Pavine-benzylisoquinoline alkaloids

F. TYPES VII AND VIII - BENZYLISOQUINOLINE-PHENANTHRENE AND PAVINE-BENZYLISOQUINOLINE ALKALOIDS... 

Species belonging to the section Stenocraspedontae are characterized by the presence of benzylisoquinoline alkaloids, for example, E. oregana Greene contains escholamine (33) as the major alkaloid. Eschscholtzia lobbii Greene appears to be exceptional since neither pavine nor benzylisoquinoline alkaloids have been detected therein. The presence of aporphine alkaloids is characteristic for all the species. 

Several types of data based on feeding experiments, isolation of intermediates and in vivo NMR experiments, indicate that norcoclaurine (23) serves as a precursor to both coclaurine (24) and (S)-reticuline (20) (Stadler et al., 1987, 1989), and that (5)-coclaurine (24) serves as a specific precursor to other classes of benzylisoquinoline alkaloids, such as the protoberberines, benzophenanthridines, and morphinandie-nones, as well as for pavine and benzophenanthridine alkaloids in intact plants (Stadler et al., 1987, 1989). The five enzymes involved in the conversion of dopamine and 4-hydroxyphenylacetaldehyde (19) to (S)-reticuline (20) have been elucidated (Frenzel and Zenk, 1990b). 

Various species of Argemone and Eschscholtzia (Papavera-ceae) and Thalictrum (Ranunculaceae) contain pavine alkaloids (about 20) and isopavine alkaloids (about 10) with a tetracyclic nucleus derived from benzylisoquinoline alkaloids (Gozler, 1987 Guinaudeau and Bruneton, 1993 Schiff, 1987). The formation of argemonine (93) and related alkaloids is rationalized as follows (Fig. 32.31) (Geissman and Crout, 1969). An alternate mode of cyclization also has been observed in the formation of (— )-eschscholtzine (94) and (- )-munitagine (95). 

H. Guinaudeau, M. Leboeuf, and A. Cave, J. Nat. Prod. 42, 133 (1979). Dimeric aporphine-benzylisoquinoline and aporphine-pavine alkaloids. Tabulates physical properties, sources, and references to synthesis of 28 alkaloids. 

Fourteen alkaloids were isolated from extracts of the whole plant of ThaUctrum fauriei Hayata, among which were seven alkaloids of novel structure including three aporphines (3-0-demethyloconovine, faurine, and O-methylfaurine), three aporphine-benzylisoquinoline dimers (fauridine, faurithaline, and 3-methoxyfaurithaline), and one aporphine-pavine dimer (fauripavine). Alkaloids of previously established structure that were isolated and identified included five aporphines (corydine, isocorydine, isooconovine, oconovine, and thalisopynine), and two morphinans (ocobotrine and pallidine). 

The term aporphinoids covers aporphines and their close biogenetic precursors, the proaporphines. Alkaloids derived from relatively straightforward biological transformations of proaporphines or of aporphines are also encompassed, so that proaporphine-benzylisoquinolines, aporphine-benzylisoquinolines, aporphine-pavines, oxoaporphines, dioxoaporphines, aristolactams, and aristolochic acids, as well as phenanthrenes, will be discussed. Azafluoranthenes are also included within the scope of aporphinoids for reasons which will become clear toward the end of the present chapter. 

A continuing investigation of the alkaloids of Thalictrum polygamum Muhl. has resulted in the isolation of members of an interesting and novel isoquinoline group, the aporphine-pavine dimers. Pennsylpavine (59) and pennsylpavoline (60) are weakly basic phenolic alkaloids which are accompanied in the plant by the aporphine-benzylisoquinolines pennsylvanine (46) and pennsylvanamine (47). It therefore seems likely that (46) and (47) are biogenetic precursors for (59) and (60), respectively. ... 

S)-(+)-reticuline (20) and orientaline (25). The alkaloids of the Papaveraceae and Fumariaceae can be subdivided into several constitutional types (Fig. 3), viz., simple isoquinolines, benzylisoquinolines, pavines, isopavines, cularines, proaporphines, aporphines, promorphinanes, morphinanes, protoberberines, retroprotoberberines, secoberbines, benzophenanthridines, protopines, phthali-deisoquinolines, secophthalideisoquinolines, indenobenzazepines, spirobenzyl-isoquinolines, and rhoeadines. 

Among the isoquinoline alkaloids, the aporphine-benzylisoquinolines had been considered a terminal stage of anabolic development in the biogenetic tree. The discovery of pennsylpavine and pennsylpavoline, two examples of a new group of dimeric alkaloids, the aporphine-pavines, has extended the biogenetic locus, since they are probably derived from aporphine-benzylisoquino-line dimers. 

The following groups of alkaloids occur in the plant family of the Papaveraceae benzylisoquinoline, cularine, aporphine, proaporphine, morphine, protoberberine, protopine, narceine, benzophenanthridine, phthalide-isoquinoline, rhoeadine, papaverrubine, pavine, isopavine and ochotensimine. Many of these alkaloid groups are formed by one genus only, whereas others occur in many genera and even in plants of other families. Alkaloids of all these groups must thus be taken into considera-... 

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