title: Total Synthesis of Atisane-Type Diterpenoids: Application of Diels-Alder Cycloadditions of Podocarpane-Type Unmasked ortho-Benzoquinones.
abstract: Few examples of [4 + 2] cycloaddition with unmasked ortho-benzoquinones (UMOBs) as carbodiene have been reported in complex molecule synthesis. Herein we report that this cycloaddition with podocarpane-type UMOB was developed and applied to construct fully functionalized bicyclo[2.2.2]octanes. Based on this methodology, divergent total syntheses of atisane-type diterpenoids, including (±)-crotobarin, crotogoudin, atisane-3β,16α-diol, and 16S,17-dihydroxy-atisan-3-one, were accomplished in 14, 14, 12, and 16 steps, respectively. Key elements in these total syntheses include: (1) FeCl3-catalyzed cationic cascade cyclization to construct podocarpane-type skeleton; (2) Mn(III)/Co(II)-catalyzed radical hydroxylation of alkene with high regio-, diastereo-, and chemoselectivities; (3) and a ketal-deprotection/lactone-opening/deprotonation/lactonization cascade. Additionally, the synthetic utility of the fully functionalized bicyclo[2.2.2]octane framework was further elucidated by applying ring distortion strategy to afford different skeleton-rearranged natural product-like compounds.
authors.affiliation: Key Laboratory of Green Chemistry & Technology of the Ministry of Education, College of Chemistry, Sichuan University , Chengdu, Sichuan 610064, China.
authors.forename: Liqiang
authors.initials: L
authors.lastname: Song
authors.affiliation: Key Laboratory of Green Chemistry & Technology of the Ministry of Education, College of Chemistry, Sichuan University , Chengdu, Sichuan 610064, China.
authors.forename: Guili
authors.initials: G
authors.lastname: Zhu
authors.affiliation: Key Laboratory of Green Chemistry & Technology of the Ministry of Education, College of Chemistry, Sichuan University , Chengdu, Sichuan 610064, China.
authors.forename: Yongjiang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Key Laboratory of Green Chemistry & Technology of the Ministry of Education, College of Chemistry, Sichuan University , Chengdu, Sichuan 610064, China.|State Key Laboratory of Natural Medicines, China Pharmaceutical University , Nanjing 210009, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Liu
authors.affiliation: Key Laboratory of Green Chemistry & Technology of the Ministry of Education, College of Chemistry, Sichuan University , Chengdu, Sichuan 610064, China.
authors.forename: Song
authors.initials: S
authors.lastname: Qin