Cyathin diterpenoids

Drege, E., Morgant, G. and Desmaele, D. (2005) Asymmetric synthesis of the tricychc core of cyathin diterpenoids via intramolecular Heck reaction. Tetrahedron Lett., 46, 7263-6. 

Cyathin diterpenoid model Intramolecular HR of an alkenyl triflate [460[... 

In 2008, Stoltz and Enquist disclosed a novel approach to the total synthesis of the related cyathin diterpenoid (—)-cyanthiwigin F (119) [80]. They applied a simultaneous alkene RCM and cross metathesis (CM) protocol to achieve the required closure of the seven-membered ring as well as elaboration of the terminal allyl group (Fig. 31). This process was effectively and selectively conducted by treating polyene (120) with Grubbs-Hoveyda catalyst (81) and a vinyl boronate species to produce the desired bicycle (121) in 51% yield. 

Cleomeolide (91) is an unusual bicyclic diterpenoid obtained156 from Cleome viscosa (Capparaceae). The Basidiomycetes contain a number of unusual terpenoid metabolites such as the cyathins. These have now been thoroughly reviewed.157... 

An unusual diterpenoid, cyathin A3 (121). has been isolated from the bird s nest fungus, Cyathus helenae. Its structure, which followed from a careful examination of the n.m.r. spectrum supported by an X-ray analysis, represents a unique cyclization and rearrangement of geranylgeranyl pyrophosphate (122). 

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