3,5-Octanedione,7-[[(1,1-dimethylethyl)dimethylsilyl]oxy]-1-[(2R,3R)-3-[2-[(2R,3R)-3-[[[(1,1-dimethylethyl)dimethylsilyl]oxy]methyl]-2-methyloxiranyl]ethyl]-2-methyloxiranyl]-4-methyl-, (4S,7R)-