A urethane derivative from amino acids has the formula ##STR1## wherein R represents --CH.sub.2 OH, --CHOH--CH.sub.3 or --(CH.sub.2).sub.3 --NH--CO--NHY, Y represents --H or --COOR', R' represents linear or branched alkyl, optionally unsaturated, having 8-24 carbon atoms, or a monocyclic cycloalkyl substituted by an alkyl whose total number of carbon atoms is equal to or greater than 10, or to the salts of the derivative of formula I or to a mixture of the derivatives of formula I and/or their salts. A method is given for the preparation of the urethane derivative of formula I, as are examples of cosmetic or pharmaceutical compositions containing the urethane derivative, as a hydrating agent, for the treatment of dry skin.