Pheromones, preparation

Other pheromones prepared using CM include 11 -tetradeceny 1 acetate (Omnivorous Leafroller), 8,10-dodecadienol (Codling Moth), 9-tetradecenyl formate (Diamondback Moth),47 9,11-hexadec-adienal (Pecan Nut Casebearer),48 and 4-tridecenyl acetate (Tomato Pinworm)49... 

The so-called "pheroboa/ "(referring to an aerosol spray) - a pheromone preparation consisting of a mixture of 5a-androst-16-en-3-one and 5a-androst-16-en-3-ol - Is used In veterinary medicine and by pig farmers to stimulate sows prior to artificial Insemination.The pheromone Induces the release of oxytocin, which leads to contraction ofthe Fallopian tube and the uterus, and thereby Increases the conception rate. [12]... 

A further application of this calorimeter was for airbom irritations like attrac-tants, toxic compounds, anaesthetics or allochemicals on individual insects [47]. Larvae of the cabbage looper Trichoplusia ni) were tested against microgram amounts of benzene. They produced a strong, but short exothermic effect because the benzene was washed out by the air stream. A young male of the rootworm Diabrotica longicomis answered with a pronounced exothermic heat output to the exposure to pheromones prepared as extracts from female com rootworms. Moreover, the male moved immediately towards the source of the stimulant. 

Slow release formulations incorporate nonpersistent compounds, eg, methyl parathion, insect growth regulators, and sex pheromones, in a variety of granular, laminated, microencapsulated, and hoUow-ftber preparations. 

Z)-9-Tricosene [(Z)-CH3(CH2)7CH=CH(CH2)i2CH3] is the sex pheromone of the female housefly. Synthetic (Z)-9-tricosene is used as bait to lure male flies to traps that contain insecticide. Using acetylene and alcohols of your choice as starting materials, along with any necessary inorganic reagents, show how you could prepare (Z)-9-tricosene. 

The preparation of the sex pheromone of the bollworm moth, ( )-9,ll-dodecadien-l-yl acetate, from compound A has been described. Suggest suitable reagents for each step in this sequence. 

Construction of the carbon frameworks by using the activating property of the nitro group followed by denitration provides a useful tool for the preparation of various naniral products as shovm in Schemes 3 5-3 7 For example, fZ -jasmone and dihydrojasmone, constinients of the essential oilof jasmone flowers, have been prepared as shown in Scheme 3 5 Schemes 3 6 and 3 7 present a synthesis of pheromones via denitration of ct-nitro ketones " ... 

The Barton-Zard pyrrole synthesis has now been extensively applied to synthesis of naniral and unnaniral products containing pyrrole units Methyl 4-methylpyrrole-3-carboxylate is the trail-maker pheromone of the Texas leaf-aitting ant Arm lexaiia It is readily prepared by the Barton Zard method in 60% yield fEq 10 33 ... 

Gas chromatography (GC) has also been used for preparative purposes, but is restricted to relatively volatile racemates such as anesthetics, pheromones or monoterpenes and, therefore, very few applications are reported. Nevertheless, in the cases to which GC may be applied, it could be considered as an economical alternative to HPLC. Most of the resolutions of enantiomers were performed on cyclodex-trin-derived CSPs [109, 144-153], and only on very few occasions were other chiral selectors used [153]. 

Despite of the disadvantage, that at least one symmetrical dimer is formed as a major side product, mixed Kolbe electrolysis has turned out to be a powerful synthetic method. It enables the efficient synthesis of rare fatty acids, pheromones, chiral building blocks or non proteinogenic amino acids. The starting compounds are either accessible from the large pool of fatty acids or can be easily prepared via the potent methodologies for the construction of carboxylic acids. 

Muscalure 20, the pheromone of the housefly has been prepared from oleic acid or erucic acid, similarly (Z)-l 1-heneicosene 21, the synergist of muscalure was obtained [189]. The intermediate 22 for the pheromone of the Cabbage looper was prepared using (Z)-methyl-4-octenedioate [166bJ, that was obtained by partial ozonolysis of (Z,Z)-l,5-cyclooctadiene. Similarly disparlure 23, the sex attractant of the gypsy moth, has been synthesized by two successive crossed-couplings with (Z)-4-octene dioate [191],... 

