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SwitzerlandDiese ilrbeit ist Herrn Prof. V . PreZug zu seinem 70. Geburtstag gewidmet (24. IX.76)Sunzwzary. Bulbocapnine methyl ether (2), on treatment with boron halides, affords the aporphine-l,Z-diol (3), the novel aporphines 5 and 6 or the phenanthrenc derivative 11 depending on the reaction conditions. 3 can be further transformed into corydine methyl ether (4); 6 has been converted t o corytuberine (8). Similarly, dehydrobulbocapnine methyl ether 9 was convertcd to 10.The aporphine alkaloid, (S)-bulbocapnine (l), can be easily isolated from the roots of Corydalis cava. Its substitution pattern, a methylenedioxy group on ring A, a hydroxy and a methoxy group on ring D, offers the possibility of manifold selective transformations to different semisynthetic aporphines.For our present studies, we decided to start from the known bulbocapnine methyl ether (2). Following earlier work with 1-hydrastine [l], we used boron trichloride as reagent, rather than boron tribromide, which seems to be less selective.As expected, the treatment of bulbocapnine methyl ether (2) with 2 mol of boron trichloride in dichloromethane at room temperature affords the known catecliol 3 [a-41, which can be 0-methylated to the known corydine [3] and corydirie methyl ether (4) [a]. Under the conditions chosen, only a part of 2 is cleaved to the catechol 3. An increase of the ratio of boron trichloride to substrate does not improve the yield of 3, but rather favours the formation of the novel aporphine 6. Similarly, treatment of 2 with boron tribromide affords the diphenol 5. In both cases, the original methylenedioxy group opens and subsequently cyclizes to the oxygen at C(11), forming a 7-membered ring. The diphenol 5 can also be obtained, althougli in lower yield, directly from bulbocapnine (1) and boron tribromide.The structure assignements of compounds 5 and 6 containing a newly formed 7-membered, instead of the original 5-membered ring, is based on spectral as well as chemical evidences. In the 1H-NMR. spectrum, the signals of the two protons of the methylenedioxy group, which appear as two well separated doublets, are very characteristic. In the 5-membered ring compounds 1 and 2, the coupling constant is in the order of about 1.5 Hs [5], but increases significantly to ca. 6 Hz in the 7-membered ring compounds 5 and 6. Both compounds can be methylated to the same dimethyl ether 7. Prolonged hydrolysis of 7 with dilute hydrochloric acid gives the known aporphine alkaloid (S)-corytuberine (8) [6]. 1) 2)3)

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Three poly-oxygenated aporphines have been transformed into a variety of desoxy congeners. This was readily accomplished by O-dealkylation with BBr3 and BC13 to cleave methoxyl and methylenedioxy groups, respectively, followed by reductive elimination of the resulting phenols as their tetrazoyl ethers or diethyl phosphate esters. The simultaneous elimination of two o-positioned hydroxy groups by these procedures was difficult to accomplish without racemization. t~edicated to Professor Robert Burns Woodard on the occasion of his sixtieth birthday.