Process for treating the skin comprising applying to the skin at least one composition comprising at least one N-aminoacylamide

1. A cosmetic process for treating skin that has at least one sign of ageing, comprising applying to the skin at least one composition comprising, in a physiologically acceptable medium, at least one compound chosen from compounds of formula (I):

wherein:

Y is chosen from O and S,

R 1 is chosen from:

(i) hydrogen;

(ii) linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 18 carbon atoms,

optionally substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR; —O—COR; —SH; —SR; —S—COR; —NH 2 ; —NHR; —NRR′; —NH—COR; -Hal (halogen); —CN; —COOR; —COR; —P(O)—(OR) 2 ; and —SO 2 —OR;

wherein R and R′, which may be identical or different, are each chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen, R and R′ optionally forming, together with N in the —NRR′, a 5- or 6-membered carbon-based ring which may further comprise at least one hetero atom chosen from O, N and S in the ring, and/or which may be substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR″; —O—COR″; —SH; —SR″;

—S—COR″; —NH 2 ; —NHR″; —NH—COR″; -Hal (halogen); —CN; —COOR″; and —COR″; wherein R″ is chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen; and

(iii) radicals chosen from —OR; —NH 2 ; —NHR; —NRR′; —NH—COR; —COOR; and —COR;

wherein R and R′, which may be identical or different, are each chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen, R and R′ optionally forming, together with N in the —NRR′, a 5- or 6-membered carbon-based ring which may further comprise at least one hetero atom chosen from O, N and S in the ring, and/or which may be substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR″; —O—COR″; —SH; —SR″;

—S—COR″; —NH 2 ; —NHR″; —NH—COR″; -Hal (halogen); —CN; —COOR″; and —COR″; wherein R″ is chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen;

R 2 is chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 18 carbon atoms,

optionally substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR; —O—COR; —SH; —SR; —S—COR; —NH 2 ; —NHR; —NRR′; —NH—COR; -Hal (halogen); —CN; —COOR; and —COR;

wherein R and R′, which may be identical or different, are each chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen, R and R′ optionally forming, together with N in the —NRR′, a 5- or 6-membered carbon-based ring which may further comprise at least one hetero atom chosen from O, N and S in the ring, and/or which may be substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR″; —O—COR″; —SH; —SR″;

—S—COR″; —NH 2 ; —NHR″; —NH—COR″; -Hal (halogen); —CN; —COOR″; and —COR″; wherein R″ is chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen;

R 3 is a radical chosen from those of formulae (II) and (III):

-A-C 6 H (5-y) —B y   (II)

—C 6 H (5-y′) —B y′   (III)

wherein:

y is an integer ranging from 0 to 5 and y′ is an integer ranging from 1 to 5;

A is chosen from linear and branched, saturated and unsaturated divalent hydrocarbon-based radicals containing from 1 to 18 carbon atoms,

optionally substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR; —O—COR; —SH; —SR; —S—COR; —NH 2 ; —NHR; —NRR′; —NH—COR; -Hal (halogen); —CN; —COOR; —COR; —NO 2 ; and —SO 2 —OR;

wherein R and R′, which may be identical or different, are each chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen, R and R′ optionally forming, together with N in the —NRR′, a 5- or 6-membered carbon-based ring which may further comprise at least one hetero atom chosen from O, N and S in the ring, and/or which may be substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR″; —O—COR″; —SH; —SR″;

—S—COR″; —NH 2 ; —NHR″; —NH—COR″; -Hal (halogen); —CN; —COOR″; and —COR″; wherein R″ is chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen;

