Pheromone endo brevicomin

The addition of diorganozinc reagents to a-alkoxyaldehydes furnishes selectively protected 1,2-diols.19 Applications toward the synthesis of pheromones like (-)-exo- and (-)-endo-brevicomin 2 and 3 exploits the catalytic nature of the stereochemical induction, e.g. the newly formed chiral centre depends only on the configuration of the chiral catalyst 1. 

Recently in 2005, we synthesized 10 g of (+)-endo-brevicomin, the minor component of the pheromone of the male southern pine beetle, Dmdroctonus frontalis [22-24]. We used lipase AK in this synthesis to desymmetrize the prochiral diol. Dr. B. T. Sullivan at the U.S. Forest Service is currently studying the practicality of the pheromone traps with a mixture of (+)-endo-brevicomin, frontaKn and a-pinene. 

When MBH adducts 169 are heated in a high-boiling aromatic hydrocarbon, they undergo an intermolecular dehydrative double cyclization to produce functionalized 6,8-dioxabicyclo[3.2.1]octanes 171 (Scheme 3.68), which are often present as the basic framework in several pheromones, e.g. frontalin, exo-and endo-brevicomins, ot-multistriatin, However, the stereoselectivity in... 

An illustrative example for the strength of this methodology was reported by Kim et al. who used an enamine-catalyzed a-oxidation in the synthesis of the bark beetle pheromones (+)-exo- and (-)-enrfo-brevicomin (124) (111). The asymmetric proline-catalyzed a-hydroxylation of butyraldehyde (125) with 123 gave the crude anilinooxy compound 126 in excellent enantioselectivity (>98%). Compound 126 was used directly further to give (+)-exo- and (-)-endo-brevicomin (124) in just three more steps (Scheme 29) (111). 

As an alternative to baker s yeast, the use of plant tissues (e.g., from apple, carrot, cucumber, onion, or potato) has been suggested [112,113]. It remains unclear, however, whether endophytic microorganisms are involved in these reductions [114]. Heterocyclic ketones [111, 115-117] as well as many a-hydroxy ketones [96,118-121] have been the subject of yeast-mediated reductions. For the latter compounds very high ee values have been obtained, albeit the yields were moderate. Monobenylated (S)-l,n-diols have been prepared using highly diluted yeast suspensions, and ee values up to 95% could be achieved [122]. Yeast-mediated reductions of acyclic ketones were key steps in the total synthesis of the pheromone sulcatol [123], brefeldin A [124], and endo-brevicomin [125]. 

Erythritol-derived diol 8 was acetylated with vinyl acetate and lipase AK (Amano) to give (2S,3R)-9 (Figure 24.5) [8]. This half-acetate 9 was converted to (+)-endo-brevicomin, a male-produced component of the southern pine beetle pheromone. 

The frass of females of the western pine beetle Dendroctonus brevicomis is enriched with endo- (XIX) and exo-7-ethyl-5-methyl-6,8-dfoxabicyclot3.2.1]octane (XX), which are assigned the trivial epithets endo- and exo-brevicomin (61). Males of 2 brevicomis synthesize 1,5-dimethyl-6,8-dioxabicyclo[3.2.1]octane (frontalin) (XXI) in their hind guts (62), and this compound, in combination with the brevicomins and host-derived myrcene, constitutes a potent attractant for both sexes of J). brevicomis (63). Frontal in, also produced by females of . frontalis (62T7 is reported to function as a powerful aggregative pheromone when combined with host monoterpenes such as a-pinene (64). J). pseudotsugae... 

The consecutive addition of alkyl halide to activated olefins by photoelectrocatalysis (PEC) of hydroxocobalamin hydrochloride allows the construction of extended carbon chains as shown for the synthesis of pheromone queen substance 9. The mild conditions of the B12/PEC reaction are suited for the addition of primary alkyl halides 10 containing a potential leaving group. This is illustrated in the synthesis of endo- and exo-brevicomin (11) (Scheme 4). 

The addition of an allylic group was reported in the synthesis of heneicos-6-en-ll-one, the sex pheromone of the Douglas fir tussock moth (Fig. 55)P Short syntheses of frontalin and endo and exo-brevicomin are based on this principle.292 Several authors compared this method to the classical process using the toxic tin hydrides. Thus, adamantane derivatives were prepared from 1-adamantyl iodide and a,p-unsaturated carbonyl compounds in better yields than by the tin hydride method.293... 

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