2'-O-acetyl-3-de[(2,6-dideoxy-3-C-methyl-3-O-methyl-α-L-ribohexopyranosyl)oxy]-11,12-dideoxy-6-O-methyl-3-oxo-12,11-[oxycarbonyl[[4-[4-(3-pyridinyl)-1H-imidazol-1-yl]butyl]imino]]erythromycin