Lineatin

The insect pheromone lineatin (21) contains a four-membered ring it also contains an acetal and disconnection of this reveals the carbon skeleton (22). Lineatin analysis... 

Early syntheses of lineatin reconnected the 1,5-di-functionalised part to give structures like (23) so that syntheses by 2 + 2 cycloaddition would ensure the correct stereochemistry. 

The intermediate (19), used on p382-3 in a synthesis of lineatin, is a more surprising ketene product. It can be made on a large scale by the BF catalysed addition of ketene to enone (16). This is presumably not a 2 + 2 cyeloaddition to (17), but an ionic reaction via (18). Synthesis ... 

Linear-variable-differential-transformer (LVDT) transducers, 20 652-653 Linear velocity, exponents of dimensions in absolute, gravitational, and engineering systems, 8 584t Lineatin, 24 473 Line-block coders, 7 691 Line-edge roughness (LER), 15 181 Line exposures, in photography, 19 209-210 Linen... 

Fig. 5.13 Oxidation by RuO,i of an alkane-ester intermediate in the synthesis of -lineatin [85]...

Cycloaddition to a cyclic allyl ether The key step in a synthesis of lineatin (3), the aggregation pheromone of the bark beetle, is the addition of dichloroketene to the alkene 1. Under usual conditions (POCl3, 8,156) the desired adduct is obtained in 7% yield. Fortunately, substitution of 1,2-dimethoxyethane for POCl3 increases the yield of 2 to 50-60%. 

This structure had originally been assigned to lineatin, an aggregation pheromone of the female ambrosia beetle, which has since been shown to have structure 3. The same laboratory has effected synthesis of 3 from 4. Both 1 and 4 were obtained from a common intermediate in the total synthesis. 

The synthesis of lineatin, a pheromone of the insect Trypodendron lineatum, involves the enantioselective addition of methane to the double bond of alkene A in the presence of a chiral rhenium catalyst on silica (Re /silica see Figure 2.19). Michael performed eight separate experiments for this reaction in a 500 mL high-pressure stirred autoclave reactor using liquid methane as a solvent and 0.05 mmol catalyst. The results are shown in Table 2.2. 

Figure 2.19 The methane asymmetric addition step in the synthesis of lineatin.

Borden J. H., Oehlschlager A. C., Chong L., Slessor K. N. and Pierce H. D., Jr, (1980a) Field tests of isomers of lineatin, the aggregation pheromone of Trypodendron lineatum (Coleoptera Scolytidae). Can. Entomol. 112, 107-109. 

Hoover S. E. R., Lindgren B. S., Keeling C. I. and Slessor K. N. (2000) Enantiomer preference of Trypodendron lineatum and the effect of pheromone dose and trap length on response to lineatin-baited traps in interior British Columbia../. Chem. Ecol. 26, 667-677. 

MacConnell J. G., Borden J. H., Silverstein R.M. and Stokkink E. (1977) Isolation and tentative identification of lineatin, a pheromone from the frass of Trypodendron lineatum (Coleoptera Scolytidae). J. Chem. Ecol. 3, 549-561. 

The [2 + 2]-photocycloaddition chemistry of a,(3-unsaturated lactones has been widely explored. The factors governing regio- and simple diastereoselectivity are similar to what has been discussed in enone photochemistry (substrate class Al, Section 6.2). The HT product is the predominant product in the reaction with electron-rich alkenes [84]. A stereogenic center in the y-position of ot,P-unsaturated y-lactones (butenolides) can serve as a valuable control element to achieve facial diastereoselectivity [85, 86]. The selectivity is most pronounced if the lactone is substituted in the a- and/or P-position. The readily available chiral 2(5H)-furanones 79 and 82 have been successfully employed in natural product total syntheses (Scheme 6.30). In both cases, the intermediate photocycloaddition product with 1,2-dichloroethylene was reductively converted into a cyclobutene. In the first reaction sequence, the two-step procedure resulted diastereoselectively (d.r. = 88/12) in product 80, which was separated from the minor diastereoisomer (9%). Direct excitation (Hg lamp, quartz) in acetonitrile solution was superior to sensitized irradiation (Hg lamp, Pyrex) in acetone, the former providing the photocycloaddition products in 89% yield, the latter in only 45%. Cyclobutene 80 was further converted into the monoterpenoid pheromone (+)-lineatin (81) [87]. In the second reaction... 

Racamonde, M., Alibes, R., Figueredo, M., Font, J., and de March, P. (2008) Photochemical cycloaddition of mono-1,1-, and 1,2-disubstituted olefins to a chiral 2(5H)-furanone. Diastereoselective synthesis of (+ (-lineatin. Journal of Organic Chemistry, 73, 5944-5952. 

The synthesis of grandisol(I) and lineatin(II) is discussed. Grandisol is a pheromone component in the cotton boll weevil and in Pissodes weevils. 

The enantiomeric composition of lineatin in Trypodendron lineatum was not determined, but the synthesized (racemic) material was highly active in field tests (13,14). Mori et al. (Scheme 4) (13) and Slessor et al. (Scheme 5) (16) synthesized the lineatin enantiomers and reported similar optical purities, but because different solvents were used, the optical rotations cannot be compared. Since the (+) enantiomer was active in field tests (16), we may assume that it is the naturally occurring enantiomer however the presence of the antipode cannot be ruled out. 

Keto acid V, a known compound, was used for the synthesis of both grandisol and lineatin. The first step of the two step synthesis is an ene reaction (23,24) of isobutylene with maleic... 

Webster and silverstein Grandisol and Lineatin Enantiomers 105 Literature Cited... 

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