2'-deoxy-2'-S-(4-ethoxycarbonylbutyl)uridine

5'-O-DMT-2'-deoxy-2'-S-(4-ethoxycarbonylbutyl)uridine

2'-deoxy-2'-S-(4-phthalimidobutyl)uridine

4-[(2R,3R,4R,5R)-2-(2,4-Dioxo-3,4-dihydro-2H-pyrimidin-1-yl)-4-hydroxy-5-hydroxymethyl-tetrahydro-furan-3-ylsulfanylmethyl]-heptanedioic acid dibenzyl ester