66 BULLETIN 824, U. S. DEPARTMENT OF AGRICULTURE 
In 1918 Yamamoto (S31) obtained a preparation of the active 
principles of C. cinerarizfolium of Japanese origin in a state of purity 
probably surpassing anything previously reported. He extracted the 
finely powdered flowers with ether and removed the acid constituents 
from the partially evaporated extract by 2 per cent caustic soda. 
The ether was then evaporated and the residue treated with 90 per 
cent alcohol. This treatment removed a waxy substance. The 
alcohol was then evaporated in vacuum, and the resulting yellow sirup 
obtained was taken up in light petroleum ether. Evaporation of the 
solvent left a light-colored oil, which corresponded to about 0.8 per 
cent of the powder. This material contained no nitrogen and was 
soluble in organic solvents but insoluble in water. It consisted largely 
of an ester, and its iodin value showed that it contained a highly 
unsaturated compound. Upon treatment with alcoholic potash at 
room temperature it lost its insecticidal power. Its toxic character 
was also reduced by heating and long exposure to the air. The 
preparation, which could not be further purified, is probably prac- 
tically the same as Fujitani’s ‘‘Pyrethron.” It was highly toxic to 
flies but had no effect on dogs when introduced into the stomach. 
Upon saponification with alcoholic potash solution in the cold, 
evaporating the alcohol, diluting with water, and extraction with 
ether, the material gave a mass of crystals and an oily substance. 
Most of the crystalline material consisted of an alcohol with a melt- 
ing point of 199° C. and the formula C.,H;,0. Its acetyl compound 
melted at 222-230°. Several other alcchols were isolated, but 
Yamamoto believes that they are impure and consist largely of the 
higher melting compound. The alcohol was not toxic to insects. 
The products of saponification of the pyrethron gave an acid frac- 
tion in a 50 per cent yield. This acid mixture was esterified with 
alcohol and hydrochloric acid and the ester was separated by distilla- 
tion into several fractions. From the lower boiling fractions (77-115°, 
1 mm.) a liquid acid (‘‘pyrethronic acid”), having the formula 
C,,His0. and one double bond, was obtained. From the higher 
boiling ester fraction (113-179° C., 1 mm.) a solid acid, identified as 
palmitic acid, was obtained. 
Later work by Yamamoto (S32) established the formula C,.H,,.O, 
for pyrethronic acid. Reducing the acid with hydrogen in the 
presence of platinum black gave the saturated dihydropyrethronic 
acid, represented by the formula C,,His0.. Several salts and deriva- 
tives of this acid were prepared and analyzed. 
Dihydroxypyrethronic acid was prepared by partial oxidation of 
pyrethronic acid with permanganate. This compound was further 
oxidized by potassium dichromate to a dibasic acid, which was shown 
to be identical with transcaronic acid. The same dibasic acid was 
obtained by oxidation of pyrethronic acid with ozone. Yamamoto 
believed that he had identified propionic aldehyde as a second oxida- 
tion product and deduced the following formula for pyrethronic acid: 
Z(CHs)2 
HOOCC——CHCH=CHOoH; 
H 
When pyrethronic acid was reesterified with the crude material 
containing the alechol component from the saponification of pyre- 
thron, the insecticidal properties of the product were regenerated. 
