The structure of utilin, C41H52O17, a complex meliacin has been shown by X-ray analysis to be the 1,29-cycloswietenan derivative (I); the functional groups are methoxycarbonyl, acetate, orthoacetate, R-2-methylbutyrate, 2S,3R-2,3-epoxy-2-methylbutyrate, two hydroxyls, and a δ-lactone; and a β-substituted furan ring is also present.
