(R)-4-Amino-1-[5-O-[[2,3-bis(hexadecanoyloxy)propoxy]hydroxyphosphinyl]-2-cyano-2-deoxy-beta-D-arabinofuranosyl]-2(1H)-pyrimidinone monosodium salt; (R)-1-[5-O-[[2,3-Bis(hexadecanoyloxy)propoxy]hydroxyphosphinyl]-2-cyano-2-deoxy-beta-D-arabinofuranosyl]c