Guaiane

Two total syntheses of racemic bulnesol (349) have now been reported. In a consideration of the stereochemical features incorporated in the bicyclo[5,3,0]- 

In another approach to the guaiane skeleton. Piers and Cheng prepared the enone (355) by photolysis of the known dienone (354). A scheme involving eight steps was used to convert (355) to a-bulnesene (356), the dehydration product of bulnesol. 

Guaioxide (357, R = -Me) and liguloxide (357, R = a-Me) have been shown to be epimeric at C-4 and the chemistry of these and related compounds has been fully described. 

Kato et have synthesised kessane (359) in 30% yield by solvolysis of the mesylate (358) cf. solvolysis of (352) above]. 

Ourisson and co-workers have published full details of the isolation and structural elucidation of both y-gurjenene (360) and seychellene (361, R = Seychellene, which can formally be derived from patchouli alcohol (362) by a 

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A group of guaiane diterpenoids including dictyol B acetate (149) and dictyotadiol... 

These compounds range through monocyclic (with a bisabolane framework), bicyclic (with an eudesmane, amorphane, axane, guaiane, isodaucane, or gorgonane framework), tricyclic (with an aromadendrane, cubenane, maaliane, pupukeanane, or trachyopsane framework), and spiro[4,5]decane carbon skeletons. 

The Chinese Eupatorium chinense has afforded ten new sesquiterpenoids, three of which are chlorinated, eupachinilides C (263), E (264), and F (265) (518). The Chinese medicinal plant Eupatorium lindleyanum contains the chlorinated guaianes eupalinilides A (266), D (267), E (268), and H (269), amongst other non-chlori-nated eupalinilides and nine known sesquiterpenoids (579). The Oregon coastal perennial plant Artemisia suksdorfii contains four novel chlorinated sesquiterpene lactones 270-273 520). 

Rodriguez, A. D. and Boulanger, A., New guaiane metabolites from the Caribbean gorgonian coral, Pseudopterogorgia americana, J. Nat. Prod., 60, 207, 1997. 

What, then, about the cyclobutylcarbinyl radical Eq. 3.108 shows the treatment of tricyclic cyclobutylmethyl iodide (268) with Bu3SnH in the presence of AIBN in refluxing benzene solution to generate bicyclic exo-methylene compound (269), via 13-cleavage of the cyclobutylcarbinyl radical. This bicyclic exo-methylene (269) is the skeleton of a terpenoide natural product, guaiane alismol [277-280]. 

A continuing investigation of sweet flag oil [Acorns calamus) has resulted in the isolation and identification of calamusenone (573) and its isomer (574) together with the unusual trisnor-sesquiterpenoid (575). Two other simple guaiane sesquiterpenoids are (576) and (577), isolated from Athanasia dregeana (DC.). ... 

New guaian-6a,12-olides are listed in Table while others are illus-... 

A rather different approach to the hydroazulenic synthesis has been adopted by Hendrickson and Boeckman. Treatment of 1-cyclopentenylcarboxalde-hyde (411) with the pyrrolidine enamine of cyclopentanone (412) yielded the thermodynamically most stable adduct (413) which, on quaternization and base-induced fragmentation, gave the acid (414) in 25% yield. Furthermore, the acid (414) has been converted into the epoxide (415) and the (5-lactone (416), both of which are potential synthetic precursors of guaiane-type sesquiterpenoids, e.g. pseudoguaianolides. 

Drimane, farnesane, glutinopallane, protoilludane, isolactarane, and guaiane sesquiterpenes have been isolated so far in a few Lactarius species therefore, they may be considered chemotaxonomic markers. By contrast, large quantities of marasmane, lactarane and secolactarane metabolites occur in almost all Sections, as reported in Table 24. 

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