Stereocontrolled Epoxidations of Cycloheptene Derivatives in the Palladium-Catalyzed Route to Tropane Alkaloids. Total Syntheses of Scopine and Pseudoscopine

Article abstract of DOI:10.1021/jo00008a037

Stereoselective total syntheses of the tropane alkaloids scopine (1) and pseudoscopine (3) have been developed via the chloroacetoxylation approach.Palladium-catalyzed 1,4-chloroacetoxylation of diene 6 afforded the key intermediate 7.Subsequent substitution of the allylic chloride by TsNH^- with either retention (Pd(0) catalysis) or inversion (S_N2) of configuration gave 10 and 16, respectively.The epoxy oxygen was introduced syn to the nitrogen function prior to cyclization by utilizing the syn-directive effect of the allylic sulfonamido group in the epoxidation.Cyclization of the epoxides 12 and 21, followed by replacement of the tosyl group by a methyl group and subsequent debenzylation, afforded the title compounds 1 and 3, respectively.