Dithiophosphoric acid O-{(3aR,4R,6R,6aR)-6-[6-imino-1-(2-{2-[(4-methoxy-phenyl)-diphenyl-methoxy]-ethoxy}-ethyl)-1,6-dihydro-purin-9-yl]-2,2-dimethyl-tetrahydro-furo[3,4-d][1,3]dioxol-4-ylmethyl} ester S,S'-diphenyl ester

S,S-Diphenyl 5'-O-<4,4',4''-tris(levulinoyloxy)trityl>thymidine 3'-phosphorodithioate

S,S-diphenyl 2'-O-(tetrahydropyran-2-yl)-5'-O-(4,4'-dimethoxytrityl)-N3-anisoyluridine-3'-phosphorodithioate