Acetic acid (2R,3R,4R,5S,6S)-5-acetoxy-4-benzyloxycarbonylamino-2-{(R)-1-[(R)-1-ethyl-4-((S)-2-ethyl-hex-5-enoylamino)-butyl]-4-methyl-pent-4-enyloxy}-6-methyl-tetrahydro-pyran-3-yl ester