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 inventionare of formula I wherein A is A1, A2, A3 or A4 and R, R, R,R, R, R, R, Ar, X,X, X, X and X are as herein defined.Also disclosed in the present invention are methods of treating an HIV infectionwith compounds defined herein and pharmaceutical compositions containingsaid compounds.