(2S,3S)-2-({1-[3-Azido-5-(5-methyl-2,4-dioxo-3,4-dihydro-2H-pyrimidin-1-yl)-tetrahydro-furan-2-ylmethoxycarbonyl]-methanoyl}-amino)-3-methyl-pentanoic acid AIDS-122347 AIDS122347 AZT ANALOGS AZT-iLeu