141684-56-2 AIDS-003931 AIDS003931 [N4-Acetyl-1-[2',5'-bis-O-(tert-butyldimethylsilyl)-.beta.-D-xylofuranosyl]cytosine]-3'-spiro-5-[4-amino-1,2-oxathiole 2,2-dioxide] diSilyxyloC TSAO deriv.