Lubimin

The diastereoselectivity observed can be explained by a synclinal transition state, probably influenced by chelation and/or stereoelectronic effects of the developing cation38. The minor product is formed via an antiperiplanar transition state. All compounds obtained are useful precursors for several spirocyclic natural products, such as terpenes like lubimine or acoradi-ene. 

Lubimin, a phytoalexin found in several Solanaceae, has been assigned the spiro-structure (57) on n.m.r. and biosynthetic evidence,83 whilst the new sesquiterpenoid skeleton of taylorione (58) from the liverwort Mylia taylorii is thought84 to be biosynthesized via an aromadendrene-type precursor which may also generate the co-occurring myliol (59). 

A new HPLC technique has been developed for the rapid analysis of sesquiterpene phytoalexins such as capsidiol, rishitin, luminin, and phytuberol. This method employs a cyanopropyl-bonded phase column with an isocratic mixture of hexane and isopropanol. Flame ionization and UV detection were used for the analysis of capsidiol, rishitin, lubimin, phytuberol, and debneyol. Although both detectors proved to be useful, the signal response with the flame ionization detector was proportional to the mass of each of the phytoalexins, while the signal with the UV detector was proportional to the number of carbon—carbon bonds in each of the compounds. 

Thus it has been shown that addition of sodium [ C2]acetate to potato tuber slices, which have been inoculated with Monilinia fructicola or Glomeralla cingulata, provides rishitin (549), lubimin (550), hydroxylubimin (551), 15-dihydrolubimin (552), solavetivone (553), isolubimin (554), 10-epilubimin (555),... 

Katsui et al.,76 isolated two phytoalexins sesquiterpenes lubimin (144) and oxylubimin (145) from white potato tubers (Rishri) infected by an incompatible race of Phytophthora infestans. It has already been mentioned that from white potato tubers also have been isolated sesquiterpene rishitin (40). In the year 1971 Metliskii and coworkers77 isolated lubimin (144) along with rishitin (40) from white potato tubers (S.tuberlosum Lubimets ) stressed with various pathogens. 

These spectral data were indistinguishable from the corresponding data reported by Metliskii and coworkers.77 78 The same structures and configurations for these phytoallexin sesquiterpenes have been reported independently by Stoessl and collaborators.79 80Lubimin and oxylubimin have been synthesized81 by Murai-Masamune and Iwata. As we are writing a review on the synthesis of spiro vetivane sesquiterpenes, the discussions of synthesis of lubimin and oxylubimin have been omitted n this review. 

Jimsonweed - Datura stramonium. Like other Solanaceae, Datura stramonium produces antifungal sesqulterpenold compounds In response to inoculation with Monlllnla fructlcola and several other fungi (Ref. 39). Three of the four phytoalexins thus far identified are also accumulated by other Solanaceous species. Lubimin (2) is also produced both In potato and eggplant, capsldlol (20) is the main phytoalexin in sweet pepper fruit, and hydroxylubimln (5) is also found In potato. The fourth compound 2,3-dihydroxygermacrene, is unique to Datura and could serve as an almost direct precursor of lubimin and 4-hydroxylubimin as well as other Solanaceae phytoalexins (Ref. 39a). 

Vetispiranes (spirovetivanes). A group of sesquiterpenes with the skeleton (1). Important sources include vetiver oil [e.g., /S- vetivone and a-vetispirene (2)], a valuable fragrance substance for the perfume industry, and potatoes (Solanum tuberosum) [e.g., sola-vetivone (3), isolubimin (4), lubimin (5), and hydroxy lubimin (6)]. 

A number of sesquiterpene phytoalexins accumulate in potato (Solanum tuberosum) in response to attack by Monol-inia fruticola, Phytophthora infestans, mdAlternaria solani. Among these are rishitin (32), lubimin (33), phytotuberin (34), and several other sesquiterpenes (Brooks and Watson, 1985 Kuc, 1992). Cell walls of P. infestans contain an elici-tor of ph) oalexin accumulation in potato (Kuc, 1982). Similar phytoalexins are synthesized by a number of other solana-... 

Fig. 2. Biosynthesis of some sesquiterpene phytoalexins. Phytub rin, solavetivone, lubimin, hydroxylu-bimin and rishitin are produced by Phytophthora-iniected potatoes (Soianum tuberosum) and by potato tuber disks treated with Elicitor (see). Capsidiol is a phytoalexin from Capsicum, [P.A.Brindle D.R.Threlfall Biochem. Society Transactions ft (1983) 516-522]...

Further Species. Interestingly, tropane alkaloid accumulating species like Datura stramonium L. or Hyoscyamus albus L. were also found to accumulate major solanaceous phytoalexins such as solavetivone, lubimin, and rishitin as a consequence of an inoculation with fungi (Stoessl et al. 1976 Miguel and Barroso 1994). Eurthermore, 2a,3P-dihydroxygermacrene A (Eig. 7.5) was identified as another stress metabolite in the former species. 

Terpenoid phytoalexins are present in economically important solanaceous plants (Solanaceae). Phytuberin (10-152), lubimin... 

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