(S)-2-[[3-Azido-5-(5-methyl-2,4-dioxo-tetrahydro-pyrimidin-1-yl)-tetrahydro-furan-2-ylmethoxy]-(2-cyano-ethoxy)-phosphorylamino]-3-phenyl-propionic acid methyl ester AIDS-097618 AIDS097618 AZT Phosphoramidates