Hirsutane synthesis

Diels-Alder reaction. The Diels-Alder reaction of 1 with 2 provides a key step in a total synthesis of alternative mode, the less stable trans-fusion ol the bicyclopcntanc system is formed. The product is converted in two steps into... 

The suggested intermediacy of hirsutene (239) in the biosynthesis of the hirsutane sesquiterpenoids has been supported by its recent isolation from Coriolus consors. In addition an alternative synthesis of this compound has been accomplished by the route outlined in Scheme 26. 

Full details of the total synthesis of the more complex hirsutane sesquiterpenoids coriolin (410) and coriolin B (411) have been published.198 Another route to hirsutic... 

A representative example for n = 1 is the synthesis of the hirsutane carbon skeleton130. Irradiation of the dicyclopentenylmethane 2 in methanol led to the cis-syn-cis tricyclo[6.3.0.02 6]-undecanone derivative 4. The reaction is presumed to proceed via the highly strained head-to-head adduct 3, this implies the intermediacy of a 1,4-diradical of type B. The intermediate 3 rearranges rapidly via a nucleophilic ring opening by the solvent. 

Fused Five-membered Rings.—Structures based on the linear fusion of three five-membered rings are easily synthesized by intramolecular photocyclizations of dicyclopent-l-enylmethanes [viz. (75)], followed by in situ addition of methanol to the presumed intermediate bicyclo[2,l,0]pentanes (76) the general method has been applied in a synthesis of the hirsutane carbon skeleton (77) found in hirsutic acid and related natural sesquiterpenoids. 

Photochemical oxa-di-jt-methane rearrangement of bicyclo[3.2.1]octa-noid scaffolds affords multifunctional, donor-acceptor cyclopropanes (34). Application of this reaction to bicyclo[2.2.2]octenones has been used as a key step in the total synthesis the hirsutane-type sesquiterpenes (-)-connatusin A (35), (+)-connatusin B (36), and the marine sesquiterpenoid 2-isocyanoallopupukeanane (37). ... 

Bon DJYD, Banwell MG, Cade lA et al (2011) The total synthesis of (—)-connatusin A, a hirsutane-type sesquiterpene isolated from the fungus Lentinus connatus BCC8996. Tetrahedron 67 8348-8352... 

Most of the trends which were apparent in previous years have continued to manifest themselves. The feverish activity directed towards the synthesis of the hirsutane class of sesquiterpenes has not abated and other natural products containing annulated cyclopentane rings have also proved popular synthetic targets. In the field of steroid synthesis. Stork and his co-workers have developed an outstandingly elegant approach to 11-oxygenated steroids. 

Four syntheses of the related sesquiterpene, modhephene (9) have also been reported. " One of these also proceeds via a [2 + 2]photocycloaddition route to give (7) followed by an acid-catalysed Cargill rearrangement to (8), which was converted to modhephene (9) by conventional methods. The bulk of the work in this area continues to be directed at the synthesis of sesquiterpenes of the hirsutane group. Details have appeared of the previously reported synthesis... 

Another member of the hirsutane family of sesquiterpenes, coriolin (65), which is a metabolite of Coriolus consor, has yielded to total synthesis. Key steps in the approach to coriolin by Danishefsky et al. include the conversion of (61) into (63) via the Diels-Alder adduct (62), and introduction of the hydroxyl group into ring B by deconjugation of the enone (64) followed by epoxidation of the isolated double bond (Scheme 10). 

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