Acoradienes

A substituent placed in the side chain may also cause asymmetric induction. This has been utilized in a total synthesis of acoradiene, in which 3-[l,5-dimethyl-6-(trimethylsilyl)-4-hex-... 

P-acoradiene [295]. These compounds were seen in all other trees but apparently at significantly different quantitative levels. For structures 286-298 see Fig. 3.13. 

The aggregation pheromone of the broad-horned flour beetle (Gnatocerus cornutus) was reported to be (lJR,4i, 5S)-(+)-acoradiene (33) by Tebayashi et al. [72]. Scheme 47 shows Mori s synthesis of (lRy4Ry5S)-33 [73]. The key-step was the ring-closing olefin metathesis of A to give B. An X-ray analysis of C confirmed the structure shown. The product (lJR,4JR,5S)-33, however, was different... 

While the pheromones of Tenebrio and Tribolium originate from a mixed biosynthesis, those produced by males of the broad horned flour beetle, Gnatho-cerus cornutus, represent true terpenes. Initially, the configuration of this new pheromone had been erroneously proposed to be (IR,4R,5S) a-acoradiene [325] however, independent syntheses of pure stereoisomers [326,327] proved the correct structure to show (lS,4A,5A)-configuration 165. The scope of the synthesis is shown by Mori (see chapter by Mori in volume 1 and [15]). A minor component of the G. cornutus was reported to be a-cedren-14-al 166 [328]. 

There are other examples of volatile hydrocarbon pheromones in beetles that have been researched less extensively. One of these is from the broad-homed flour beetle, Gnatocerus cornutus (F.) (Coleoptera Tenebrionidae), a common stored-product pest. Tebayashi et al. (1998) found that males produce at least one compound that was attractive to both sexes in laboratory bioassays and at sub-nanogram levels. The compound was identified as the sesquiterpene (+)-acoradiene. The beetle-derived enantiomer was subsequently synthesized... 

Tashiro, T., Kurosawa, S. and Mori, K. (2004). Revision of the structure of the major aggregation pheromone of the broad-homed flourbeetle (Gnatocerus comutus) to (lS,4R,5R)-a-acoradiene by its synthesis. Biosci. Biotechnol. Biochem., 68,663-670. 

However, the composition of the volatile oil obtained from the herb also differs markedly from that of the seeds. Eleven components out of 21 are similar in both herb and seed oils, while some differences have been observed between the relative amounts of /J-pinene, a-terpinene, p-cymene, a-terpineol, perilla aldehyde, thymol, a-cis-bergamotene, acoradiene and... 

Application of microelements spray increased the main constituents, such as cumin aldehyde, p-cymene, a-terpineol, thymol and acoradiene. On the other hand, spraying the cumin plant with microelements decreased other constituents, especially /Tpinene. No marked differences between the relative percentages of the minor constituents of cumin herb oil, due to application of trace element treatments, were observed. However, for seed oil, an increase in cumin aldehyde, acoradiene and... 

The identification of acoradiene (58) as a minor by-product in the conversion of carotol (56) into daucene (57) has shown32 that the absolute configuration of this compound is enantiomeric to that previously assigned. Stereoselective routes from... 

R-pulegone (59) to y-acoradiene (63), 5-acoradiene (65), and the enantiomers (67) and (68) of acorone and isoacorone have been described (Scheme 12).33 An interesting feature of the synthetic sequence is the use of stannic chloride to improve... 

IR,4R,5S)- acoradiene Broad-hfirned Hour beelie G/Jaiocetvs cornufiLs) A Grubbs Olefin methatesis [1571... 

Further studies cf. Vol. 6, p. 61) on the formic acid-catalysed conversion of carotol (101) into daucene (102) and acoradienes (103) have shown that prolonged exposure to 90% HCO2H results in the disappearance of (102) and (103) and the formation of a mixture of at least five compounds. Two of these compounds have been identified... 

Prezizaene (119) and the related tricyclic sesquiterpenoids (120)—(122) have been isolated from Eremophila georgii. The absolute stereochemistry of these compounds is antipodal to that of the zizaene sesquiterpenoids found in vetiver oil cf. Vol. 3, p. 123 Vol. 4, pp. 94—96) and their biosynthesis probably involves cyclization of 8-acoradiene (115) and rearrangement of the intermediate allocedryl (116) or cedryl (117) carbonium ions or their biological equivalents cf. Scheme 14). ... 

Two sesquiterpenes, y- and 5-acoradiene (118 and 119), were synthesized efficiently using an electrochemical method as a key step. The readily available 4-substituted phenol 120 was submitted to constant current electrolysis in 2 1 MeOH-THF to afford three spiro compounds (121, 122 and 123) in 43% yield (relative ratio 121/122/123 = 1 2 1). All of them were readily converted to both 118 and 119. However, the use of only THF as a solvent provided the corresponding dimer 124 in 80% yield 5 (Scheme 22). 

Acoradienes, electrosynthesis of 1177 Acourtia isocedrene, retrosynthetic pathways toward 1185, 1188 Acrylophenones, formation of 631 Acylation, of phenols 629-632, 933, 934 fluorescent labels for 951 C-Acylation 685, 686 O-Acylation,... 

Previously it had been shown that low temperature irradiation of the enone (168) gave the tricyclic ketone (169) as the major product. It has now been reported99 that further photolysis of (169) at 0—5 °C promotes a Norrish type II process to give the ketone (170) which can be converted into a-acoradiene (171). Epimerization of the isopropenyl group in (170) can be achieved by silver nitrate, thus paving the way for a synthesis of acorenone B (172). Pertinent to these results is the finding... 

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