Acetic acid (3aR,4R,6R,6aS)-6-(N'-acetyl-N-tert-butoxycarbonyl-hydrazino)-2,2-dimethyl-tetrahydro-cyclopenta[1,3]dioxol-4-ylmethyl ester

[((3aR,4R,6R,6aS)-6-tert-Butoxycarbonylamino-2,2-dimethyl-tetrahydro-cyclopenta[1,3]dioxol-4-ylmethoxy)-hydroxy-phosphorylmethyl]-phosphonic acid mono-[(2R,3S,4R,5R)-5-(6-amino-purin-9-yl)-3,4-dihydroxy-tetrahydro-furan-2-ylmethyl] ester