B, which may be identical or different, is chosen from —OH; —OR; —O—COR; —SH; —SR; —S—COR; —NH 2 ; —NHR; —NRR′; —NH—COR; -Hal (halogen); —CN; —COOR; —COR; —NO 2 ; and —SO 2 —OR, and linear and branched, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 18 carbon atoms,

optionally substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR; —O—COR; —SH; —SR; —S—COR; —NH 2 ; —NHR; —NRR′; —NH—COR; -Hal (halogen, or even perhalogen); —CN; —COOR; —COR; —NO 2 ; and —SO 2 —OR;

wherein R and R′, which may be identical or different, are each chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen, R and R′ optionally forming, together with N in the —NRR′, a 5- or 6-membered carbon-based ring which may further comprise at least one hetero atom chosen from O, N and S in the ring, and/or which may be substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR″; —O—COR″; —SH; —SR″;

—S—COR″; —NH 2 ; —NHR″; —NH—COR″; -Hal (halogen); —CN; —COOR″; and —COR″; wherein R″ is chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen;

X is a radical chosen from —OH, —OR 4 , —NH 2 , —NHR 4 , —NR 4 R 5 , —SR 4 , —COOR 4 and —COR 4 ;

wherein R 4 and R 5 , which may be identical or different, are each chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, optionally substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR; —O—COR; —SH; —SR; —S—COR; —NH 2 ; —NHR; —NRR′; —NH—COR; -Hal (halogen); —CN; —COOR; and —COR;

wherein R and R′, which may be identical or different, are each chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen, R and R′ optionally forming, together with N in the —NRR′, a 5- or 6-membered carbon-based ring which may further comprise at least one hetero atom chosen from O, N and S in the ring, and/or which may be substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR″; —O—COR″; —SH; —SR″;

—S—COR″; —NH 2 ; —NHR″; —NH—COR″; -Hal (halogen); —CN; —COOR″; and —COR″; wherein R″ is chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen;

R 4 and R 5 optionally forming, together with N in the —NR 4 R 5 , a 5- or 6-membered carbon-based ring which may further comprise at least one hetero atom chosen from O, N and S in the ring, and/or which may be substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR″; —O—COR″; —SH; —SR″;

—S—COR″; —NH 2 ; —NHR″; —NH—COR″; -Hal (halogen); —CN; —COOR″; and —COR″; wherein R″ is chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen;

the mineral acid and organic acid salts thereof, and the optical isomers thereof, in isolated form and as a racemic mixture,

with the exception of the following compounds:

N-acetylglycyl-N-(benzyl)-DL-valylglycine tert-butyl ester;

N-acetylglycyl-N-(2-nitrobenzyl)-DL-valylglycine tert-butyl ester; and

N-acetylglycyl-N-(2,4-dimethyloxybenzyl)-DL-valylglycine tert-butyl ester.

2. The process according to claim 1 , wherein the skin is chosen from facial skin and body skin.

3. The process according to claim 1 , wherein the skin is the scalp.

4. The process according to claim 1 , wherein the at least one sign of ageing is generated by at least one of a reduction in the elasticity of the skin and a degradation of the collogen in the structure of the tissues.

5. The process according to claim 1 , wherein

Y is oxygen, and/or

R 1 is chosen from (i) hydrogen;

(ii) linear and branched, saturated and unsaturated, hydrocarbon-based radical containing 1 to 12 carbon atoms, optionally substituted with at least one group chosen from —OH, —OR and —P(O)—(OR) 2 with R representing a linear, branched or cyclic, saturated or unsaturated hydrocarbon-based radical containing 1 to 6 carbon atoms, which is optionally substituted with at least one halogen; and/or

R 2 is chosen from linear, branched and cyclic, saturated and unsaturated, hydrocarbon-based radical containing 1 to 12 carbon atoms optionally substituted with at least one group chosen from —OH and —OR with R representing a linear, branched or cyclic, saturated or unsaturated hydrocarbon-based radical containing 1 to 6 carbon atoms, which is optionally substituted with at least one halogen; and/or

