[[(2R,3S,4R,5R)-5-(6-aminopurin-9-yl)-3,4-dihydroxyoxolan-2-yl]methoxy-hydroxyphosphoryl] 5-[(6S)-2-oxo-1,3,3a,4,6,6a-hexahydrothieno[3,4-d]imidazol-6-yl]pentanoate