(1S,2S,3S,4R)-3-[(1S)-1-Amino-2-ethylbutyl]-4-[[(1,1-dimethylethoxy)carbonyl]amino]-2-hydroxycyclopentanecarboxylic Acid Methyl Ester is an intermediate used in the synthesis of peramivir (P285500), a neuraminidase inhibitor developed as an antiviral agent for the treatment of influenza.