Of -a-eudesmol

Conversion of ekmol to eudesmals. Thermolysis of elemol (1) at 210-220 results in partial isomerization to hedycaryol (2). Addition of a trace of silver nitrate to the thermolysis leads to formation, in addition to (2), of a-eudesmol (3) and -cudcsmol (4), both in about 0.8 % yield. This transformation appears to be the first instance of silver(l) ion-catalyzed transformations involving tc-bonds. 

The protic reaction on occasion is a useful method of alkene formation, but is far from general because the cation intermediate tends to undergo rearrangements.Further, even for cases in which elimination to an alkene is the predominant pathway, the regioselectivity of the process is often mediocre. A key step in the synthesis of (+)-a-eudesmol and (-)-a-selinene exemplifies this point (Scheme 60). There are, however, isolated examples of excellent selectivity, such as the reaction of a 3-ketotetrahydrofuran tosyl-hydrazone salt to give the corresponding cyclic enol ether as the major product (Scheme 61), the intro-... 

FIGURE 20.50 Biotransformation of a-eudesmol (153) and (i-eudesmol (157) by Aspergillus niger and Aspergillus cellulosae. 

Stylotelline (23) is a constituent of a Stylotella sp. collected offshore in New Caledonia. 13C NMR spectra involving 2D NMR techniques provided the bulk of information leading to its structure. The absolute configuration was demonstrated after the tertiary isocyano group was removed to yield the known conjugated diene, ( + )-d-selinene (24). Optical rotation and spectral data of the transformation product were identical in all respects to those of the corresponding product obtained from eudesmols [42], Although neither the isothiocyanato nor the formamido compounds were isolated, the latter was prepared, which allowed an nOe observation between the axial C-3 and the amide protons. 

Quatemization of the resulting tetrahydro-l,3-oxazine (20) and subsequent hydrogenolysis with lithium in liquid ammonia provided the nitrogen-free ( )-5-epi-a-eudesmol. 

The volatiles of fresh leaves, buds, flowers and fruits were isolated by solvent extraction and analysed by capillary gas chromatography-mass spectrometry. Their odour quality was characterized by gas chromatography-olfactometry—mass spectrometry (HRGC-O-MS) and aroma extract dilution analysis (AEDA). In fresh bay leaves, 1,8-cineole was the major component, together with a-terpinyl acetate, sabinene, a-pinene, P-pinene, P-elemene, a-terpineol, linalool and eugenol. Besides 1,8-cineole and the pinenes, the main components in the flowers were a-eudesmol, P-elemene and P-caryophyllene, in the fruits (EJ-P-ocimene and biclyclogermacrene, and... 

Similar strategies were used by Booker-Milburn et al. in approaches toward the synthesis of dictyol C and a-eudesmol [215], and by Blake et al. in approaches toward the synthesis of ophiobolin F and fusicoccin A [216]. 

The protic Bamford-Stevens reaction has been successfully utilized in the asymmetric synthesis of the naturally occurring sesquiterpenes (+)-a-eudesmol and (-)-a-selinene. Here, the more-substituted alkene was formed preferentially (equation 4,1). ... 

This class of compounds may be found in essential oils extracted with both polar solvents and non-polar solvents. The structure of a sesquiterpene alcohol, newly isolated from the oil extracted from the wood of Amyris balsamifera (Rutaceae), has been reported [76]. These investigators either identified by GC-MS or isolated a total of 23 sesquiterpenoids, including valerianol (23) (21.5% of oil), 1-epi-a-eudesmol (24) (10.7%), 10-e/ i -y-eudesmol (25) (9.7%), elemol (26) (9.1%), P-eudesmol (27) (7.9%), y-eudesmol (28) (6.6%), a-eudesmol (29) (4.8%) and P-sesquiphellandrene (30) (4.7%) as the major constituents. 7-... 

Three agaroflirans (85-87) and P-eudesmol (88) were isolated from the petroleum ether-soluble fraction of the methanolic extract of the fresh rhizomes of A. japonica [63]. It is biogenetically interesting that P-eudesmol was present in the same plant with agaroflirans which possess a 10-epieudesmol skeleton. From the rhizomes of A. japonica, three eudesmane-type sesquiterpenes, 10-ep/-5P-hydroperoxy-p-eudesmol (89), 10-e /-5a-hydroperoxy-P-eudesmol (90) and 4,10-e/ /-5P-hydroxydihydroeudesmol (91) were isolated and their structure were determined by spectroscopic methods and chemical conversions [64]. Compounds 89-91 are considered to be biosynthesized from lO-ep/ -y-eudesmol (92), which was a possible precursor of agarofuran-type... 

Figure 1. Structures of hop oil components. Key I, humulene II, humulene epoxide I III, humulene epoxide II IV, humulol V, humulenol II VI, humula-dienone VII, a-eudesmol VIII, -eudesmol IX, hop ether X, karahana ether XI, p-ionone and XII, j3-damascenone.

The dried stem bark material of Magnolia obovata (Magnoliaceae) is known as Koh-boku. It is an important crude drug in Kampo medicine, used for the treatment of stomach ache and rush of the blood to the head, etc. From this crude drug, magnocurarine, classified as a benzylisoquinoline alkaloid, was isolated [9], in addition to sesquiterpenoids, such as a-eudesmol, and phenylpropanoids, such as magnolol. 

The stereoisomeric farnesols have been similarly investigated [300]. These possess juvenile hormone activity [225, 226] and could be detected thin-layer chromatographically as the sexual attractant of the male bumble bee [269, 270]. The chromatography was carried out with benzene-ethyl acetate (95 + 5) on silica gel V- and szial gel 47-layers (Firm 114) [303, 309]. The trans4rans-ia,mesol (hi / 27) then lay below the as- mns-farnesol (hi / 36). This sequence remains also when pure benzene is used for development [304] and is observed with the farnesol esters too [307—309]. Seikel and Rowe [237] have studied the TLC of the eudesmols. They separated milligram amounts of a- and p-eudesmol with benzene-petroleum ether (50 + 50) on alumina layers, 500 (xm thick. The use of ascending technique is said to augment the differences in the hi /-values. 

Only a few volatile sesquiterpenes presenting important central activities are currently known. P-Eudesmol (34) was found to be one of the volatile active principles of the Chinese medicinal herb Atractylodes lancea DC. (Asteraceae) with alleged antagonist properties useful in intoxication by anticholinesterase agents of the organophosphorous type (Chiou et al., 1997). Experimental data show that P-eudesmol (34) prevents convulsions and lethality induced by electroshock but not those induced by PTZ or picrotoxin (Chiou et al., 1995). With a very similar chemical structure, a-eudesmol (35) protects the development of postischemic brain injnry in rats by blocking tS-Aga-IVA-sensitive Ca + channels (Asakura et al., 2000). 

Maatooq, G.A., 2002a. Microbial transformation of a P- and y-eudesmols mixture. Z Naturforsch., 57C 654-659. 

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