R 3 is a radical of formula C 6 H (5-y′) —B y′ , in which y′ is an integer ranging from 1 to 3, or a radical of formula -A-C 6 H (5-y) —B y in which y is an integer ranging from 0 to 2; and/or

the radical A of R 3 is a linear or branched, saturated or unsaturated, divalent hydrocarbon-based radical containing 1 to 12 carbon atoms optionally substituted with at least one group chosen from halogen; —CN; —COOR; —NO 2 ;

SO 2 —OR, with R representing a linear, branched or cyclic, saturated or unsaturated hydrocarbon-based radical containing 1 to 6 carbon atoms, which is optionally substituted by at least one halogen; and/or

the radical B of R 3 , which may be identical or different, is chosen from OR; —NHR; —CN; —COOR; —COR and linear and branched, saturated and unsaturated, hydrocarbon-based radical containing 1 to 12 carbon atoms optionally substituted with at least one group chosen from halogen; —CN; —COOR; —NO 2 ;

SO 2 —OR, with R representing a linear, branched or cyclic, saturated or unsaturated hydrocarbon-based radical containing 1 to 6 carbon atoms, which is optionally substituted by at least one halogen; and/or

X is a radical chosen from —OH and OR 4 with R 4 representing a linear, cyclic or branched, saturated or unsaturated hydrocarbon-based radical containing 1 to 6 carbon atoms, which is optionally substituted by at least one group chosen from —OH and OR with R representing a linear, branched or cyclic, saturated or unsaturated hydrocarbon-based radical containing 1 to 6 carbon atoms, which is optionally substituted by at least one halogen.

6. The process according to claim 1 , wherein

R 1 is chosen from methyl, ethyl, propyl and isopropyl radical, each of which is optionally substituted with at least one group chosen from OH and —P(O)—(OR) 2 with R representing methyl, ethyl, propyl or isopropyl; and/or

R 2 is chosen from methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl and isobutyl radical; and/or

R 3 is chosen from one of the following formulae:

in which the divalent radical A is a methylene, an ethylene or a propylene and/or the radical B, which may be identical or different, represents —OR; —NHR; —CN; —COOR; —COR in which R represents a methyl, ethyl, propyl or isopropyl, or B represents a methyl, ethyl, propyl or isopropyl each of which is optionally substituted with at least one halogen, and/or

X represents a radical chosen from —OH, OCH 3 , —OC 2 H 5 , —O—C 3 H 7 and —OC 4 H 9 .

7. The process according to claim 6 , wherein B represents CF 3 .

8. The process according to claim 1 , wherein

R 1 is methyl, optionally substituted with a group P(O)—(OR) 2 with R representing ethyl; and/or

R 2 is isopropyl radial; and/or

R 3 represents a group chosen from one of the following formulae:

in which the divalent radical A is methylene, and/or the radical B represents CF 3 , and/or

X represents a radical chosen from —OH and —OC 2 H 5 .

9. The process according to claim 1 , wherein the at least one compound of formula (I) is chosen from

{2-[acetyl(3-trifluoromethylphenyl)amino]-3-methylbutyrylamino}acetic acid,

ethyl {2-[acetyl(3-trifluoromethylphenyl)amino]-3-methylbutyrylamino}acetate,

[2-(acetylbenzylamino)-3-methylbutyrylamino]acetic acid,

ethyl [2-(acetylbenzylamino)-3-methylbutyrylamino]acetate, and

ethyl (2-{benzyl[(diethoxyphosphoryl)acetyl]amino}-3-methylbutyrylamino)-acetate.

10. The process according to claim 8 , wherein the at least one compound of formula (I) is {2-[acetyl(3-trifluoromethylphenyl)amino]-3-methylbutyrylamino}acetic acid.

11. The process according to claim 1 , wherein the skin that has at least one sign of ageing is chosen from skin with wrinkles, skin with fine lines, wizened skin, skin lacking elasticity, skin lacking tone, skin suffering from a thinned dermis, skin suffering from degradation of collagen fibres, flaccid skin, thinned skin, and skin suffering from internal degradation following exposure to ultraviolet radiation.

