ANCISTROGUINEINE-A AND ANCISTROGUINEINE-B AS WELL AS ANCISTROTECTORINE-NAPHTHYLISOQUINOLINE ALKALOIDS FROM ANCISTROCLADUS-GUINEENSIS

The isolation of three naphthylisoquinoline alkaloids from the leaves of Ancistrocladus guineensis is described. Their complete structures w ere established by spectroscopic, chiroptical and degradative methods. Thus, two hitherto unknown 5,8'-coupled naphthylisoquinolines, named ancistroguineines A and B, were isolated, constituting the first examp le of a pair of 3-epimeric naphthylisoquinoline alkaloids. Moreover, a ncistrotectorine, a 7,3'-coupled alkaloid previously known only from t he South-East Asian species Ancistrocladus tectorius, was isolated. It s absolute stereostructure was confirmed by oxidative degradation and by comparison of experimental and calculated CD spectra. (C) 1997 Else vier Science Ltd.