The Oxoaporphines

A new botanical source of oxoaporphines is the family Eupomatiaceae. Some recently identified oxoaporphines are shown below. 

Pontevedrine, which was originally believed to be a C-7 oxoaporphine derivative, has now been shown to possess a C-4,5-dioxoaporphine structure (see Sec. 16.2). The green alkaloid glauvine, found in Glaucium spp. (Papa-veraceae), is identical with corunnine.  

For a description of methods of oxidation of aporphines and noraporphines to oxoaporphines, see Sec. 10.3.1. Total syntheses of oxoaporphines usually involve the elaboration of a C-2 or a C-6 appropriately functionalized aromatic benzylisoquinoline, which is then cyclized by a Pschorr or photochemical sequence. 

Corunnine and nandazurine have been prepared by oxidative photocyliza-tion of appropriately substituted phenolic benzylisoquinolines.  

When the photolysis was carried out through a Vicor filter, the yield of 5 decreased substantially. 

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The oxoaporphine alkaloids Teliglazine (126), Corunnine (127), Nandazurine (128), PO-3 (129), A-Methylliriodendronine (130), and A,(9-Dimethylliriodendronine (131) contain the 6-methyl-7-oxo-dibenzo [Je,g]quinolinium-l-olate ring system 125 which is isoconjugate with the l-methyl-7-methylene-7H-benzo[Je]anthracene anion (Scheme 46). Therefore, these alkaloids belong to class 1, i.e., heterocyclic mesomeric betaines isoconjugate with odd alternant hydrocarbon anions. Another... 

Alternatively, reduction of the keto-imine (20) with sodium borohydride gave a mixture of two carbinols corresponding to N-demethylated (16) and (17). Irradiation of this mixture produced norushinsunine together with a little noroliveroline. Photolysis of the alcohol (21) gave rise to the oxoaporphine liriodenine (22).21 Synthetic routes to those aporphines that incorporate a hydroxyl group at C-7 that is trans to the proton at C-6a are already known.22 23 A novel synthesis of aporphines via 3-phenylphenethylamines has been developed, and is described in Scheme 1. The aporphine (23) and related species were then synthesized by a modified route.24... 

The dehydrogenation of 66 to 6a,7-dehydroglaucine (79) proceeded in a yield of 60% with Fusarium solani ATCC 12823. This microorganism also produced a 21% yield of the oxoaporphine 80, but control experiments indicated that the latter was an artifact produced by air oxidation of 79 during the incubation. 

N,O-DimethyIIiriodendronine (95), isolated in fairly large amounts from G. chrysopetala (21), stands out among the oxoaporphine alkaloids found in Guat-teria in that it is a zwitterion related to the highly colored compounds of Glau-cium (Papaveraceae). Neutral and basic solutions of the rather insoluble N.O-... 

The Reissert compound 289 was condensed with the 1 -iodobenzaldehyde 290 to give the 1-benzyl compounds 291, which were then irradiated. The photocyclized products 292 were the oxoaporphines, which were then converted to the respective alkaloid corunnine, nandazurine, ( )-caaver-ine, ( )-isoboldine, ( )-thalicmidine, and ( )-domesticine in good yields (Scheme 109). 

An investigation of the alkaloidal content of the Australian Eupomatia laurina R. Br. (Eupomatiaceae), yielded a number of alkaloids, among which are the oxoaporphine liriodenine and the 7-hydroxynoraporphine norushinsunine. A new minor alkaloid from this source is eupolauridine (48) whose structure was proven conclusively by total synthesis (Scheme 6). ... 

A novel syrTEhesis of the aporphine system has been achieved from the diphenylethylamine (149) by condensation with diethyl oxalate followed by Bischler-Napieralski ring closure to the dihydroisoquinoline (150) and further cyclisation with polyph-osphoric acid to the oxoaporphine (151). A -methylation and reduction of this gave the trimethoxyaporphine 0,iV-dimethyl-tuduranine (M. Grecke and A. Brossi, Helv., 1979, 62. 1549). 

A Reissert compound has been prepared from 9-methoxyellipticine and both it and 10 give a fluoroborate salt of the type 19. The Reissert compound of 6,7-dimethoxyphthalazine has been used to prepare an azapa-paverine. The oxoaporphine alkaloid subsessiline has been synthesized using the Reissert compound of 5,6,7-trimethoxyisoquinoline. The reaction of vanillin Schiff bases with benzoyl cyanide yields open-chain analogs of Reissert compounds. a-Acylaminonitriles, which can be considered as open-chain Reissert compounds, have been converted to open-chain analogs of Reissert salts (5-imino-3,5-dihydrooxazole derivatives). - ... 

The oxoaporphine alkaloid pontevedrine stands apart from these two subgroups. Its unique feature is that it possesses an A-methyl pyridone moiety. 

The numbering system for the oxoaporphines follows that of the aporphines and is shown for liriodenine (1). 

Most of the NMR spectral data that have been reported for the oxoaporphines are summarized in Table III. The solvent was not indicated in all cases but was usually trifluoroacetic acid. 

Chapter 6. The Oxoaporphine Alkaloids Maurice Shamma and R. L. Castestson... 

The unusual alkaloids imeluteine (99) and rufescine (100), found in Abuta imene and A. rufescens, probably originate biogenetically from decarbonylation of oxo-aporphine precursors. Such an in vivo pathway is supported by the observation that Abuta imene also produces the oxoaporphine homomoschatoline (1,2,3-trimethoxyoxoaporphine). It is unlikely, on the other hand, that azafluoranthenes... 

The oxoaporphine alkaloids have been the subject of a recent review. Table 4 presents new isolation and structural elucidation studies of this class of alkaloids. 

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