The optically active Trogoderma -pheromones ( )- and (Z)-24have been synthesized starting from (5)-citronellol and 4-pentynoic acid [192], Alkatrienes 25, sex attractants of Lepidoptera, were prepared by mixed Kolbe electrolysis with linolenoic acid [193], 26, the pheromone of the German cockroach Blattela Germanica has been prepared from 3-methylheneicosanoic acid [194], ( ) — Tuberculostearic acid (27) has been... 

Two illustrations that show the power of this reaction for the preparation of strained cycloalkenes are the contractions of 102 to the propellane 103 , an application that has been reviewed , and of 104 to the bicyclo[2.1.1]hexene 105 . The utility of the Ramberg-Backlund rearrangement in the preparation of various natural products such as steroids , terpenoids and pheromones has been demonstrated. In addition to the synthetic applications mentioned in the previous subsection, several selected examples taken from the recent literature are given in equations 66-69. These examples further demonstrate the potential of this method for alkene synthesis in general. 

This is the first example of a reaction for which the presence of a chelating ligand was observed to facilitate rather than retard metal-catalysed epoxidation (Gao et al., 1987). It was found that the use of molecular sieves greatly improves this process by removing minute amounts of water present in the reaction medium. Water was found to deactivate the catalyst. All these developments led to an improved catalytic version that allows a five-fold increased substrate concentration relative to the stoichiometric method. Sensitive water-soluble, optically active glycidols can be prepared in an efficient manner by an in situ derivatisation. This epoxidation method appears to be competitive with enzyme-catalysed processes and was applied in 1981 for the commercial production of the gypsy moth pheromone, (-1-) disparlure, used for insect control (Eqn. (25)). 

This procedure has been used with good results to prepare certain long-chain ketones that are precursors of pheromones.204... 

If the alkyne is hydroborated and then protonolyzed a Z-alkene is formed. This method was used to prepare an insect pheromone containing a Z-double bond. 

The substrate-controlled addition of 18 to 19 proceeded with good enantioselec-tivity and was used to prepare the epoxide (+)-dispalure, a gypsy moth pheromone.184... 

In another approach, the alcohol moiety, formed by an enzymatic hydrolysis of an ester, can act as a nucleophile. In their synthesis of pityol (8-37a), a pheromone of the elm bark beetle, Faber and coworkers [17] used an enzyme-triggered reaction of the diastereomeric mixture of ( )-epoxy ester 8-35 employing an immobilized enzyme preparation (Novo SP 409) or whole lyophilized cells of Rhodococcus erythro-polis NCIMB 11540 (Scheme 8.9). As an intermediate, the enantiopure alcohol 8-36 is formed via kinetic resolution as a mixture ofdiastereomers, which leads to the diastereomeric THF derivatives pityol (8-37a) and 8-37b as a separable mixture with a... 

The reduction of nitro ketones with baker s yeast is a good method for the preparation of chiral nitro alcohols.89 The reduction of 5-nitro-2-pentanone with baker s yeast gives the corresponding (5)-alcohol, which is an important chiral building block. Various chiral natural products are prepared from it. In Scheme 7.16, the synthesis of the pheromone of Andrena haemorrhoa is described, where the acylation of the chiral nitro alcohol followed by radical denitration is involved as key steps.89a... 

Pheromone synthesis was thoroughly reviewed in the past. In 1989, synthetic methods useful in preparing optically active pheromones were reviewed by Mori [1]. More comprehensive reviews are also available [2,3]. The present chapter follows the style adopted in Mori s encyclopedic review [3] to classify the pheromones according to the compound types. In comparison to 1229... 

Scheme 7 summarizes the synthesis of (7JR,llS)-7,ll-dimethylheptadecane (1), the female sex pheromone of the spring hemlock looper (Lambdina athasaria) by Mori [ 18]. Enantiopure alkanes are usually synthesized by coupling enantio-pure building blocks derived from natural products or compounds prepared by asymmetric synthesis. Even among hydrocarbons, chirality is very important for pheromone activity, and in this particular case meso-1 was bioactive, while neither (7R,11R)-1 nor (7S,11S)-1 showed bio activity. 

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