monensin

{{chembox | Verifiedfields = changed | Watchedfields = changed | verifiedrevid = 408764013 | Name = Monensin A | ImageFile = Monensin A.svg | ImageClass = skin-invert-image | ImageSize = | PIN = (2S,3R,4S)-4-[(2S,5R,7S,8R,9S)-2-{(2S,2′R,3′S,5R,5′R)-2-Ethyl-5′-[(2S,3S,5R,6R)-6-hydroxy-6-(hydroxymethyl)-3,5-dimethyloxan-2-yl]-3′-methyl[2,2′-bioxolan]-5-yl}-9-hydroxy-2,8-dimethyl-1,6-dioxaspiro[4.5]decan-7-yl]-3-methoxy-2-methylpentanoic acid | OtherNames = Monensic acid |Section1= |Section2= | Section6 = |Section8= }} Monensin is a polyether antibiotic isolated from Streptomyces cinnamonensis. It is widely used in ruminant animal feeds.

The structure of monensin was first described by Agtarap et al. in 1967, and was the first polyether antibiotic to have its structure elucidated in this way. The first total synthesis of monensin was reported in 1979 by Kishi et al.