Alkaloids Derived from 5,10b-Ethanophenanthridine

The fourteen alkaloids discussed in this section constitute a remarkable series of structurally and stereochemically interrelated substances. Superficially, all the alkaloids contain the same basic ring system, 5,10b-ethanophenanthridine (145), but alkaloids are elaborated from both enantiomorphs of this basic nucleus. Further variations are produced by differences in aromatic substitution and the functional groups attached to rings C.and D. It has been possible to interrelate all the alkaloids of this section through a combination of simple oxidation, reduction, and dehydration reactions coupled with four rather specific degradative techniques. These reactions are (1) aromatic demethoxylation by sodium and amyl alcohol (82), (2) replacement of OH by H via the action of lithium aluminum hydride on an intermediate chloro compound (146), (3) acid hydrolysis of ally lie methyl ethers to alcohols (147, 148), and (4) 0-methylation of hydroxylic alkaloids with 

Crinine was first isolated from two unidentified South African Crinum species by Mason et al. (65). Subsequent isolations have shown it to be present in the bulbs of C7. moorei (70), C. powdlii (56), Bodphone jischeri 

Since the most probable explanation for the failure of crinine and its derivatives to undergo the reactions characteristic of caranine is the presence of a spiro ring system in crinine, 5,10b-ethano-8,9-methy-lenedioxy-l,2,3,4,4a,5,6,10b-octahydrophenanthridine (CLXIII) was synthesized as a possible basic nucleus for the alkaloid. Cyanoethylation 

The chemical reactions of powelline parallel those of crinine. Dihydro-powelline, oxopowelhne, epipowelline, dihydrooxopowelline, and powel-lane have been prepared by the same methods that were reported for crinine. Rotational correlations, measured at 589 m/x, between compounds in the crinine and powelline series are excellent, and it has been suggested that powelline is ar-methoxycrinine (CLXIVb) (147). Like oxocrinine methiodide, oxopowelline methiodide was converted to an optically inactive methine (CLXVII, plus an aromatic methoxyl) with dilute alkali (148). 

Recently, it has been found that methylation of the potassium salts of crinine and powelline with methyl p-toluenesulfonate proceeds without excessive quaternization of the nitrogen to yield buphanisine and buphanidrine, respectively. Since neither epicrinine nor epipowel-line could be detected in the reaction mixtures when the potassium 

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Galanthamine-type alkaloids derived from a dibenzofuran ring Crinine-type alkaloids derived from 5,10b-ethanophenanthridine Montanine-type alkaloids derived from 5, 11b-... 

The alkaloids derived from 5,10b-ethanophenanthridine (crinine and haemanthamine types), 2-benzopyrano[3,4c]indole (tazettine type), phenanthridine (narciclasine type) and 5,11b-methanomorphanthridine (montanine type) originate from a para-para oxidative phenolic coupling (Fig. 9). 

Supplementary stereochemical studies relating tazettine to the alkaloids of the family derived from 5,10b-ethanophenanthridine are... 

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