5'-O-({[2-(2-nitrophenyl)-4-(9-oxo-9H-thioxanthen-2-yl)butyl]oxy}carbonyl)thymidine

5'-O-({[2-(2-nitrophenyl)-5-(9-oxo-9H-thioxanthen-2-yl)pent-4-yn-1-yl]oxy}carbonyl)thymidine

5'-O-{[2-(2-nitro-4-{[(9-oxo-9H-thioxanthen-2-yl)oxy]carbonyl}phenyl)propoxy]carbonyl}thymidine

5 -O-acetyluridine