From Protopines and Protoberberines

Oxidation of pseudobase 10 with oxygen leads to the stable peroxide 16 which furnishes 12 upon borohydride reduction.  

Finally, the Hofmann methine base from a C-10 hydroxylated protober-berine can be oxidized to a quinol acetate using lead tetraacetate. Subsequent treatment with sulfuric acid and acetic anhydride leads to a C-5 acetoxylated benzophenanthridine which can be aromatized in ring B by further treatment with hydrochloric acid in boiling ethanoP  

A short synthesis of nitidine involves Mannich cyclization of the cis amine 17 as indicated below 

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