Selective ther cleavage in the aporphine series. Conversion of (S)-bulbocapnine into (S)-corytuberine and (S)-corydine methyl ether.

Bulbocapnine methyl ether ( 2 ), on treatment with boron halides, affords the aporphine-1,2-diol ( 3 ), the novel aporphines 5 and 6 or the phenanthrene derivative 11 depending on the reaction conditions. 3 can be further transformed into corydine methyl ether ( 4 ); 6 has been converted to corytuberine ( 8 ). Similarly, dehydrobulbocapnine methyl ether 9 was converted to 10 .