Synthesis of Phenethylisoquinoline Alkaloids

In the following section, Banwell s synthesis of colchicine is discussed in detail [160]. The route features a biomi-metic ring enlargement as key step. The ring system is elaborated via an oxidative coupling approach. Key steps of other approaches that utilize oxidative coupling reactions for the elaboration of the colchicine ring system are briefly outlined. 

After the successful elaboration of the 6,7,7-ring system of colchicine, the only remaining synthetic operation was the installation of the acetamide moiety. Alcohol 267 was allowed to react with diisopropyl azodicarboxylate 

Reagents and conditions (a) FeQ3 6H20, H2SO4 (6 N), EtOH, CHQ3 4-5%. Desacetmidocolchiceine Kaneko and Matsui [167]  

Reagents and conditions (a) Isoamylnitrite, H2SO4 (cone), 7-10°C then Cu, dioxane, rt, 24 h, 5%. SCHEME 1247 Key steps in Scott s and Kaneko s syntheses of desacetamidocolchiceine. 

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