2-(3-Fluoropropyn-1-yl)-9-(.beta.-D-ribofuranosyl)hypoxanthine 9-[(4S,2R,3R,5R)-3,4-Dihydroxy-5-(hydroxymethyl)oxolan-2-yl]-2-(3-fluoroprop-1-ynyl)hydropurin-6-one AIDS-167864 AIDS167864