Additionsreaktionen an der alicyclischen Doppelbindung von Eburnamenin und Apovincamin

Addition reactions on the alicyclic double bond of eburnamenine and apovincamine The addition of alcohols, amines or thiols on the 14, 15‐double bond of (−)‐eburnamenine ( 3a ) or (+)‐apovincamine ( 9a ) yielded the corresponding analogues of vincanol ( 5b‐h ), epivincanol ( 7b‐d ), vincamine ( 10b‐e ) and epivincamine ( 11b‐g ) with varying stereoselctivity. The reaction was achieved by addition of hydrogenbromide at −78° followed by nucleophilic attack, or in the (−)‐eburnamenine series also by direct addition of alcohols and thiols under acidic conditions. Without exception the analogues of epivincamine ( 11a‐g ) exhibited two carbonyl absorption bands in thier IR. spectra. (−)‐Eburnamenine ( 3a ) was obtained from (+)‐apovincamine ( 9a ) in a simple one pot reaction.