in particular the production of 7-octenoic acid, by isomerization of 2,7- 35 octadien-1-01 to give 7-octen-I-al, and then oxidation of the latter to give an acid. The 2,7-octadien-1-01 is produced industrially by reaction ("telomerization") of butadiene with water in the presence of a palladium catalyst according to the process described in patent documents GB 2074156A and DE 3112213. This type of process uses starting materials of fossil origin. 5 Alternatively, the unsaturated fatty nitriles are produced from unsaturated fatty acids or esters of renewable origin, derived from natural oils. These processes developed recently by Arkema are described in particular in patent documents: WO 20101055273, FRI 1.55174, FRI 1.56526 and FRI 1.57542. For the purposes of the invention, the term "unsaturated fatty nitrile" is preferably 10 intended to mean those obtained at least partially from unsaturated natural fatty acids. Advantageously, the process according to the invention therefore comprises a step of producing said fatty nitrile from an unsaturated fatty acid or ester of natural origin of formula: (Rf-CH=CH-[(CH2),-CH=CH],-(CH2)r-COO-),-G in which p is an integer index such that 1 5 p 5 3, and G is H (a hydrogen), an alkyl radical having from 1 to 11 15 carbon atoms or a radical comprising 2 or 3 carbon atoms bearing I or 2 hydroxyl function@), it being possible for the C=C double bond(s) to be in the cis or trans conformation, said production comprising: - the ammoniation (action which consists in introducing ammonia into a product) of the carbonyl function of the unsaturated fatty acid (or ester) of natural origin, to give a 20 nitrile function. The reaction scheme for the synthesis of nitriles from acids, by amrnoniation (or nitrilation, the two terms being used without distinction), well known to those skilled in the art, can be summarized in the following way. R-COOH + NH3 -t [R-COO-NH4+] -t [R-CONHz] + Hz0 4 RCN + Hz0 25 This scheme applies just as much to natural fatty acids (esters) as it does to w-unsaturated fatty acids. The process can be carried out batchwise in the liquid or gas phase or continuously in the gas phase. The reaction is carried out at a high temperature above 250°C and in the presence of a catalyst which is generally a metal oxide and most commonly zinc oxide. The continuous removal of the water formed 30. while in addition entraining the ammonia which has not reacted enables rapid completion of the reaction. Liquid-phase ammoniation is very suitable for long fatty chains (comprising at least 10 carbon atoms). However, when operating with shorter chain lengths, gas-phase ammoniation may become more appropriate. It is also known practice, from GB 641 955, to carly out the ammoniation using urea or cyanuric acid as agent. Any other source of ammonia may also be used. According to one particular embodiment, the unsaturated fatty nitrile used according to the invention is produced from natural unsaturated long-chain fatty acids. The term 5 "natural long-chain fatty acid" is intended to mean an acid derived from a plant background or from an animal background, including algae and other microorganisms, and which is therefore renewable, comprising from 6 to 24 carbon atoms, with preferably at least 7 (if the final amino acid has at least 8 C) carbon atoms, preferably at least 8 carbon atoms, preferably at least 10 carbon atoms, and preferably at least 14 10 carbon atoms per molecule. These various acids are derived from vegetable oils extracted from various plants, such as sunflower, rapeseed, camelina, the castor oil plant, lesquerella, olive, soya, the palm tree, coriander, celery, dill, carrot, fennel or Limnanthes alba (meadowfoam). They are also derived from the terrestrial or marine animal world, and, in the latter case, equally in the form of fish, mammals and algae. It 15 is generally a question of fats originating from ruminants, from fish such as cod, or from tnarine mammals such as whales or dolphins. As unsaturated fatty acid suitable more particularly for implementing the invention, mention may be made of: petroselenic acid (cis-6-octadecenoic acid), its derivative 6-heptenoic acid obtained by ethenolysis (cross metathesis with ethylene), a-linolenic 20 acid (6,9,12-octadecatrienoic acid), it being possible for these acids to be obtained from coriander for example; cis-8-eicosenoic acid, cis-5,8,11,14-eicosatrienoic acid (arachidonic acid), ricinoleic acid which gives, after dehydration, conjugated 8,lOoctadecadienoic acid; caproleic (cis-9-decenoic) acid, palmitoleic (cis-9-hexadecenoic) acid, myristoleic (cis-9-tetradecenoic) acid, oleic (cis-9-octadecenoic) acid, 9-decenoic 25 acid obtained by ethenolysis of an oleic acid for example, elaidic (trans-9- octadecenoic) acid, ricinoleic (12-hydroxy-cis-9-octadecenoic) acid, gadoleic (cis-9- eicosenoic) acid, linoleic (9,12-octadecadienoic) acid, rumenic (9,ll-octadecadienoic) acid, conjugated linoleic (9,ll-octadecadienoic) acid, it being possible for these acids to be obtained from sunflower, rapeseed, the castor oil plant, olive, soya, the palm tree, 30 flax, avocado, sea buckthorn, coriander, celery, dill, carrot, fennel, Limnanthes (meadowfoam); 10,12 conjugated linoleic acid (10,12-octadecadienoic acid), 10-undecylenic acid obtained by thermal cracking of the methyl ester of ricinoleic acid for example; vaccenic (cis-I I-octadecenoic) acid, gondoic (cis-I I-eicosenoic) acid, lesquerolic (14-hydroxy-cis-11-eicosenoic) acid, cetoleic (cis-11-docosenoic) acid, 35 - which can be obtained from Lesquerella oil (lesquerolic), from Camelina sativa oil (gondoic), from the oil of a plant of the family Sapindaceae, from fish fat, from oils of microalgae (cetoleic), by dehydration of 12-hydroxystearic acid itself obtained by hydrogenation of ricinoleic acid (vaccenic acid and its trans equivalent), conjugated linoleic acid (9,ll-octadecadienoic acid), obtained for example by dehydration of 5 ricinoleic acid; (cis or trans) 12-octadecenoic acid obtained for example by dehydration of 12-hydroxystearic acid (abbreviated as 12HSA), itself obtained by hydrogenation of ricinoleic acid, 10,12 conjugated linoleic acid (10,12-octadecadienoic acid), 12-tridecenoic acid obtained by thermal cracking of the (in particular methyl) ester of lesquerolic acid; erucic (cis-13-docosenoic) acid and brassidic (trans-13-docosenoic) 10 acid which can for example be obtained from erucic rapeseed, from Honesty or from sea kale (sea cabbage); (cis or trans) 13-eicosenoic acid obtained by dehydration of 14-hydroxyeicosanoic acid, itself obtained by hydrogenation of lesquerolic acid, (cis or trans) 14-eicosenoic acid obtained by dehydration of 14-hydroxyeicosanoic acid (abbreviated as 14HEA), itself obtained by hydrogenation of lesquerolic acid (the 15 dehydration can be carried out on both sides of the OH), ne~onic(c is-15-tetracosoic) acid which can be obtained from Malania oleifera and from Honesty (Lunaria annua also known as Pope's coin or moneyplant); or mixtures thereof. It is also possible to dispense with the step of dehydration of the acids 12HSA and 14HEA by carrying out the conversion to nitrile directly on these saturated and hydroxylated fatty acids, as 20 described in the patent document having the filing number FRI 1.56526. An advantage of this solution is that the hydrogenation of ricinoleic acid in a mixture with the other fatty acids of castor oil results in a mixture no longer containing as majority species only 12HSA, stearic acid and palmitic acid. The dehydration following (or simultaneously with) the conversion into nitrile results in a very clean nitrile containing 25 more than 85% of monounsaturated nitrile. The same is true with 14HEA, as described in patent document FRI 1.56526. Among the abovementioned unsaturated fatty acids, preference is given to those which are the most abundantly available, and in particular fatty acids unsaturated in the 6-9 or 6-10 position, the numbering being from the acid group. The use of nitriles and of fatty 30 acids comprising from 10 to 24 carbon atoms, and preferably those comprising 10 carbons or 11 carbons with an unsaturation in the omega or o position, i.e. at the end of the chain with respect to the acid group, is in fact preferred. Preference is given, for example, to fatty acids containing 18 carbons comprising an unsaturation in the 6-9 or 10 position with respect to the nitrile or acid group, i.e. in the w-9 or 8 position, 35 respectively, which by ethenolysis will result in o-unsaturated acids, and also ricinoleic acid which, by thermal cracking of its methyl ester, gives the methyl ester of undecylenic acid. The fatty acids mentioned above can be isolated by any of the techniques well known to those skilled in the art: molecular distillation, including short path distillation, 5 crystallization, liquid-liquid extraction, complexation with urea, including extraction with supercritical C02, andlor any combination of these techniques. According to one particular embodiment of the process of the invention, the unsaturated fatty nitrile is obtained from a fatty acid ester, it being possible for the latter to be advantageously chosen from the esters of the abovementioned fatty acids, in 10 particular their methyl esters. The routes for obtaining a fatty nitrile from a fatty acid ester are, for example, described in document WO 20101089512. According to another embodiment, the unsaturated fatty nitrile is obtained from a hydroxy fatty acid, such as 12HSA and 14HEA. More generally, the hydroxy fatty acid can advantageously be chosen from those described in the patent application having 15 the filing number FRI 1.56526. Alternatively, the unsaturated fatty nitrile is obtained from a triglyceride, it being possible for the latter to be advantageously chosen