Pyrethrin, insecticides

STAHL, for instance, was able to demonstrate that on irradiation with long-wavelength UV light the naturally occurring contact insecticides pyrethrin I and II, cinerin I and II and jasmolin I and II present in Chrysanthemum cinerariifolium are converted to inactive pyrethrin oxides by the incorporation of oxygen [7]. 

Pyrethrin and pyrethroid insecticides Pyrethrin I, IP, fenvalerate, permethrin... 

Pyrethroids are based on mimicking the structure of the natural insecticide pyrethrin. Pyrethins are found in the flowers of chrysanthemums. Ground flowers were traditionally used to obtain pyrethin insecticides and used to kill lice in the early 1800s. Synthetic pyrethins were first produced in the early 1970s. The exact nature of how pyrethroids work is unknown, but because they paralyze insects it is speculated that they affect the nervous or muscular system. Pyrethroids are effective in low dosages and are nonpersistent. 

Traditional insecticides were derived from plants. Key amongst them are nicotine and rotenone. Increasing interest is being shown in azadirachtin from the neem tree. The classical natural insecticide pyrethrin is derived from the flowers of Pyrethrum cinerariaefolium, from which the major insecticide group the pyrethroids were derived. 

D. Chemical Use Classes. This includes the toxicology aspects of the development of new chemicals for commercial use. In some of these use classes, toxicity, at least to some organisms, is a desirable trait in others, it is an undesirable side effect. Use classes are not composed entirely of synthetic chemicals many natural products are isolated and used for commercial and other purposes and must be subjected to the same toxicity testing as that required for synthetic chemicals. Examples of such natural products include the insecticide, pyrethrin, the clinical drug, digitalis, and the drug of abuse, cocaine. 

Pyrethrin is an extract from several types of chrysanthemum, and is one of the oldest insecticides used by humans. There are six esters and acids associated with this botanical insecticide. Pyrethrin is applied at low doses and is considered to be nonpersistent. 

Cinosulfuron and byproducts Carbonyl 2,4-dinitrophenylhydrazones Insecticidal pyrethrin esthers Pyrethroid insecticides... 

Sulfur ylides, like the phosphorus ylides of Chapter 21, are useful intermediates in organic synthesis, as shown in Problem 21.79. Methyl frans-chrysanthemate, an intermediate in the synthesis of the insecticide pyrethrin I (the chapter-opening molecule), can be prepared from diene A and a sutfur ylide. Draw a stepwise mechanism for this reaction. 

Bruce, W.N. (1967). Detector cell for measuring picogram quantities of orga no-phosphorus insecticides, pyrethrins synergists and other compounds by gas-chroinatography. A grit-, food Chem. 15. 178-181. 

The simple enone 74 was needed for a synthesis of trails chrysanthemic acid 73, a component of the natural insecticide pyrethrin.16 An aldol approach would require a cross-condensation between two enolisable ketones, one of them 75 unsymmetrical, and although this could easily be done an alternative was sought. 

Pyrethroids represent a new class of highly selective insecticide. These preparations are almost completely non-toxic towards mammals. Pyrethroids are related to natural insecticide pyrethrin, which is obtained from Pyrethrum, a daisy-like flower grown in large quantities in Kenya, Africa (Figure 9). 

Allylic oxidation. A recent, simple synthesis of ( )-chrysanthemic acid (5, the (+) acid is the most active constituent of the insecticide pyrethrine) is outlined in scheme 1. The overall yield is A key step involves an allylic oxidation of (1) with rearrangement to give the benzoate (2) this product can be cyclized by a 1,3-elimination to give a mixture of (3) and (4), both of which are convertible into ( )-chrysanthemic acid (5). Various homologs can be prepared in the same way. 

A CEC separation of insecticidal pyrethrin esters was accomplished by Henry et al. [63]. Here it was shown that it is possible to identify pyrethrin esters (cinerin I, pyrethrin I, jasmolin I, cinerin II, pyrethrin II, and jasmolin II) in a commercially available pyrethrin dip and flea and tick mist (Figure 5.20). The column inner and outer diameters were 100 and 350 (im, respectively, and the total and effective lengths were 33 and 25 cm, respectively. The column was packed with 3 xm particle size Hypersil C18. The mobile phase was composed of 55 35 10, pH 9, ACN-25 mM Tris-tetrahydrofuran. Other parameters were an applied voltage of 30 kV, column temperature of 25°C, and UV detection at 254 mn. 

Synthetic pyrethroids have been developed to improve the specificity and activity of the natural insecticide pyrethrin, which are present in pyrethrum, an extract from the flowers of Chrysanthemum cinerarifolium. Pyreihroid pesticides have achieved remarkable effectiveness and set new standards for contact insecticides through improvements made during decades of research. Therefore, several structural modifications have been introduced over time in order to inaease photostability, air stability and insecticidal activity (Sogorb and Vilanova 2(X)2). 

Pyrethrins and their synthetic analogs represent both the oldest and newest of insecticides. Extracts of dried chrysanthemum or pyrethrum flowers, which contain pyrethrin I and related compounds, have been known for their insecticidal properties for a long time, and may have even been used as botanical insecticides in China almost 2000 years ago. The most important commercial sources of insecticidal pyrethrins are chrysanthemum varieties grown in Kenya. Pyrethrins have several... 

Pyrethrins Natural insecticide originally extracted from chrysanthemums and used for insect control in households and storage facilities. Among insecticides, pyrethrins are known to have the least toxic effects for humans. There are synthetic pyrethrins with a similar structure to natural pyrethrins. 

From a public health perspective, the most important group of monoterpenes is the insecticidal pyrethrins, which are harvested from the dried heads of flowers in the Chrysanthemum genus, used in mosquito coils and sprays. The pyrethrins are a pair of natural organic compounds that... 

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