Triquinane framework

It should be noted that this strategy could also be utilized to build up the linear triquinane framework 3-257 in 45% yield, employing the 11-membered ring system 3-256 in which the BMDMS group is simply moved from one to the other side of alkyne moiety as compared to 3-252 (Scheme 3.66) [105],... 

A third strategy was proposed by Saicic [14] and us [15] in order to functionalize more elaborate triquinane frameworks. The key step is a radical [3-1-2] condensation between a homoallylic radical and a Michael acceptor such as acrylonitrile. Using the bromomethyldimethylsilyl (BMDMS) ether of a propargyl alcohol (precursor... 

Oxa-di-7C-methane Reactions in Polycyclic-Bridged P,y-Enones Leading to the Linear Triquinane Framework ... 

The aforementioned examples of ewdo-annulated bicyclo[2.2.2]octenones led to photoproducts containing a linear c/s a ti ds-triquinane framework. The stereochemical feature of the photoproducts in these examples is a direct consequence of stereoselectivity in the ODPM reaction and the orientation of the annulated ring. It is interesting to note that the sensitized irradiation of compound 198 with an exo-annulated five-membered ring gave the tetracychc compound 199 containing a folded cis syn cis-triquinane ring system (Scheme 37). ... 

Hirsutene (1) and A9(,2,-capnellcnc (2), the parent members of the hirsutane and capnellane families of triquinane natural products, respectively, are isomeric molecules that possess four contiguous stereogenic centers, one of which is quaternary. The linearly fused tricyclopentanoid frameworks of compounds 1 and 2 are obviously very similar, differing only with respect to the positions of the three methyl groups. An asset of Curran s tandem radical cyclization strategy is that it provides a unified entry into a wide variety of linear condensed cyclopentanoid natural products. As a result, it is possible to devise nearly identical retrosynthetic pathways for these structurally related molecules. 

The versatile applicability of this photocyclization concept was demonstrated through the synthesis of important structural frameworks as for example triquinanes [49a] or furanosides [49b], respectively. 

Photochemical transformations of bicyclo[2.2.2]octenones derived from Diels-Alder reaction of spiroepoxycyclohexa-2,4-dienones 116 have been exploited by Singh s group in their synthetic studies towards triquinane 119 and oxa-triquinane 121, protoilludane 120, and oxa-sterpurane 122 frameworks (Figure 30) [120, 154]. Spiroepoxycyclohexa-2,4-... 

The potential of sequential radical addition as a powerful method to achieve the formation of five-membered rings was fully realized in the tandem radical cyclization strategy devised by Curran for the synthesis of triquinanes. In the case of linearly fused triquinanes, such as hirsutene 90 (Scheme 3.40), this strategy implies the retrosynthetic disconnection of the tricyclic framework by the application of two sequential radical cyclization transforms at rings A and... 

Triquinanes rank among the most important natural carbon frameworks [12, 19], Angular- and linear-fused carbon skeletons possess three five-membered rings which share one or two carbon-carbon bonds, respectively. Natural products from a wide array of biological sources produce these compounds with a considerable range of functionality. A new radical anion tandem process to prepare two triquinane skeletons, linear and angular, was initiated by the radical anion of strained ring systems... 

Triquinanes 137 serve as good examples of a challenging framework in natural product synthesis [53]. In 2012, a domino radical cyclization to give vinylogous carbonates and carbamates was developed by Gharpure and coworkers [54], which involves an unprecedented, highly stereoselective formation of heterocyclic rings (Scheme 5.28). 

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