The present invention relates to new adjuvants and the uses in pharmaceutical compositions, like in vaccines. In particular, the present invention provides new conjugates of the bisacyloxycysteine type useful as adjuvants and/or immunomodulators for prophylactic and/or therapeutic vaccination in the treatment of infectious diseases, inflammatory diseases, autoimmune diseases, tumours, allergies as well as for the control of fertility in human or animal populations. The compounds are particularly useful not only as systemic, but preferably as mucosal adjuvants. In addition, the invention relates to its uses as active ingredients in pharmaceutical compositions.