Asymmetric Synthesis of Seven-Membered Carbocyclic Rings via a Sequential Oxyanionic 5-Exo-Dig Cyclization/Claisen Rearrangement Process. Total Synthesis of (−)-Frondosin B

Abstract

Appropriately substituted nonracemic allyl alcohols, readily prepared from the corresponding enones by application of the CBS methodology, were converted to optically active cycloheptenone derivatives with almost complete transfer of chirality via an efficient “one-pot”, cycloisomerization/Claisen rearrangement process. This methodology was directly applied to the expedient total synthesis of (−)-frondosin B.

Synthesis of Medicinally Relevant Terpenes: Reducing the Cost and Time of Drug Discovery

“…Trauner’s synthesis also suffered from high step count, but a more reasonable overall yield of 7.3% was obtained [90,91]. More recently, Ovaska published an eight-step racemic synthesis of frondosin B in 2007 and followed up with a ten-step asymmetric synthesis of (-)-frondosin B in 2009 [92,93] .…”

Microwaves in the Synthesis of Natural Products

“…This has generated considerable interest in their total synthesis. Ovaska and co-workers [24][25][26] described the MW-assisted total synthesis of these natural products.…”

Gold‐Catalyzed Cyclopenta‐ and Cycloheptannulation Cascades: A Stereocontrolled Approach to the Scaffold of Frondosins A and B

“…In situ hydrolysis and subsequent equilibration with NaOMe/ MeOH yielded the thermodynamically favored ketone 7 in 68 % yield and more than 90 % ee (Scheme 3). [12] Since this bicyclic enone has been recently elaborated into Frondosins A and B, [20] our approach represents a streamlined formal enantioselective synthesis of both molecules.…”