12. A process for at least one of inhibiting the activity of elastases, limiting degradation of elastic fibres, and combating degradation of elastic fibres, comprising applying to the skin at least one composition, comprising, in a physiologically acceptable medium, at least one compound chosen from compounds of formula (I):

wherein:

Y is chosen from O and S,

R 1 is chosen from:

(i) hydrogen;

(ii) linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 18 carbon atoms,

optionally substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR; —O—COR; —SH; —SR; —S—COR; —NH 2 ; —NHR; —NRR′; —NH—COR; -Hal (halogen); —CN; —COOR; —COR; —P(O)—(OR) 2 ; and —SO 2 —OR;

wherein R and R′, which may be identical or different, are each chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen, the said radicals R and R′ optionally forming, together with N in the —NRR′, a 5- or 6-membered carbon-based ring which may further comprise at least one hetero atom chosen from O, N and S in the ring, and/or which may be substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR″; —O—COR″; —SH; —SR″;

—S—COR″; —NH 2 ; —NHR″; —NH—COR″; -Hal (halogen); —CN; —COOR″; and —COR″; wherein R″ is chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen; and

(iii) radicals chosen from —OR; —NH 2 ; —NHR; —NRR′; —NH—COR; —COOR; and —COR;

wherein R and R′, which may be identical or different, are each chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen, the said radicals R and R′ optionally forming, together with N in the —NRR′, a 5- or 6-membered carbon-based ring which may further comprise at least one hetero atom chosen from O, N and S in the ring, and/or which may be substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR″; —O—COR″; —SH; —SR″;

—S—COR″; —NH 2 ; —NHR″; —NH—COR″; -Hal (halogen); —CN; —COOR″; and —COR″; wherein R″ is chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen;

R 2 is chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 18 carbon atoms, optionally substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR; —O—COR; —SH; —SR; —S—COR; —NH 2 ; —NHR; —NRR′; —NH—COR; -Hal (halogen); —CN; —COOR; and —COR;

wherein R and R′, which may be identical or different, are each chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen, R and R′ optionally forming, together with N in the —NRR′, a 5- or 6-membered carbon-based ring which may further comprise at least one hetero atom chosen from O, N and S in the ring, and/or which may be substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR″; —O—COR″; —SH; —SR″;

—S—COR″; —NH 2 ; —NHR″; —NH—COR″; -Hal (halogen); —CN; —COOR″; and —COR″; wherein R″ is chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen;

R 3 is a radical chosen from those of formulae (II) and (III):

-A-C 6 H (5-y)—B y   (II)

—C 6 H (5-y′)—B y′   (III)

wherein:

y is an integer ranging from 0 to 5 and y′ is an integer ranging from 1 to 5;

A is chosen from linear and branched, saturated and unsaturated divalent hydrocarbon-based radicals containing from 1 to 18 carbon atoms,

optionally substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR; —O—COR; —SH; —SR; —S—COR; —NH 2 ; —NHR; —NRR′; —NH—COR; -Hal (halogen); —CN; —COOR; —COR; —NO 2 ; and —SO 2 —OR;

wherein R and R′, which may be identical or different, are each chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen, R and R′ optionally forming, together with N in the —NRR′, a 5- or 6-membered carbon-based ring which may further comprise at least one hetero atom chosen from O, N and S in the ring, and/or which may be substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR″; —O—COR″; —SH; —SR″;

—S—COR″; —NH 2 ; —NHR″; —NH—COR″; -Hal (halogen); —CN; —COOR″; and —COR″; wherein R″ is chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen;

