The present invention provides for compounds useful for treating an HIV infection, or preventing an HIV infection, or treating AIDS or ARC. The compounds of the invention are of formula I wherein R<;SUP>;1<;/SUP>;, R<;SUP>;2<;/SUP>;, R<;SUP>;3<;/SUP>;, R<;SUP>;4<;/SUP>;, X<;SUP>;1 <;/SUP>;and X<;SUP>;2 <;/SUP>;are as herein defined. Also disclosed in the present invention are methods of treating an HIV infection with compounds defined herein and pharmaceutical compositions containing said compounds.