74. BULLETIN 824, U. S. DEPARTMENT dy AGRICULTURE 
This formula was confirmed by synthesis of the racemic form. 
The semicarbazone of the ketone-alcohol is best hydrolyzed by long 
shaking in benzol solution with an aqueous solution of potassium 
bisulphate. The free alcohol can then be purified by distillation in a 
high vacuum. It has been named pyrethrolon. 
The constitution of this ketone-alcohol was werked out from its 
products of oxidation and reduction and by synthesis of the fully 
reduced tetrahydropyrethron obtained by reduction with hydrogen in 
the presence of platinum black. Tetrahydropyrethron was shown to 
have the formula 
and pyrethrolon the formula 
CH3 
H 
ay aang 
HC CHCE:CH=C=CH(CHi)s 
HOHC——CO 
The acid chlorid was prepared from chrysanthemum acid and 
combined with pyrethrolon to form pyrethrn I. Although neither 
the acid nor the alcohol showed any toxic properties, the resyn- 
thetized ester showed the same toxicity as the original pyrethrin. 
Thus pyrethrin I may be represented by the formula 
CH3 
ABN 
a CHCH2»CH=C=CH(CHz3): 
Co 
| 
| 
CO 
CHCH=C(CBHs3)2 
OCOCH 
C(CHs3)2 
Treating the crude undistilled oil with semicarbazid gave an 
impure mixture of two semicarbazones, which it was not practical 
to separate. The mixture was therefore saponified with methyl 
alecholic-sodium hydroxid solution, by which treatment pyrethrolon 
semicarbazid, together with a mixture of acids, was obtained. More 
of these products was obtained by saponification of mother liquor 
from the first crystallization. It was not possible to prepare the 
second semicarbazone directly. 
From the mixture of acids, chrysanthemum monocarboxylic acid 
and two other acids (chrysanthemum dicarboxylic and chrysanthe-_ 
mum dicarboxylic-acid-mono-methyl-ester) were obtained. When 
treated with ozone chrysanthemum dicarboxylic acid yielded trans- 
caronic acid and levulinic acid. [ts methyl ester yielded trans- 
caronic acid and levulinic acid methyl ester. 
From these results it follows that chrysanthemum dicarboxylic 
acid methyl ester must have the structural formula 
CHs 
(CH3)2,cC—CH CH=C 
\coocHs 
H C COOH 
eae —_—_ | 
a ee a a ee 
nd a Pe, 
ee ae ae a ee 
