Abstract: The invention relates to a compound of formula (I) wherein X represents an activating radical such as a chlorine atom or imidazoyl, Y represents a saturated aliphatic C6-C20 radical, and Z represents an aliphatic C2-C10 radical. The invention also relates to a method for synthesising the compound of formula (I), according to which the compound of formula (II) is formed by the reaction between an alcohol and an acid anhydride, and by the activation of the carbonyl function. Furthermore, the invention relates to the use of the compound of formula (I) for increasing the hydrophobic character of polymers comprising amine and/or hydroxyl functions by means of grafting, and to a support based on natural textile fibres onto which the compound of formula (I) is grafted.