{(S)-2-Methyl-1-[(2S,5S)-2-methyl-5-((2S,4R)-4-methyl-5-oxo-tetrahydro-furan-2-yl)-3-oxo-[1,4]diazecane-1-carbonyl]-propyl}-carbamic acid tert-butyl ester

{(1S,2S)-2-Methyl-1-[(2S,5S)-2-methyl-5-((2S,4R)-4-methyl-5-oxo-tetrahydro-furan-2-yl)-3-oxo-[1,4]diazecane-1-carbonyl]-butyl}-carbamic acid tert-butyl ester