Compounds of formula I, wherein R
1
, R
2
, R
3
, X
1
, X
2
and Ar, are as defined herein or pharmaceutically acceptable salts thereof, inhibit HIV-1 reverse transcriptase and afford a method for prevention and treatment of HIV-1 infections and the treatment of AIDS and/or ARC. The present invention also relates to compositions containing compounds of formula I useful for the prevention and treatment of HIV-
1
infections and the treatment of AIDS and/or ARC.
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 A is A2 and R
1
, R
2
, R
3
, R
4a
, R
4b
, R
5
, R
6
, Ar, X
1
, X
2
, X
4
, X
4
and X
5
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.