from: a vegetable oil comprising a mixture of unsaturated fatty acid triglycerides, such as sunflower oil, rapeseed oil, castor oil, lesquerella oil, camelina oil, olive oil, soya bean oil, palm oil, Sapindaceae 20 (soapberry) oil, in particular avocado oil, sea buckthorn oil, coriander oil, celery oil, dill oil, carrot oil, fennel oil, mango oil, Limnanthes alba (meadowfoam) oil, and mixtures thereof; microalgae; animal fats. According to another embodiment, the unsaturated fatty nitrile is obtained from a plant wax, for example jojoba wax. 25 Advantageously, the process according to the invention also comprises, before the ammoniation step described above: - either a catalytic cross metathesis with ethylene (or other C2 to C4 light alpha-olefin) carried out on the unsaturated fatty acid (or ester or triglyceride) of natural origin, - or a pyrolysis of the unsaturated fatty acid or ester of natural origin, followed by 30 distillation (then optionally hydrolysis to give an acid in the case of the ester), so as to produce an omega-unsaturated fatty acid (or ester) of formula: CH2=CH-(CH2)rCOOR2, R2 being H or a C1-C4 alkyl radical, and such that, after the ammoniation step carried out on this omega-unsaturated fatty acid (or ester), an omega-unsaturated fatty nitrile of formula: 35 CH2=CH-(CH2),-CN is obiained. The obtaining of such an unsaturated fatty nitrile from an unsaturated fatty acidlester is in particular described in patent application W0 2010105527, in particular in the paragraphs describing the "first stage" of the process which is the subject of said document: i.e. on page 5, lines 12 to 32, on page 7, lines 17 to 26, on page 8, lines 1 to 5 9, on page 10, line 29 to page 11, line 19. According to one particular embodiment of the process of the invention, use is made of an w-unsaturated nitrile of formula CH2=CH-(CH,),-CN obtained by conversion of an unsaturated fatty acidlester in two successive steps (the order being unimportant): ethenolysis (cross metathesis with ethylene) and ammoniation, as described in lo document WO 20101055273. According to another variant of the process, hydroxylated fatty acids are used as starting material, such as ricinoleic acid and lesquerolic acid which correspond to the general formula R1-CH=CH-(CH,),-COOH with R, equal to CH,-(CH2)5CHOH-CH2- and p equal, respectively, to 7 and 9. The acid in its methyl ester form is subjected to a pyrolysis resulting in an w-unsaturated ester of formula 15 CH2=CH-(CH,)p+l-COOCH3 which is converted by ammoniation, directly or via the acid, into an w-unsaturated nitrile, According to yet another embodiment, the unsaturated fatty nitrile is produced as described in document FR11.55174, by ammoniation of a compound of fatty acid, ester or glyceride type, resulting in the corresponding unsaturated nitrile. According to one particular embodiment of the process of the 20 invention, the hydrogenation of unsaturated hydroxylated fatty acids comprising at least 18 carbon atoms per molecule, resulting in saturated hydroxylated fatty acids, followed by the dehydration thereof, resulting in monounsaturated fatty acids, are carried out as in the process of document FR11.56526, with, in addition, either an intermediate step of nitrilation of the acid function of the monounsaturated fatty acid, resulting in an 25 unsaturated nitrile, or an intermediate step of nitrilation of the acid function of the saturated hydroxylated fatty acid resulting from the hydrogenation step with concomitant dehydration, resulting in an unsaturated fatty nitrile. Particular conditions for obtaining unsaturated fatty nitriles are described in document FR11.57542, comprising the nitrilation of an w-unsaturated acidlester of formula CH2=CH-(CH2),- 30 COOR in which n is 7 or 8 and R is either H or an alkyl radical comprising 1 to 4 carbon atoms, by reacting ammonia in a reactor operating continuously in the gas phase or in the mixed liquid-gas phase, in the presence of a solid catalyst. Whether it is a question of metathesis on the fatty nitrile or else on the unsaturated acid (or fatty ester), the cross metathesis reaction with an alkene, such as ethylene, 35 implemented in certain variants of the process of the invention, is caried out at a temperature of between 20 and 100°C at a pressure of 1 to 30 bar, in the presence of a conventional metathesis catalyst, for example of ruthenium type. The reaction time is chosen according to the reagents used and so as to be as close as possible to the equilibrium of the reaction. The reaction is carried out under an alkene pressure 5 The pyrolysis reaction implemented in one variant of the process of the invention is preferably carried out on the ester form of the fatty acid concerned, generally the methyl ester. The reaction is carried out at high temperature, of between 400 and 750°C and preferably between 500 and 600aC, in the presence of overheated water