7964. Pyrethrins

Description and references

Active insecticidal constituents of pyrethrum flowers. Isoln: Staudinger, Ruzicka, Helv. Chim. Acta 7, 177 (1924). Prepn by reconstitution from pyrethrolone and chrysanthemic acid: Elliott, Janes, Chem. Ind. (London) 1969, 270. Structure: Crombie et al., J. Chem. Soc. 1956, 3963; Godin et al., J. Chem. Soc. C 1966, 332. Stereochemistry: Begley et al., Chem. Commun. 1972, 1276. Biosynthesis: Crowley et al., Biochim. Biophys. Acta 60, 312 (1962). Review: Crombie, Elliott, Fortschr. Chem. Org. Naturst. 19, 120 (1961). Review of toxicology and human exposure: Toxicological Profile for Pyrethrins and Pyrethroids (PB2004-100004, 2003) 332 pp.

Chemical structure

Derivative

Pyrethrin I.

Nomenclature

CAS number: 121-21-1
(1R,3R)-2,2-Dimethyl-3-(2-methyl-1-propenyl)cyclopropanecarboxylic acid (1S)-2-methyl-4-oxo-3-(2Z)-2,4-pentadienyl-2-cyclopenten-1-yl ester; chrysanthemummonocarboxylic acid pyrethrolone ester.
C21H28O3; mol wt 328.45.
C 76.79%, H 8.59%, O 14.61%.

Properties

Viscous liquid. bp0.0005 146-150°. nD20 1.5242. [α]D20 -14° (isooctane). uv max (95% ethanol): 225 nm (ε 36400). Oxidizes readily and becomes inactive in air. Should be refrigerated and stored in darkness. Stability data of pyrethrins I and II: Godin, Pyrethrum Post 9, 17 (1968), C.A. 71, 12031q (1969). Practically insol in water. Sol in alcohol, petr ether, kerosene, carbon tetrachloride, ethylene dichloride, nitromethane.

Derivative

Pyrethrin II.

Nomenclature

CAS number: 121-29-9
(1R,3R)-3-[(1E)-3-Methoxy-2-methyl-3-oxo-1-propenyl]-2,2-dimethylcyclopropanecarboxylic acid (1S)-2-methyl-4-oxo-3-(2Z)-2,4-pentadienyl-2-cyclopenten-1-yl ester; chrysanthemumdicarboxylic acid monomethyl ester pyrethrolone ester.
C22H28O5; mol wt 372.45.
C 70.95%, H 7.58%, O 21.48%.

Properties

Viscous liquid. Oxidizes rapidly and becomes inactive in air. bp0.007 192-193°. nD20 1.5355. [α]D19 +14.7° (isooctane-ether). uv max (95% ethanol): 229 nm (ε 45850). Practically insol in water. Sol in alc, petr ether (less sol than pyrethrin I), kerosene, carbon tetrachloride, ethylene dichloride, nitromethane.

Caution

Direct skin contact or inhalation may cause severe allergic attacks in sensitive people. Potential symptoms of overexposure are erythema, dermatitis, papules, pruritus; asthma, sneezing, vasomotor rhinitis, anaphylactic reactions; numbness of lips and tongue, sneezing, vomiting, diarrhea; tinnitus, headache, restlessness, incoordination, clonic convulsions, stupor, prostration; death due to respiratory paralysis. See: Clinical Toxicology of Commercial Products, R. E. Gosselin et al., Eds. (Williams & Wilkins, Baltimore, 5th ed., 1984) Section III, pp 352-355; NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 270.

Use

Insecticide.