B, which may be identical or different, is chosen from —OH; —OR; —O—COR; —SH; —SR; —S—COR; —NH 2 ; —NHR; —NRR′; —NH—COR; -Hal (halogen); —CN; —COOR; —COR; —NO 2 ; and —SO 2 —OR, and linear and branched, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 18 carbon atoms,

optionally substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR; —O—COR; —SH; —SR; —S—COR; —NH 2 ; —NHR; —NRR′; —NH—COR; -Hal (halogen, or even perhalogen); —CN; —COOR; —COR; —NO 2 ; and —SO 2 —OR;

wherein R and R′, which may be identical or different, are each chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen, R and R′ optionally forming, together with N in the —NRR′, a 5- or 6-membered carbon-based ring which may further comprise at least one hetero atom chosen from O, N and S in the ring, and/or which may be substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR″; —O—COR″; —SH; —SR″;

—S—COR″; —NH 2 ; —NHR″; —NH—COR″; -Hal (halogen); —CN; —COOR″; and —COR″; wherein R″ is chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen;

X is a radical chosen from —OH, —OR 4 , —NH 2 , —NHR 4 , —NR 4 R 5 , —SR 4 , —COOR 4 and —COR 4 ;

wherein R 4 and R 5 , which may be identical or different, are each chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, optionally substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR; —O—COR; —SH; —SR; —S—COR; —NH 2 ; —NHR; —NRR′; —NH—COR; -Hal (halogen); —CN; —COOR; and —COR;

wherein R and R′, which may be identical or different, are each chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen, R and R′ optionally forming, together with N in the —NRR′, a 5- or 6-membered carbon-based ring which may further comprise at least one hetero atom chosen from O, N and S in the ring, and/or which may be substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR″; —O—COR″; —SH; —SR″;

—S—COR″; —NH 2 ; —NHR″; —NH—COR″; -Hal (halogen); —CN; —COOR″; and —COR″; wherein R″ is chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen;

R 4 and R 5 optionally forming, together with N in the —NR 4 R 5 , a 5- or 6-membered carbon-based ring which may further comprise at least one hetero atom chosen from O, N and S in the ring, and/or which may be substituted with 1 to 5 groups, which may be identical or different, chosen from —OH; —OR″; —O—COR″; —SH; —SR″;

—S—COR″; —NH 2 ; —NHR″; —NH—COR″; -Hal (halogen); —CN; —COOR″; and —COR″; wherein R″ is chosen from linear, branched and cyclic, saturated and unsaturated hydrocarbon-based radicals containing from 1 to 6 carbon atoms, which are optionally substituted with at least one halogen;

the mineral acid and organic acid salts thereof, and the optical isomers thereof, in isolated form and as a racemic mixture,

with the exception of the following compounds:

N-acetylglycyl-N-(benzyl)-DL-valylglycine tert-butyl ester;

N-acetylglycyl-N-(2-nitrobenzyl)-DL-valylglycine tert-butyl ester; and

N-acetylglycyl-N-(2,4-dimethyloxybenzyl)-DL-valylglycine tert-butyl ester.

13. The process according to claim 12 , wherein the skin is chosen from facial skin and body skin.

14. The process according to claim 12 , wherein the skin is the scalp.

15. The process according to claim 12 , wherein

Y is oxygen, and/or

R 1 is chosen from (i) hydrogen;

(ii) linear and branched, saturated and unsaturated, hydrocarbon-based radical containing 1 to 12 carbon atoms, optionally substituted with at least one group chosen from —OH, —OR and —P(O)—(OR) 2 with R representing a linear, branched or cyclic, saturated or unsaturated hydrocarbon-based radical containing 1 to 6 carbon atoms, which is optionally substituted with at least one halogen; and/or

R 2 is chosen from linear, branched and cyclic, saturated and unsaturated, hydrocarbon-based radical containing 1 to 12 carbon atoms optionally substituted with at least one group chosen from —OH and —OR with R representing a linear, branched or cyclic, saturated or unsaturated hydrocarbon-based radical containing 1 to 6 carbon atoms, which is optionally substituted with at least one halogen; and/or