vapor. lo Preferably, the starting acid is a hydroxylated acid, and it is preferably ricinoleic acid or lesquerolic acid, ricinoleic acid being preferred since it results in 12-aminododecanoic acid according to the process of the invention. According to one preferred embodiment, the process according to the invention consists of a process for synthesizing an w-amino acid compound of formula 15 HOOC-(CH2)w2-CH2NH2, from a monounsaturated fatty nitrile compound of formula CHz=CH-(CH2)rCN comprising the following steps: - the hydroformylation of the unsaturated nitrile compound so as to obtain a nitrile- 20 aldehyde compound of formula HOC-(CH,),-CN, then - the oxidation of the nitrile-aldehyde compound so as to obtain the corresponding nitrile-acid compound of formula HOOC-(CH2),2-CN, and - the reduction of the nitrile-acid compound to give an w-amino acid of formula 25 HOOC-(CHz),+z-CHzNH2. 1) HYDROFORMYLATION Hydroformylation, also known as 0x0 process, is a synthesis route for producing aldehydes from alkenes that was discovered in 1938 by Otto Roelen from Ruhrchemie. 30 The basib reaction is the following: R-CH =C:H2+CO+H,sR-C2H.,-CHO+ R-CH(CHC))-CN, This process is widely used industrially to produce aldehydes in a range of C3-C19, Butanal is, moreover, the main product synthesized by this reaction, with approximately 75% of total production using hydroformylation as synthesis route. The 35 hydroformylation step according to the process of the invention uses the methods and devices that are well known and already used by conventional hydroformylation processes. All the usual methods for adding and mixing the reagents and the components of a catalyst or catalysts, like the usual separation techniques for the conventional hydroformylation reaction, can therefore be used for this step of the 5 process of the invention. The hydroformylation step according to the process of the invention has the advantage of being able to be used directly in the numerous devices that exist. This would not be the case with methoxycarbonylation nor with hydroxycarbonylation, for example. Advantageously, the hydroformylation step is catalyzed in the presence of a catalyst 10 system comprising: - at least one metal of groups V to XI of the periodic table of elements, selected for its activity for converting the unsaturated nitrile, preferably at least one metal of group VIII, preferably at least one metal chosen from rhodium, palladium, cobalt and ruthenium, and mixtures thereof; and 15 - at least one bidentate ligand selected for the selectivity of the hydroformylation reaction in favor of the linear aldehyde, preferably at least one chelating diphosphine, or a monodentate ligand of monophosphine or monophosphite type. The [ligand]l[metal] molar ratio is advantageously included in the range of from 60:l to I: 97%) and also good yields in terms of linear aldehyde. The examples below describe tests of 15 undecenenitrile hydroformylation catalyzed by the Rh-biphephos system. General ~rocedure: The hydroformylation reactions were carried out in 30 ml stainless steel autoclaves. Under the typical conditions, a solution, in toluene (IQml), of Rh(acac)(CO)* (from 0.001 to 0.0001 mmol), phosphine (from 0.002 to 0.02 mmol) and undecenenitrile 20 (5.0 mmol) is mixed in a Schlenk tube under an inert argon atmosphere so as to form a homogeneous solution. After stirring at ambient temperature for 1 hour, this solution is introduced, via a pipe, into the autoclave preconditioned under an inert atmosphere. The reactor is sealed, flushed several times with a COIH, mixture (1:1), then pressurized at 20 bar of this CO/H2 mixture at ambient temperature, and then heated to 25 the desired temperature using a waterbath or an oil bath. During the reaction, several samples are taken in order to monitor the conversion. After an appropriate reaction time, the autoclave is brought back to ambient temperature and then to atmospheric pressure. The mixture is collected and then analyzed by NMR. Table 3: Effect of femperature during the undecenenitrile h v d r o f o r m ~ l a t i o n ' ~ ~ Temp C O ~ V . [ ~ ~ Internal Sel. (%)Ib1 Entry PC) (yo) alkenes (%) 2 3 1 80 52 20 99 1 2 100 75 20 99 1 3 120 88 22 99 1 4 140 94 26 99 1 [undecenenitrile] = 5.0 mmol, [undecene~~itrile]I[Rb=] 20 000, [biphephos]/[Rl~] = 20, toluene = 10 rill, P = 20 bar COIH, ($:I), 4 h. lbl Cot~version of the nitrile I selectivity I % of internal alkenc and 2 and 3 detereiined by 'H 5 NlMR and GLC analyses. %of internal alkeae, residual or formed during the reaction. The previous examples show that the Rh-biphephos system is very active and selective in undecenenitrile hydroformylation (table 3). In a temperature range of 80- 10 120"C, good conversions (52-94% of 20 000 equiv) were obtained in 4 h, and also excellent selectivities ranging up to 99%. In order to overcome the possible problem of isomerization leading