Abstract: The compounds of formula (I) cyclo[X.sub.1.sup.1 --Z.sub.1.sup.2 --X.sub.2.sup.3 --X.sub.3.sup.4 --Z.sub.2.sup.5 --X.sub.4.sup.6 ]cyclo(2.beta.-5.beta.) wherein: X.sub.1 =(D or L)Cys(Y) or (D or L)SeCys(Y), Z.sub.1 =Asp and Z.sub.2 =Dap or Z.sub.1 =Dap and Z.sub.2 =Asp and X.sub.2, X.sub.3 and X.sub.4 =natural or synthetic hydrophobic amino acids, having Z.sub.1, Z.sub.2, X.sub.2, X.sub.3 and X.sub.4 the same D or L configuration; Y=is a glycosidic group selected from the aldo and keto hexoses in the furanose or pyranose form bound to the cysteine with an .alpha. or .beta. thioacetalic bond or a cyclithol or a polyvinyl alcohol or PEG, constituted of 5 to 10 monomeric unities, bound to the cysteine with a thioether bond, are endowed of high solubility and of potent tachykinin-antagonistic activity.