2,2-Dimethyl-succinic acid, 4-((1R,3aS,5aR,5bR,7aR,9S,11aR,11bR,13aR,13bR)-3a-carboxy-1-isopropenyl-5a,5b,8,8,11a-pentamethyl-eicosahydro-cyclopenta[a]chrysen-9-yl) ester 3-O-(3',3'-Dimethylsuccinyl)-betulinic acid AIDS-028530 AIDS028530 Bevirimat DSB PA-457