R 3 is a radical of formula C 6 H (5-y′) —B y′ in which y′ is an integer ranging from 1 to 3, or a radical of formula -A-C 6 H (5-y) —B y in which y is an integer ranging from 0 to 2; and/or

the radical A of R 3 is a linear or branched, saturated or unsaturated, divalent hydrocarbon-based radical containing 1 to 12 carbon atoms optionally substituted with at least one group chosen from halogen; —CN; —COOR; —NO 2 ;

SO 2 —OR, with R representing a linear, branched or cyclic, saturated or unsaturated hydrocarbon-based radical containing 1 to 6 carbon atoms, which is optionally substituted by at least one halogen; and/or

the radical B of R 3 , which may be identical or different, is chosen from OR; —NHR; —CN; —COOR; —COR and linear and branched, saturated and unsaturated, hydrocarbon-based radical containing 1 to 12 carbon atoms optionally substituted with at least one group chosen from halogen; —CN; —COOR; —NO 2 ;

SO 2 —OR, with R representing a linear, branched or cyclic, saturated or unsaturated hydrocarbon-based radical containing 1 to 6 carbon atoms, which is optionally susbstituted by at least one halogen; and/or

X is a radical chosen from —OH and OR 4 with R 4 representing a linear, cyclic or branched, saturated or unsaturated hydrocarbon-based radical containing 1 to 6 carbon atoms, which is optionally substituted by at least one group chosen from —OH and OR with R representing a linear, branched or cyclic, saturated or unsaturated hydrocarbon-based radical containing 1 to 6 carbon atoms, which is optionally substituted by at least one halogen.

16. The process according to claim 12 , wherein

R 1 is chosen from methyl, ethyl, propyl and isopropyl radical, each of which is optionally substituted with at least one group chosen from OH and —P(O)—(OR) 2 with R representing methyl, ethyl, propyl or isopropyl; and/or

R 2 is chosen from methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl and isobutyl radical; and/or

R 3 is chosen from one of the following formulae:

in which the divalent radical A is a methylene, an ethylene or a propylene and/or the radical B, which may be identical or different, represents —OR; —NHR; —CN; —COOR; —COR in which R represents a methyl, ethyl, propyl or isopropyl, or B represents a methyl, ethyl, propyl or isopropyl each of which is optionally substituted with at least one halogen, and/or

X represents a radical chosen from —OH, OCH 3 , —OC 2 H 5 , —O—C 3 H 7 and —OC 4 H 9 .

17. The process according to claim 16 , wherein B represents CF 3 .

18. The process according to claim 12 , wherein

R 1 is methyl, optionally substituted with a group P(O)—(OR) 2 with R representing ethyl; and/or

R 2 is isopropyl radial; and/or

R 3 represents a group chosen from one of the following formulae:

in which the divalent radical A is methylene, and/or the radical B represents CF 3 , and/or

X represents a radical chosen from —OH and —OC 2 H 5 .

19. The process according to claim 12 , wherein the at least one compound of formula (I) is chosen from

{2-[acetyl(3-trifluoromethylphenyl)amino]-3-methylbutyrylamino}acetic acid,

ethyl {2-[acetyl(3-trifluoromethylphenyl)amino]-3-methylbutyrylamino}acetate,

[2-(acetylbenzylamino)-3-methylbutyrylamino]acetic acid,

ethyl [2-(acetylbenzylamino)-3-methylbutyrylamino]acetate, and

ethyl (2-{benzyl[(diethoxyphosphoryl)acetyl]amino}-3-methylbutyrylamino)-acetate.

20. The process according to claim 19 , wherein the at least one compound of formula (I) is {2-[acetyl(3-trifluoromethylphenyl)amino]-3-methylbutyrylamino}acetic acid.

21. A process for treating facial skin comprising, applying to the facial skin a composition comprising, in a cosmetically acceptable medium, 2-[acetyl(3-trifluoromethylphenyl)amino]-3-methylbutyrylamino}acetic acid.