Abstract: Compounds of the general Formula (I) ##STR1## in which R is a hydrogen atom or a bromine atom, and R.sub.1 is a hydrogen atom, an SO.sub.2 OM group wherein M is a hydrogen or sodium atom, various sulphatide or phosphatide groups or a glucuronide group are disclosed for use in the prophylaxis and therapy of retroviral infections, especially infection by Human Immunodeficiency Virus. These compounds may be used concomitantly or in combination with various immunomodulators and/or antiviral agents.