Azaphenanthrenes, synthesis

Aza-Payne rearrangements, 60, 1 Azaphenanthrenes, synthesis by photocyclization, 30, 1 Azides, synthesis and rearrangement of, 3, 9... 

Azaphenanthrenes magnetic circular dichroism, 2, 129 Azaphenoxathiin synthesis, 3, 985... 

Intramolecular nucleophilic ring opening of 4-methoxycarbonyl-l-azaphenanthrene 5,6-oxide (262) has been utilized in the total synthesis of eupolaramine (263).155... 

The key step in the synthesis of the azaphenanthrene alkaloid eupoulauramine 27 (56% yield) is an intramolecular SRN1 reaction, followed by in situ stilbene photo-cyclization, and further methylation (Scheme 10.52) [68]. 

An intramolecular Diels-Alder reaction of oxazoles with alkenes has not been investigated (83T2869). Recently, Levin and Weinreb (83JA1397 84JOC4325) applied an intramolecular Kondrat va pyridine synthesis (74AHC(17)99 81MI1) to the total synthesis of azaphenanthrene alkaloids eupolauramine (506). Independently, some examples of intramolecular... 

The azaphenanthrene alkaloid eupolauramine appeared to be an ideal target for exploring the applicability of an intramolecular Kondrat eva pyridine synthesis in the construction of natural products. Despite the fact that 2-phenyloxazoles are unreactive in intermolecular cycloadditions, the Diels-Alder reaction of oxazole-olefin 97 was expected to provide the tricyclic framework of eupolauramine... 

Multicyclic nitrogen heterocycles can also be prepared by extension of the Bischler-Napieralski synthesis. Thus, the azaphenanthrene system (4.21) can be prepared as shown in Scheme 4.19. 

An important example is the formal synthesis of eupolauramine, an alkaloid from the bark of the African plant Eupomatia laurina. This approach involves addition of the carbanion of allyl phenyl sulfone to l-methoxy-4-nitronaphthalene followed by cOTiversion of the o adduct formed into the conesponding nitrosoarene. Further intramolecular condensation affords phenylsulfonyl-substituted azaphenanthrene (Scheme 83) [82]. The sulfone obtained was transformed into tricyclic azaaromatic acid, from which in turn the final alkaloid can be obtained following the known procedure [206],... 

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