1,2,4-Triazine-3,5(2H,4H)-dione, 2-.beta.-D-ribofuranosyl- 2-.beta.-D-Ribofuranosyl-1,2,4-triazine-3,5(2H,4H)-dione 54-25-1 6-Azauridine AIDS-008706 AIDS008706 NSC32074