![]() ![]() ![]() Such pieces are preferably produced from a powdered plastic material containing glass fiber and are made according to the process described in U.S. ![]() Three synthetic gamma-butenolide oximes were also prepared and characterized by infrared and 13C NMR spectroscopy.Puzzle pieces in the form of fine powder that are compacted by means of pressure-filled pistons are known and are described, for example, in U.S. This general procedure was also used to determine the structures of the three major components of the lacrimatory factor in tears of patients with vernal keratoconjunctivitis. 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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