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DOI: 10.1055/s-0034-1378588
Total Synthesis of (–)-Nitidasin
Publication History
Publication Date:
18 August 2014 (online)
Significance
(–)-Nitidasin is a sesterterpenoid isolated in 1999 from the Peruvian folk medicine plant Gentianella alborosea. Structurally, the molecule is characterized by a tetracyclic 5-8-6-5 carbon framework bearing a tetrasubstituted epoxide. Trauner and co-workers present the first total synthesis of this natural product. Their convergent strategy relies on a highly diastereoselective addition of the organolithium derived from vinyliodide F to ketone C.
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Comment
The synthesis of C proceeds with high overall yield from known ketone A. The choice of (–)-citronellene as the starting material allows for an asymmetric entry to iodide F. Lithium–halogen exchange with t-BuLi and subsequent addition to ketone C gave the desired adduct along with only 7% of the undesired product. Directed epoxidation of the allylic alcohol gave epoxide G in 71% as a single diastereomer. The medium-sized ring was generated by ring-closing metathesis. Deprotection followed by reduction of the endocyclic olefin gave diol J, which was oxidized under Ley conditions to give the target compound (–)-nitidasin.
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