AIDS-031469 AIDS031469 TSAO-T hexofuranosyl analog [1-[2'-O-(tert-Butyldimethylsilyl)-5',6'-O-(tetraisopropyldisiloxan-1,3-diyl)-.beta.-D-allofuranosyl]thymine]-3'-spiro-5-(4-amino-1,2-oxathiole-2,2-dioxide)