1-(1,7-Dihydroxy-2-(6-methoxy-2,2-dimethyltetrahydrofuro[2,3-d][1,3]dioxol-5-yl)hexahydro-2H-furo[3,2-d][1,3]oxazin-6-yl)-2,4(1H,3H)-pyrimidinedione AIDS-141395 AIDS141395 NSC656912