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Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions
Published on: July 17, 2020
Total Synthesis and Structural Confirmation of Curcusone I
Yang-Chao Peng1,2, Dong-Yun Lin1, Xuanhao Deng1
1Shenzhen Grubbs Institute, Department of Chemistry, Guangming Advanced Research Institute, Southern University of Science and Technology, Shenzhen518055, China.
None:
The first asymmetric total synthesis of curcusone I, an unusual Euphorbiaceae diterpenoid, has been accomplished, unambiguously confirming its true structure, as previously revised by computational studies. The common [5-7-6] tricyclic core, which is found in rhamnofolane-type curcusones as well as in daphnane and tigliane diterpenes, was efficiently and diastereoselectively assembled via a Rh-catalyzed selenium-involved [2,3]-sigmatropic rearrangement cascade and an additive-controlled SmI2-mediated cyclization. The oxabicyclo[3.2.1]octane framework of curcusone I was successfully constructed by a unique transannular 5-endo-trig oxa-Michael addition. All eight desired stereocenters were installed diastereoselectively.
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