Abstract
Treatment of phthalideisoquinolines such as α- (1) and β-narcotine (2) as well as β- (3) and α-hydrastine (4) with ethyl chloroformate (ECF) at room temperature afforded, via the chloro-carbamates, the corresponding diastereomeric carbinols with high stereoselectivity. Instrumental analyses of each diastereomeric pair indicate that the major isomers derived from α- and β-narcotine as well as from α- and β-hydrastine are enantiomers of each other. The absolute configuration of the major carbinol 6a from α-narcotine (1) was determined by X-ray analysis. The probable difference between the reaction course of α-and β-narcotine is discussed. On the other hand, treatment of α-narcotine with ECF under reflux furnished Z-(8) and E-(9) enol lactones, while only the Z-isomer 12 could be isolated from the degradation of β-hydrastine (3) even at room temperature.
