title: Stereoselective Total Syntheses of Guanacastepenes N and O.
abstract: Total syntheses of (±)-guanacastepenes N and O were accomplished with 2-cycloheptenone as starting material. The six- and five-membered rings of the core [5, 7, 6] ring skeleton were constructed with an intramolecular Diels-Alder reaction and α-carbonyl radical cyclization. The quaternary centers and their stereochemistry were established with sequential Cu(I)-mediated conjugate additions. A sequence with dihydroxylation, conjugate addition, and β-elimination was devised to incorporate all oxygen functionalities at positions. The total synthesis is adaptable for the synthesis of enantiopure guanacastepenes N and O using chiral intermediate (R)-3-vinyl-2-cycloheptenol obtained from lipase-catalyzed kinetic resolution.
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu 300, Taiwan, ROC.
authors.forename: Shao-Zheng
authors.initials: SZ
authors.lastname: Peng
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu 300, Taiwan, ROC.
authors.forename: Chin-Kang
authors.initials: CK
authors.lastname: Sha