2,4(1H,3H)-Pyrimidinedione, 1-[(3x)-3-C-(cyanomethyl)-2-O-[(1,1-dimethylethyl)dimethylsilyl]-3-S-phenyl-3-thio-5-O-(triphenylmethyl)-.beta.-L-erythro-pentofuranosyl]- AIDS-153649 AIDS153649 NSC701709