to the formation of internal alkenes, other experiments are carried out while increasing the reaction time, since, after total conversion of the substrate, the catalyst can isomerize the internal 15 alkenes to terminal alkene and hydroformylize the latter to linear aldehyde (table 4). Example of table 4, entrv 4: Hvdroformvlation of I ,lo-undecenenitrile (Rh-biphephosl with SlRh = 20 000 and URh = 20 and recvclina of the catalyst: A solution, in toluene, of Rh(acac)(CO)~ (0.65 mg, 0.0025 mmol), biphephos (4 mg, 20 0.005 mmol) and undecenenitrile (826 mg, 5.0 mmol) is prepared in a Schlenk tube under an inert argon atmosphere so as to form a homogeneous solution which is stirred at ambient temperature for 1 h. The biphephoslrhodium molar ratio is 20:l and the substratekhodium molar ratio is 20 000:l. The solution is introduced, via a pipe, into a 30 ml autoclave preconditioned under an inert atmosphere. The reactor is 25 sealed, flushed several times with a CO/H2 gas mixture (1:1), then pressurized with 20 bar of CO/H2 (I:?) at ambient temperature, and then heated to 120°C. After 4 h, 67% of the undecenenitrile has been consumed. After 24 h, the medium is brought back to ambient temperature and to atmospheric pressure. The mixture is collected and analyzed by NMR. The analysis shows that the reaction is.complete and that there 30 remains an internal olefin proportion of 13%, while 87% of products formed correspond to branched (1%) and linear (99%) aldehydes. If the reaction is allowed to continue, the internal alkenes will be isomerized and hydroformylized. Thus, after 48 h of reaction, there then remains only a 5% proportion of internal olefins, while 95% of products formed correspond to branched (1%) and linear (99%) 5 aldehydes. Once the reaction has finished, recycling by distillation is carried out, under an inert atmosphere, using a Kugelrohr ("ball oven") distillation system at a temperature of 180°C and a pressure of 1 mbar. The hydroformylation products obtained in a first fraction are stable and no trace of residual catalyst or ligand was detected after NMR 10 analysis ('H and 3 ' ~ ) .T he catalyst contained at the bottom of the column was reused for a second run. For this, the catalyst is reintroduced into the Schlenk tube with 10 ml of toluene, a new amount of biphephos (0.0005 mmol, 5equiv) and 5 mmol of 1,lOundecenenitrile. The solution is again introduced, via a pipe, into a 30 ml autoclave preconditioned under an inert atmosphere. The reactor is sealed, flushed several times 15 with a COIH, gas mixture (?:I), then pressurized with 20 bar of COIH2 (1:l) at ambient temperature, and then heated to 120°C. After 48 h, the medium is then brought back to ambient temperature and to atmospheric pressure. The mixture is collected and analyzed by NMR. The analysis shows that the reaction is complete and that there remains a 2% proportion of internal olefin, while 98% of products formed correspond to 20 branched (2%) and linear (98%) aldehydes. This recycling can be carried out on several cycles without loss of selectivity. Example of table 4, entry 7: Hydroformylation of 1.10-undecenenitrile (Rh-biphephos) with SlRh = 50 000 and URh = 20: 25 A solution, in toluene (0.65 mg, 0.0025 mmol), of Rh(a~ac)(CO)b~i,p hephos (2.0 mg, 0.0025 mmol) and undecenenitrile (826 mg, 5.0 mmol) is prepared in a Schlenk tube under an inert argon atmosphere so as to form a homogeneous solution which is stirred at ambient temperature for 1 h. The biphephoslrhodium molar ratio is 10:l and the substratelrhodium molar ratio is 20000:l. The solution is introduced, via a pipe, 30 ' into a 30 ml autoclave preconditioned under an inert atmosphere. The reactor is sealed, flushed several times with a COIH2 gas mixture (1:1), then pressurized with 20 bar of CO/H2 (1:l) at ambient temperature, and then heated to 120°C. After 48 h, the medium is brought back to ambient temperature and to atmospheric pressure. The mixture is collected and analyzed by NMR. The analysis shows that the reaction is 3; complete and that there remains an 18% proportion of internal olefin, while 82% of products formed correspond to branched (2%) and linear (98%) aldehydes. If the reaction is allowed to continue, the internal alkenes will be isomerized and hydroformylized. m 4 Biphephos Time Conv. Internal sel. (%) ['I Entry [S]/[Rh] (h) alkenes (equiv) Internal (Oh) Ic1 n-2 is03 4 aldehydes 5 la] [undecenenitrile] = 5.0 mmol, [undecenenitrile]/[Rh] = 20 000, [biphephos]/[Rh] = 20, toluene = 10 ml, P = 20 bar COIH, ($:I), 4 h. Ib1 Conversion of the nitrilelselectivity/% of internal alkene and 2 and 3 determined by 'H NMR and GLC analyses. ['I % of internal alkene, residual or formed duiing the reaction. nd = not detected. 