1-((2R,3S,4S,5R)-3,4-Dihydroxy-5-hydroxymethyl-tetrahydro-furan-2-yl)-5-iodo-2-thioxo-2,3-dihydro-1H-pyrimidin-4-one 2-Thio-5-iodouracil arabinoside AIDS-164973 AIDS164973