Concise Synthetic Approaches for the Laurencia Family: Formal Total Syntheses of (±)-Laurefucin and (±)-E- and (±)-Z-Pinnatifidenyne

摘要

Herein is presented a cohesive strategy to rapidly fashion diverse members of the lauroxocane family of natural products, leading to the shortest syntheses of any member to date. These efforts include racemic formal total syntheses of laurefucin and E- and Z-pinnatifidenyne as well as a facile preparation of the oxocene core of 3E-dehydrobro- molaurefucin. The key elements of the design are novel diastereoselective ring-expanding bromoetherifications of tetrahydrofurans triggered by a unique bromonium source (BDSB, Et_2SBr·SbBrCl_5) and strategically positioned nucleophilic traps, where altering the identity and position of these traps affords diverse functionality on the eight-membered ring backbone. Its biogenetic relevance is also discussed in light of the range of substrates that successfully undergo this key rearrangement.