11,12,4''-Tri-O-methylazithromycin Monohydrate

The title compound, [2R-(2R*,3S*,4R*,5R*,8R*,10R*,11R*,12S*,13S*,14R*)]-13-[(2,6-dideoxy-3-C–methyl-3-O-methyl-4-O-methyl-α-L-ribo-hexopyranosyl)­oxy]-2-ethyl-10-hydroxy-3,4- dimethoxy-3,5,6,8,10,12,14-heptamethyl-11-{[3,4,6-trideoxy-3-(dimethylamino)- β-D-xylo-hexopyranosyl]oxy}-1-oxa-6-azacyclopentadecan-15-one monohydrate C₄₁H₇₈N₂O₁₂.H₂O, is an O-methylated derivative (in positions O11, O12 and O4′′) of the 15-membered semisynthetic azalide antibiotic azithromycin. The aglycone ring adopts a `folded-out' conformation as found for azithromycin in the solid state, thus indicating that the introduced methyl groups do not affect essentially the molecular conformation. Both the α-L-cladinose and β-D-desosamine sugars are in the expected chair conformation. The intramolecular hydrogen bond of 2.750 (9) Å between the methylated atom N9a and the hydroxyl O atom O61 is characteristic of this compound and the whole class of the analogous compounds. Both H atoms of the water molecule participate in the hydrogen bonding with the aglycone as well as with the cladinose ring.