A straightforward synthesis of a Stemona alkaloid stemoamide by Chida and coworkers published in 2017. Relatively simple reagents and reactions leads to a elegantly constructed tricycle. Identify intermediates A and B, alongside mechanisms of each reaction. Exceptional care is needed for reaction 4!
For reference:
Yoritate, M., Takahashi, Y., Tajima, H., Ogihara, C., Yokoyama, T., Soda, Y., Oishi, T., Sato, T. and Chida, N. (2017).
“Unified Total Synthesis of Stemoamide-Type Alkaloids by Chemoselective Assembly of Five-Membered Building Blocks.”
Journal of the American Chemical Society, 139(50), 18386–18391.
doi:10.1021/jacs.7b10944