科研之友
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摘要
Asymmetric synthesis of the tetracyclic skeleton of arborisidine is reported. Starting from the enantiomerically pure compound 10,9-di-tert-butyl5-ethyl(4S,8R)-6-hydroxy-7,8-dihydro-9H-8a,4b-(epiminoethano)carbazole-5,9,10-tricarboxylate (11) which was reported earlier by our group, a Krapcho decarboxylation reaction was used to afford the ketone, and then a reductive ring-opening method was applied to open the pyrrolidine ring of the substrate. The C(15)-C(16) double bond and the methyl group at C(16) of A/B/D tricyclic skeleton were introduced via Saegusa oxidation and Michael reaction, respectively. Finally, an intramolecular aza-Michael addition reaction was used as a key reaction to construct the C-ring and C(16) quaternary center, which led to the efficiently asymmetric synthesis of A/B/C/D tetracyclic skeleton of arborisidine.
