Total Synthesis of Diterpenoid Steenkrotin A

• Published in: Angewandte Chemie International Edition 2015-06, Vol.54 (23), p.6905-6908
• Main Authors: Pan, Saiyong, Xuan, Jun, Gao, Beiling, Zhu, An, Ding, Hanfeng
• Format: Article
• Language: English
• Subjects: aldol reaction; carbenoids; Diterpenes - chemical synthesis; Diterpenes - chemistry; Models, Molecular; Molecular Conformation; natural products; radical reactions; Stereoisomerism; total synthesis
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201502034

A concise and diastereoselective total synthesis of the diterpenoid (±)‐steenkrotin A is described for the first time. The strategy mainly features three key ring formations: 1) a rhodium‐catalyzed OH bond insertion followed by an intramolecular carbonyl‐ene reaction to build up the tetrahydrofuran subunit; 2) sequential SmI2‐mediated Ueno–Stork and ketyl–olefin cyclizations to construct the [5,7] spirobicyclic skeleton; and 3) an intramolecular aldol condensation/vinylogous retro‐aldol/aldol sequence to form the final six‐membered ring with inversion of the relative configuration at the C7 position. Work of steen: A concise and diastereoselective total synthesis of the diterpenoid (±)‐steenkrotin A is reported for the first time. The key features of the strategy are based on a rhodium‐catalyzed OH bond insertion, an intramolecular carbonyl‐ene reaction, sequential SmI2‐mediated Ueno–Stork and ketyl–olefin cyclizations, and a cascade intramolecular aldol condensation/vinylogous retro‐aldol/aldol process.