10 The Rh-biphephos catalyst can also be recycled by distilling the solvent and the organic products (aldehydes, residual internal alkenes) with a Kugelrohr ("ball oven") system, at 180°C under a dynamic vacuum of 1 mbar. The solid residue (still with a small amount of organic products) thus recovered can then be reused on several 5 cycles without substantial loss of selectivity, after having occasionally added fresh ligand between two cycles so as to prevent a modification of the active species in catalysis. This procedure is first carried out using an SIRh ratio of 20 000 and an LlRh ratio of 10 (table 5). Thus, very good selectivities were obtained on 4 cycles and the isomerizationlhydroformylation of the internal alkenes appears to be just as efficient lo since there was no accumulation of these internal alkenes. Table 5. Hvdrofomvlation of undecenenitrile during 4 cvcles["' biphephos Time Conv. Internal sel. (%)PI ~ n t r y ' ~ ' Cycle alkenes added (eq) rC) (h) (%)Ib1 (%) "I fso- internal 17-2 3 aldehydes 1 I 120 24 95 11 99 1 0 la' [undecenenitrile] = 10 mmol, [undecenenitrile]l[Rh] = 20 000, [biphephos]/[Rh] = 10, toluene = 5 ml, P = 20 bar CO/H2 (1:l). 15 lb'C~nver~ioonf the nitrilelselectivity/% of internal alkene and 2 and 3 determined by 'H NMR and GLC analyses. % of internal alkene, residual or formed during the reaction. nd = not detected. Iq The catalyst is recycled under an inert atmosphere, 5 equiv of biphephos were added, toluene = 5 mi, P = 20 bar COIH2 (?:I). 20 IeT1h e catalyst is recycled under an inert atmosphere, and reused without addition of ligand, toluene = 5 ml. P = 20 bar COIH, (1 :I). These results prove that it is easy, according to the process of the invention, to recycle this catalyst via the distillation route. Other tests are carried out while increasing the 25 SlRh ratio to 100 000 with a higher LlRh ratio (initially 20). Table 6 shows that this procedure operates without any great reduction in activity; the productivity is very good since it reaches close to 200 000 on two cycles (the first + the recycling), while using only 25 equivalents of biphephos. Examples of table 6, entries 1 and 2: Hvdroformylation of 1.10-undecenenitrile (Rh- 5 biphephos) with SlRh = 100 000 and URh = 20; and recvclinn of the catalyst: A solution, in toluene (0.026 mg, 0.0001 mmol), of Rh(aca~)(CO)b~ip, hephos (1.6 mg, 0.002 mmol) and undecenenitrile (1.65 g, 10.0 mmol) is prepared in a Schlenk tube under an inert argon atmosphere so as to form a homogeneous solution which is stirred at ambient temperature for 1 h. The biphephoslrhodium molar ratio is 20:l and 10 the substratelrhodium molar ratio is 100 000:l. The solution is introduced, via a pipe, into a 30 ml autoclave preconditioned under an inert atmosphere. The reactor is sealed, flushed several times with a CO/H2 gas mixture (I:$), then pressurized with 20 bar of COIH, (1:l) at ambient temperature, and then heated to 120°C. After 48 h, 85% of the undecenenitrile has been consumed. The temperature is then adjusted to 15 130°C, over the course of a further 48 h reaction time, and the medium is brought back to ambient temperature and to atmospheric pressure. The mixture is collected and analyzed by NMR. The analysis shows that the reaction is complete and that there remains a 9% proportion of internal olefin, while 91% of products formed correspond to branched (2%) and linear (98%) aldehydes. 20 Once the reaction has finished, recycling by distillation is carried out, under an inert atmosphere, using a Kugelrohr distillation system at a temperature of 180°C and a dynamic vacuum of 1 mbar. The hydroformylation products obtained in a first fraction are stable and no trace of residual catalyst or ligand is detected after NMR analysis ('H and 3'P). The catalyst contained at the bottom of the column is reused for a second 25 run. For this, the catalyst is reintroduced into the Schlenk tube with 10 ml of toluene, a fresh amount of biphephos (0.5 Jmol, 5 equiv) and 10 mmol of 1,lO-undecenenitrile. The solution is again introduced, via a pipe, into a 30 ml autoclave preconditioned under an inert atmosphere. The reactor is sealed, flushed several times with a COIH2 gas mixture (1:1), then pressurized with 20 bar of COlH2 (1:l) at ambient temperature, 30 and then heated to 120°C. After 48 h, 72% of the undecenenitrile is consumed. The temperature is then adjusted to 130"C, over the course of a further 48 h reaction time, and the medium is brought back to ambient temperature and to atmospheric pressure. The mixture is collected and analyzed by NMR. The analysis shows that the reaction is complete and that there remains an 11% proportion of internal olefins, while 89% of the 35 products formed correspond to branched (2%) and linear (98%) aldehydes. Table 6. Hvdroformvlation of undecenenitrile on 2 cvcles at hiah S/Rh ratio@ Biphephos Time ~ o n v . inte%rn al Sel. (%)[bl EntryEa1 Cycle added (eq) TrC) (h) (%)'I alkenestcl n-2 iso-3 ss-pdt a Cvcle 120 48 85 23 99 1 la[]u ndecenenitrile] = 10 mmol, [undecenenitrile]/[Rh] = 100 000, [biphephos]l[Rh] = 20, toluene = 10 ml, P = 20 bar CO/H2 (1:l). 