The invention relates to the cosmetic use, as a skin moisturizer, of a compound of formula (I): with (i) R1 and R2 represent a hydrogen atom or a C1-C6 alkyl group, or (ii) R1 and R2 can form, together with the nitrogen atom which bears them, a saturated heterocycle with 5 to 7 ring members; R5 representing a hydrogen atom or a (C1-C3) alkyl group; R6 representing a hydrogen atom or a (C1-C4) alkyl group; R3 represents a hydrogen atom or a (C1-C6) alkyl group, or —OR3 represents a phosphate group; it being possible for the two groups R3 to form, together, an isopropylidene group; R4 represents a hydrogen atom or —OR4 represents a phosphate group; and the salts, solvates and isomers thereof. The invention also relates to a cosmetic composition comprising a compound (I) and the corresponding new compounds.