A general procedure for the stereospecific preparation of gamma-butenolide oximes was developed which entails iodolactonization of alpha,beta-unsaturated esters in the presence of p-toluenesulfonic acid-dioxane and followed by the acid-catalyzed reaction of oximes with n-butyllithium. Iodolactonization of alpha,beta-unsaturated esters, followed by treatment with n-butyllithium, gives formation of all-cis-gamma-butenolide oximes, whereas alpha,beta-unsaturated carboxylic esters are converted to oximes that contain two stereogenic centers, that is, a ketone and an oxime. Gamma-Butenolides and flavonoids are found in a variety of natural sources and have shown biological activity.
Sep 20, 2019Structure elucidation of butanolide and flavonoid derivatives: stereospecific iodolactonization.
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