142102-76-9 5'PhCO-2'Silyl-SpiroT AIDS-003913 AIDS003913 TSAO analog [1-[5'-O-Benzoyl-2'-O-(tert-butyldimethylsilyl)-.beta.-D-ribofuranosyl]thymine]-3'-spiro-5-(4-amino-1,2-oxathiole-2,2-dioxide)