142102-81-6 3Allyl-2',5'diSilylSpiroT AIDS-003920 AIDS003920 TSAO analog TSAO-a3T [1-[2',5'-Bis-O-(tert-butyldimethylsilyl)-.beta.-D-ribofuranosyl]-3-N-allylthymine]-3'-spiro-5-(4-amino-1,2-oxathiole-2,2-dioxide)