Eremophilane

This reaction was used to prepare an intermediate suitable for synthesis of the sesquiterpenes a- and p-eremophilane and related structures.306... 

The position of the functional groups along the eremophilane core was confirmed by an HMBC experiment. In particular, the correlations C-lO/OH-1, H-6, H-9 C-8/H-9, H-6, H-13 C-2/OH-1, H-4 and C-12/H-13 were consistent with the disposition of the ketone, hydroxyl and lactone functionalities. 

Kingston DGI, Rao MM, Spittler TD, Isolation and structure determination of fluorensic acid, a new sesquiterpene of the eremophilane type. Tetrahedron Lett... 

Sesquiterpenoids isolated form Pluchea indie, Hibiscus tiliaceus, and Thespesia populnea were given full attention. Most sesquiterpenoids isolated form Pluchea indie were eudesmane and eremophilane diterpenoid skeleton, For example, the compounds were depicted in Figure 4. 

This Sakurai reaction has been used for a stereoselective synthesis of nootkatone (2),4 an eremophilane sesquiterpene. Thus the trienone 1 cyclizes to 2 at 0° in the presence of C2H5A1C12 in 50% yield. TiCl4 and BF3 0(C2H5)2 are less effective catalysts (28% and 23% yields of 2). 

Haring, H. G. Rijkens, F. Boelens, H. van der Gen, A. Olfactory studies on enantiomeric eremophilane sesqui-terpenoids. J. Agric. Food Chem., 1972, 20, 1017-1020. 

Figure 10.8 Famesyl diphosphate (FPP) can be cyclized in many different ways by sesquiterpene synthases giving rise to different classes of sesquiterpenes. The eremophilane class of sesquiterpenes has received considerable attention because the genes coding for the corresponding synthase enzymes were the first to be isolated. 25...

Figure 10.9 Each class of sesquiterpenes (see Fig. 10.8) consists of many structural variants that arise from stereochemical positioning of methyl groups and sites of double bond formation. Depicted are the possible variants within the eremophilane class of sesquiterpenes, which are hypothesized to arise from an equally related class of sesquiterpene synthases. Only those structural derivatives that have been found in nature or synthesized are denoted by name. The remaining structures should, therefore, be considered novel.

A second stereoselective total synthesis of ( )-eremophilone (243) has been accomplished using 7-epinootkatone (242) as intermediate.109 The latter compound was synthesized from (—)-/3-pinene (241) by modification of the published procedure"0 and subsequently converted into eremophilone (243) by the series of functional-group transformations shown in Scheme 30. A mycotoxin isolated from Penicillium roqueforti has been assigned the highly oxygenated eremophilane structure (244) on the basis of chemical and spectroscopic evidence."1 The structure and... 

Eremoohllanes. Many eremophilanes have been Isolated from fungi. 

The isolation and identification of new eremophilane sesquiterpenoids from various plant species continues to be an active area of research. For the sake of simplicity new furanoeremophilanes are shown in Table 89 Other new eremophilane sesquiterpenoids include (518)—(532). A number of other eremophilanes have been isolated from various South African... 

Both (+)-nootkatone (566) and its (+)-4-isomer (565) have been synthesized from (+)-nopinone (564) (Scheme 69). ° On the other hand, Hiyama et have used a completely different approach for the synthesis of nootkatone (566) (Scheme 70) which involves as a key step the acid-induced cyclopentenone annulation. In an alternative route to eremophilane and valencane sesquiterpenes, NM et have used a stereoselective intramolecular Diels-Alder... 

In their synthesis of fukinone, Marshall and Cohen converted the known ene-ol (340) into (341) by acetylation, allylic oxidation, and conjugate methylation with dimethylcopperlithium. A Wolff-Kishner reduction of (341) followed by oxidation of the resultant alcohol and enol-acetylation yielded (342). The epoxide of (342) was thermolysed to give (343) which, on reaction with iso-propenyl-lithium and selective oxidation, gave the ketol (344) which was converted in two steps into fukinone (335). A number of sesquiterpenoids, e.g. fukinanolide (345), with the rearranged eremophilane skeleton viz. fukinane (346 R = Me) are known. Nay a and Kobayashi have now prepared this parent hydrocarbon by Raney nickel reduction of the thioacetal of fukinan-8-al (346 R = CHO). 

Some new eremophilane sesquiterpenoids have been identified. These include flourensic acid (351), petasalbin methyl ether (352), " furanofukinol (353 ... 

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