(+)-1-[(1S,4R)-2,3-Dideoxy-2,3-didehydro-2-fluoro-4-thio-beta-L-ribofuranosyl]uracil 1-(3-Fluoro-5-hydroxymethyl-2,5-dihydro-thiophen-2-yl)-1H-pyrimidine-2,4-dione AIDS-163228 AIDS163228