5 Ib'Conversion of the nitrilelselectivityl% of internal alkene determined by 'H NMR and GLC analyses. '" 1 of internal alkene, residual or formed during the reaction. Id' The catalyst is recycled under an inert atmosphere, 5 equiv of biphephos were added. toluene = 10 mi, P = 20 bar CO/H2 (I:?). 10 Comparative example with methyl 10-undecenoate Other tests are carried out in order to compare the performance levels of the Rh-biphephos system on undecenenitrile and methyl 10-undecenoate (table 7). The tests are carried out with methyl undecenoate which was distilled beforehand. In the light of the results (in particular when comparing entry 4 of table 7 with entry 1 of table 15 6), it appears that the Rh-biphephos system is less selective and less active with respect to methyl 10-undecenoate than with the fatty nitrile. Example of table 7, entry 4: Hvdroformvlation of methvl 10-undecenoate (Rhbiohephos) with SlRh = 100 000 and LlRh = 20: 20 This test is carried out under the same conditions as those described above in the example of table 6, with the 1,lO-undecenenitrile being replaced with methyl 10- undecenoate. There is no recycling of the catalyst in this case. Afler 48 h, 68% of the methyl 10-undecenoate has been consumed. A sample is collected and analyzed by NMR. The analysis shows that there remains a 45% proportion of internal olefin, while 25 23% of products formed correspond to branched (15%) and linear (85%) aldehydes. Table 7. H~droformylationo f methyl 10-undecenoafeI aJ T Time Conv. inte%rn al Sel. (%)[bl Entry SlRh URh rC) (h) (')'b' alkenes[cl n-2 iso-3 ss-pdt 4 100 000 20 120 48 68 45 85 12 3 la' distilled methyl 10-undecenenitrile = 5.0 mmol, toluene = 10 ml, P = 20 bar COIH2 (I:<). 5 Ib1 Conversion of the methyl 10-undecenoatelselectivityl% of internal alkene determined by 'H NMR and GLC analyses. '" 1 of internal alkene, residual or formed during the reaction. When all is said and done, the process according to the invention has numerous 10 advantages compared with the existing processes. It is simple to implement. It does not require any particular equipment and can be implemented in existing industrial devices, which makes it possible to initiate marketing, even with small tonnages in terms of production capacity. It also does not require expensive starting materials or expensive catalysts. The process according to the invention is versatile since it makes it possible 15 to use a wide range of starting materials; it is not linked to one oil in particular. Contrary to the prior art processes which necessarily use a metathesis step, and result in an amino ester when the starting materials are, for example, a fatty ester and acrylonitrile, or a fatty nitrile and methyl acrylate, an amino acid is obtained according to the process of the invention. Furthermore, the number of carbons of non-renewable 20 origin of the amino acid obtained according to the process of the invention is zero, or is limited to 1 when the syngas (CO) used during the hydroformylation is not produced from biomass. CLAIMS 1- A process for synthesizing an o-amino acid compound of formula HOOC-R'-CH2NH2, where R' is an alkyl radical comprising from 6 to 15 carbon atoms or an alkylene radical comprising from 6 to 15 carbon atoms and from 0 to 2 unsaturations, comprising: I ) a step of hydroformylation of an unsaturated fatty nitrile chosen from the compounds 10 of formula: RI-CH=CH-[(CH~)~-CH=CH],-(CH~)&N where RI is H or an alkyl radical comprising from 1 to 11 carbon atoms comprising, where appropriate, a hydroxyl function, q, m and r are integer indices such that q = 0 or I , 0 S m 5 2 and 4 S r 5 13, and 15 mixtures thereof, by reacting said nitrile with carbon monoxide and dihydrogen so as to obtain at least one fatty nitrile aldehyde of formula: HOC-R'-CN, 2) a step of oxidation in the presence of dioxygen, during which the nitrile-aldehyde 20 obtained in step 3 is converted into a fatty nitrile-acid of formula: HOOC-R'-CN, 3) a reduction step during which the nitrile-acid obtained in step 2J is converted into an 01-amino acid of formula: HOOC-R'-CH2NH2. 2- The process as claimed in claim 1, also coniprising a step of catalytic cross metathesis with an alkene chosen from ethylene, propylene, but-I-ene and but-2-ene, carried out on the fatty nitrile before step 1) so as to produce an omega-unsaturated fatty nitrile corresponding to the formula R2-CH=CH-(CH2)iCN where R, is H or an 30 alkyl radical comprising from 1 to 3 carbon atoms. 3- The process as claimed in claim 1, also comprising a step of producing said fatty nitrile from an unsaturated fatty acid or ester of natural origin of formula: (R1-CH=CH-[(CH2),-CH=CH]m-(CH2)&OO-),-G, where p is an integer index such that 1 5 p r 3, G is H, an alkyl radical having from 1 to 11 carbon atoms or a radical comprising 2 or 3 carbon atoms bearing 1 or 2 hydroxyl function(s), said production comprising the ammoniation of the carbonyl function of the unsaturated fatty acid or ester of natural origin to give a nitrile function. 