141781-19-3 AIDS-003930 AIDS003930 N4-Acetyl-1-[2',5'-bis-O-(tert-butyldimethylsilyl)-.beta.-D-ribofuranosyl]cytosine]-3'-spiro-5-[4-amino-1,2-oxathiole 2,2-dioxide] diSilyC TSAO deriv.