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Construction of the [6,5,7,5] Tetracyclic Core of Calyciphylline A Type Alkaloids via a Tandem Semipinacol Rearrangement/Nicholas Reaction

2017; American Chemical Society; Volume: 19; Issue: 17 Linguagem: Inglês

10.1021/acs.orglett.7b02274

1523-7060

Hui Shao, Wen Bao, Ze‐Ran Jing, Yunpeng Wang, Fu‐Min Zhang, Shao‐Hua Wang, Yong‐Qiang Tu,

Synthetic Organic Chemistry Methods

A novel and efficient approach toward the assembly of the synthetically challenging tetracyclic [6,5,7,5] core structure of calyciphylline A-type alkaloids is developed. The synthetic route features a tandem semipinacol rearrangement/Nicholas reaction that has been devised strategically to construct the spirocyclic A/B ring and the sterically congested vicinal all-carbon quaternary carbon centers in high diastereoselectivity. Late-stage installation of the hydropyrrole ring and the strained 7-membered ring via a double-reductive amination and ring-closing metathesis, respectively, has also been realized.