5 4- The process as claimed in claim 3, also comprising, before ammoniation: - either a catalytic cross metathesis with ethylene carried out on the unsaturated fatty acid or ester of natural origin, - or a pyrolysis of the unsaturated fatty acid or ester of natural origin, followed by lo distillation, then optionally hydrolysis to give an acid in the case of the ester, so as to produce an omega-unsaturated fatty acid or ester of formula: CH2=CH-(CH2),COOR2, R2 being H or a C2-C4 alkyl radical, and such that, after the ammoniation step carried out on this omega-unsaturated fatty acid or ester, an omega-unsaturated fatty nitrile of formula CH2=CH-(CH2),CN is 15 obtained. 5- The process as claimed in claim 3 or 4, wherein the unsaturated fatty acid (or ester) of natural origin is a hydroxylated acid (or ester), preferably ricinoleic acid (or ester) or lesquerolic acid (or ester), more preferably ricinoleic acid. 20 6- The process as claimed in claim 1, for synthesizing an o-amino acid compound of formula HOOC-(CHZ)~+~-CH~NHZ, from a monounsaturated fatty nitrile compound of formula 25 CHz=CH-(CH2)rCN comprising: - the hydroformylation of the nitrile compound so as to obtain a nitrile aldehyde compound of formula HOC-(CH2),2-CN, then - the oxidation of the nitrile aldehyde compound so as to obtain the corresponding ' 30 nitrile acid compound of formula HOOC-(CH2),2-CN, and -the reduction of the nitrile acid compound to give an m-amino acid of formula HOOC-(CH2)c+z-CH2NHz. 7- The process as claimed in any one of the preceding claims, wherein the 35 hydroformylation is catalyzed in the presence of a system comprising: 150°C, preferably from 100 to 140°C, preferably from 120 to 140°C, preferably at a temperature approximately equal to 140°C. 15- The process as claimed in any one of the preceding claims, wherein the 5 hydroformylation is carried out for a period of time ranging from 2 to 24 hours, preferably from 2 to 6 hours. 16- The process as claimed in any one of the preceding claims, wherein the hydroformylation is carried out at a partial COIH, pressure included in the range of from 10 5 to 50 bar, preferably from 10 to 40 bar, preferably from 10 to 30 bar, preferably at 20 bar of COIH,, and according to a CO:H, ratio included in the range of from 1:3 to 3:l. 17- The process as claimed in any one of the preceding claims, wherein the 15 [Substrate]/[Metal] ratio is included in the range of from 5000 to 500 000, preferably from 5000 to 400 000, preferably from 5000 to 300 000, preferably from 5000 to 200 000, preferably from 5000 to 150 000. 18- The process as claimed in any one of the preceding claims, wherein the 20 oxidation step is carried out by sparging dioxygen or a dioxygen-containing gas mixture in the product resulting from the hydroformylation, optionally in the presence of the hydroformylation catalyst. 19- The process as claimed in one of the preceding claims, wherein the oxidation 25 step is carried out without the addition of solvent andlor without the addition of dioxygen activation catalyst. 20- The process as claimed in one of the preceding claims, wherein the oxidation step is carried out at a partial dioxygen pressure ranging from 1 bar to 50 bar, in 30 particular from 1 bar to 20 bar, preferably from 1 to 5 bar. 21- The process as claimed in one of the preceding claims, wherein the dioxygen is continuously injected into the reaction medium by bubbling, preferably in the form of an air or oxygen stream, preferably injected in excess with respect to the stoichiometry 35 of the oxidation reaction. 22- The process as claimed in one of the preceding claims, wherein the molar ratio of the dioxygen relative to the product resillting from the hydroformylation step is included in the range of from 3:2 to 100:2. 5 23- The process as claimed in one of the preceding claims, wherein the oxidation is carried otrt at a telnperatlrre included in the range of from 0% to 100"C, preferably from 20°C to 10O0C, in particular from 30°C to 90"C, preferably from 40°C to 80°C, optionally in 2 consecutive increasing stationary temperature phases. 24- The process as claimed in any one of the preceding claims, also comprising a step of synthesis of polyalnide by polymerization using the w-antino acid obtained in step 3. 15 25- The process as claimed in any one of claims 7 to 24, wherein the hydroformylation step comprises the recycling of the hydroformylation catalyst system, optionally supplemented by a provision of new catalyst and/or ligand during a subsequent hydroformylation cycle. : .> 20 26- The process as claimed in claim 25, wherein the recycled catalyst system is obtained by at least partial evaporation of solvent andlor of nitrile-aldehyde andlor of ~rnreactedre agent.