Synthetic studies toward penitrem E: enantiocontrolled construction of B-E rings.

@article{Yoshii2015SyntheticST,
  title={Synthetic studies toward penitrem E: enantiocontrolled construction of B-E rings.},
  author={Yu Yoshii and Takanori Otsu and Norihiko Hosokawa and Kiyosei Takasu and Kentaro Okano and Hidetoshi Tokuyama},
  journal={Chemical communications},
  year={2015},
  volume={51 6},
  pages={
          1070-3
        }
}
Enantiocontrolled construction of B-E rings of penitrem E was accomplished from 4-iodoindole in 13 steps with an overall yield of 1.7%. Diastereoselective Tf2NH-catalyzed (2+2)-cycloaddition between silyl enol ether and methyl acrylate furnished a tetracyclic product possessing the characteristic cyclobutane ring bearing a hydroxyl group. 
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