Studies of a Diazo Cyclopropanation Strategy for the Total Synthesis of (−)‐Lundurine A |
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| Authors: | Hong‐Xiu Huang Shuai‐Jiang Jin Jin Gong Dr Dan Zhang Dr Hao Song Prof Yong Qin |
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| Affiliation: | Key Laboratory of Drug Targeting and Drug Delivery Systems of the Ministry of Education, West China School of Pharmacy and State Key Laboratory of Biotherapy, Sichuan University, Chengdu 610041 (P. R. China) |
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| Abstract: | The bioactive Kopsia alkaloids lundurines A–D are the only natural products known to contain indolylcyclopropane. Achieving their syntheses can provide important insights into their biogenesis, as well as novel synthetic routes for complex natural products. Asymmetric total synthesis of (?)‐lundurine A has previously been achieved through a Simmons–Smith cyclopropanation strategy. Here, the total synthesis of (?)‐lundurine A was carried out using a metal‐catalyzed diazo cyclopropanation strategy. In order to avoid a carbene C?H insertion side reaction during cyclopropanation of α‐diazo‐ carboxylates or cyanides, a one‐pot, copper‐catalyzed Bamford–Stevens diazotization/diazo decomposition/cyclopropanation cascade was developed, involving hydrazone. This approach simultaneously generates the C/D/E ring system and the two chiral quaternary centers at C2 and C7. |
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| Keywords: | Bamford– Stevens reaction diazo cyclopropanation Kopsia alkaloid lundurine A total synthesis |
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