(S)-4-(2,6-Difluoro-benzyl)-1-[(2S,4R)-2-hydroxy-4-((1S,2R)-2-hydroxy-indan-1-ylcarbamoyl)-5-pyridin-4-yl-pentyl]-piperazine-2-carboxylic acid tert-butylamide AIDS-059359 AIDS059359 Difluorobenzyl analog