The molecule is an erythromycin cation that is the conjugate acid of erythromycin C, arising from protonation of the tertiary amino group on the 3,4,6-trideoxy-3-(dimethylamino)-beta-D-xylo-hexopyranosyl residue; major species at pH 7.3. It is a conjugate acid of an erythromycin C.
[(2S,3R,4S,6R)-2-[[(3R,4S,5S,6R,7R,9R,11R,12R,13S,14R)-4-[(2R,4R,5S,6S)-4,5-dihydroxy-4,6-dimethyloxan-2-yl]oxy-14-ethyl-7,12,13-trihydroxy-3,5,7,9,11,13-hexamethyl-2,10-dioxo-oxacyclotetradec-6-yl]oxy]-3-hydroxy-6-methyloxan-4-yl]-dimethylazanium