1-(2,3-Dideoxy-2,3-difluoro-5-O-trityl-.beta.-D-ribofuranosyl)thymine 132776-17-1 AIDS-002763 AIDS002763 Trityl-FFLT Uridine, 2',3'-dideoxy-2',3'-difluoro-5-methyl-5'-O-(triphenylmethyl)-